InfoWater
Student Analysis and Design Workbook
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Contents 1.0
Overvi Overview ew ................................... .................. ................................... ................................... ................................... ................................... ................................... ................................... ................. 5
1.1 2.0
InfoWa InfoWater ter Software Softwa re Capabilities Capabilit ies ................. ................................... ................................... ................................... .................................... ............................. ........... 5 Modeling Background/Preliminaries......... ................... ................... .................. .................. .................. .................. .................. .................. .................. ............... ...... 6
2.1.0
Gener General al Flow Charact Characterist eristics ics ................................. ............... ................................... ................................... .................................... ................................ .............. 6
2.1.1
Conservation Conser vation of Mass................................... .................. ................................... ................................... ................................... ................................... .................... ... 6
2.1.2
Conservation Conser vation of Energy .................. ................................... ................................... ................................... ................................... ................................... ................. 7
2.2.0
Summar Summary y of Basic Equations .................................. ................ ................................... ................................... .................................... ................................ .............. 7
3.0 Modeling Background ........................................................................................................................... 11 3.1
Refer References ences ................ ................................. .................................. ................................... ................................... ................................... .................................... ........................... ......... 16
4.0 Case Study I ........................................................................................................................................... 17
4.1.0
5.0
4.1.1
Steady State Test for Adequate Pressure .................. ........................... ................... ................... .................. .................. .................. ........... .. 19
4.1.2
Design a Parallel Pipe to Meet Pressure Constraints ......... .................. .................. .................. .................. .................. ............. .... 29
4.1.3
Locating Locati ng New Storage Storag e Tank ................................... ................. ................................... ................................... .................................... ........................... ......... 31
Case Study II ................................... .................. .................................. ................................... ................................... ................................... .................................... ........................... ......... 37
5.1.0
Sufficient Pump Power in Water Distribution Systems................... ............................ .................. .................. .................. ........... .. 37
5.1.1
Extended Simulation Test for Sufficient Pump Power ......... .................. .................. .................. .................. .................. ........... .. 38
5.1.2
New Pump Design ................. .................................. ................................... ................................... ................................... ................................... ........................ ....... 53
5.2.0
6.0
Adequate Pressures in Water Distribution Systems .......................................................... 17
Emergency Response ............................................................................................................ 62
5.2.1
Fireflow Analysis Exercise ................................................................................................ 62
5.2.2
Discussion of Fireflow Results ......................................................................................... 67
5.2.3
Fireflow Design Problem .................................................................................................. 68
5.2.4
Pipe Break Analysis Example ........................................................................................... 70
Case Study III ................................................................................................................................ 74
6.1.0
Water Quality Analysis .......................................................................................................... 74
6.1.1
Standard Water Quality Analysis ..................................................................................... 74
6.1.2
Decision Support for Water Quality Analysis .................................................................. 79
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1.0
Overview
This manual is designed to engage students in a hands-on learning approach to water distribution systems analysis. Students will discuss the fundamental theory behind water wate r distribution system analysis and how to apply it to design problems using the InfoWater software software package developed by Innovyze. Built atop ArcGIS (Esri, Redlands, CA), InfoWater ’s ’s innovative network modeling technology addresses every facet of utility infrastructure management and protection — delivering the highest rate of return in the industry. The software seamlessly integrates sophisticated predictive analytics, systems dynamics and optimization functionality directly within the powerful ArcGIS setting. From fire flow and dynamic water quality simulations, valve criticality and energy cost analysis to pressure zone management and advanced Genetic Algorithm and Particle Swarm optimization, the suite comes equipped with everything water utility owner-operators need to best plan, design, operate, operate , secure and sustain their distribution systems. InfoWater also serves as a base platform for advanced smart network modeling, operation, capital planning and asset management extensions. Among these critical applications are IWLive IWLive (real-time operations and security); InfoWater UDF (unidirectional (unidirectional flushing); CapPlan CapPlan (risk-based (risk-based capital planning); InfoMaster and and InfoMaster Mobile (asset Mobile (asset integrity management and condition assessment); InfoWater MSX (multi-species (multi-species modeling); InfoWater BTX (event/particle backtracking); InfoSurge backtracking); InfoSurge (surge/transient analysis); Sustainability (carbon footprint calculation); BalanceNe BalanceNett (real-time energy management and operations optimization); PressureWatch PressureWatch (real-time (real-time network hydraulic integrity monitoring); QualWatch QualWatch (real-time network water quality integrity monitoring); SCADAWatch monitoring); SCADAWatch (real-time (real-time business intelligence and performance monitoring); monitoring); DemandWatch DemandWatch (water demand forecasting); and DemandAnalyst (real-time water demand and diurnal pattern estimations).
1.1
InfoWater Software Capabilities
InfoWater offers DIRECT ARCGIS INTEGRATION enabling engineers and GIS professionals to work simultaneously on the same integrated platform. It allows you to command powerful GIS analysis and hydraulic modeling in a single environment using a single dataset. dataset . You can create, edit, modify, run, map, analyze, design, and optimize your water network models and instantly review, query, and display simulation results from within ArcGIS. InfoWater powerful powerful ArcGIS integration features: ArcGIS™ Build/Run Network Model in ArcGIS™ Model-Building Tools Provide Native ArcGIS™ Model-Building Construct/Update Models Directly from Geodatabase and Geometric Network or Any External
Data Source o n Geometric and/or Non-Geometric Data with Allow Complete or Filtered Data Exchange on
Geodatabase or RDBMS
Treat Pumps and Valves as Nodes (Points) Create/Edit Multiple Scenarios in the Same Geodatabase
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View fully Animated Extended Period Simulation (Dynamic) Results Sequentially Using VCR-Style
Controls Directly in ArcGIS™ ArcGIS™
Generate Contours, Graphs and Tables of Modeling Results Directly in ArcGIS™ ArcGIS™
Combine Input and Output Attribute Tables
Use Relational Database and Geodatabase to Store Model Data
Fully Automate GIS Data Exchange with ESRI Data Sources (e.g., Valve Status)
Pick any GIS Attributes Automatically Without Mapping any Fields Automatically Publish Simulation Results to Enterprise Geodatabase and/or RDBMS Fully Compatible with Intergraph GeoMedia and GeoMedia Professional
2.0
Modeling Background/Preliminaries
This section will look at the main principles, theories, and equations governing water distribution systems and hydraulics. Specifically, this section will discuss general flow characteristics and several of the governing equations used when analyzing fluids.
2.1.0 General Flow Characteristics In order to sufficiently understand and analyze hydraulic systems, it is first necessary to understand the general principles that govern flow characteristics. character istics. Water distribution networks can generally be analyzed and solved using the three conservation laws: mass, energy and momentum. The basic analysis can generally be accomplished with mass and energy conservation principles. InfoWater strategically applies these principles to solve and analyze water distribution networks, hence a brief overview is discussed.
2.1.1 Conservation of Mass The principle of conservation of mass states that the mass in a closed c losed system must remain constant over time. The quantity of mass in a system cannot change unless more mass is added to a system or mass has been removed from a system. As most networks primarily deal with water, we assume a constant density, or the fluid is incompressible. Hence for open systems, the mass flow rate into the system must equal the mass flow rate out of the system (no internal storage since the working fluid is incompressible). For example, if water were to flow into a pipe at 10 cubic feet per second, it m must ust exit the pipe at a flow of 10 cubic feet per second. The principle of conservation of mass (based on volumetric flow) can be summarized by the following equation:
∑ = ∑ 6
Where
ΣQin is the mass/volumetric flow rate entering the system ΣQout is the mass/volumetric flow rate exiting the system
This equation assumes that the change in storage of o f the system is equal to ze zero. ro. By definition, volumetric flow is equal to the average velocity of the fluid entering a pipe multiplied by the cross sectional area of the pipe. This is summarized by the following equation:
= Where
Q represents volumetric flow represents cross sectional averaged velocity V represents A represents represents the cross c ross section of the pipe (if the pipe flows full) A
Therefore, by multiplying the velocity of a fluid traveling through a pipe by the ccross-sectional ross-sectional area of the inside of the pipe (assuming that the system is a closed conduit), the flow of the fluid can be found. If the pipe does not flow fully, then the flow can be found by multiplying the average velocity that the fluid travels with the cross sectional area of o f the fluid in the pipe.
2.1.2 Conservation of Energy The principle of conservation of energy states that the total energy at a certain cert ain location in a system equals the energy at a further point in a system plus the energy change due to losses (i.e, friction) or gains (i.e., pumps). This principle is derived from Newton’s second second law of motion, or the Thermodynamic Laws. The conservation of energy states that energy can neither be created nor destroyed, but that it transfers from one form to another. In water distribution systems, energy can be measured using the Bernoulli Be rnoulli Equation.
2.2.0 Summary of Basic Equations Extended Bernoulli’s Equation While energy can be expressed in two fundamental forms in a distribution system: potential and kinetic energy, there are several detailed components that show up in the Bernoulli Equation:
Static Head – Head – the the potential energy gained from the elevation of the fluid
Pressure Head – Head – the the potential energy from the pressure on the fluid
Velocity Head – Head – the the kinetic energy gained from the movement of the fluid
Head Gains – Gains – energy energy gained from an external input, such as a pump Head Losses – Losses – energy energy lost due to friction, fittings, valves, or turbines, etc. 7
When a term is expressed as a head , it has dimensions of length [L], representing a depth of water. Typically, the units of head are in feet or meters. The following equation shows the extended Bernoulli Equation:
+ + + 2 + = = + + + 2 + Where:
is equal to the Pressure Head [L]
Z 1 is equal to the Elevation Head [L]
is equal to the Velocity Head [L]
G ain [L] HG is equal to the Head Gain HL is equal to the Head Loss [L]
In order to solve this equation, typically two points along a network are analyzed. Flow and pressure monitoring devices such as manometers (or pressure gages) and Pitot tubes (velocity doppler meters) help to analyze these points. Similarly, there are several simplifying conditions/assumptions that can be made pertaining to the energy equation at specific points along a water distribution network that help to analyze a system. For example, water that is exposed to the atmosphere has zero gauge pressure. Typically, water is exposed to the atmosphere at elevated storage tanks and reservoirs. Also, water at the surface of an elevated storage tank or reservoir is assumed to move very slowly. This means that the velocity head is assumed to be zero at the surface of these elevated storage tanks and reservoirs.
Hydraulic/Energy Grade Line The energy grade line is a term ter m that represents the summation of the pressure head, elevation e levation head, and the velocity head. It represents the total amount of energy at a certain location in a water distribution system. Head gains and head losses can be quantified between two points by finding the difference in hydraulic grade line between the two points. The following equation shows the energy grade line:
= + + 2 Where:
is equal to the Pressure Head
z is equal to the Elevation Head
is equal to the Velocity Head
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The hydraulic grade line represents just the t he potential energy terms, namely pressure and elevation.
= + Energy Loss In pipe flow, the energy loss between two points is defined as total head loss ( ). Total head loss consists of frictional head loss ( ) due to the fluid’s fluid’s contact with the pipe wall, wall, and minor head losses ( ) due
to various pipe network components/form (i.e. valves, bends, fittings, etc.). In most systems, frictional head loss accounts for the vast majority of energy losses. Minor losses are often assumed to have a negligible effect on the system. The equation e quation for total head loss is shown below:
= + Quantifying Frictional Head Loss There are several ways to account for the frictional losses. The Darcy Weisbach Equation and Hazen Williams Equation are two widely accepted methods for quantifying frictional head loss in pipe flow. Both equations calculate head loss as a function of the fluid velocity, pipe length, diameter, and pipe roughness.
Darcy Weisbach Equation The Darcy Weisbach Equation for frictional head loss is:
= 2 Where:
f is the friction factor, an empirical quantification of the friction-causing elements of the pipe or
channel
L is the length of pipe, typically measured in meters or feet
D is the diameter of the pipe, measured in meters or feet
V is is the velocity of the fluid, measured in meters per second or feet per second
g is the gravitational constant
HLf is the head loss measured in meters or feet
The pipe roughness is imbedded in the friction factor ( f f ), ), which can be quantified by a variety of approaches (i.e. Moody Diagram, Colebrook-White Eq., Jain Eq., Wood Eq., etc.). Friction factors generally gene rally vary from 0.008 to 0.038.
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Hazen Williams Equation The Hazen Williams Equation for head loss represents the pipe roughness through the Hazen Williams C Coefficient. C coefficients coefficients generally vary between 100 and 140. The Hazen Williams head loss equation is shown below:
= .54.7 × .5 Where:
L is the length of the pipe measured in feet or meters
C is the Hazen Williams C coefficient coefficient
D is the diameter of the pipe measured in feet or meters
Q is the volumetric flowrate measured in cubic feet per second or cubic meters per second
HLf is the head loss measured in feet or meters
C u is the units coefficient, 4.73 for SI, 10.68 for English
The Hazen Williams Equation is an empirical equation, hence the need for the units coefficient.
Quantifying Minor Head Loss Energy losses from pipe fittings, transitions, bends, valves, etc., are called minor losses. These are termed minor losses due to the fact that they are often insignificant with respect to frictional head loss. The equation for minor head loss is shown below:
= × 2 Where: is the minor head loss coefficient, K is
g is the acceleration due to gravity is the velocity of the water V is
Minor head loss
is also in units of length. Minor head loss coefficients vary for different types of
bends, fittings, valves, etc, and are typically given by the manufacturer.
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3.0 Modeling Background Networks are comprised of a collection of pipes, nodes, and other components. The equations developed in the previous section apply to the network in general, but but they are specifically implemented in pip pipes. es. In network modeling, each pipe must be represented by the appropriate head loss-discharge relationship (i.e., Darcy-Weisbach Equation). There are a number of methods that have been developed to analyze water distribution networks for flows and pressures (e.g. hardy cross, simultaneous node, simultaneous pipe). InfoWater uses uses a method called the Global Gradient Algorithm (GGA) which was w as developed by Todini and Pilati in 1987. This is also called the Gradient Method or the Simultaneous Network Method, which is a variant of the NewtonRaphson Method. The GGA utilizes a set of mass balance equations for each junction node, and energy equations for each pipe, which are solved in matrix form for the change in flow ( ) and the change in head ( ) in the system. New flow values are then calculated (updated) and used as inputs for the next iteration. The system is iterated until the and values converge to zero (or a small error tolerance). When the and converge to zero, the flows and grades in the network are known, and the appropriate head lossdischarge relationship is maintained in each pipe.
∆
∆
∆
∆
∆
∆
Example of the Global Gradient Algorithm: Figure 3.0.1 below shows a simple network layout, comprised of pipes, nodes, outflows, and a supply reservoir (top left of figure). The following tables detail the characteristics of each network component. c omponent.
Figure 3.0.1: Example Network
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Table 3.0.1: Pipe Character Characteristics istics
Table 3.0.2: Junction Character Characteristics istics
The continuity and energy equations for the junction nodes in the network are shown below for junctions 1, 2, 3, 4, 5, and 6, respectively. Continuity Equations:
− − 7 = 0 − 3 − = 1 3 − 4 = 1 4 + 5 = 1 6 + − 5 = 1 7 − 6 = 1 The energy equations for each pipe are shown below for pipes 1, 2, 3, 4, 5, 6, 7, and 8, respectively. r espectively. Whether or not the Q terms are positive or negative is a sign convention based on (assumed) flow directions. Energy Equations:
|| + − = 0 12
|| + − = 0 3|3| + 3 − = 0 4|4| + 4 − 3 = 0 5|5| + 5 − 4 = 0 6|6| + 6 − 5 = 0 7|7| + 6 − = 0 || + 5 − = 0 The table of initial heads, flows, and calculated gradients and head loss terms is shown in the next table. The right hand side term for each pipe is calculated by first calculating the value of the left hand side of the energy equation (shown above), and multiplying by negative 1. These values will ultimately become part of the B matrix. Units for elevation, head (H), diameter, length, and head loss are all feet. Flow is in cubic feet per second. Node 1 2 3 4 5 6 A
El ev. 100 90 90 90 80 80 200
H 150 150 150 150 150 150 200
Pi pe 1 2 3 4 5 6 7 8
Length Di ameter 1000 1.166667 500 1 500 1 700 1 900 1 600 1 300 1 400 1
C 130 130 130 130 130 130 130 130
K 0.27418 0.290426 0.290426 0.406597 0.522767 0.348512 0. 0.174256 0.232341
Qi 5 5..000 3.000 1.500 0.500 0.500 1.000 2.000 0 0..500
nK|Q|^n-1 1.999 1.370 0.759 0.417 0.536 0.645 0.582 0.238
KQ^n 5.401663 2.221593 0.615399 0.112631 0.144811 0.348512 0 0..629064 0.06436
RHS 44.59834 -2.22159 -0.6154 -0.11263 -0.14481 -0.34851 -0.62906 -0.06436
Initial Q values are based on assumed flows which satisfy the mass conservation equations. The next step is to set up the A and B matrices based on the continuity and energy equations and the values calculated in the table above. The A matrix can be divided into four quadrants (as shown below). The upper left quadrant consists of diagonal terms, which are the gradient terms (derivative of the energy equation) for each pipe, and all other terms in the upper left quadrant are zeros. The upper right quadrant includes the coefficients for the continuity equations. A positive 1 means flow is into the junction and a -1 means flow is out of the junction. Once this section of o f the matrix is constructed, the upper right quadrant may be transposed to obtain the lower left quadrant. The lower left quadrant may also be obtained from coefficients of the energy equations for each pipe. The lower right quadrant is comprised of all zeros. The B matrix is comprised of the RHS terms from the table values and then zeros for the bottom section of this matrix.
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A Matrix
1.999 0 0 0 0 0 0 0
0 1.370 0 0 0 0 0 0
0 0 0.759 0 0 0 0 0
0 0 0 0.417 0 0 0 0
0 0 0 0 0.536 0 0 0
0 0 0 0 0 0.645 0 0
0 0 0 0 0 0 0.582 0
0 0 0 0 0 0 0 0.238
1 -1 0 0 0 0 -1 0
0 1 -1 0 0 0 0 -1
0 0 1 -1 0 0 0 0
0 0 0 1 1 0 0 0
0 0 0 0 -1 1 0 1
0 0 0 0 0 -1 1 0
1 0 0 0 0 0
-1 1 0 0 0 0
0 -1 1 0 0 0
0 0 --1 1 1 0 0
0 0 0 1 --1 1 0
0 0 0 0 1 --1 1
-1 0 0 0 0 1
0 -1 0 0 1 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
B Matrix
44.5983366 -2.221593 -0.6153992 -0.1126306 -0.1448108 -0.3485116 -0.6290639 -0.0643603 0.000 0.000 0.000 0.000 0 0
The solution vector is comprised of the dQ and dH terms, the updated information for flows and heads. By solving the system of equations [A]{x}=[B], the following results are obtained for the {x} matrix.
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X Matrix
0.0000 -0.4889 -0.3258 -0.3258 0.3258
dQ1
dQ2
dQ3
dQ4
dQ5
0.4889 0.4889 -0.1631 44.5983 43.0466 42.6785 42.7016345 43.0210333 43.6847762
dQ6 dQ7 dQ8 dH1 dH2 dH3 dH4 dH5 dH6
New Q and H values are calculated using dQ and dH terms. The new flow and head values were then substituted into the same procedure and the system was iterated until the dQ and dH values converged to zero. The tables below show the values for Q, dQ, H, and dH as they were updated for each iteration until they converged. converge d. The values for all 4 iterations are in the tables below, with the final answer highlighted in green. These tables illustrate the robustness of the solution procedure. Node #
ΔH
Iteratio Iter ation n1
Iter Iteratio ation n2
Iteratio Iteration n3
1
44.5983
0.0000
0.0000
0.0000
2
43.0466
- 0.0630
0.0000
0.0000
3
42.6785
- 0.0835
- 0.0001
0.0000
4
42.7016
- 0.1220
- 0.0001
0.0000
5
43.0210
- 0.0715
- 0.0001
0.0000
6
43.6848
- 0.0197
0.0000
0.0000
Node #
Iter Iteratio ation n4
H Iteratio Iter ation n1
Iter Iteratio ation n2
Iteratio Iteration n3
Iter Iteratio ation n4
1
150
194.5983
19 194.5983 194.5983
2
150
193.0466
19 192.9836 192.9836
3
150
192.6785
19 192.5950 192.5949
4
150
192.7016
19 192.5796 192.5796
5
150
193.0210
19 192.9496 192.9495
6
150
193.6848
19 193.6651 193.6651
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Pipe #
ΔQ
Iterat Iter ation ion 1
Iter Iterat ation ion 2
Iterat Iteration ion 3
1
0.0000
0.0000
0.0000
0.0000
2
- 0.4889
0.0142
0.0000
0.0000
3
- 0.3258
- 0.0038
0.0000
0.0000
4
- 0.3258
- 0.0038
0.0000
0.0000
5 6
0.3258 0.4889
0.0038 - 0.0142
0.0000 0.0000
0.0000 0.0000
7
0.4889
- 0.0142
0.0000
0.0000
8
- 0.1631
0.0180
- 0.0001
0.0000
Q
Pipe #
3.1
Iterat Iteration ion 4
Iterat Iter ation ion 1
Iter Iterat ation ion 2
Iterat Iteration ion 3
Iterat Iteration ion 4
1
5.000
5.000
5.000
5.000
2
3.000
2.511
2.525
2.525
3
1.500
1.174
1.170
1.170
4
0.500
0.174
0.170
0.170
5
0.500
0.826
0.830
0.830
6
1.000
1.489
1.475
1.475
7
2.000
2.489
2.475
2.475
8
0.500
0.337
0.355
0.355
References
Nicklow, J.W. and Boulos, P.F. Essential Water and Wastewater Calculations for Engineers and Operators, Operators, 1st edition, MWH Soft (Innovyze), Broomfield, Colorado, 2007, 372 pp. Lansey, K.E. and Boulos, P.F. Comprehensive Handbook on Water Quality Analysis in Distribution Systems, Systems, 1st edition, MWH Soft (Innovyze) Press, Broomfield, Colorado, 2005, 448 pp. Lansey, K.E., Boulos, P.F. and Karney, B.W. Comprehensive Water Distribution Systems Analysis Handbook For Engineers and Planners, Planners, 2nd Edition, MWH Soft (Innovyze) Press, Broomfield, Colorado, 2006, 660 pp.
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4.0 Case Study I With a general look at how the network is setup and solved, the robustness of InfoWater InfoWater can can be shown through various examples. The examples are also used to illustrate the types of analysis and design considerations the practicing engineer would encounter.
4.1.0 Adequate Pressures in Water Distribution Systems One of the main purposes of water distribution systems is to adequately deliver water to a utility company’s customers. How do we know when water is adequately delivered? There are a few criteria that can be assessed to see if the water distribution system is doing everything that it should. Firstly, water must be delivered at adequate pressure. This concept will be the subject of this case study. If pressures in the system are too low, paying customers may become upset, and more importantly, the system may not be able to combat fires, which is another criterion that must be assessed. We will look more into fireflow analyses in Section 5.2.1. If pressures are too high, then there may be damage to check valves and pipe infrastructure. In order to prevent these problems from occurring, it is the job of the engineer to design the water distribution system such that pressures within the system are within a set of constraints. For example, in the following case study, pressures of KYTown must be greater than 40 psi and less than 100 psi. Through the use of hydraulic modeling software like InfoWater , it is possible for the design engineer to test pressures in the system and analyze junctions where problems of possible high or low pressures may occur. Also, distribution systems should limit inconveniences to the utility company’s company’s customers. customers. It is most convenient for pipes to follow streets and city-owned property edges. This prevents water lines from existing on private property – property – something something that could delay construction and maintenance on pipes and cause pipe installation to be tedious. Water must also be delivered at good quality. Water quality will be discussed more in Section 6.0 Case Study III . Often time, problems with pressure are a result of too much or too little energy existing within the distribution system. When pressures are lower than the allowable constraint, there are too many energy losses in the system. One way to model energy losses is through the use of the Darcy-Weisbach equation, which was introduced in Section 2.2.0:
ℎ = 8 5 Here, h f represents represents head loss in dimensions of length (ft or m), f m), f is is a dimensionless friction factor and can be found using the Moody Diagram, L is the length of pipe in question (ft or m), Q is the flow of water through the pipe (cms or cfs), g is the gravity constant (ft/s2 or m/s2), and D is the diameter of the pipe (ft or m).
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There are a few options that help to lower the amount of head loss through pipes. Firstly, head loss can be reduced by increasing pipe diameter. Notice from the Darcy-Weisbach equation that head loss and pipe diameter are inversely related. Therefore, increasing the diameter of the pipe will decrease the amount of head loss. This is not always a pragmatic option in the real world, however, since pipe price increases dramatically as diameter increases.
Another common practice to reduce head loss is to install additional pipes parallel to existing pipes. This is especially practical when pipes have previously been installed or when the installation of large pipes is too expensive. The installation of parallel pipes involves implementing new pipe parallel to pipes that may already exist. This allows for more water to be delivered to jjunction unction without decreasing the pressure. This practice effectively increases the diameter of the pipe while minimizing cost and inconvenience to customers. Another option to account for low pressure (energy) in a system is to simply add more energy to the system. More energy can be added to a system through the use of pumps. If there is too little energy in the system, engineers can choose to implement a new, more powerful pump that can increase the overall energy of the system or implement a booster pump that can increase energy in a specific section of the water distribution system. This option can quickly become expensive when considering life cycle and operational costs, however, and may be unnecessary if there is only one junction with low pressure in a distribution system. An indication of too much energy in the t he system is seen whenever pressures are greater than the allowable constraint. Keeping the Darcy-Weisbach equation in mind, there are a few solutions to problems of high pressure: pipe sizes can be be decreased, pump size can be decreased, or more valves and fittings (loss devices) can be added to the system. With this in mind, it is now possible to analyze the system of KYTown. It will be the engineer’s job engineer’s job to analyze the system for adequate pressure. If pressure constraints are not met in KYTown, then it will be the engineer’s job engineer’s job to find a solution that brings pressures pre ssures within those constraints.
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4.1.1 Steady State Test for Adequate Pressure Introduction Through the use of hydraulic modeling software, it is possible to model pressure throughout a water distribution system. In this first case study, you will analyze a system given various nodal demands to see if pressure constraints are met everywhere within the system. If a pressure constraint is not met, it will be your job to find a solution that brings pressures within the required range. This is the type of problem that design engineers may face on a day-to-day basis. The system that will be used in this case study will be provided from Innovyze as an extension in the Examples Examples folder. folder. The system that will be used for this case study is titled, “CaseStudy1.mxd” and can be found in the downloaded InfoWater Student Analysis and Design Workbook folder. folder.
Step 1: Open and Set Up the CaseStudy1.mxd Project The first step is to open the CaseStudy1.mxd file in InfoWater . Many of the following steps are supplemental to the InfoWater Users Guide. Guide. It is assumed that the InfoWater Users Guide has been read before starting this workbook. If you feel as though basic set up procedures are unnecessary, you may skip the next seven steps: 1. Choose the “Start” menu, select Programs Programs,, choose the InfoWater Version X program group and choose InfoWater . Choosing InfoWater automatically automatically starts your version of ArcMap of ArcMap since since InfoWater is is an extension of ArcMap of ArcMap.. 2. In the ArcMap the ArcMap window, window, select An select An Existing Map option Map option in the Start Using ArcMap With area With area and then click the “OK” button. This can also be accessed by choosing File » Open from the ArcMap the ArcMap command menu. 3. Navigate to the directory containing the CaseStudy1.mxd project and choose that file. The directory containing the CaseStudy1.mxd file was specified in the introduction of Section 4.1.1. 4. The KYTown network, which will be the primary model for the subsequent case studies, will now be displayed in the ArcMap the ArcMap window. window.
Figure 4.1.1.1: KYTown Pipe Network 19
5. It is now necessary to initialize InfoWater. This is found on the InfoWater Control Center toolbar toolbar that was previously installed following the steps in the InfoWater Users Guide Guide Quick Start
Tutorial. Press the Red Down Arrow icon
to initialize InfoWater.
6. Make sure that the InfoWater Control Center toolbar and the InfoWater Edit Network toolbar toolbar are shown. To do this, choose Customize Customize from from the Menu Menu bar bar in ArcMap in ArcMap.. Click Toolbars Toolbars,, and then make sure that InfoWater Edit Network and InfoWater Control Center are are selected as shown below.
Figure 4.1.1.2: Opening the InfoWater Control Center and InfoWater Edit Network Toolbars 7. It is also important that the Model Explorer and Table of Contents windows are open. To open the Model Explorer window, click the icon on the InfoWater Control Center toolbar. toolbar. To open the Table of Contents window, which should open by default, click the icon on the Standard toolbar. The Standard toolbar toolbar should be available by default, but if it is not, click Customize Customize » » Toolbars » Toolbars » Standard . The following image shows what your screen should look like when the Table of Contents and and Model Model Explorer windows have been properly opened. Note that the aforementioned icons have been denoted by a red box:
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Figure 4.1.1.3: Opening the Table of Contents and Model Explorer Windows Now that InfoWater has been initialized and the CaseStudy1.mxd file has been opened in ArcMap in ArcMap,, the next step is to prepare the KYTown system for an analysis. It is necessary to first define the basic project units and hydraulic properties. You will also input the demands that are located at each node/junction. Information pertaining to pipe diameters, roughness, minor loss coefficients, and lengths has previously been entered. Similarly, information pertaining to nodal and reservoir/tank parameters has already been entered. It is not necessary for the user to input information pertaining to the KYTown system unless explicitly stated otherwise. Information pertaining to an element of the system can be inspected by clicking the DB Editor icon icon
in the InfoWater Control Center toolbar or by selecting the Select Element
from the InfoWater Edit Network toolbar and then selecting an individual element. This
information can then be viewed in the Model Explorer – Attribute Attribute Tab. Tab. 1. In this system, Standard English units are used. Flow is measured m easured in Gallons/Minute. Head loss is measured using the Hazen-Williams equation. Pressure is measure in psi. These settings are the default for InfoWater, but we should make sure that the CaseStudy1.mxd file follows the default settings. 2. From the Model Explorer window, select the Operation tab
located at the bottom of the
window. Next, select Simulation Options » BASE, Base Simulation Option. Option. The following screen will appear:
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Figure 4.1.1.4: Changing Analysis Units for KYTown 3. Make sure “Gallon/Minute” is chosen from the Flow Unit drop down list. By choosing “Gallon/Minute”, all input data, such as elevations and diameters, will be in Standard English units. Similarly, Similarly, make sure that “Hazen“Hazen-Williams” is chosen from the Head loss Equation dropEquation dropdown list and “psi” is chosen from the Pressure Unit drop-down drop-down list. All other parameters should match those shown in the “Simulation Options” window. 4. Click the Save Save icon icon
and press the “OK” button
to close the window.
5. Next, it is necessary to enter the demands located at each node. This can quickly be done by choosing the DB Editor icon
» Element Hydraulic Data » Junction Demand (Modeling) Data. Data .
The entire table should be displayed showing all nodes in the system. 6. Enter the demands for each of the t he nodes. Since this is a steady state simulation, it is only necessary to enter information in the Demand 1 column of the Junction the Junction Demand (Modeling) (Modeling) Data table. The following table shows the demands at each junction j unction in the system: J10
J12 20
J30
J14 30
J32 25
J16 50
J36 50
J20 60
J38 45
J22 30
J40 15
J24 20
J42 15
J26 25
J44 35
J28 15
J46 25
50 J48
20
50
7. After entering this information in Junction in Junction Demand (Modeling) (Modeling) Data table, the table will appear as follows:
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Figure 4.1.1.5: Inputting Junction Demands 8. The system is now ready to be analyzed. Save the system as “CaseStudy1Analysis1.mxd”. This file will be used in subsequent exercises, so it is important that these changes have been saved so that they can later be edited. An additional satellite image has been provided with the CaseStudy1.mxd file so that the user has an idea of the topographical lay of the land surrounding the KYTown system. It is possible to load this image by completing the following steps: 1. In the same directory mentioned previously, you will find a .jpg file that has been included in this folder. The name of this file is KYTown.jpg (be sure to keep the KYTown.jpg.aux.xml file in the same directory as the .jpg to ensure a spatial matching of the image with the network). 2. Drag the .jpg file from the t he aforementioned folder into the the ArcMap ArcMap window. window. The following image shows the KYTown system with satellite images placed behind it.
Figure 4.1.1.6: KYTown with Satellite Images 23
Note that by checking or unchecking the box in the Table of Contents window Contents window pertaining to the satellite image, the layer can be turned on or off.
Figure 4.1.1.7: Turning off the KYTown.jpg Layer
Step 2: Test the KYTown System for Adequate Pressures Using the nodal demand input from the previous step, it is possible to run a steady state simulation to determine if pressure constraints are met throughout the KYTown system. For this particular case study, we will assume that in order to maintain adequate pressure in the system, pressures must be greater than 40 psi and less than 100 psi. It is now possible to analyze the system by running a simulation. It is first necessary to identify this simulation as steady state. This means that all conditions in the system are assumed to be constant and unvarying over the simulation time. 1. In order to specify that the t he simulation is steady state, choose the Operation tab
from the
Model Explorer window. window. Next, click Simulation Time » Time » BASE, Base Simulation Time. Click the box next to “Steady State”. The simulation will will now now run as a steady ste ady state analysis.
Figure 4.1.1.8: Specifying a Steady State Simulation 2. Click the “OK” button
to close the Simulation Time window.
3. Next, it is necessary to run the simulation. Click the InfoWater button
in the
InfoWater Control Center toolbar, then choose Tools » Run Manager . The following dialog box will appear: 24
Figure 4.1.1.9: Use the Run Manager to Run a Simulation 4. Choose the “Run” icon indicate a green light
at the top of the screen. The stoplight on the Run Manager should should if the simulation has run successfully. Click the “OK” button
to
close the Run Manager window. It is now possible to review the results of the simulation. There are several ways to look at these results. They can be viewed individually, as a table, or directly direc tly on the map. 1. In order to view each node’s individual information, select the Select Element icon
from the
InfoWater Edit Network toolbar toolbar and then select an individual node. The information pertaining to the pressure of the node can be seen in the Model Explorer – Attribute Attribute tab under the Output section
. For example, at J48 (the north-most node), the pressure is determined to
be 41.41 psi (as highlighted in Figure 4.1.1.12). 2. In order to view these pressures in tabular form, select the Report Manager icon
. Next,
choose New » *Active*:Standard » Junction » Junction Report . The following table has been generated:
Figure 4.1.1.10: Results from a Steady State Analysis 25
3. To view the pressures on the map, click the Map Display icon
. Next, choose Junction choose Junction.. Under
the Classes tab, choose choose Active Active Output . The Data Field drop down list should read PRESSURE :
Figure 4.1.1.11: Process of Showing Results on the Map 4. Click Click Apply Apply » OK . You should see the following results. J48
Figure 4.1.1.12: Results from a Steady State Analysis [Graphical] After viewing the pressures at each node, it is evident that all pressures in the system are between 40 psi and 100 psi. Therefore, there is adequate pressure throughout the KYTown system. In the next step of this case study, it is assumed that a new development causes an increased demand at certain nodes. You will analyze the system given these changes and determine if the pressure in the system falls within the allowable constraints.
Step 3: Test for Adequate Pressures Given a New Development We will now consider that a new development has been implemented in northern part of KYTown near the node J48. Because of this new development, a new demand of 150 gpm now exists at J48. This is 100 26
gpm higher than the previous demand that existed ex isted at J48. As a reminder, J48 can be seen in the following figure:
Figure 4.1.1.13: Location of J48 It is necessary to once again analyze the system for adequate pressures. This is done using the same methods previously mentioned in Step 1 and Step 2. 1. It is first necessary to update the demand at J48. This can quickly be updated by choosing the Select Element icon
from the InfoWater Edit Network toolbar toolbar and then choosing J48.
2. Under the Modeling section
, Demand 1 (gpm) should (gpm) should be changed from 50 to
150. Once this has been done, click the t he Save Current Record icon
in the Model Explorer –
Attribute tab. 3. Next, we will run the simulation using the same parameters as before. Go to InfoWater » Tools » Run Manager . All previous inputs should remain unchanged, i.e. this simulation will also be run at steady state. 4. Click the “Run” icon
and then press “OK”
.
5. After pressing “OK”, the new pressures pre ssures should automatically update on the the ArcMap ArcMap window. window. Note that the pressure at J48 changes from 41.41 psi to 38.78 psi. Figure 4.1.1.14 shows the model results on the following page. 6. The system can now be saved using the same file name as before.
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Figure 4.1.1.14: Second Analysis Results This increase in demand has caused a pressure decrease throughout the system. Most notably, the pressure at J48 has decreased below 40 psi, which is below the minimum allowable pressure for the city of KYTown. It now becomes the designer’s task to propose and design design a practical solution to this problem. Before continuing, recall the discussion from Section 4.1.0, which identifies possible solutions to pressure issues in water distribution systems.
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4.1.2 Design a Parallel Parallel Pipe to Meet Meet Pressure Constraints Introduction When dealing with problems of low pressure, it is often common practice to install a parallel pipe next to the existing pipe to help fix the pressure issues. Adding parallel pipes helps to deliver more flow to a certain location while reducing head losses. It also allows for the original line to remain in place something that is beneficial because water can still be delivered to customers even when construction is taking place.
Step 1: Implement a Parallel Pipe In this section of the case study, we will show a step-by-step solution in the creation of a parallel pipe to reduce losses and hence solve the problem of low pressure that exists at J48. 1. First makes sure that the Auto the Auto Length Calculation is turned off. By default, InfoWater automatically calculates the length of pipe based on their position. We want to specify the length ourselves, so it is necessary to turn turn Auto Auto Length Calculation off. Calculation off. This can be done by choosing InfoWater » Tools » Project Preferences. Preferences. The box next to Auto to Auto Length Calculation Calculation should be unchecked
. Click the OK box box to close the Preferences dialogue box.
2. We will now add in a parallel pipe between betwee n J36 and J48 to solve the issue. First, click the Add the Add Pipe icon on the InfoWater Edit Network toolbar. 3. Next, left click node J36. Follow the existing pipe towards J48. The pipe you implement should have the same contour as the existing pipe between J36 and J48 labeled P89. 4. By clicking the left button on the mouse mo use a single time, it is possible to add bends in the pipe. Since the Auto the Auto Length Calculation Calculation has been turned off, the exact location of where you click does not have an effect on the length of the pipe. 5. Double click on J48 to connect the J36 and J48. A window labeled Pipe Identification will Identification will appear. In the box next to Pipe ID, ID, type, “P100, New Pipe”.
Figure 4.1.2.1: Pipe Identification 6. The length of this pipe automatically defaults to 100 feet. Enter “2000” into the Length (ft) field. (ft) field. Enter “8” into the Diameter (in) field. Lastly, enter “120” into the Roughness field. All of this information can be edited in the Model Explorer – – Attribute Attribute tab. Once this has been done, click the Save Current Record icon
in the Model Explorer – Attribute Attribute tab.
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Figure 4.1.2.2: New Pipe Specifications 7. Run a new analysis on the system. Go to t o InfoWater » Tools » Run Manager . All previous inputs should remain unchanged, i.e. this simulation will also be run at steady state. 8. Click the “Run” icon
and then press “OK”
.
9. Note that after pressing “OK”, all pressures have been updated. The following following image shows the updated system. Note the addition of the parallel pipe between J36 and J48.
Figure 4.1.2.3: Analysis Results The parallel pipe that you have implemented has brought pressures within the allowed constraints. All nodes have pressures within the allowable range of 40 psi to 100 psi. It should be noted that though the problem has been solved, this is not the only procedure that can increase energy in a water distribution system. It is advised to the user to attempt to add in parallel pipes in other locations or to change the pipe sizes in some locations. Changing a pipe’s size can easily be done by changing c hanging the Diameter (in) (in) field field in the Model Explorer – Attribute Attribute tab. This is an action that can be easily modeled, but not easily implemented in the field. 30
4.1.3 Locating New Storage Tank Introduction Developers have begun construction of a new Veteran’s Center at the north end e nd of KYTown. It is estimated that a demand of 180 gallons per minute (gpm) will be required re quired at the establishment once construction is complete. A 6 inch pipe has been already been placed along the road leading to the veteran’s center as shown in Figure 4.1.3.1 to deliver water to residents in the area. Your job is to add the 6 inch waterline to the model, and assess assess the system’s response based on the new demand at the veteran’s center. With W ith the exception of the veteran’s center, which requires a minimum pressure of 50 psi due to the building’s multiple floors, everywhere else in the system must maintain pressure between 40 psi and 100 psi. Step 1: Model New Additions to System System As shown in Figure 4.1.3.1, a 6 inch waterline should be modeled along the road leading to the veteran’s center. From an aerial view, waterlines wate rlines typically follow roads because they are often placed in state rightof-way for practical reasons such as cost and obtaining easements.
Figure 4.1.3.1: Schematic of Waterline to Veteran’s Center Model the addition to the system by following the procedure below: 1. Add aerial imaging to the map by following fo llowing the steps presented in Section 4.1.1. If aerial images are already saved under Folder Connections, C onnections, just drag and drop them into the map area. 2. Choose the Add/Insert the Add/Insert Junction icon and left click just above the northern-most corner of the veteran’s veteran’s center to add junction J56 to t o the system as shown in Figure 4.1.3.1. 3. Next, we must add elevation and demand data at junction J56. Left click on jjunction unction J56 and edit the elevation and demand cells in the Model Explorer Window with the following data. Junction J56 Characteristics Elevation (ft) 915 Demand 1 (gpm) 250
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4. Choose the Add/Insert the Add/Insert Pipe Pipe icon to connect the new junction to the rest of the system. Left click junction J24 and follow the road on the aerial imaging to the veteran’s center. Left click when you need to change c hange directions, as this will add intermediate nodes to the pipe. When you arrive at the veteran’s center, veteran’s center, double click junction J56 and name the pipe “P113”. 5. Next, we must add characteristic data to pipe P113. Left click on P113 to select it, and edit the length, diameter, and roughness cells in the Model Explorer Window with the following data. Pipe “P113” Characteristics Characteristics Length (ft) 3500 Diameter (in) 6 Roughness 120
Step 2: Test System for Adequate Pressures Once the model has been updated, click the Save icon to save your progress. Run a steady state analysis with the same input parameters as before. When the analysis is complete, check all pressures in the system to ensure the constraints are still satisfied. Run the steady state analysis by following these steps: 1. Open the Run Manger Window by clicking InfoWater , Tools Tools,, and Run Manager , or by clicking the Run Manager icon in your Model Explorer Window. 2. Make sure simulation options and time settings are the same as previous runs (these should not change between simulations unless they are manually changed). 3. Click the Run icon ; make sure the stoplight is green press “OK” to close the Run Manager window.
which indicates a successful run, and
4. Check the analysis results by clicking the Report Manager icon ; select New » *Active*:Standard » Junction Report . The table shown in Figure 4.1.3.2 will be generated.
Figure 4.1.3.2: Junction Report Table with Inadequate Pressures
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Pressures for all junction nodes are shown in the far right column of the junction report table as shown in Figure 4.1.3.2. Pressures which are lower than the minimum constraint are indicated by red arrows. Junctions J48 and J56 are in violation of the minimum pressure constraint, thus action must be taken to solve these issues. Adding a parallel pipe along the road to the veteran’s center will decrease the head loss head loss enough to meet the minimum pressure constraint at junction J56. However, the pressure at junction J48 will still violate the minimum pressure constraint. Adding parallel pipes from tank T5002 to junction J48 will lower head loss thus allowing the pressure constraint to be satisfied, however any additional development in the north end of town will cause more problems with low pressures. To mitigate the pressure issues in the north end of town due to increased development, you will install a new storage tank.
Step 3: Design a New Storage Tank A land permit has already been approved for the new storage tank at the location shown as the red square in Figure 4.1.3.3. Your job is to design a new storage tank using the software (maximum and minimum tank elevations; not capacity) in order to mitigate the pressure issues at nodes “J48” and “J56”. “J56” .
Figure 4.1.3.3: Location of New Storage Tank The storage tank you will be designing will be an elevated storage tank, commonly known as a water tower. Elevated storage tanks are typically used in areas with flat topography where a man-made structure is needed to elevate the water to ensure the system maintains adequate pressure. For modeling purposes, the elevated storage tank has 5 main input parameters: elevation, minimum level, maximum level, initial level, and capacity. Capacity issues are mainly related to extended period simulations which will be covered in a later section; for now we will look at the first 4 parameters. Elevation of the storage tank is the elevation of the ground on which the storage tank is built. For storage tanks that are not elevated, this will also act as the minimum water level. However, the elevated storage tank’s minimum water level is located at the bottom of the tank which holds the water which is often 33
elevated 50 feet or more into the air. The maximum m aximum water level is the top of the water tank and the initial level is the distance from the ground to the water surface in the tank. A graphical explanation of the elevated storage tank characteristics can be viewed below in Figure 4.1.3.4.
Figure 4.1.3.4: Graphical Representation of Modeling Parameters for Elevated Storage Tank (original image taken from USACE) To add the elevated storage tank to the system model, you will need to add a tank node and a pipe connecting the tank another junction in the system. We will add this tank to the t he area depicted by the red square in Figure 4.1.3.3. Follow the steps below to add the tank to your model. 1. Click the Add/Insert the Add/Insert Tank icon in the InfoWater Edit Network Toolbar and and click in the area depicted by the red square in Figure 4.1.3.3 to add the tank and name it “T5”. “ T5”. 34
2. Next we must input characteristic data for the new tank, which you will see cells for in the Model Explorer Window. Left click on tank T5 to select it and match the values for the following characteristics in the table below. (Note: The values for diameter and minimum volume are an arbitrary estimate for a half million gallon tank.) Storage Tank T5 Elevation (ft) Minimum Level (ft) Maximum Level (ft) Initial Level (ft) Diameter (ft) Minimum Volume (ft3)
940 100 150 130 50 67,000
3. Now we must connect the tank to the system by adding a pipe betwee between n tank T5 and junction J56. Click the Add/Insert the Add/Insert Pipe icon and click on the tank T5 to start drawing the pipe. Double click on junction J56 and name the pipe “P115” to finish drawing the pipe. pipe. 4. Next, add characteristic data to pipe P115. Left click on P115 to select it, and edit the length, diameter, and roughness cells in the Model Explorer Window with the following data. Pipe “P115” Characteristics Characteristics Length (ft) 500 Diameter (in) 8 Roughness 120
Step 4: Test System for Adequate Pressures with Tank Once the model has been updated, click the Save icon to save your progress. Run a steady state analysis with the same input parameters as before. When the analysis is complete, check all pressures in the system to ensure the constraints are still satisfied. Run the steady state analysis by following these steps: 1. Open the Run Manger Window by clicking InfoWater , Tools Tools,, and Run Manager , or by clicking the Run Manager icon in your Model Explorer Window. 2. Make sure simulation options and time settings are the same as previous runs (these should not change between simulations unless they are manually changed). 3. Click the Run icon press “OK”
; make sure the stoplight is green
which indicates a successful run, and
to close the Run Manager window.
4. Check the analysis results by clicking the Report Manager icon ; select New » *Active*:Standard » Junction Report . The table in Figure 4.1.3.5 will be generated.
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Figure 4.1.3.5. Junction Report Table with Adequate Pressures With the addition of the elevated storage tank, all pressures now fall within the constraints. Junctions J48 and J56 have pressures above 40 psi and 50 psi, respectively. Also, the tank did not increase pressures above the maximum constraint of 100 psi. (Note: These results are for a steady state analysis with a set value for the Tank’s initial level; pressures will change with increases or decreases in water elevation.)
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5.0
Case Study II
As we have mentioned, one of the main purposes of a water distribution system is to adequately deliver water to a utility company’s customers. In previous examples, you have only analyzed systems under a steady-state analysis. In this case study, you will analyze the KYTown system when conditions change throughout the day. This better models the way that a water distribution system behaves in reality since demands fluctuate throughout the day. It should be noted that there is a similarity between the challenges seen during steady state simulations and extended period simulations; i.e. no matter the type of simulation, water must be delivered at adequate pressure to customers. Recall from previous discussion that if pressures in the system are too low, paying customers may become upset, and more importantly, the system may not be able to combat c ombat fires. We will look more into fireflow analyses in Section 5.2.1. On the other hand, pressures too high could co uld cause the failure of check valves and damage pipe infrastructure.
5.1.0 Sufficient Pump Power in in Water Distribution Distribution Systems In order to prevent these types of problems from occurring, it is the job of the engineer to design the water distribution system such that pressures within the system are within a set of constraints. For example, in the following case study, we will see that the pressures of KYTown must be greater than 40 psi and less than 100 psi. Through the use of hydraulic modeling software, it is possible for the design engineer to simulate pressures in the system and analyze junctions where problems of possible high or low pressures may occur. When pressures are lower than the allowable constraint, it is possible that not enough energy is input into the system or there is too much energy loss in the system. There ar are e multiple indicators of a system where not enough energy is supplied. Firstly, pressures at individual nodes will decline over the course of extended periods. This means that even if the initial pressures are within the required constraints, they eventually will lower to a point where they no longer are acceptable. Secondly, the elevation of water in tanks will not refill to its initial position over the course of a day. This is an immediate indicator of too little energy in the distribution system. If the tank is supplying more water than it is receiving, meaning that the tank does not fill back up over the course of the day, then the system requires more energy than the pump can provide. There are multiple solutions to this type of problem. Firstly, design engineers may increase the diameter of the pipes transporting fluid. Recall from the DarcyDar cyWeisbach Equation that head loss and diameter are inversely related. Therefore, increasing the t he diameter of the pipe will decrease the amount of head loss. This is not always a pragmatic option in the real re al world, especially when considering an extended period simulation. When not enough energy exists, pressures throughout the system will decline as daily usage patterns continue. By replacing sections of the system with pipes of larger diameter, it is possible to reduce the amount of head loss in the system. However, this quickly could become very expensive considering that pipe prices greatly increase as diameter increases. Therefore, trying to solve this issue by replacing the pipes in the system is not a practical solution. 37
One of the most pragmatic solutions to issues concerning low pressures throughout a water distribution system is to simply increase the amount of energy input into the system. More energy can be added to a system through the use of pumps. There are several actions design engineers can take to increase the amount of energy input into the distribution system: head/energy gy The pump can be replaced with a new, more powerful pump that supplies more head/ener
into the system, more pumps could be implemented at the pump station in series or parallel with the original pump,
or booster pumps can be installed to increase energy in specific locations of the distribution
system. Adding pumps in parallel at the pump station is commonly practiced by hydraulic design engineers. This is because pumps in parallel add more flow to the system and in the event of a malfunction or necessary maintenance, one pump can still operate while the other is shut down. This means that the distribution system can still be supplied with water even eve n if there are issues with one of the pumps. An indication of too much energy in the t he system is seen whenever pressures are greater than the allowable constraint. Keeping the Darcy-Weisbach equation in mind, there are a few solutions to problems of high pressure: pipe sizes can be decreased, pump size can be decreased, or more valves and fittings (loss devices) can be added to the system. With this in mind, it is now possible to analyze the system of KYTown. It will be your job to analyze the system for adequate pressure. If pressure constraints are not met in KYTown, then you will find a solution that brings pressures within those constraints.
Test for for Sufficient Pump Pump Power 5.1.1 Extended Simulation Test Introduction Another important use of hydraulic modeling software is running extended period simulations. In water distribution systems, nodal demands are not constant throughout the day. There are instances where elevated storage tanks fill up and other instances when elevated storage tanks drain. Typically, demand patterns follow a diurnal curve. This curve is consistent with the times of the day when people are most active at their homes. Typically, there are two peak demand periods throughout the day – day – one one during the morning and one at the start of the evening. In this second case study, you will analyze a system given various nodal demands that change throughout a day to see if pressure constraints are met at all locations and at all times. If a pressure constraint is not met, it will be your job to design a solution that brings pressures within the required range. The system that will be used in this case study will be provided from Innovyze as an extension in the Examples Examples folder. folder. The system that will be used is titled, “CaseStudy2.mxd” and can be found in the downloaded InfoWater Student Analysis and Design Workbook folder.
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Step 1: Open and set up the CaseStudy2.mxd Project The first step is to open the CaseStudy2.mxd file in in InfoWater . Many of the following steps are supplemental to the InfoWater Users Guide. Guide. If you feel as though basic set up procedures are unnecessary, you may skip the next six steps: 1. Choose the “Start” menu, select Programs Programs,, choose the InfoWater Version X program group and choose InfoWater . 2. In the ArcMap the ArcMap window, window, select An select An Existing Map option Map option in the Start Using ArcMap With area With area and then click the “OK” button. This can also be accessed by choosing File » Open from the ArcMap the ArcMap command menu. 3. Navigate to the directory containing the CaseStudy2.mxd project and choose that file. file . The location of this file can be found in the Introduction section of 5.1.1. 4. The KYTown network, which will be the primary model for the t he subsequent case studies, will now be displayed in the ArcMap the ArcMap window: window:
Figure 5.1.1.1: KYTown Pipe Network 5. Note that this system has been altered altere d from the previous case study, although it looks similar. DO NOT use the previous system saved from Case Study 1 for this case study, or your results will differ from the ones provided in this case study. 6. It is now necessary to initialize InfoWater . This is found on the InfoWater Control Center toolbar toolbar that was previously installed following the steps in the InfoWater Users Guide Guide Quick Start
Tutorial. Press the Red Down Arrow icon
to initialize InfoWater.
7. Make sure that the InfoWater Control Center toolbar and the InfoWater Edit Network toolbar toolbar are shown. To do this, choose Customize Customize from from the Menu Menu bar bar in ArcMap in ArcMap.. Click Toolbars Toolbars,, and then make sure that InfoWater Edit Network and InfoWater Control Center are are selected as shown below: 39
Figure 5.1.1.2: Opening the InfoWater Control Center and InfoWater Edit Network Toolbars 8. It is also important that the Model Explorer and Table of Contents windows are open. To open the Model Explorer window, click the
icon on the InfoWater Control Center toolbar. toolbar. To open
the Table of Contents window, which should open by default, click the
icon on the Standard
toolbar. The Standard toolbar toolbar should be available by default, but if it is not, click Customize Customize » » Toolbars » Toolbars » Standard . The following image shows what your screen should look like when the Table of Contents and and Model Model Explorer windows have been properly opened. Note that the aforementioned icons have been denoted by a red box:
Figure 5.1.1.3: Opening the Table of Contents and Model Explorer Windows
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Now that InfoWater has been initialized and the CaseStudy2.mxd file has been opened in ArcMap in ArcMap,, the next step is to prepare the KYTown system for an analysis. To do this, first define the basic project units and hydraulic properties. You will also need to define the demand pattern for the system throughout a 24-hour day. Information pertaining to pipe diameters, roughness, minor loss coefficients, and lengths has previously been entered. Similarly, information pertaining to nodal and reservoir/tank rese rvoir/tank parameters has already been entered. It is not necessary for the user to input information pertaining to the KYTown system unless explicitly stated otherwise. Information pertaining to an element of the system can be viewed through the DB Editor icon Element icon
in the InfoWater Control Center toolbar or by selecting the Select
from the InfoWater Edit Network toolbar and then selecting an individual element.
Information pertaining to the selected element can then be viewed in the Model Explorer – Attribute Attribute Tab. Tab. 1. In this system, Standard English units are used. Flow is measured in Gallon/Minute. Head loss is measured using the Hazen-Williams equation. Pressure is measured in psi. These settings are the default for InfoWater, but you should make sure that the CaseStudy2.mxd file follows the default settings. 2. From the Model Explorer window, select the Operation Operation tab tab located at the bottom of the window. Next, select Simulation Options » BASE, Base Simulation Option. Option. The following screen will appear:
Figure 5.1.1.4: Changing Analysis Units for KYTown
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3. Make sure “Gallon/Minute” is chosen from the Flow Unit drop down list. By choosing “Gallon/Minute”, all input data, such as elevations and diameters, will be in Standard English units. Similarly, make sure that “Hazen“Hazen-Williams” is chosen from the Head loss Equation dropEquation dropdown list and “psi” is chosen from the Pressure Unit drop-down drop-down list. All other parameters should match those shown in the Simulation Options window. Options window. 4. Next, it is necessary to enter the demand pattern for the KYTown system throughout the 24 hour day. This defines how demands will change throughout the system over the day. 5. In order to enter this demand pattern, go to the Model Explorer – Operation Operation tab
. Right
click on Pattern Pattern » » New . The Pattern Identification Identification window will open. Type, “2, New Pattern” in the Pattern ID box. ID box.
Figure 5.1.1.5: Pattern Identification
6. Next, define the number of rows by clicking the icon. The Pattern window will then open. In the Value box, enter “24”. This indicates indicates that at each hour of the t he day, a new demand will exist. Click “OK” to close the Pattern Pattern window window that specifies the number of pattern factors. The Pattern Pattern window should look as follows:
Figure 5.1.1.6: Pattern Window without Factors 42
7. Enter the following 24 factors in the t he Value column column in the currently opened Pattern Pattern window: window:
Factor 1
Factor 2
Factor 3
Factor 4
Factor 5
Factor 6
0.5
0.4
0.4
0.5
0.7
1
Factor 7
Factor 8
Factor 9
Factor 10
Factor 11
Factor 12
1.6 Factor 13
1.5 Factor 14
1.4 Factor 15
1.2 Factor 16
1.2 Factor 17
1.2 Factor 18
1.1
1
1
1.1
1.2
1.4
Factor 19
Factor 20
Factor 21
Factor 22
Factor 23
Factor 24
1.3
1.2
1.1
1
0.8
0.6
8. The Pattern window should now look as follows:
Figure 5.1.1.7: Pattern Window with Factors
9. Click the save save icon
and press the “OK” icon
to close the Pattern window.
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10. Next, apply this pattern to the system. In order to do this, click the t he DB Editor icon
, choose
Junction Demand (modeling) (modeling) Data Data,, choose Entire Table in Table in the Data Scope box, Scope box, and press “OK” “OK”.. 11. The DB Editor window will open. Select the entire Pattern 1 (Char) column by clicking in the space surrounding the text at the top of the column. Next, click the Block Editing icon
.
12. The Block Edit window will now open. In the Value Value box, box, enter “2”. This will indicate will indicate that the pattern that you labeled as “2” will be used during the simulation. The DB Editor window window should look as follows:
Figure 5.1.1.8: Applying the Pattern to the Demands 13. Save the Junction the Junction Demand (Modeling) (Modeling) Data by Data by clicking the save icon
and close the DB Editor .
The system is now prepared for an extended ex tended period simulation to be run. An additional satellite image has been provided with the CaseStudy2.mxd file so that the user has an idea of the topographical lay of the land surrounding the KYTown system. It is possible to load this image by completing the following steps: 1. In the same directory mentioned previously, you will find a .jpg file that has been included in this folder. The name of this file is KYTown.jpg (be sure to keep the KYTown.jpg.aux.xml file in the same directory as the .jpg to ensure a spatial matching of the image with the network). 2. Drag the .jpg file from the t he aforementioned folder into the the ArcMap ArcMap window. window. The following image shows the KYTown system with satellite images placed behind it.
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Figure 5.1.1.9: KYTown with Satellite Images Note that by checking or unchecking the box in the Table of Contents window Contents window pertaining to the satellite image, the layer can be turned on or off.
Figure 5.1.1.10: Turning off the KYTown.jpg Layer L ayer
Step 2: Run the Extended Period Simulation Using the pattern set up previously, it is possible to run an extended period simulation to see if pressure constraints are met throughout the KYTown system at all times. If the pressure at a node falls outside of the allowable constraints, it is likely that the pump does not supply sufficient horsepower to the system. For this particular case study, we will assume that in order to maintain adequate pressure in the system, pressures must be greater than 40 psi and less than 100 psi. It is now possible to analyze the system by running the extended period simulation. 1. We will first need to identify this simulation as an extended period simulation. This means that conditions in the system are dynamic as time changes. c hanges. 2. In order to specify that the simulation is an extended period simulation, choose the Operation tab
from the Model Explorer window. window. Next, click Simulation Time » Time » BASE, Base
Simulation Time. Make sure that the box next to “Steady State” is State” is unchecked. Make sure that under the Unit column, column, each is specified as being in Hours Hours.. In the Duration row, make sure that the Decimal Time column states 24. This represents the 24 hours of the day. The following figure shows what the Simulation Time window Time window should look like prior to the EPS analysis:
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3. Click the “OK” button
Figure 5.1.1.11: Simulation Time Window to close the Simulation Time window.
4. Next, we will run the simulation. Click the InfoWater button
in the InfoWater Control
Center toolbar, then choose Tools » Run Manager . The following dialog box will appear:
Figure 5.1.1.12: Run Manager Window 5. Choose the “Run” icon indicate a green light
at the top of the screen. The stoplight on the Run Manager should should if the simulation has run successfully. Click the “OK” button
to
close the Run Manager window. It is now possible to review the results of our simulation. We have generated individual nodal and flow results for the entire system over the course of 24 hours. Through the use of the the Model Explorer – – Attribute tab, Attribute tab, it is possible organize the data by time. By doing this, you can see the flow and pressure results in the entire system at a specific hour. There are a few ways that you can specify the time. Firstly, by clicking the Time dropdown menu, it is possible to choose a specific time for which we wish to see results. 46
Figure 5.1.1.13: Time Dropdown Menu Specification
For example, by choosing “00:00 hrs”, the results for the initial hour will be displayed. Alternatively, it is possible to change the simulation hour by moving the slider bar to a desired time. This is located to the right of the Time Time drop drop down menu in the Model Explorer – Explorer – Attribute Attribute tab.
Figure 5.1.1.14: Time Slider Bar After we have chosen a specific time, there are several ways for us to view these results. They can be viewed individually, as a table, or directly on the map. m ap. 1. In order to view each node’s individual information, select the Select Element icon
from the
InfoWater Edit Network toolbar toolbar and then select an individual node. The information pertaining to the pressure of the node can be seen in the Model Explorer – Attribute Attribute tab under the Output section
. The output information for J48 at hour 12 is shown below:
Figure 5.1.1.15: J48 Results Information 2. As a reminder, J48 can be seen in the following figure:
Figure 5.1.1.15: J48 Location 47
3. In order to view these pressures in tabular form, select the Report Manager icon
. Next,
choose New » *Active*:Standard » Junction » Junction Report . The following table has been generated:
Figure 5.1.1.16: Pressures at Hour 12:00 Similarly, it is possible to define a specific time at which the results are shown. In this instance, click the Time Time dropdown dropdown menu located on the Junction the Junction Report [*Active*:Standard] [*Active*:Standard] table table and choose a specific hour of the day. This table shows the results for hour 12:00. 4. To view the pressures on the map, m ap, click the Map Display icon
. Next, choose Junction choose Junction under under
the Element Type box. Type box. Under the Classes tab, tab, choose choose Active Active Output . The Data Field drop down list should read PRESSURE :
Figure 5.1.1.17: Setting the Map Display 5. Click Click Apply Apply » OK . The pressures are now displayed on the screen. For the map at hour 12:00, you should see the following results:
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Figure 5.1.1.18: Pressures at Hour 12:00 After viewing the pressures at each node, it is necessary to do an analysis of the results. It is evident that all pressures are located between 40 psi and 100 psi for the 12:00 hour. Therefore, it is possible to see that all pressure constraints are met for this particular hour. By viewing the data for each hour interval, it is evident that for the first 24 hours, all pressure constraints are met for the KYTown system. It would appear as though there is sufficient pump horsepower for the system to function sufficiently for 24 hours. However, you may notice something peculiar about the system over the 24 hours. When the Model Explorer – Attribute Attribute tab reads a time of “00:00 hrs”, open the Report Manager
. Choose New »
* Active*:Standard » Tank Report . Make sure that Complete Report/Graph is Report/Graph is indicated, and click Open Open.. The following report should appear:
Figure 5.1.1.19: Tank Levels at Hour 0:00 Notice from the Tank Report [*Active*Standard] table [*Active*Standard] table that at 00:00 hrs, T5 is 60% full and T5002 is 53% full. Now, click the Time drop down menu and indicate a time of 24:00 hrs. hrs. Notice that at the end of the day, T5 is 39.03% full and T5002 is 31.03% full.
Figure 5.1.1.20: Tank Levels at Hour 24:00 49
Over the course of the day, the tanks do not refill to their original height. This means that over extended periods, it is likely that the pressures in the system may fall below the minimum constraint. If this trend continues, it is also likely that the tanks in the system will drain entirely. In the next step of this case study, you will further analyze the system for sufficient pressures at a length of time greater than 24 hours.
Step 3: Run the Extended Period Simulation for 72 Hours Next, run the extended exte nded period simulation for 72 hours to test for adequate pressure. 1. In the Model Explorer – Operation tab, Operation tab, choose Simulation Time » BASE, Base Simulation Time. Time. 2. Make sure that the box next to “Steady State” is unchecked. Make sure that under the Unit column, each is specified as being in Hours Hours.. In the Duration row, make sure that the Decimal Time column states 72.This means that the simulation will now represent three days, rather than just one. Save the Simulation Time by pressing the Save icon
, and then press “OK”
.
3. Next, we will run the simulation. Go to InfoWater » Tools » Run Manager . 4. Click the “Run” icon
and then press “OK”
.
5. To view the pressures on the map, m ap, click the Map Display icon . Next, choose Junction choose Junction under under the Element Type box. Type box. Under the Classes tab, tab, choose choose Active Active Output . The Data Field drop down list should read PRESSURE . 6. Click Click Apply Apply » OK . The pressures are now displayed on the screen. View pressures at hour 72 by indicating 72:00 hrs from the slider on the Model Explorer – Explorer – Attribute tab. Attribute tab.
Figure 5.1.1.21: Tank Levels at Hour 72:00 Notice that at hour 72, pressures have fallen below the minimum allowable pressure of 40 psi at node J48. The system does not operate efficiently because there are too many losses. 50
It is possible to also view graphical data regarding the tank heights over the course of the 3 days. 1. Use the Select Element tool
from the InfoWater Edit Network toolbar toolbar to select tank T5002 in
the western part of the city.
Figure 5.1.1.22: Tank T5002 2. In the Model Explorer – Attribute Attribute tab, click the Graph Graph icon
to open the Report Manager
window. A Tank Graph now appears. We want to see the head at the tank, so under the drop down menu that states Flow , choose Head.
Figure 5.1.1.23: Specifying “Head” on Tank Graph
3. The graph of the head in the tank over the course of the 72 hours can then be seen.
Figure 5.1.1.24: Graph of Tank Head over 72 Hours 51
Through this graph, it is possible to see that the tank does NOT refill over the course of 24 hours. This means that throughout the day, the water elevation in the tank is lowering. Recall from Section 5.1.0 that this is indicative of a few different things. Firstly, this could indicate that the head losses in our system are too high. It could also mean that our pump does not supply enough energy to overcome these losses and refill the tanks over the course of the day. Essentially, this means that the pump does not supply enough horsepower to maintain the system. If this trend continues, it is likely that the elevated storage tanks in KYTown will empty completely. This is very problematic for two reasons. Firstly, it will cause the decline of pressure in the system as time progresses and secondly, it will not allow the tanks to store sufficient water to combat fires. It is evident that the pump in the system has not been sized correctly since the pressure in the system falls outside of our allowable constraints. It now becomes the task of the design engineer to figure out a way to increase the energy of the system. Before continuing, recall the discussion from Section 5.1.0, which identifies possible solutions to poorly sized pumps in systems.
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5.1.2 New Pump Design Introduction When dealing with problems such as declining water elevations in elevated storage tanks, it is necessary to recognize that a lack of energy is the t he root of the problem. Since the elevation of water in both elevated storage tanks declines, it is indicative that there is too little pressure throughout the entire system, rather than just at one node, which was the case in case study 4.1.1. Therefore, it would be impractical to implement parallel pipes, as was the suggested solution in Section 4.1.2. Typically, when energy is too low throughout the system, booster pumps or additional pumps at the pump station are commonly implemented to input more energy into the system. In this section of the case study, we will show a stepby-step solution in the creation of a parallel pump at the pump station to reduce losses and increase energy in the system. By inputting this parallel pump and sizing it correctly, the water in the tank should rise and drain to about the same elevation over the course of the day. IIff the tanks do this and all pressure constraints are met within the system, then you have successfully designed this aspect of a water distribution system. This also means that our water distribution system is very stable.
Step 1: Create a New Pump Station 1. First makes sure that the Auto the Auto Length Calculation is turned off. By default, InfoWater automatically calculates the length of pipe based on their position. You will specify the length of pipes yourself, so it is necessary to turn Auto turn Auto Length Calculation Calculation off. This can be done by choosing InfoWater » Tools » Project Preferences. Preferences. The box next to Auto to Auto Length Calculation Calculation should be unchecked
. Click the OK box box to close the Preferences dialogue box.
2. Next, add in nodes before and after the previously installed pump, U7000, to replicate the pump station. To do this, click the Add/Insert the Add/Insert Junction Junction icon
and click in between the pump and the
reservoir. A Confirmation Confirmation dialog dialog box will appear. Click, Click, “Yes”.
Figure 5.1.2.1: Confirmation Box 3. Next, a Junction a Junction Identification box Identification box appears. In the Junction the Junction ID box, input, “J58” and in the Pipe ID box, input, “P117”. “P117”.
Figure 5.1.2.2: Junction Identification Box 53
4. Repeat the previous two steps and implement a node between J28 and the pump. To do this, click the Add/Insert the Add/Insert Junction Junction icon
and click in between the pump and the reservoir. A
Confirmation dialog box will appear. Click, “Yes”. Confirmation
Figure 5.1.2.3: Confirmation Box 5. Next, a Junction a Junction Identification box Identification box appears. In the Junction the Junction ID box, input, “J60” and in the Pipe ID box, input, “P119”. “P119”.
Figure 5.1.2.4: Junction Identification Box 6. To see the labels of each node, navigate to the InfoWater Control Center toolbar and click InfoWater » View » ID Labeling » Node Node.. The pump station should then appear as follows:
Figure 5.1.2.5: Map Display Near Pump Station 7. Make sure that the junction elevation for the t he new nodes (J58 and J60) is 893 ft (the default elevation for this model) in the Model Explorer Attribute tab. t ab.
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Figure 5.1.2.6: Model Explorer Junction Attribute tab 8. It is now necessary to specify the lengths and diameters of each of the pipes that we divided. Since the Auto the Auto Length Calculation Calculation is turned off, new pipes default to 100 feet in length. Match each pipe length to the following table: Pipe
Length (ft)
Diameter (in)
Roughness
P69
230
10
120
P117
230
10
120
P103
230
10
120
P119
230
10
120
9. Next input a new pipe that connects J58 to J60. First, click the the Add Add Pipe icon
. Then, left click
J58. Create the pipe so that it looks as follows. Double click on J60 to end the editing sequence. First, a Pipe Identification window appears. In the Pipe ID ID box, type, “P121”. Click “OK”. Your map will appear as follows:
Figure 5.1.2.7: Parallel Pipe Station Implemented
55
10. With the pipe in place, it is now possible to implement a pump. In order to do tthis, his, click the Add the Add Pump icon
. Then, specify a place that you wish your pump pump to to be located. This should be
approximately half way between J58 and J60. A Confirmation Confirmation box will appear. Click “Yes”.
Figure 5.1.2.8: Confirmation Box 11. A Pump Identification window then appears. In the Pump ID box, type “U7002” and in the Pipe ID ID box, type “P123”. Then click “OK” “OK”
Figure 5.1.2.9: Pump Identification Box 12. The pump has now been implemented into the water distribution system. Our system now looks as follows:
Figure 5.1.2.10: System with Pump New Pump Station 13. Make sure to specify the length of each pipe around the pump station using the following table: Pipe P121 P123
Length (ft) 400 400
Diameter (in) 10 10
Roughness 120 120
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14. Next, it is necessary to define the pump characteristics. Specify a pump that has the same qualities as the previously implemented pump. In the Model Explorer – Attribute tab, Attribute tab, it is possible to specify the parameters of the pump. 15. Under the Modeling row
in the Model Explorer –
Attribute tab, we will edit several pump attributes. In the Type Type box, box, click the drop down and choose 2: Exponential 3-Point Curve. Curve. In the Elevation (ft) box, (ft) box, type, type, “893”. In the diameter box, box, type, “10”. In the Shutoff Head (ft) (ft) box, type, “200”. In the Design Head (ft) (ft) box, type, “150”. In the Design Flow (gpm) (gpm) box, type, “860”. In the High Head (ft) box, type, “70”. Finally, in the High Flow (gpm), (gpm), type “1720”. Your “1720”. Your Model Explorer – Attribute Attribute tab should look as follows:
Figure 5.1.2.11: Specifying Pump Attributes
Through this process, you have specified the pump curve for this newly new ly installed pump. This curve is based on a standard pump curve, where an operating point was identified – identified – i.e. i.e. the design head and the design flow. In this standard pump curve, the shutoff head is 133% of the design head and the high flow is twice the amount of the design flow. We have matched the pump curve that pertains to the pump previously installed. This is beneficial for a few reasons. Firstly, from our first analysis from Section 5.1.1, we know that one of these pumps can sustain the system for at most one day (although the pressure does decrease over time). In addition, if one pump were to go out of commission, it would give maintenance crews at least 24 hours to work on the pump and fix the issue while the other pump could still supply energy to the system. This may lower the probability of a transient event occurring. We will discuss transient events in detail in a subsequent workbook.
Step 2: Run another Extended Period Analysis Now it is necessary to see how the system responds to this newly installed pump.
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1. Run an extended period simulation. Click the InfoWater button
in the InfoWater
Control Center toolbar, then choose Tools » Run Manager . The following dialog box will appear:
Figure 5.1.2.12: Run Manager Window 2. Choose the “Run” icon indicate a green light
at the top of the screen. The stoplight on the Run Manager should should if the simulation has run successfully. Click the “OK” button
to
close the Run Manager window. 3. You can now review the results from fr om this analysis. To view the pressures on the map, cclick lick the Map Display icon
. Next, choose Junction choose Junction under under the Element Type box. Type box. Under the Classes tab, tab,
choose Active choose Active Output . The Data Field drop down list should read PRESSURE :
Figure 5.1.2.13: Setting the Map Display 4. Click Click Apply Apply » OK . The pressures are now displayed on the screen. Use the slider in theModel the Model Explorer – Attribute Attribute tab to view the pressures for the 72 hour analysis. Notice now that all pressures are within the required constraints. At hour 72, you should see the following results:
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Figure 5.1.2.14: Results for Hour 72 5. Note that the pressure at node J58 before the pumps exhibits a low pressure; this is common and acceptable as there is no demand at this junction. 6. Since the pressures in the system are within the allowable constraints, we likely have enough energy input into the system for it to be considered considered stable. Let’s now look at graphs gr aphs showing the elevation of water in the tanks. 7. Use the Select Element tool
from the InfoWater Edit Network toolbar toolbar to select tank T5002 in
the western part of the city.
Figure 5.1.2.15: Tank T5002
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8. In the Model Explorer – Attribute Attribute tab, click the Graph Graph icon
. A Tank Graph will open. We want
to see the head at the tank, so under the drop down menu that states Flow , choose Head. Head.
Figure 5.1.2.16: Specifying “Head” on Tank Graph 9. The graph of the head in the tank over the course o off the 72 hours can then be seen as follows. Note that the tank rises and drains to the same peak and trough every day. This means that the tank is not emptying:
Figure 5.1.2.17: Graph of Tank 5002 Head over 72 Hours 10. Next, look at the tank graph for T5 using the same method previously described. You should see the following results. As you can see from this t his graph, the tank rises and drains to the same peak and trough every day. This means that the tank t ank is not emptying:
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Figure 5.1.2.18: Graph of Tank 5 Head over 72 Hours After viewing all nodes in this system and the t he elevations of water in the tanks over 72 hours, it is evident that this new pump implementation has solved the problem. All nodes have pressures within the allowable range of 40 psi to 100 psi and the tanks drain and fill to the same level every day. As we have mentioned, there are other solutions so lutions to this type of problem. For example, it would be possible to take out the original pump and input a completely new one o ne with more power. At times, however, however , this can become quite expensive. It is advised to the user to attempt to add in pumps with different pump curves or to change the pipe sizes in certain locations to see how the t he system responds.
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5.2.0 Emergency Response There are two types of o f emergency responses relating to wate waterr distribution systems. One type of response is directed at correcting a failure of one or more components of the system (i.e. pipe, pump, valve, etc.). The other type of emergency response uses the water in the distribution system to mitigate effects of a societal emergency (i.e. fire). In Section 5.2.1 we will simulate a societal emergency (i.e. fire) and analyze residual pressures in the system. In Section 5.2.4, we will also simulate an internal system failure (i.e. pipe break) and identify the best emergency response plan. Problems in a distribution system which require a designed solution will generally deal with high or low pressures. Low pressures in a system are simply the result of not having enough energy in the system. In this instance, there are two things we can do: 1) we can increase the energy in the system, or 2) we can decrease the energy losses in the system. If high pressures are an issue, we can either 1) increase the losses in the system, or 2) decrease the amount of energy we put into the system.
Another problem that may arise in a distribution system is a pipe break. If a pipe breaks, water will continue to flow out of the system through the break until that portion of the system is isolated (i.e. specific valves are closed). The InfoWater model of your system will allow you to know exactly which valves to close, and where each valve is located. This can help you minimize the water that is lost and also help shut down your system quickly in order to repair the break.
5.2.1 Fireflow Analysis Exercise Introduction Fire emergencies are unexpected events, meaning that we won’t know when or where a fire is going to start. This is where the genius in our distribution systems really shows itself. Distribution systems provide a constant supply of water anywhere there is a water main installed, which is near most buildings, structures, and other things which tend to catch fire. Our systems also have a fast and easy way to access large quantities of water from the mains when needed via fire hydrants. Does this idea pose any other problems? Is there a limit to how much water can be used to fight a fire? Consider if a fire occurs in a neighborhood in the middle of the day. Firefighters will access the nearest hydrant and start using a large amount of water to put out the fire. This fire demand may cause the residual system pressure at another house to drop to the point that water could not be accessed. This would be considered a type of internal failure in the system. The point of this scenario is to show that an emergency response to fire demand should not cause internal system failures. There are regulations which state that residual pressures in the system should not fall below a cer certain tain threshold. There are also fireflow regulations which require a certain flow rate for a specific amount of time at a hydrant without
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causing internal failures. Note that regulations for fireflow depend on the type of building (e.g. residential, commercial, etc.) and often vary from city to city and state to state. In this exercise, you are an engineer working for a water utility company. Say that your boss, the director of the company, asks you to run a fireflow analysis to ensure the system meets regulations and to report the results back to him. The first thing you should do is understand the fireflow requirements and how to input these constraints into the model. You will apply fire demands to all junction nodes within the system and analyze residual pressures. The minimum residual pressure in the system will be 20 psi (i.e., 20 psi is the minimum pressure requirement). To analyze the system for fireflow, follow the steps hereafter.
Step 1: Applying Fire Demands In order to add fire demands at every junction in the system, you must first select all junctions in the system at once. This is done using the Domain Manager . 1. Click the Domain Manager icon on the InfoWater Edit Network Toolbar. 2. Select Network and All Junctions from the drop down menu as shown below. Click Add to add all junctions. All junctions on the map should now now appear red.
Figure 5.2.1.1: Selecting Fire Nodes 3. Next Select Map Selection and click Remove on the right side. This will bring you to the map. Drag a box over the new nodes created for the second pump (adjacent pipes will be included). Selected elements will turn yellow. Right click on o n the map and select Enter from the drop down menu. The two nodes should become green, while all other nodes are colored red signaling they are in the domain (shown below). You may now close the Domain D omain Manger by clicking Close.
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Figure 5.2.1.2: Remove Nodes 4. Next click on the Group Editing Editing icon in the InfoWater Edit Edit Network Toolbar. Make sure “Domain” is selected at the top and click “Fireflow”. En Enter ter the value “1000 1000”” in the empty cell and click “Apply”. Click “Close” to exit the Group Editing window. window.
Figure 5.2.1.3: Editing Fireflow
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Now that all junction nodes in the system have a fire demand of 1,000 gpm, we can run a fireflow analysis to check residual pressures and the maximum allowable flow rate. Follow the steps below to run the fireflow analysis. Note that the simulation only applies one fire demand to the system at a time; there are never multiple fires simulated together.
Step 2: Analyze System System with Fire Demands 1. Click on the Run Manager icon Window.
in the Model Explorer Window to open the Run Manager
2. Click the Fireflow tab , check the Design Fireflow option, and make sure all the values match what is displayed in Figure 5.2.1.4.
Figure 5.2.1.4: Fireflow Analysis Input Parameters 3. Click the Run Run icon icon and press “OK” to close the Run Manager Window. W indow. 4. The Report Manager Window should automatically appear on your screen and you can c an maximize it to view all of the results on one screen. To include the Fireflow Analysis Results, click New in the top left, and in the Output Report Window select *Active*:Fireflow and Fireflow as shown below.
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Figure 5.2.1.5: Output Fireflow Results 5. You should now have the Fireflow and Fireflow Design reports available as shown below in Figures 5.2.1.6 and 5.1.2.7.
Figure 5.2.1.6: Fireflow Report
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Figure 5.2.1.7: Fireflow Design Report The Fireflow Report in Figure 5.2.1.6 shows the results for each node when both static and Fire-Flow demand are applied. Based on the total demand at the fire node (Static demand in Column 2 plus fire demand in Column 5), InfoWater calculates residual pressure at that fire node (Column 6), and computes the available flow at hydrant (Column7) to keep that fire node pressure at the minimum pressure constraint. The Fireflow Design Report in Figure 5.2.1.7 shows the most critical node (Column 4) in the system which is not the fire node and the critical node pressure (Column 5). If the critical node pressure is below the minimum pressure, InfoWater will adjust the fireflow at the fire node to maintain the minimum pressure at the critical node. The design flow (Column 7) is the minimum value of the available flow at hydrant (Column 3) and the adjusted fireflow.
5.2.2 Discussion of Fireflow Results Now that we have performed our fireflow analysis, we can analyze our results to see if we have any potential issues in our system. Remember that the minimum pressure and residual pressure due to any fire demand must be above 20 psi. If we look at the Residual Pressure column in the Figure 5.2.1.6, we see that pressure falls below the minimum constraint at nodes J12, J14, J40, and J44, when the fire demand is applied to the junctions J12, J14, J40, and J44, respectively. InfoWater automatically calculates the Available Flow at Hydrant in order to bring the Residual Pressure up to 20 psi.
The Fireflow Design table (Figure 5.2.1.7) takes into consideration the pressure at critical cr itical nodes in the network, since it is desired that no nodes throughout the system fall below 20 psi. If we look at the 67
Critical Node Pressure when fireflow is drawn from each fire node, we see that nodes J38, J14, and J48 fall below the minimum pressure. InfoWater automatically adjusts the fire flow at the fire node to maintain the Critical Node Pressure at 20 psi. Notice that when Critical Node Pressure falls below 20 psi, the Design Flow becomes lower than the Available Flow at Hydrant. If we wanted to look at just one of these columns co lumns to analyze our fireflow analysis, the best column to look at would be the Design Flow column. This column lets us know how much flow our hydrant can handle without violating a low pressure constraint in the system. We can then compare these flows to our fireflow requirements to make sure they are greater than or equal to the required fireflow.
5.2.3 Fireflow Design Problem Introduction When you report the fireflow analysis back to your boss, he is impressed with w ith how quick you got him the results and now asks you to provide him with a solution to mitigate the fireflow issues at junctions J14 and J44 before the end of the work day. Remember that in the last exercise, we applied a fire demand of 1,000 gpm to each node. However, based on fireflow codes for the area, it is found that junctions J14 and J44 are required to supply only 600 gpm and 700 gpm during an emergency event respectively. These values will be our constraints for this design problem. Based on the results you handed your boss, you know that the fire demand at either of those nodes drops the pressures below the minimum 20 psi requirement (available flow is less than required flow). Based on your understanding of water distribution systems you know that the fire demands cause too much head loss through pipes P29 and P59, resulting in a decrease in pressure. In I n order to bring the pressure back up to standards, we must refer back to Section 5.2.0 when we discussed theoretical solutions to design problems. Based on that discussion, there are two ways we can fix the low pressure situation: 1) we can add energy to the system (i.e. booster pump), or 2) we can decrease the losses in the system (i.e. larger or additional pipe). Similar to Section 4.1.2, this seems like a great time to add a parallel pipe. However, by digging around in the company’s historical database you find that pipes P29 and P59 were installed in 1932, and should be nearing the end of their usable lives. Now you realize that you can knock out two birds with one stone by replacing the two pipes with w ith larger diameter mains. This solution will decrease head loss enough to satisfy the fireflow pressure requirements, and it will eliminate the imminent need for pipe replacement. Instead of deleting the old pipes and adding new ones to the model model,, the existing pipe sizes can simply be increased. Increase the pipe diameters and analyze the system by following the steps below.
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Step 1: Change Pipe Diameters 1. Click the Select Element tool located in the InfoWater the InfoWater Network Network Edit toolbar and left click on pipe P29. 2. Left click in the Diameter (in) field (in) field and enter the number 8. Press Enter. 3. Repeat steps 1 and 2 for pipe P59. 4. Once the diameters for pipes P29 and P59 have been changed, repeat step 2 in Section 5.2.2 for analyzing a system for fireflow.
Figure 5.2.3.1: Fireflow Results with Adjusted Pipe Diameters. As you can see in the figure above, the available flow at hydrant for nodes J14 and J44 are greater than 600 gpm and 700 gpm respectively. Thus, the constraints for fireflow are now met at these nodes and the new design is deemed adequate.
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5.2.4 Pipe Break Analysis Example Introduction Now that we have looked at a societal emergency, we will now focus on an internal system failure, specifically a pipe break. There has been much research in recent years on pipe breaks, nevertheless it is still very difficult to predict which pipes will break and when. Since we cannot fully predict the future breaks, we must be ready to respond to an unexpected pipe break in order to minimize damage, loss of water, contamination, etc. Having an accurate schematic of your system’s components, especially valves, will help utilities to efficiently shut down whatever part of the system experiences a break. The model will also be able to run a hydraulic analysis of the system to analyze pressures and flows with parts of your system shut down for repair. Open the demo map in in InfoWater called “PipeBreakDemo.mxd”. The model can be found in the downloaded InfoWater Student Analysis and Design Workbook folder. This is mostly the same system which we have been working with for previous exercises, except for the addition of valves. Each of these valves has a specific ID as you can see by selecting a valve and observing the information in the model explorer window. With this detailed schematic of your distribution system, you can be prepared to give specific instructions to your emergency response team in order to shut down a segment of the system. The system should look like Figure 5.2.4.1 below.
Figure 5.2.4.1: Pipe Break Demo Network with Valves
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Before we analyze a pipe break scenario, go ahead and run a steady state analysis and observe the pressures in the system. Refer back to Section 4.1.1 for how to run a steady state analysis. Now let’s go let’s go back to the example scenario scenar io where you are an engineer working for a wat water er utility company. As one of the director’s most trusted trusted engineers, you are given the responsibility of managing the emergency response team. In the case of a pipe break, the emergency response team will be ready to leave at a moment’s notice to close the appropriate valves. Say that you are notified of a pipe break in pipe P121 (this is between junction J20 and valve V8004). The break is shown by the red explosion symbol below in Figure 5.2.4.2.
Figure 5.2.4.2: Location of Pipe Break The emergency team gets in their trucks and starts driving toward the site of the break. It is now your responsibility to tell them exactly where to go, and which valves to shut in order to isolate the break. Ideally, you would only like to shut down the broken pipe, pipe P121, however the placement of valves on your map indicates that other segments of pipe must also be shut. To isolate the break, valves V8004, V8030, and V8032 must all be closed. You relay this information to the emergency eme rgency response team, telling them exactly where to go in KYTown to find the appropriate valves. Figure 5.2.4.3 shows the location of the break as well as the appropriate valves to close and the isolated pipe segment.
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Figure 5.2.4.3: Pipe Break with Closed Valves and Isolated Pipe Segments Now that you have figured out which valves are going to be closed to isolate the break, you need to analyze the system’s system’s response (i.e. how the pressures react to the valve closures). To model the closed valves in InfoWater , follow these steps:
Step 1: Close the Valves 1. Click the Select Element tool located in the InfoWater Network Network Edit toolbar. 2. Click on the Valve you want to close. 3. 4. 5. 6.
Select the Initial Status button located in the Model Explorer Window. Select Select “Closed” and click “Update”. Repeat steps 2-4 for each e ach valve you want to close. For the last step, all junctions j unctions which are located within the isolated pipe segment must have the their ir demand removed. The reason that the demand must be removed for these junctions, is because a non-zero demand violates the conservation of mass law. A demand is a flow out of the system. However, because the junction is isolated from the rest of the system, there is no flow into the demand. To remove the demand, simply select the t he junction you wish to edit, then enter 0 in the demand box in the Model Explorer window.
After the valves are closed, run another steady state analysis and observe the resulting pressures. Note the general decrease in pressures for junctions J16, J12, J44, and J14 on the right side of the network. The decrease in pressure is a result of the same flow which used to travel through pipe P121 being re-routed through pipe P145 due to the valve closures. If you click on pipe P145 you will notice that this is a much smaller pipe than P121 (3 inch diameter vs. 6 inch diameter). This increases head loss between the water
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source and the junctions on the right side of the system, thus lowering pressure by the time it reaches junctions J16, J12, etc. Even though the pressure has been significantly reduced, customers at junction J14 will still have access to water while pipe P121 is being repaired. Thus we are able to give the green light to our emergency response team, who are now at the proper locations, to close the valves. The valves will remain closed until the pipe is fixed. Once the pipe is fixed, valves may be reopened and the system can go back to its original steady state scenario. Another important thing to consider is transient events which can be caused by pipe breaks and valve closures. The topic of transient events is covered in the InfoSurge the InfoSurge student manual.
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6.0
Case Study III
Another criterion of water distribution system design is to make sure that water is supplied to customers with adequate quality. InfoWater has the capability to model water age and chemical concentrations within the bulk flow, at the pipe wall, in storage tanks, and mass transport between the bulk flow and the pipe wall. In this case study, you will analyze water quality conditions in KYTown and create a design that will improve impaired water quality conditions.
6.1.0 Water Quality Analysis In the mid 1980’s, water distribution system modelers began to add water add water quality capabilities to their software. Using the results of extended period simulations, researchers were able to apply water quality calculations to the flow dynamics to track various constituents and their concentrations throughout a water distribution system. Water quality modeling generally consists of identifying identifying a constituent’s transport through a system, representing how water with different concentrations are mixed at junctions, and accounting for the decay or growth of constituents within a system. Water quality modeling can also be used to track the t he water age (i.e. time since leaving the treatment plant) in a system. InfoWater has the capability to model multiple constituents throughout a system, among many other advanced features, with its Multi-Species eXtension e Xtension (MSX). However, we will use the standard capabilities of InfoWater to to model the fate of a single constituent for this introductory case study to water quality analysis. The first part of this case study will cover the basics of water quality analysis, specifically tracking chlorine residual through an extended period simulation of a distribution system. The second part of this case study will deal with implementing a booster station in order to raise the chlorine residual to an acceptable level.
6.1.1 Standard Water Quality Analysis There are many sources of water pollution. Many surface waters such as lakes and rivers, which we get our drinking water from, are polluted with sediment, chemicals, and fecal material, among other things. To avoid illness, we must spend time and money treating our water prior to drinking it. Water treatment plants consist of a series of treatment processes which remove pollutants. The last step before water is pumped into the distribution system is disinfection, where a disinfectant such as chlorine or chloramine is added to kill viruses and other pollutants that sneak through the treatment plant. Now that the water has been thoroughly purified at the treatment tr eatment plant, you can turn on your faucet with confidence that clean water will flow into your glass, right? Despite thorough cleansing at the water treatment plant, your drinking water could become contaminated before it gets to your home through many different scenarios. These include pipe breaks, biofilm buildup on the inside of pipes, system pressure drops that cause water to enter through leaks, chemical reactions with the pipe walls, and even birds taking up residence in your local water tower.
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In order to provide a safety factor against post treatment contamination, operators add a strong dose of chlorine at the treatment plant which naturally decays as it travels through the system. Chlorine found in the system after it leaves the treatment t reatment plant is referred to as the ‘chlorine ‘ chlorine residual’. Maintaining certain chlorine residual throughout your system acts as a good safety factor for unplanned (or unknown) contamination of the water, as it will still disinfect some pollutants. For the first part of this case study, we will observe the fluctuation in chlorine residual at various points in a system over a 24-hour time period.
Step 1: Open and set up the CaseStudy3.mxd Project The first step is to open the CaseStudy3.mxd file in in InfoWater . Many of the following steps are supplemental to the InfoWater Users Guide. Guide. If you feel as though basic set up procedures are unnecessary, you may skip the next six steps: 1. Choose the “Start” menu, select Programs Programs,, choose the InfoWater Version X program group and choose InfoWater . 2. In the ArcMap the ArcMap window, window, select An select An Existing Map option Map option in the Start Using ArcMap With area With area and then click the the “OK” button. This can also be accessed by choosing File » Open from the ArcMap the ArcMap command menu. 3. Navigate to the directory containing the CaseStudy3.mxd project and choose that file. The location of this file can be found in the downloaded InfoWater Student Analysis and Design Workbook folder.
Step 2: Set up the Water Quality Analysis The second step involves setting up the model to run the water quality analysis. This includes setting your constituent and decay information, initial concentrations, and your constituent source, as well as ensuring you are set up to run an extended period simulation. 1. We will first need to identify this simulation as an extended period simulation. This means that we are modeling the system dynamics over a specified time period. 2. In order to specify that the t he simulation is an extended period simulation, choose the Operation tab from the Model Explorer window. window. Next, click Simulation Time » Time » BASE, Base Simulation Time. Make sure that the box next to “Steady State” is unchecked. Make sure Make sure that under the Unit column, column, each is specified as being in Hours Hours.. In the Duration row, make sure that the Decimal Time column states 24. This represents the 24 hours of the day. The following figure shows what the Simulation Time window Time window should look like prior to the EPS analysis:
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Figure 6.1.1.1: Simulation Time Window 3. Click the “OK” button
to close the Simulation Time window.
4. Next, set parameters for the water quality analysis. Choose the Operation tab
from the
Model Explorer window. window. Next choose Simulation Options and double click BASE, Base Simulation Option.. Choose the Option
tab and select Chemical/Temp Chemical/Temp.. Enter “Chlorine” as the Chemical
Name and Name and ensure the Mass Unit is “mg/L”. Set the Global Bulk parameter to -1 and the Global Wall to to -0.5. The window should match Figure 6.1.1.2 below.
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Figure 6.1.1.2: Simulation Options Window 5. Click the “OK” button
to close the Simulation Options window. Options window.
6. Next you will assign all junction nodes in the system an initial chlorine residual concentration of 0.5 mg/L. Select InfoWater » Tools » Domain Manager . Click Network and and then select All select All Junctions and click Add click Add . This will add all junctions in the network to the domain for group editing. Also select the All the All Tanks option Tanks option and click Add click Add to add tanks to the domain. 7. Change the initial quality value for all junctions and tanks in group editing. Choose the Group Editing icon Editing
. Select Initial Quality and and input the value 0.5 into the Initial Value box. Click
Apply and and Close Close.. 8. Next you will add a “Quality Source” to model chlorine dosing at the treatment plant. Choose the Select Element icon
and select the reservoir in the network. Click the Tools Tools icon
and
select Quality Source. Source. Choose Concentration Concentration and and input a value of 1.2 in the Baseline Concentration box. Concentration box. Leave the Concentration Pattern blank. Pattern blank. Click Update Update to to apply this change. 9. Now you are ready to run the model. Click the Run Manager icon successful run will be indicated by a green light the “OK”
and the Run Run icon
.A
. Close the Run Manager window by clicking
button.
Step 3: Analyze the Results Results Once you have successfully run the water quality analysis, you may view the results in either a tabular or graphical format.
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1. Choose the Select Element icon
and select junction J46. Click the Graph icon
to display a
graph of J46. Change the parameter being graphed to Chlorine Chlorine and and observe the drop and rise of the chlorine residual over the 24 hour time period. The graph should look like Figure 6.1.1.3 below.
Figure 6.1.1.3: Chlorine Residual Plot at J46 2. Select other nodes and follow step 1 to observe their chlorine residual plot. Or use the group graphing tool in the Report Manager window. window. 3. If you are going to take a break, make sure to save your work. Section 6.1.2 builds directly from this section.
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6.1.2 Decision Support for Water Quality Analysis Recall the chlorine residual levels at Junction J46 from the previous section. It is plotted vs. time in Figure
6.1.1.3. After the dosing at the reservoir rese rvoir reaches the junction, the chlorine residual concentration rises to 1.0 mg/L and fluctuates around this value for the rest of the 24 hours. Let’s assume that 1.0 mg/L is our target value (i.e., the appropriate chlorine residual concentration for safe drinking water) which should be applied to all junctions in the system. Now let’s look let’s look at Junction J14. The chlorine residual plot for J14 for the same analysis shows that the concentration drops significantly at first and then fluctuates around 0.5 mg/L for the remained of the simulation. The chlorine residual plot of J14 is shown below in Figure 6.1.2.1.
Figure 6.1.2.1: Chlorine Residual Plot at J14
What are some actions that we (as the system operators) can take to boost our chlorine residual in this part of the system? One option is to increase the dose at the water treatment treatme nt plant. However, this is likely a bad solution because it will also raise chlorine residual levels everywhere else in the system (too much chlorine has negative effects). Another option that we could take is installing a chlorine booster station. A booster station “boosts” the chlorine residual level at a specific location in the distribution system which is away from the treatment plant. We will select junction J44 as a location for the booster station. To model this booster station, follow these steps:
Step 1: Insert Booster Station into Model The first step is to insert the booster station into the model. The junction for which we have selected to place the booster station is J44.
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1. Choose the Select Element icon 2. Choose the Tools icon
and select the junction J44.
and select Quality Source. Source.
3. Select Setpoint Booster and and insert a value of 1 in the Baseline Concentration box. Concentration box. Click Create Create..
Step 2: Run the Water Quality Analysis and Investigate the Results Now the booster station has been inserted into the model at junction j unction J44, run the analysis and investigate the results. 1. Click the Run Manager icon green light
and the Run Run icon
. A successful run will be indicated by a
. Close the Run Manager window by clicking the “OK”
2. Choose the Select Element
button.
icon and select junction J14. Click the Graph icon
to display a
graph of J14. Change the parameter being graphed to Chlorine Chlorine and and observe the drop and rise of the chlorine residual over the 24 hour time period. The graph should look like Figure 6.1.2.2 below.
Figure 6.1.2.2: Chlorine Residual Plot for J14 3. As you can see from Figure 6.1.2.2 the chlorine residual for J14 fluctuates around 0.85 mg/L after the booster station is added, which is much better than our original plot which fluctuated around 0.5 mg/L. The chlorine residual levels at J14 may be adjusted by increasing or decreasing the dose at the booster station.
