Engineering Hydrology

HYDROLOGY AND HYDROLOGIC CYCLE

_____________________________________

Research paper in engineering hydrology Presented to The Faculty of the Department of Engineering College of Engineering Eastern Visayas State University Ormoc City

_____________________________________

In Partial Fulfilment Of the Requirement for the Degree of BACHELOR OF SCIENCE IN CIVIL ENGINEERING

MEMBERS: ANDRO S. REBUYAS JOHN LAURENCE H. MAGNO ALDRIN T. TUMAMPO KINNETH RICHIE O. PLEÑOS ELEGHEM RAM C. SACAY RAMIL P. GARBE

INSTRUCTOR: ENGR. ANTONIO E. NABOYA JR. JANUARY 2015

ii

TABLE OF CONTENTS Page title Page no. Preliminaries Cover page i Table of contents ii Abstract iii 1.1DIFFERENCE

BETWEEN

HYDROLOGY

AND

HYDRAULICS

1 a. Hydrology b. Hydraulics

2 1.2THE HYDROLOGIC CYCLE AND THE HUMAN IMPACT a. Hydrologic cycle b. Human impact 1.3INTER-RELATIONSHIPS

OF

PHASES

OF

THE

HYDROLOGIC

CYCLE

9 a. Evapo-transpiration b. Precipitation c. Infiltration/Percolation d. Surface/Subsurface Runof e.

Groundwater.

11 1.4PHILIPPINE

WATERSHEDS

12 a. Delineation of Drainage Area b. Sub-Basing/Physical Properties Determination Definition

of

terms

14 Literature

15

cited

iii ABSTRACT

This document, HYDROLOGY AND HYROLOGIC CYCLE discusses about the hydrology and the hydrologic cycle including each significant components that belong in each topics that related in each subject. This document contains four topics that cover (1.1) Diference between Hydrology and Hydraulics. (1.2) the Hydrologic Cycle and the Human Impact. (1.3) Interrelationships of Phases of the Hydrologic Cycle: Evapo-transpiration, Precipitation, Infiltration/Percolation, Surface/Subsurface Runof, and Groundwater. (1.4) Philippine Watersheds: Delineation of Drainage Area, Sub-Basing/Physical Properties Determination. Explanations in hydrology and hydrologic cycle are conveyed in direct and simple language for easy understanding. Pictures are clearly presented to be easy interpreted by the readers.

1

1.1 Diference between Hydrology and Hydraulics. Hydrology Hydrology is an earth science. It encompasses the occurrence, distribution, movement, and properties of the waters of the earth and their environmental relations. Hydrology has both applied and pure science aspects. On the one hand, it is an important science that studies how the water flows on the Earth. On the other hand, understanding of fundamental hydrologic processes is necessary for proper use and protection of water resources. Water is also an agent for many other processes (weathering, transport of chemicals, erosion, and deposition).Hydrology may be defined as applied science concerned with water of the Earth in all its states, their occurrences, distribution and circulation through the unending hydrologic cycle of precipitation, consequent runof, stream flow, infiltration and storage, eventual evaporation and re-precipitation.

Hydrology is a highly inter-disciplinary science. It draws many principles from other branches of science like –        

Meteorology and Climatology Physical Geography Agronomy and Forestry Geology and Soil science Oceanography Hydraulics Probability and Statistics Ecology

Hydrology concerns itself with three forms of water – 1. Above land as atmospheric water or precipitation. 2. On land or surface as stored water or runof 3. Below the land surface as ground water or percolation

The Importance of Hydrology is seen in



DESIGN OF HYDRAULIC STRUCTURES: - Structures such as bridges, causeways, dams, spillways etc. are in contact with water. Accurate hydrological predictions are necessary for their proper functioning. Due to a storm, the flow below a bridge has to be properly predicted. Improper prediction may cause failure of the structure. Similarly the spillway in case of a dam which is meant for disposing excess water in a dam should also be designed properly otherwise flooding water may overtop the dam. MUNICIPAL AND INDUSTRIAL WATER SUPPLY: - Growth of towns and cities and also industries around them is often dependent on fresh water availability in their vicinity. Water should be drawn from rivers, streams, ground water. Proper estimation of water resources in a place will help planning and





implementation of facilities for municipal (domestic) and industrial water supply. IRRIGATION: - Dams are constructed to store water for multiple uses. For estimating maximum storage capacity seepage, evaporation and other losses should be properly estimated. These can be done with proper understanding of hydrology of a given river basin and thus making the irrigation project a successful one. Artificial recharge will also increase ground water storage. It has been estimated that ground water potential of Gang etic basin is 40 times more than its surface flow. HYDROELECTRIC POWER GENERATION: - A hydroelectric power plant need continuous water supply without much variations in the stream flow. Variations will afect the functioning of

2







Turbines in the electric plant. Hence proper estimation of river flow and also flood occurrences will help to construct efficient balancing reservoirs and these will supply water to turbines at a constant rate. FLOOD CONTROL IN RIVERS: - Controlling floods in a river is a complicated task. The flow occurring due to a storm can be predicted if the catchment characteristics are properly known. In many cases damages due to floods are high. Joint work of hydrologist and meteorologists in threatening areas may reduce damage due to floods. Flood plain zones maybe demarked to avoid losses. NAVIGATION: - Big canals in an irrigation scheme can be used for inland navigation. The depth of water should be maintained at a constant level. This can be achieved by lock gates provided and proper draft to be maintained. If the river water contains sediments, they will settle in the channel and cause problems for navigation. Hence the catchment characteristics should be considered and sediment entry into the canals should be done. POLLUTION CONTROL: - It is an easy way to dispose sewage generated in a city or town into streams and rivers. If large stream flow is available compared to the sewage discharge, pollution problems do not arise as sewage gets diluted and flowing water also has self-purifying capacity. The problem arises when each of the flows are not properly estimated. In case sewage flow is high it should be treated before disposal into a river or stream.

Hydraulics Hydraulics deals with the application of fluid mechanics to engineering devices involving liquids, usually water or oil. Hydraulics deals with such problems as the flow of fluids through pipes or in open channels, the design of storage dams, pumps and the water turbines, and with other devices for the control or use of liquids, such as nozzles, valves, jets, and flow meters.

1.2 The Hydrologic Cycle and the Human Impact. Hydrologic Cycle Water, which is found everywhere on the earth, is one of the most basic and commonly occurring substances. It is the only substance on earth that exists naturally in the three basic forms of matter, i.e., liquid, solid, and gas. The quantity of water varies from place to place and from time to time. Although at any given moment the vast majority of the earth's water is found in the world's oceans, there is a constant interchange of water from the oceans to the atmosphere to the land and back to the ocean. This interchange is called the hydrologic cycle.

The next figure (2.1a and b) descries the hydrological cycle that illustrate the movement of water in the earth atmosphere, surface and below the ground. Some of these movements are caused by external factors, i.e. the evaporation is caused by the solar energy, while other is just naturally; i.e. infiltration and percolation.

Figure 2.1a Hydrologic Cycle 3

Figure 2.1b Hydrologic Cycle

What is hydrological cycle? It is a sequence of conditions through which water passes or circulates on and below the earth’s surface and the atmosphere. It is commonly known as the water cycle. In simpler term, Water cycle is the nature’s way of recycling water on Earth.

Imagine? Only 3% of the world’s water is safe for human consumption.

Let’s take a look at this

4 The hydrological cycle

Evaporation This is the process by which state of substance (water) is changed from liquid state to vapor form. Evaporation occurs constantly from water bodies, soil surface and even from vegetation. In short evaporation occurs when water is exposed to atmosphere (during sunlight). The rate of evaporation depends on the temperature and humidity.

  

Water converted from liquid to gas (water vapor) Surface water (lakes, rivers, & mostly oceans) Sun provides energy needed to change state

Transpiration This is the process by which the water extracted by the roots of the plants is lost to the atmosphere through the surface of leaves and branches by evaporation. Hence it is also known as evapo-transpiration.



Emission of water vapor from plants - Plants absorb water from soil to use in photosynthesis - Water vapor released through stomata (pores) under leaves

5

Condensation 

Water vapor (gas) turns into liquid water - Warm, moist air rises in atmosphere - Vapor in air cools as it rises, thus turning back to liquid

Precipitation It is the return of atmospheric moisture to the ground in solid or liquid form. Solid form; (Snow, sleet, snow pellets, hailstones) Liquid form; (drizzle, rainfall)  

Water falling from the atmosphere Vapor molecules collide & join to from droplets



Falls as, rain, snow, sleet, or hail

6

Human activities that impacts the water cycle:

Vast usage of chemicals, pesticides, fertilizers and other forms of pollutions can cause Eutrophication What is Eutrophication? Eutrophication is a process in which bodies of water (lakes, ponds, and river) receive excess nutrients that stimulate excessive growth of algae.

Algal bloom results to this:

7 Another human activity leads to this;

Manila bay for example has become a huge floating dump in metro manila.

Human activities like usage of chemicals, pesticides and dumping wastes in the bodies of water can lead to total hydrological cycle destruction.

Human impact on water cycle Human impacts on the hydrological cycle are not new! However, as population growth continues and standards of living rise, there is increasingly more impact on all aspects of the hydrological cycle. Many of these impacts are negative but some are positive. The earth's water supply is constant, but man is able to changing the series of this fundamental supply. Population increases, rising living standards and industrial and economic growth have placed greater stress on the natural environment. Man activities can cause inequity in the hydrologic equation and can afect the quantity and quality of natural water resources available to current and future generations. Water used by households, industries, and farms have increased. People demand clean water at reasonable costs, yet the amount of fresh water is limited and the easily accessible sources have been developed. As the

8 Population increases, so will our need to withdraw more water from rivers, lakes and aquifers, threatening local resources and future water supplies. A larger population will not only use more water but will discharge more wastewater. Domestic, agricultural, and industrial wastes, including the intensive use of pesticides, herbicides and fertilizers, after overload water supplies with hazardous chemicals and bacteria. Also, poor irrigation practices raise soil salinity and evaporation rates. These factors contribute to a reduction in the availability of potable water, putting even greater pressure on existing water resources. Large cities and urban sprawl particularly afect local climate and hydrology. Urbanization is accompanied by accelerated drainage of water through road drains and city sewer systems, which even increases the magnitude of urban flood events. This

alters the rates of infiltration, evaporation, and transpiration that would otherwise occur in a natural setting. The replenishing of ground water aquifers does not occur or occurs at a slower rate. Together, these various efects determine the amount of water in the system and can result in extremely negative consequences for river watersheds, lake levels, aquifers, and the environment as a whole. Therefore, it is vital to learn about and protect our water resources. The human impact on the hydrological cycle can be subdivided into three main areas: 

Water quantity.



Water quality.



Water ecology.

Human activities can be divided into the following categories: 

Surface water regulation such as rivers and lakes.



Water abstractions and release.



Activities in the catchments

The impacts can be either direct or indirect, they can operate at any scale from the local to global, and the results may be positive or negative. •

Four categories that either directly or indirectly impact the water cycle: –

Changes to Earth’s surface

–

Changes to Earth’s climate

–

Atmospheric pollution

–

Withdraws for human use

Deforestation •

As land is cleared or overgrazed, the pathway for the water cycle shifts from infiltration and groundwater recharge to runof. –

Consequences include flooding, decreased ground water, increased sanitization, loss of biodiversity

9

1.3 Inter-relationships of Phases of the Hydrologic Cycle Evapo-transpiration Evapo-transpiration is the combined result of two processes: evaporation and transpiration. Evapo-transpiration uses a larger portion of precipitation than the other processes linked with the hydrologic cycle.

Evaporation is the process of returning damp to the atmosphere. Water on any surface, especially the surfaces of mud holes, ponds, streams, rivers, lakes, and oceans, is warmed by the sun's heat until it reaches the point at which water turns into the vapor, or gaseous, form. The water vapor then rises into the atmosphere. Evapo-transpiration (ET) is a term used to describe the sum of evaporation and plant transpiration from the earth’s land surface to atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and water bodies.Transpiration accounts for the movement of water within a plant and the subsequent loss of water as vapor through stomata in leaves. Evapo-transpiration is an important part of the water cycle. An element (such as a tree) that contributes to evapo-transpiration can be called an evapo-transpirator. Takes place at the land where plant exist; also lose moisture by the evaporation of water from soil and water bodies.

Evapo-transpiration terms: 

Potential evapotranspiration (PET) - it is defined as the amount of evaporation that would occurs if a sufficient water source were available.



Actual evapotranspiration (AET) – actual evapotranspiration is the quantity of water that is actually removed from a surface due to the process of evaporation and transpiration.



Field capacity – is the maximum quantity of water that the soil can retain against the force of gravity. Any higher moisture input to a soil at field capacity simply drains away.

10 

Permanent wilting point – is the moisture content of the soil at which the moisture is no longer sufficient quantity to sustain the plants.

Infiltration/Percolation

Infiltration is the passage of water across the soil surface. The vertical downward movement of water within the soil is known as percolation. The infiltration capacity is the maximum rate of infiltration for the given condition of the soil. Obviously the infiltration capacity decreases with time during/ after a storm.     

Water absorbed into subsurface of dirt & rocks Water percolates down between spaces in soil Groundwater empties into streams/rivers/oceans or is underground in aquifers Saturation = all the spaces in soil & rock are filled with water Flooding occurs: - When soil becomes saturated, or - When precipitation falls faster than infiltration can occur

stored

Percolation  

Percolation is the movement of water through the soil, due to gravity and by capillary forces. All ground water originates as subsurface water.

11 Surface/Subsurface Runof

Surface runof When the overland flow enters a well-defined stream it is known as surface runof (SRO). 

Water flows over the ground instead of sinking into the ground - Snow melts, rain runs of surfaces, etc. - Streams and rivers carry water back to oceans

Subsurface runof Subsurface runof is the water that infiltrates in the vadose zone (unsaturated zone), from rain, snowmelt, or other sources, and moves laterally towards the streams. Vadose zone extends from the top of the ground surface to the water table. It is one of the major components in the water cycle. Subsurface runof can be expressed in water volume (or mass) per unit of area per unit of time.

Groundwater

12

• •

Precipitation seeps down through soil & rock Layers act as filters that trap contaminants  -

Water table: imaginary line between the water logged soil and the soil not saturated with water Varies with seasonal precipitation, pumping & geography

Two types of aquifers: - Unconfined: water supply which has a solid layer of rock under it, but a permeable layer of rocks above it. - Confined: water supply sandwiched between two solid rock layers through which water cannot pass  Pressure builds up and can form artesian well

1.4

Philippine Watersheds

A watershed is the land area that drains water to a particular stream, river, or lake. It is a land feature that can be identified by tracing a line along the highest elevations between two areas on a map, often a ridge.

Importance of watersheds

 

Watersheds sustain life, in more ways than one. According to the environmental protection agency, more than $450 billion in foods, fibre, manufactured goods and tourism depend on clean, healthy watersheds.



Healthy watersheds are also important for the very sustenance of human life

13

a. Delineation of Drainage Area

Watershed delineation is the process of identifying the drainage area of a point or set of points.

For many years, civil engineers have been using USGS paper maps for watershed delineation. Watershed delineation and drainage area measurement Watersheds or drainage basins are comprised of a network of stream channels that link from Smaller to larger, providing conduits for surface water runof and sediment transport on the Earth’s surface. Drainage basins are defined by topographic contour patterns with drainage Divides (bounding ridges) and stream channels (defined by “V-shaped contour lines”).When defining watershed boundaries and stream channels it is important to remember that water flows from high elevation to low elevation, and in a simple sense, perpendicular to contour line.

Drainage area of a watershed is considered the most important parameter of it. The drainage area reflects the volume of water the can be generated from rainfall and that is available for runof. The area of watershed is defined by watershed delineation that can be done manually or using computer programs. b. Sub-Basin

Sub-basin is a structural geologic feature where a basin forms within a larger basin. It is sometimes spelled ‘’sub basin’’. Sub-basin is basically a smaller watershed that makes up a piece of the large watershed. 14 DEFINITION OF TERMS

Actual evapotranspiration (AET) is the quantity of water that is actually removed from a surface due to the process of evaporation and transpiration. Evapo-transpiration is the combined result of two processes: evaporation and transpiration.

Eutrophication is a process in which bodies of water (lakes, ponds, and river) receive excess nutrients that stimulate excessive growth of algae. Field capacity is the maximum quantity of water that the soil can retain against the force of gravity. Any higher moisture input to a soil at field capacity simply drains away. Hydraulics is the study of the mechanics of the flow of a fluid. Hydrology is an earth science. It encompasses the occurrence, distribution, movement, and properties of the waters of the earth and their environmental relations.

Infiltration is the passage of water across the soil surface. Percolation is the movement of water through the soil, due to gravity and by capillary forces. Permanent wilting point is the moisture content of the soil at which the moisture is no longer sufficient quantity to sustain the plants. Potential evapotranspiration (PET) it is defined as the amount of evaporation that would occurs if a sufficient water source were available. Precipitation it is the return of atmospheric moisture to the ground in solid or liquid form. Sub-basin is basically a smaller watershed that makes up a piece of the large watershed. Water cycle is the nature’s way of recycling water on Earth.

Watershed is the land area that drains water to a particular stream, river, or lake. It is a land feature that can be identified by tracing a line along the highest elevations between two areas on a map, often a ridge.

15 LITERATURE CITED

http://en.wikipedia.org/wiki/Hydrology http://en.wikipedia.org/wiki/Hydraulics http://m.nhcefiles.com/CIVIL/5th%20semcivil/CIVIL-V-HYDROLOGY %20AND%20IRRIGATION%20ENGINEERING%20%5B10CV55%5DNOTES.pdf http://www.ngdir.ir/sitelinks/kids/html/water_en_co_hydrologic %20cycle.html.htm http://www.slideshare.net/jedelsa/human-impacts-on-hydrologicalcycle westernreservepublicmedia.org/.../images/Human_Impact_on_water. ppt Dr. Ashraf m. Elmoustafa, “Engineering Hydrology”unpublished Documents. K Subramanya,“Engineering Hydrology 3th edition” Copyright © 2008McGraw-Hill Publishing Company Limited, 7 west patel nagar, NewDelhi 110 008 H.M. Raghunath, “Hydrology”Copyright © 2006 New Age International (P) Ltd., Publishers Published by New Age International (P) Ltd., Publisher https://www.wou.edu/las/physci/taylor/g302/watershed_delineation_ drainage_area_exercise.pdf http://water.epa.gov/scitech/datait/models/basins/upload/Lecture-3Watershed-Delineation.pdf http://www.slideshare.net/lizbasile/watershed-delineation