Full Report Infiltration Rate

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INTRODUCTION Some of the precipitation that falls on land infiltrate into the ground where it is stored

in aquifers and is transported to streams and lakes by subsurface flow. The amount of infiltration is influenced by the permeability and moisture content of the soil, the presence of vegetation and the volume and intensity of precipitation. The amount of water in an aquifer is indicated by the height of the water table. This the effect of soil permeability (large particles have large spaces between them and let more water in) and precipitation volume (large rain events can lead to more infiltration) on the amount of water stored in the aquifer. 2.0

OBJECTIVE 1. To identify the characteristics of the infiltration rate of water into soils in the field.

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THEORY The volume of water used during each measured time interval is converted into an

incremental infiltration velocity for both the inner ring and annular space using the following equations; V_IR= ∆V_IR / (A_IR .∆t) where, V_IR is the inner ring incremental infiltration velocity (cm/hr), ∆V_IR is the volume of water used during time interval to maintain constant head in the inner ring (mL), A_IR is the internal area of inner ring (〖cm〗^2) and ∆t is the time interval (hour). For the annular space between rings, calculate as follows; V_A = ∆V_A /( A_A.∆t ) where, V_Ais the annular space incremental infiltration velocity (cm/hr), ∆V_Ais the volume of water used during time interval to maintain constant head in the annular space between the rings (mL), A_A is the area of annular space (〖cm〗^2) and ∆t is the time interval (hour). The infiltration rate calculated with the inner ring should be the value used for the result if the rates for the inner ring and annular space differ. The difference in rates is due to divergent flow.

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APPARATUS

Figure 4.1 : Infiltration rate equipment 1. Infiltration rings measure 12” and 24” diameter × 20” high.

2. Level float valve.

3. Stop watch. 2

4. Hammer.

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PROCEDURE 1. The outer ring placed with the cutting edge facing down on the ground. 2. The driving cap was placed on top of the outer ring (ring fits over, between or within the pins on the bottom of the driving cap) 3. The impact absorbing hammer used to insert the infiltration ring about 5 cm – 10 cm vertically into the soil. 4. The driving cap removed from the inserted infiltration ring. 5. The inner ring placed centered inside the large ring and driving cap was placed on the top of it. Both the outer and inner ring was level. 6. The outer ring was filled with water approximately 5 cm – 10 cm and wait until the constant head. 7. The inner ring was filled with water approximately 5 cm – 10 cm after the water in outer ring constantly. 8. The level float valves were placed on the inner ring. Then, measured the change in elevation of the water level during each time interval that given in table 6.1. 9. The result was recorded.

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RESULT AND DATA ANALYSIS

TIME, t (s) 60 120 180 240 300 360 420 480 540

INNER (mm) 98 97 96 96 94 92 91 90 90

INFILTRATION

INFILTRATION RATE

CAPACITY (mm) 1.633 2.441 2.974 3.374 3.687 3.942 4.159 4.347 4.514 Table 6.1 : Table results

(mm/s) 1.633 0.808 0.533 0.400 0.313 0.255 0.217 0.188 0.167

Infiltration Capacity vs. Time (s) (mm) 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0

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Graph 6.1 : Infiltration capacity vs. Time (s)

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Infiltration Rate (mm/s) vs. Time (s) 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0

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Graph 6.1 : Infiltration rate vs. Time (s)

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DISCUSSION Our group was given a task which is conducting infiltration rate experiment. First, we

observed the equipment with lecturer to ensure that the equipment is in good condition. Instruction from lecturer, we have to conduct our experiment on the wet soil such as near the lake or drainage area. In our experiment, we found out that there was an error in our experiment. These are caused by two main factors that could influence our reading. The factors are:1. Human factor, where the readings taken are not consistent because there is more than one observer. Parallax error could also occur. 2. The rings are not knocked and set up in a right place causing the water to leaked at the bottom part of the rings. The mistake in booking will also contribute to the error. If one of the values is wrong, it will affect all the calculation. To avoid all of these errors happen, precautions must have been taken in every single step of the procedure.

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CONCLUSION A conclusion of this experiment we found that the infiltration rate is affected by the

type of soil that we used. This rate is faster in a dry soil and become slowly in a wet soil and very slow in a saturated soil. Therefore, the infiltration capacity was affected by the porosity of the soil and moisture content of the soil. From the experiment, we can see that the types of soils influence the infiltration rates. For dry soil, infiltration occurred faster, water can absorb faster than wet soil and saturated soil because inside the soil, they have a lot of voids. For wet soil, infiltration occurred in modest time between dry soil and saturated soil because the already contain amount of water in that soil. And for the saturated soil, infiltration occurred very slow because they have a lot of water that saturated in the wet soil. From that, we consider that the soil is wet, after plot a graph of infiltration rate versus time. The process of infiltration in not too fast because they already have water inside the soil. So, the water was slowly absorb inside the soil during our experiment. From this experiment, we can apply this knowledge to design the dam or drain. The application of the basic hydrology system was very important to control the flood. Beside, we also use it to avoid the high cost of constructing the drain. Then we also need to determine all of the factors that effected runoff. For example, rainfall intensity, type of surface and others involving water system.

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REFERENCE 1. https://en.wikipedia.org/wiki/Infiltration_(hydrology) 2. file:///C:/Users/user8/Downloads/174047240-BASIC-HYDROLOGYINFILTRATION-TEST.pdf

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