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UVIVERSITY OF IDAHO
CE326/BAE356/FOR
HYDROLOGIC MEASUREMENT TECHNIQUES
Laboratory Assignment
Student Name:
XXXXX
Title:
Infiltration Laboratory
[Note to Students: This is provided as a general example only. Notes are provided to show
where the report could be improved. Variations are likely โ discuss your report with the
instructor if you have questions. Do NOT plagiarize this report!]
Date of Exercise:
Date of Submission:
Introduction
Infiltration is the term applied to the process of water entry into the soil, generally by downward
flow through all or part of the soil surface. The rate of this process, relative to the rate of water
supply, determines how much water will enter the root zone, and how much, if any, will run off
(Hillel, 1998). Hydraulic conductivity is one of the most important parameters in characterizing
the transport of fluids and solutes through the vadose zone, but presents significant practical
difficulty in measurement. In vadose applications, knowledge of the saturated hydraulic
conductivity is often of limited use, as saturated conditions are rare in most locations. Yet, few
reliable methods exist for measuring the unsaturated hydraulic conductivity. One common
approach to obtain the unsaturated hydraulic conductivity relationship is to measure both the
saturated hydraulic conductivity and the water retention curve and estimate the unsaturated
conductivity based on a conceptual model relating conductivity to water content (van Genuchten,
In general, two types of laboratory methods to measure the saturated hydraulic conductivity:
constant-head and falling-head permeameters. It seems unrealistic however to measure the
unsaturated hydraulic conductivity of the field soil by making laboratory measurements on
discrete samples removed from their natural continuum. Such samples are generally dried,
fragmented, and repacked into experimental containers so that the original structure is destroyed.
Hence, it is necessary to device and test practical methods foe measuring the saturated hydraulic
conductivity on a realistic scale in situ (Hillel, 1998). Field techniques to measure the saturated
hydraulic conductivity can be divided into four categories: percolation tests, ring infiltrometers,
disk infiltrometers and sprinkler infiltrometers.
Objectives
The main objective of this laboratory was to get acquainted with field methods commonly used
to determine infiltration and/or selected soil properties. Field methods in the exercise were:
- Single Ring Infiltrometer
- Tension Infiltrometer
- Mini Disk Infiltrometer
Methodology
Infiltration experiments were conducted with three infiltrometers on a field in front of the
Buchanan Engineering Laboratory. Procedures given in the assignment sheet, included as
Appendix A, were followed. A summary of the methods used to compute hydraulic conductivity
for each of the methods is provided here.
[Note: Even though procedures on handout were followed, a brief summary in your own words
should be added. Include both Field Methods and Analysis Methods .]
Results
The ring infiltrometer measurement resulted in a hydraulic conductivity value of 1.3x
cm/s.
Table 1 shows the results of the tension infiltrometer measurements made with the Ankeney
macropores because the pressure head along the bottom of the membrane during testing is
maintained at a slight tension with respect to atmospheric pressure, so water does not flow into
macropores Stephens (1996). On the other hand I think that this prevents to mimic the natural
occurring conditions in soils with macropores.
Mini Disk Infiltrometer
The mini-disk infiltrometer is very simple, small and easy to use. It uses very little water in
comparison to the other methods and can be easily operated by one person. Like in the disc
infiltrometer method it is crucial to maintain excellent contact between the disc and the soil
which was extremely difficult while running the experiment. The soil surface must be really
smooth and level. Definitely a ring stand and clamp are necessary to suspend the infiltrometer
due to its small dimensions and light weight. There were some difficulties taking the readings
due to its small height.
The hydraulic conductivity is obviously affected by structure as well as by texture, being greater
if the soil is highly porous, fractured or aggregated than if it is tightly compacted and dense.
Hydraulic conductivity depends not only on total porosity but also on the sizes of conducting
pores. Cracks, worm holes, and decayed root channels - generally called macropores - are
present in the field and may affect flow in different ways, depending on the direction and
conditions of the flow process. In general, these passages will run full of water and contribute to
the observed flux and measured conductivity (Hillel, 1998).
Summary
In this laboratory students were acquainted with field methods commonly used to measure
infiltration and calculate the saturated hydraulic conductivity. Three methods were used: Single
Ring Infiltrometer, Tension Infiltrometer and Mini Disk Infiltrometer. The saturated hydraulic
conductivity varied depending on the method applied, and was proportional to the scale of the
instrument. Limitations associated with each device were discussed.
References
1. Hillel, D. 1998. Environmental Soil Physics. Academic Press.
2. Or, D., Jon M. Wraith, Markus Tuller. 2002. Agricultural and Environmental Soil Physics.
Not published
3. Selker, J.S. et al.1999. Vadose zone processes. Lewis Publishers.
4. van Genuchten, M.T. 1980. A closed form equation for predicting the hydraulic
conductivity of unsaturated soils.โ Soil Sci. Soc. Am. J. 44:892-
5. Klute, A. et al. 1986. Methods of Soil Analysis. Part 1. Physical and Mineralogical
Methods. Second Edition. American Society of Agronomy, Inc.
6. Hills, R.C. 1971. Lateral flow under cylinder infiltrometers: A graphical correction
procedure. J. Hydrology 13:153-162.
7. Stephens, Daniel B. 1996. Vadose Zone Hydrology. Lewis Publishers
Appendix A
Lab Handout
Appendix C
cm tension, respectively. Figures C-1 and C-2 show cumulative infiltration versus time, and results of regressions for the steady state infiltration conditions. Steady infiltration rates were used as input for calculation of the saturated hydraulic conductivities by the Ankeny Method Program.
T ab .1 T en sio n in filtro m eter d ata fo r 3 cm su ctio n H eig h t o f w ater E lap sed T im e E lap sed V o lu m e fo r C u m u lative in th e cylin d er tim e d iffer. tim e g iven h eig h t vo lu m e
- Tables 1 and 2 present the results obtained from the tension infiltrometer method for 3 cm and Tension Infiltrometer Data and Analysis
- 67.5 0 0 0.0 342.0 0. [cm ] [sec] [sec] [m in ] [cm 3] [cm 3]
- 62 22 22 0.4 314.2 27.
- 60 33 11 0.6 304.0 38.
- 58 48 15 0.8 293.9 48.
- 56 65 17 1.1 283.8 58.
- 54 83 18 1.4 273.6 68.
- 52 103 20 1.7 263.5 78.
- 50 128 25 2.1 253.4 88.
- 48 148 20 2.5 243.2 98.
- 46 167 19 2.8 233.1 108.
- 44 199 32 3.3 223.0 119.
- 42 225 26 3.8 212.8 129.
- 40 258 33 4.3 202.7 139.
- 38 290 32 4.8 192.5 149.
- 36 328 38 5.5 182.4 159.
- 34 366 38 6.1 172.3 169.
- 32 414 48 6.9 162.1 179.
- 30 461 47 7.7 152.0 190.
- 28 510 49 8.5 141.9 200.
- 26 554 44 9.2 131.7 210.
- 24 603 49 10.1 121.6 220.
- 22 656 53 10.9 111.5 230.
- 20 710 54 11.8 101.3 240.
- 18 766 56 12.8 91.2 250.
- 16 824 58 13.7 81.1 261.
- 14 884 60 14.7 70.9 271.
- 12 942 58 15.7 60.8 281.
- 10 1005 63 16.8 50.7 291.
- 8 1081 76 18.0 40.5 301.
- 6 1140 59 19.0 30.4 311.
- 4 1205 65 20.1 20.3 321.
T ab.2 T ension infiltrometer data for 0 cm suction Height of w ater Elapsed T ime Elapsed Volume for Cumulative in the cylinder time differ. time given height volume [cm] [sec] [sec] [min] [cm3] [cm3] 58.7 0 0 0.0 297.4 0. 56 29 29 0.5 283.8 13. 54 69 40 1.2 273.6 23. 52 119 50 2.0 263.5 33. 50 170 51 2.8 253.4 44. 48 221 51 3.7 243.2 54. 46 275 54 4.6 233.1 64. 44 327 52 5.5 223.0 74. 42 378 51 6.3 212.8 84. 40 432 54 7.2 202.7 94. 38 482 50 8.0 192.5 104. 36 535 53 8.9 182.4 115. 34 590 55 9.8 172.3 125. 32 640 50 10.7 162.1 135. 30 694 54 11.6 152.0 145. 28 745 51 12.4 141.9 155. 26 798 53 13.3 131.7 165. 24 844 46 14.1 121.6 175. 22 898 54 15.0 111.5 186. 20 948 50 15.8 101.3 196.
Ryc.1 Cumulative infiltration for 3cm suction
y = 10.367x + 116.
R^2 = 0.
time [min]
Infiltrated volume of water
[cm3]
Figure C-1. Cumulative infiltration volume versus time for 3 cm suction in tension infiltrometer.
Appendix D
Mini-Disc Infiltrometer Data and Analysis
Table 4 lists data for the Mini Disk infiltrometer at 2cm suction. The parameters of the Mini Disk
as well as relevant soil parameters for a silt loam soil are listed in Table 5. Figure 3 depicts the
result of the Mini Disc infiltration experiment. A polynomial regression was applied to the data
in Figure 3 to calculate the saturated hydraulic conductivity.
[Note: Again, table and figure numbering can be improved]
Tab.4 Mini Disc infiltrometer data for 2cm suction
Elapsed Elapsed Reading Infiltrated SQRT Infiltration
time time volume volume time
[min] [sec] [cm3] [cm3] [-] [cm]
Tab.5 Other Mini Disc infiltrometer data
Mini Disc parameters silt loam soil parameters
radius 1.59 cm alpha 0.02 1/cm
suction 2 cm n 1.41 -
suction area 7.94 cm2 A(0.5) 8.1 -
k 0.000074 cm/s
y = 0.0006x 2 + 0.0326x
R^2 = 0.
SQRT of time
Cumulative infiltration [cm]
Figure 3. Cumulative infiltration volume at 2 cm suction in mini disc infiltrometer.
