6.5 Problem Set

Water is ponded at a constant depth of 2.5 cm on a silt loam soil which had an initial water content of 0.15 cm³ cm^-3. The water content of the wetted soil above the wetting front is 0.49 cm³ cm^-3, and the wetting front has a pressure head of -17 cm. The hydraulic conductivity of the wetted soil is 0.65 cm h^-1. Apply the Green-Ampt model for ponded infiltration to answer the following questions:
1. What is the infiltration rate (cm h^-1) when the wetting front reaches a depth of 30. cm?
2. In total, how much water (cm) has infiltrated by that time?
3. How long did it take (h) for the wetting front to reach that depth?

For that same soil with the same initial condition, consider the infiltration process for rainfall at a constant rate of 1.5 cm h^-1. Use the Mein and Larson modification of the Green-Ampt model to answer the following:
1. How deep is the wetting front (cm) when ponding begins?
2. In total, how much water (cm) has infiltrated by that time?
3. How long did it take (h) before ponding occurred?

Repeat problem 2 but this time use a hydraulic conductivity of 0.325 cm h^-1, exactly half of the value used previously.
1. How deep is the wetting front (cm) when ponding begins?
2. In total, how much water (cm) has infiltrated by that time?
3. How long did it take (h) before ponding occurred?

License

Icon for the Creative Commons Attribution 4.0 International License