This is Exercise 4.8.1 in Introduction to Physical Hydrology by Martin Hendriks.
The water level above flat terrain during an experiment with double ring infiltrometer is 20 mm. The saturated hydraulic conductivity of soil is 20 mm/h. The wetting front of soil suction is 60 mm. The initial soil moisture content is 20% and the effective porosity is 45%.
Calculate the infiltration rate and cumulative infiltration when wetting front is 20, 40, 80, 160, 320, 640 and 1280 mm below the soil surface. Why does the infiltration rate diminish with time?