Modeling of evapotranspiration from homogenous soils

A sink term to simulate the removal of water by transpiration from the soil profile has been added to the moisture flow model of Clapp (1982). The resultant model gives results comparable to those obtained from a finite difference solution of the Richards equation modified for transpiration, but uses only about 5% of the computer time. Example applications show that the model is capable of predicting evapotranspiration rates from homogenous soils without using fitted parameters.