WATER-BALANCE MODEL FOR SMALL-SCALE WATER HARVESTING SYSTEMS

This paper describes a simple, few-parameters simulation model for a w ater harvesting-strip farming system. The model includes runoff thresh old functions for different soil types, and for different initial soil water contents. The evapotranspiration component of the model account s for dynamic root water extraction using regression equations that co rrelate canopy cover with root growth as a function of time. The model is simple to operate and uses readily available inputs. It can work w ith several crops when leaf area indices and crop stage coefficients a re provided. The agreement between simulation outputs and field-observ ed data indicates that the model accurately describes the water balanc e within the system. The model is then recommended for obtaining preli minary design of water harvesting systems. A FORTRAN77 source code has been written for the simulation procedure.