EFFECTIVE PRECIPITATION IN IRRIGATION DESIGN AND MANAGEMENT.

Effective precipitation is important in irrigation system design and operation. Numerous methods for estimating effective precipitation have been proposed in the past, including direct measurement techniques, empirical methods, and soil water balance methods. A soil water balance model (SWBM) for estimating effective precipitation was developed in the study reported herein. The simulation abilities of the model are demonstrated and are compared to the Soil Conservation Service (SCS) method for estimating effective precipitation. The comparison is quite favorable for coarse textured soils, however, the SCS method overpredicts effective precipitation for fine textured soils. This result is in agreement with remarks made by N. G. Dastane regarding the applicability of the SCS method.