Calculation and Simulation of Evapotranspiration of Applied Water

Abstract

The University of California,Davis and the California Department of Water Resources have developed a weather generator application program SIMETAW to simulate weather data from climatic records and to estimate reference evapotranspiration (ET o) and crop evapotranspiration (ET c) with the generated simulation data or with observed data.A database of default soil depth and water holding characteristics,effective crop rooting depths,and crop coefficient (K c) values to convert ET o to ET c are input into the program.After calculating daily ET c,the input and derived data are used to determine effective rainfall and to generate hypothetical irrigation schedules to estimate the seasonal and annual evapotranspiration of applied water (ET aw),where ET aw is the net amount of irrigation water needed to produce a crop.In this paper,we will discuss the simulation model and how it determines ET aw for use in water resources planning.