ABSTRACT
This chapter aims to develop procedures for estimating expected losses of water through transpiration by plants and evaporation from plant, soil, or pond surfaces. It presents several methods for determining normal-year evapotranspiration (ET0), discusses the availability and application of crop co-effcients to obtain ET, and provides a reference source for obtaining necessary long-term precipitation records for California. Estimates of annual, seasonal, or monthly losses of water from cropped or non-cropped soil or water surfaces can be obtained by applying crop coefficient values to ET0 estimates. Preliminary evaluations for storage requirements of slow-rate reclaimed water systems can be based on estimates of yearly totals of ET and/or of open water evaporation from ponds, along with measured precipitation. In the case of wastewater systems involving the growing of annual crops, irrigation system design becomes more complex due to the variation of ET with changing plant cover, stage of growth, and maturity.
