Irrigation Water Requirements in Texas

The derivation of irrigation water requirements and an explanation of their use for project planning work in Texas is presented in which effective precipitation, consumptive use, farm waste and deep percolation losses, canal and lateral losses, return flows, and diversion requirements are discussed. The steps used in developing diversion requirements and return flows are described and an explanation of their use and of land inventory data is given. Cultural practices used in the production of rice are such that the application of effective precipitation and the computation of diversions for other crops are not applicable. Thus, diversion requirements for rice are explained separately. Several references are cited that contain valuable information on the acreage irrigated from surface and from ground water sources, lands suitable for future irrigation, land classification studies, consumptive use data, typical cropping patterns, and farm budget studies. Although the material pertains only to Texas, the methods for calculating detailed water requirements for the various sub-areas can be used elsewhere.