Estimating Irrigation Diversions for Major Texas Rice‐Growing Area

Abstract

The Lower Colorado River Authority (LCRA) of Texas provides an average of 530,000 acre‐ft annually for rice cultivation. To estimate water needs better, predictive equations were developed, using least‐squares regression, for the monthly and annual water diversions for the three largest rice irrigation systems served by LCRA. The equations provide statistically significant and physically meaningful relationships for predicting changes in water diversions with changes in rainfall, rice acreage planted, gross lake evaporation, and planting time of first crop rice. Depending on the particular irrigation system, the equations estimating annual diversions explain between 85% and 88% of the variation in the data, and those for monthly diversions explain between 47% and 81%, with the majority of these equations explaining better than 60%. The relationships developed in this study may be used for drought contingency planning, evaluation of the impact of water conservation practices on water diversions, and estimation of the impact of using local supply sources, such as ground water, on reducing river water diversion demands for irrigation.