A Framework to Define Optimal Fallowing Programs: a Case Study of California Water System

Abstract

The Western region of the United States has been facing a 23-year drought, which has had a detrimental impact on California's water resources, reaching unprecedented levels. In August 2021, the United States Bureau of Reclamation announced the first-ever shortage on the Colorado River, leading to water cuts for many users. As the levels in Lake Mead and Lake Powell continued to decline in 2022, the water cuts were expanded. Industrial farming in Southern California depends on this water source for irrigation, and fallowing cropland can lead to significant water savings in a short period. By keeping cultivated land out of production during a typical growing season, farmers can reduce water usage quickly. This study proposes an optimization model to determine the optimal fallowing plan based on estimated crop water consumption, commodity prices, and other land, water, and budget constraints. To illustrate the application of the proposed optimization model, publicly available crop and weather data were used to estimate the water usage of crops in water agencies across California and to estimate optimum fallowing plans for Colorado River System and California State Water Project. The optimized fallow plans assist interested organizations in determining the best groups of crops to fallow and the payment per acre farmers may receive to achieve specific water conservation goals. The result of the optimization is compared with the current fallow rates proposed to famers.