Thesis (Ph.D., Water Resources) -- University of Idaho, 2016 | Irrigated agriculture comprises the largest consumptive use of water in the Western United States (U.S.). Thus, understanding the factors that contribute to changes in agricultural water needs is essential to ensuring that water resources can be sustainably managed in the future. This study developed an agent based model that represented the behavior of three agent types, Districts, Farms, and Crops, that work together to determine the amount of agricultural water needed for a basin. The model was able to estimate the amount of agricultural water needed within nine percent of historical volumes. For simulations that consider future climate conditions, the model indicated the need for less water over time due to crop mix and land use changes.