Effects of Economic and Climate Factors on Central Arizona Agricultural Water Use

Throughout the arid American West, agriculture is the dominant consumptive use of water, with farming operations dependent on groundwater or surface flows for necessary irrigation. Although surface flows are limited in the region, widespread availability of groundwater has allowed agricultural economies to develop in otherwise dry areas. However, groundwater withdrawals have outpaced natural aquifer recharge throughout much of the twentieth and twenty-first centuries, and as water tables decline in elevation, surface flows are adversely affected.This study seeks to model the climatic and economic factors that contribute to farmers’ water use decisions in central Arizona, a region that has been historically dependent on groundwater to satisfy the water demands of agriculture, urban expansion, and heavy industry. Today, the area’s water needs are met through a combination of groundwater, Colorado River water delivered via the Central Arizona Project, and additional surface flows. The modeling approach presented is applicable to a wide range of agricultural communities that are at least somewhat dependent on irrigation for agriculture. This study specifically examines the effect of climatic, economic, and remote sensed land cover variables on water deliveries to and irrigation intensity within irrigation districts in Central Arizona. The study’s panel data set is enumerated the level of irrigation districts annually from 2008 to 2019, and incorporates remote sensed land cover data as well as a set of economic variables and climate measures. Econometric analysis finds that climate, the prices of December Cot- ton Futures, CAP water costs, and fallowed area have significant impacts on water deliveries to irrigation districts. It is also found that climate, the prices of December Cotton Futures, and CAP water costs significantly impact the intensity of irrigation water application (water applied/planted area). Understanding irrigators’ water use decisions is useful to those concerned with the impact of water availability on local economies, ecosystems, and aquifers