Estimating effects of economic and climatic factors on irrigators' water use decisions

Brian McGreal1, Bonnie Colby1
1Department of Agricultural and Resource Economics, University of Arizona

Throughout the American West, crop irrigation is the dominant consumptive use of water, and many farming operations are mostly, or entirely dependent on groundwater for irrigation. While widespread availability of groundwater has allowed agricultural economies to develop in otherwise arid regions, groundwater withdrawals have outpaced natural aquifer recharge throughout much of the twentieth and twenty-first centuries. As water tables decline in elevation, the cost of pumping groundwater increases, as water must be lifted further to the surface. Further groundwater decline is driving the need to improve existing well infrastructure at significant cost. The alternative is seeing wells run dry and farming diminish in many regions.

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 by a combination of groundwater and Colorado River water delivered through the Central Arizona Project. The modeling approach presented is applicable to a wide range of agricultural communities that have some level of dependence on groundwater for irrigation. Models of how agricultural water use decision making is affected by various climate, hydrologic, and economic factors are useful to those concerned with the impact of groundwater levels on aquifers, local economies, and ecosystems.

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