Managing agricultural water use in the Western United States: A search for efficient climate adaptation institutions

Irrigated agriculture throughout much of the western United States relies on water resources that are under increasing stress from more frequent and severe droughts, reduced snowpack, and changes in the timing of runoff. Much of the water used for irrigation in that region passes through lands managed by irrigation organizations. These organizations play an important role in the use, allocation, and conservation of water resources through the maintenance of conveyance infrastructure, administration of rights to use water, and distribution of water to users. However, little work has been published to date systematically describing economic effects from alternative irrigation water trading arrangements for adapting to drought and climate change. The contribution of this work is to fill a gap in previous research by assessing the economic performance of various water trading arrangements for adapting to water shortages. We secured U.S. Department of Agriculture data on irrigation water use patterns in the central part of the Rio Grande Basin of the American Southwest to support formulation of a mathematical model predicting water use patterns to assess impacts on farm income associated with a range of water shortages and water trading arrangements for adapting to these shortages. Model results show that unlimited water trading minimizes farm income lost from shortages, while a more limited geographic scope for trading also moderates farm income losses. Among the three shortage sharing methods considered, a proportional sharing of shortages with no trading produces the greatest loss in farm income for adapting to shortage. These findings suggest that water trading arrangements have an important role play in adapting to water supply changes. Our results provide science-informed guidance to water managers, stakeholders, and policymakers tasked with discovering efficient water shortage adaptation plans for arid and semi-arid irrigation regions internationally.