The Arizona Department of Water Resources recently released the first seven supply and demand assessments for the state’s groundwater basins. The department is required by a state law signed in 2022 to complete a supply and demand assessment of each of Arizona’s 51 basins every five years. At least six assessments are due annually on December 1. This year, seven basins were assessed: Butler Valley, Douglas Active Management Area (AMA), Harquahala Irrigation Non-Expansion Area (INA), McMullen Valley, San Bernardino Valley, Tiger Wash, and the Willcox basin. The assessments are not groundwater flow models, but rather structured as water budgets detailing total inflows and outflows of each basin. Demand across various sectors, such as agriculture, industrial, municipal, and others, was estimated and compared with the volume of water supplies available to meet those demands. The assessments project supply and demand out to 2075 under various scenarios.
Out of the seven basins assessed this year, only one was projected to be able to keep up with demand most years—the relatively undeveloped San Bernardino Valley basin, which has no agricultural activity and minimal municipal or industrial activity—whereas the Butler, Douglas AMA, Harquahala INA, McMullen Valley, and Willcox basins are expected to have insufficient annual supply to meet yearly demand under many of their projected scenarios. This means that more water is leaving than being replenished in these basins. This is largely attributed to the water demands of agriculture, which accounted for between 87–99% of demand in each of these basins. Lastly, annual supply in the Tiger Wash basin was projected to fall short of meeting annual demand, but due to this area being relatively undeveloped, the assessment described concerns about water availability there as “low.”