POTENTIAL EFFECTS OF CLIMATE CHANGE AND HUMAN INTERACTIONS ON WATER SUPPLY AND DEMAND IN THE ELOY AND MARICOPA-STANFIELD BASINS, ARIZONA

As climate change progresses, there are increases in drought magnitude and severity in the state of Arizona. The recently passed Drought Contingency Plan (DCP) for the Colorado River basin includes additional elevation drought management thresholds for Lake Mead. At lake stages of 1,090 ft., 1,075 ft., 1,050 ft., 1,045 ft., and 1,025 ft. Arizona will voluntarily give up 192,000–720,000 acre-feet of its 2.8 million acre-feet allocation, depending on the elevation. This decrease in renewable Colorado River water supply will result in a reduction of water the Central Arizona Project (CAP) receives; the first portion of water delivery to be reduced will be agricultural. An area that will be greatly affected by these management scenarios is the Pinal Active Management Area (AMA), where ~96% of its water use is agricultural. Within the Pinal AMA there are two sub-basins of interest, the Eloy and Maricopa-Stanfield (EMS). These basins were formed by the tectonic extension that created the Basin and Range region, which is characterized by abrupt mountain ranges with alluvial fill between them. The purpose of this project was to investigate how renewable surface water supply via the CAP and nonrenewable groundwater supply and demand in the EMS basins will change in the future based on these factors. To answer this question, current supply and demand data have been collected from within the AMA and were used to better constrain the groundwater flow model developed for the EMS basins. This groundwater model was combined with an optimization function to create a hydroeconomic model. This is a new application of these methods to investigate the implications of the DCP on groundwater storage. This work is not only important for current and future users of water in the Pinal AMA, but also provides insight on how similar future drought contingency planning studies may be conducted.