Daniel Timmons
Student Watershed Research Award Recipient
Graduate Student
Dept. of Environmental Science and Policy
Northern Arizona University
dlt63@nau.edu 

Advisor: Dr. Abe Springer

Groundwater Flow Modeling and Multiple Scenario Analysis: Prescott Active Management Area, Yavapai County, Arizona

The Prescott Active Management Area (AMA) in central Arizona is required to achieve a state of safe-yield by 2025. Safe-yield is defined as the condition where longterm groundwater withdrawals do not exceed recharge to the aquifer system of the AMA. This study addresses several of the problems facing water managers and planners in the Prescott Active Management Area. Through further development of an existing numerical groundwater model, the natural hydrologic budget and flow patterns of the area have been quantitatively assessed. Applying the groundwater model to future scenarios, the varying impacts of current and future water management and development decisions have been quantified and assessed. Based on these results, policy recommendations have been made regarding optimal population growth patterns, conservation strategies, and water-supply augmentation policies.

Results indicate that conservation alone is unlikely to allow for the achievement of safe-yield by 2025. Supply augmentation is therefore necessary to bring the Prescott AMA into legal compliance with the safe-yield mandate. Scenario results also indicate that the achievement of safe-yield is possible with projected population growth rates; however, even with effective conservation strategies and the augmentation of existing water supplies, population growth at projected rates is projected to lead to significant impacts on the natural discharges from the groundwater system. Thus, safe-yield can be achieved, but only by decreasing outflow from Del Rio Springs by an additional 37% and baseflow in the Agua Fria River by 22%. Simulated results also indicate that, under conditions of continued growth at median projected rates, the AMA will likely be unable to maintain a state of compliance with the safe-yield mandate much past 2025.

With coordinated management between the water resources managers and town planners for the various communities, Yavapai County and the Arizona Department of Water Resources, the groundwater resources of the Prescott AMA can be managed in a condition of safe-yield. Through a combination of population growth management, conservation strategies and augmentation of existing supplies, the safe-yield goal for the Prescott AMA can be achieved and maintained through 2025.   

Daniel Timmons' Masters Thesis (12MB PDF)