Prescott AMA Goal
The Prescott AMA (PRAMA) has a statutory goal of achieving safe-yield by 2025. Safe-yield is a groundwater management goal which attempts to achieve and thereafter maintain a long-term balance between the amount of groundwater withdrawn in an active management area and the annual amount of natural and artificial recharge in the active management area A.R.S. § 45-561(12). The safe-yield goal is a basin-wide balance. Under current groundwater rules, pumping from one location in the AMA can be offset by recharging a volume of water at another location.
The Prescott AMA covers 485 square miles in central Yavapai County. The AMA lies within the Central Highlands physiographic province and is typified by gently rolling topography with broad sloping alluvial basins and fault block mountains. Elevations range from about 4,400 feet above sea level in the valleys to about 7,800 feet above mean sea level in the Bradshaw Mountains. Native vegetation varies from high desert grassland in the basin areas to coniferous forest in the surrounding mountains. The AMA boundary is defined by the Bradshaw Mountains to the south, Granite Mountain and Sullivan Buttes to the west, and by the Black Hills to the northeast.
The AMA consists of two sub-basins, the Little Chino (LIC) and the Upper Agua Fria (UAF), which are bisected by a surface drainage divide. Granite Creek, Big Draw, and Little Chino Creek drain the LIC sub-basin into the Verde River. Lynx Creek and other smaller ephemeral streams drain the UAF sub-basin into the Agua Fria River. The LIC sub-basin encompasses western and northern portions of the AMA, while the UAF sub-basin spans the southeast portion of the AMA.
There are a number of important issues facing the Prescott AMA, most of which involve limitations on renewable water supplies and continued growth and the Department’s statutory responsibility to attempt to reach safe-yield by 2025. Some of these issues include:
Under existing law, several categories of water users, both existing and potential new users, may withdraw groundwater without replenishing or replacing that volume of water back into the aquifer. These users contribute to overdraft and, under current regulations, may increase and continue in perpetuity.
Underground Storage & Recovery
Not all recovered water is treated identically equal under the AWS Rules. When water is stored and recovered from the same area, the stored water recharges the aquifer in the same location as the wells are withdrawing it, and the stored water is adding physical availability to the wells that recover the water from within the area of impact of storage (AOI). Historically, the majority of the recovered water in the Prescott AMA has not been recovered within the AOI. The result of this strategy is water level declines in the vicinity of the recovery wells.
Efficient use of all water supplies is prudent, especially in the arid Southwest. While the Department’s conservation programs encourage efficient use of all water supplies, conservation alone will not result in the achievement of safe-yield in the Prescott AMA. For the Prescott AMA to achieve and maintain safe-yield by 2025 and beyond, conservation, augmentation, and multiple other water management strategies are needed.
The Prescott AMA has a long history of using reclaimed water for watering turf-related facility landscaping. However, the Department’s regulatory authority and programs have not historically required the same standard of efficient water use for reclaimed water as it has for groundwater and other sources of supply.
Use of septic systems reduces the amount of wastewater that may be reclaimed and reused and septic system leachate cannot be directed to areas experiencing water level declines.
There is currently no cut to the aquifer applied to the storage of reclaimed water at a constructed Underground Storage Facility as there is for storage at a managed facility, or storage of CAP water in AMAs with access to CAP water (Phoenix, Pinal, and Tucson AMAs). This means that 100 percent of the water sent to underground storage, minus evaporative losses and other debris, is recoverable. The merits of the general benefit to the Prescott AMA of applying a cut to the aquifer - versus all effluent credits residing with individual storing parties - requires further examination and debate in the AMA.
Limits on Use of Surface Water Supplies
Complex legal agreements and the location of some surface water supplies inhibit their use in the Prescott AMA. However, shifting existing demand from groundwater to surface water supplies would serve to advance the Prescott AMA toward safe yield and/or reserve the groundwater for future use.
Timing, Cost, and Impacts of Imported Supplies
Currently, water users in the Prescott AMA have the authority to import groundwater from the Big Chino Sub-basin outside of the Prescott AMA. Although a pipeline is planned, there are several issues surrounding the importation of this supply, including potential costs and whether other water users could be affected. In addition, the timing of the construction of the pipeline may be an issue if new development is dependent on that supply to proceed.