Phoenix AMA Goal
The Phoenix AMA 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goal which attempts to achieve (and thereafter maintain) a long-term balance between the amount of groundwater withdrawn in an active management area and the annual amount of natural and artificial recharge in the Active Management Area A.R.S. § 45-561(12).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.
Phoenix AMA Description
The Phoenix AMA is located in central Arizona and is one of the five Active Management Areas (AMA) established by the Groundwater Code (Code). The Phoenix AMA covers 5,646 square miles and consists of seven groundwater sub-basins:
- East Salt River Sub-basin
- West Salt River Sub-basin
- Hassayampa Sub-basin
- Fountain Hills Sub-basin
- Rainbow Valley Sub-basin
- Lake Pleasant Sub-basin
- Carefree Sub-basin
The AMA is in the basin and range physiographic province. Elevations range from less than 800 feet above mean sea level (MSL) at Gillespie Dam to over 6,000 feet above MSL in the Superstition Mountains in the eastern portion of the AMA.
The AMA is characterized by a diverse mix of water uses, with a heavy and increasing emphasis on municipal and industrial uses. Multiple sources of water (CAP, Salt and Verde surface water, effluent and groundwater) are available and are being used to varying degrees.
Approximately 2.3 million acre-feet of water are used annually on average in the Phoenix AMA, with 1.6 million acre-feet of renewable water (CAP, Salt and Verde surface water, and effluent) used and 705,000 acre-feet of groundwater used.
The Phoenix AMA is drained by the Gila River and four principal tributaries: the Salt, Verde, Agua Fria, and Hassayampa rivers.
Other tributaries include Queen Creek, New River, Skunk Creek, Cave Creek, Waterman Wash, and Centennial Wash. Regulatory water storage reservoirs have been constructed on the Salt, Verde, and Gila rivers and for the Agua Fria River, allowing for a relatively high proportion of surface-water use in some areas of the Phoenix AMA.
Located primarily in a subtropical desert, the climate of the Phoenix AMA is semi-arid, receiving an average of seven inches of annual precipitation.
Allowable Pumping & Complex Legal Structure
Groundwater pumping is allowed under the Code, the management plans, and the AWS Rules through grandfathered rights, groundwater withdrawal permits, and service-area rights. Groundwater pumping creates a significant obstacle toward AMA efforts to achieve safe-yield. The burden of reducing mined groundwater does not apply proportionately to all water-using sectors. Since 1985, many of the Phoenix AMAs water users have reduced their use of groundwater and increased their use of renewable supplies. However, other water users in the AMA have continued or increased groundwater use, as allowed under current statutes and rules. The result has been that groundwater demand has not decreased, which affects progress towards achieving safe-yield.
Groundwater and non-groundwater sources are managed under different statutes with limited integration. In a rapidly growing AMA with multiple water sources, sound management of only one source may be problematic.
The Phoenix AMA is characterized by complex water use patterns and varying groundwater conditions. Municipal and industrial growth continues, while agricultural demand has declined moderately and will continue to do so. While the overall AMA water use has been fairly consistent for several years, certain areas within the AMA are experiencing water level declines from pumping that could restrict the potential for further growth and development. Other limited areas are exhibiting water-logging conditions. While recognizing that the goal of the Phoenix AMA is to achieve safe-yield on an AMA-wide basis, localized water management may be necessary to fully achieve the Code's stated policy of "protecting and stabilizing the general economy and welfare of this state and its citizens." A.RS. § 45-401(B).
Recharge and Recovery
Not all stored water is treated the same way in a statute. The current statute does not allow the accrual of long-term credits for storing effluent after the year 2025. Storing effluent at a managed facility receives a larger cut to the aquifer than storage of effluent at a constructed facility or storage of CAP water. As land associated with Groundwater Savings Facilities urbanizes, the ability to use GSFs for storage will decrease, which may affect storage at Underground Storage Facilities. Many of the ideal locations for large-scale recharge facilities have already been permitted in the Phoenix AMA.
Conservation & Safe Yield
Efficient use of all water supplies is prudent, especially in the arid Southwest. The Department’s conservation programs encourage efficient use of all water supplies. However, conservation alone is not sufficient to result in the achievement of safe-yield in any of the AMAs; replenishment is not required for most water demand sectors, certain types of groundwater rights are perpetual, and certain segments of municipal demand can continue to develop using groundwater.
Use of reclaimed water in the Phoenix AMA has increased more than four-fold since 1985. In the management plans, the Department included incentives to use effluent for cooling, turf, and agricultural irrigation. However, this incentive may result in users becoming less concerned about the volume of water used. Efficient use of all water supplies is prudent for sound water management.
Susceptibility of Central Arizona Project Supplies to Reduction
CAP water comprised 20 percent of the water supply used in the Phoenix AMA in 2015. However, there are indications that CAP could experience shortages in coming years, which could increase the use of groundwater in the future, thus affecting the Phoenix AMA’s ability to achieve and maintain safe-yield. However, the Arizona Water Banking Authority (AWBA) and others have stored significant volumes of CAP water and other renewable supplies that can be recovered later to mitigate the impacts of shortage.
Unresolved Tribal Water Rights Claims
Tribal water rights settlements and leases have a direct and significant influence on water-use characteristics. Amounts and types of water identified in tribal settlements will affect the Phoenix AMA’s ability to achieve safe-yield. Failure to reach a final resolution of this challenge leaves major questions about water supply and demand unanswered. The activities of off-reservation water users affect on-reservation conditions and vice versa.
Integration of Land Use Planning & Water Management
A closer association between land-use planning and water-policy planning is needed. County and local land use and economic development planning programs must continue to plan for and incorporate water supply and infrastructure requirements.
Public & Private Support for Water Management Approaches
Local governments and members of the development community need to understand the long-term implications of the decisions they make today. Responsible development and forward-thinking governmental decisions regarding growth and investments/commitments to conservation programs ensure long-term water resource sustainability. A major obstacle in developing and implementing water management programs is the lack of understanding by the public and the policymakers of the water management issues facing the Phoenix AMA. Community support is a key ingredient in the development of any local or regional program, but it is particularly important in setting water policy.
Factors Affecting Safe-Yield Outside of Influence of Department Programs
Many factors that affect the ability to achieve safe-yield are outside the influence of current water management programs. Water demand is affected by economic and demographic conditions. Increases in population and industrial growth rates have a dramatic influence on water use. More people and industries result in higher water demand. The location of new development has a dramatic effect on water resources planning. Water costs strongly affect the amount of water use in all sectors. The undervalued cost of water in most instances, as well as the cost differential between certain renewable sources of water and groundwater, provides little incentive to maximize efficiency or reduce groundwater use. The cost of using groundwater should reflect the cost of over-drafting the aquifer. These costs include the loss of a supply, land subsidence and aquifer compaction, and water quality degradation.