The Tucson Active Management Area (TAMA) 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management goal which attempts to achieve and thereafter maintain a long-term balance between the amount of groundwater withdrawn in an Active Management Area and the annual amount of natural and artificial recharge in the Active Management Area A.R.S. § 45-561(12).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 Tucson AMA covers 3,866 square miles in southern Arizona. It is one of five AMAs established pursuant to the 1980 Groundwater Management Act and administered by the Arizona Department of Water Resources.
The Tucson AMA is in the basin and range physiographic province which is characterized by broad, gently sloping alluvial basins separated by north to northwest trending fault block mountains. There are two groundwater sub-basins in the AMA, the Avra Valley Sub-basin and the Upper Santa Cruz Subbasin.
The AMA includes portions of Pima, Pinal and Santa Cruz counties, and five incorporated cities and towns: Tucson, South Tucson, Oro Valley, Marana, and Sahuarita. The Pascua Yaqui tribal lands, part of the Schuk Toak District, and the entire San Xavier District of the Tohono O'odham Nation are within the AMA. ADWR estimates the 2015 population of the Tucson AMA was about one million people.
The original boundaries of the Tucson AMA included what is now the Santa Cruz AMA, which was created in 1994.
Meeting and Maintaining the Safe-Yield Goal
During the second and third management periods, significant actions were taken toward reaching safe-yield, including the establishment of the Arizona Water Banking Authority (AWBA) and the Assured Water Supply (AWS) Program. The Tucson AMA Assessment revealed that the Tucson AMA has been at or near the safe-yield goal in recent years. However, not all municipal uses are required to replenish or offset groundwater pumping, and the municipal sector can continue to grow, representing the potential for increased groundwater demand. Additionally, agricultural and industrial users are not required to replenish or offset groundwater pumping. All of these factors will be challenges for the Tucson AMA to meet and maintain the goal of achieving safe-yield.
Utilization of Available CAP Supplies
A past challenge has been achieving full utilization of available Central Arizona Project (CAP) supplies, including excess supplies that may only be available in the short term. Augmentation efforts continue to be a focus during the Fourth Management Period (2010-2020), in order to offset future shortages and to achieve other management objectives. CAP supplies remain the primary renewable water source for the Tucson AMA, and full utilization is imperative to allow for future growth that is consistent with achieving and maintaining safe-yield.
Increased Utilization of reclaimed water
The Assessment identified the potential for reduced groundwater dependency in the Tucson AMA through increased direct reuse of reclaimed water. Reclaimed water represents an alternative renewable supply to CAP water that can be used to mitigate CAP shortages and protect against the impacts of drought. Developing mechanisms to maximize use of reclaimed water will be a water management focus in the Tucson AMA during the Fourth Management Period. The Department will participate with other stakeholders in future discussions regarding potential uses for reclaimed water.
Physical Availability of Groundwater within the Tucson AMA
Physical availability of groundwater within specific geographic sub-areas of the Tucson AMA has been a challenge in the past and must continue to be addressed. While recognizing that the groundwater management goal for the Tucson AMA is defined as achieving safe-yield on an AMA-wide basis, localized water management is also desirable to fully achieve the Code’s stated policy of “protecting and stabilizing the general economy and welfare of this state and its citizens....” Localized issues such as land subsidence may arise in areas experiencing rapid or marked declines in water tables. Other localized challenges may include water quality concerns and infrastructure limitations that constrain access to renewable water supplies. The AWS Rules require applicants to prove the physical availability of groundwater in the area for which the AWS is being applied. If there is an insufficient physical availability of groundwater to meet the current, committed and projected demand for that area, an applicant would need to demonstrate other water supply sources that are physically available and meet the other AWS Rules criteria in order for an AWS determination to be issued. Recharge activities conducted by the AWBA, the Central Arizona Replenishment District (CAGRD) and others also have the potential to address local water management issues. Addressing these major challenges is an important part of the Tucson AMA’s groundwater management strategy.