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Arizona Department of Water Resources AZ.gov Arizona's Official Web Site
Securing Arizona's Water Future

Active Management Area Water Resource Issues

A number of water resource issues exist in the AMA Planning Area.  These issues have been identified by the Department through its management plans, stakeholder processes, a Governor’s Commission, an Arizona Town Hall, and numerous community water resource groups.  Groundwater pumping, achievement of management goals, access to renewable water supplies, legal differences between groundwater and non-groundwater, environmental protection, local area management and increasing salinity are some of the important considerations in the planning area.  Discussed below are issues that have been identified in the past decade and are common to multiple AMAs. These and other AMA issues will be evaluated in detail in the Department’s AMA Fourth Management Plans.

Residual (Allowable) Groundwater Pumping and Management Goals

Groundwater withdrawals allowed under the Groundwater Code, management plans and Assured Water Supply (AWS) Rules through groundwater rights, groundwater permits, and certificates and designations of AWS are a significant obstacle towards achieving AMA management goals.  Four of the five AMAs have safe-yield as a component of their goal.  The definition of safe-yield is, “to achieve and thereafter maintain a long-term balance between the annual amount of groundwater withdrawn in an active management area and the annual amount of natural and artificial groundwater in an active management area.” A.R.S. § 45-561(12).   Groundwater pumped in excess of safe-yield is termed groundwater “mining” or overdraft.

The safe-yield AMAs (Phoenix, Prescott, Santa Cruz and Tucson) have made progress toward achieving their management goals through recharge, replenishment, retirement of agricultural land and conservation, but challenges remain.  As allowed by the Code, AWS Rules and the management plans, the responsibility to reduce mined groundwater pumping may not apply proportionately or equitably to all water-using sectors. For example, although water providers designated as having an AWS are required to use renewable supplies, they can continue to use a limited amount of groundwater. Industrial and agricultural users have management plan incentives to use renewable water supplies, but there are no mandatory requirements. In some AMAs the allowable pumping volume may be a large proportion of the overdraft.

Pinal AMA canal

Canal in the Pinal AMA

Use of domestic/exempt wells is not subject to groundwater replenishment nor management plan requirements. Exempt well pumpage can represent a significant percentage of water demand in some AMAs.  For example, over 9,000 exempt wells are estimated to be in use in the Prescott AMA and may account for as much as 25 percent of the AMA municipal water use.  (Since exempt wells are exempt from the Department’s reporting requirements, the actual amount of water use is unknown).  The number of exempt wells is expected to increase through parcel splits and dry lot developments, where each lot owner drills their own well due to the lack of a centralized water service.

Access to Renewable Water Supplies

Utilization of renewable supplies has increased over the past 20 years, facilitated by the construction of surface water treatment plants and completion of the CAP, allowing use of Colorado River water either directly or indirectly through artificial recharge and recovery projects.  Several issues are associated with using CAP water.  These issues include: limited CAP supplies; the need to construct new infrastructure to permit full utilization of supplies; financing of infrastructure; and the roles of the Central Arizona Groundwater Replenishment District (CAGRD) and the Arizona Water Banking

Authority (AWBA) to ensure long-term availability of renewable supplies for the AMAs.

As groundwater supplies diminish and more developments require groundwater replenishment or direct use of non-groundwater supplies pursuant to the AWS Rules, competition for renewable water supplies will increase. The debate on the reallocation of CAP Non-Indian Agricultural water is indicative of the level of interest in acquiring renewable supplies, even where they may be relatively expensive, subject to shortages, or available in small volumes.

Many CAP Municipal and Industrial (M&I) subcontractors lack direct access to CAP water and must utilize the resource indirectly through underground storage facilities, or groundwater savings facilities, located in close proximity to the CAP infrastructure. Because recovery is not required to occur in the area of replenishment, some areas may experience local water level declines and encounter physical availability limitations in the future. Funding for extension of the CAP canal in the Tucson AMA, as well as for water treatment and secondary infrastructure in all AMAs, limits direct renewable supply utilization in some areas.

Developers and water providers contract with the CAGRD to replenish groundwater withdrawals as required by the AWS Rules.  To meet its replenishment obligations to member lands and service areas the CAGRD competes for renewable water supplies with other users in the Phoenix, Tucson and Pinal AMAs. If the CAGRD cannot meet its obligations, its plan of operation is considered inconsistent with the AMA management goal, which could impact approval of AWS Certificates and jeopardize the status of AWS Designations.

CAP Canal in Phoenix

CAP Canal in Phoenix AMA

AMAs without access to CAP water (Prescott and Santa Cruz AMAs) must look to other water supplies in order to meet their management goals.  For the Prescott AMA, transporting alternative long-term supplies into the AMA is critical to achieving safe-yield in this groundwater-dependent AMA.  The only alternative supplies currently available are a limited amount of effluent, and  groundwater transported from the adjacent Big Chino Sub-basin pursuant to A.R.S. § 45-555.  In the Santa Cruz AMA access to both renewable and groundwater supplies is influenced by water demand in the large upstream community of Nogales, Sonora.  Some of this demand is offset by delivery and treatment of effluent generated in Mexico at the Nogales, Arizona, International Wastewater Treatment Plant (IWWTP), which discharges treated effluent to the Santa Cruz River near Rio Rico. However, there are currently no treaties or legal agreements regarding rights to the treated effluent nor for continued delivery and treatment of Mexican effluent at the IWWTP.

Effluent is a growing renewable resource in all AMAs, but physical distance between the location where the effluent is generated and the location of potential users, and lack of delivery infrastructure, limit its direct use in some areas. As with CAP water, recharge and recovery is utilized with similar concerns about the spatial disconnect between storage and pumping.

Legal Differences Between Groundwater and Non-Groundwater

Groundwater and surface water are managed under different statutes with limited integration and consistency in approach.  In the rapidly growing AMAs with multiple water sources, the statutory limitations on management of non-groundwater supplies may be problematic.  Water management efforts are currently fragmented because effluent, CAP water, surface water and groundwater are all regulated differently and in many cases owned or controlled by different entities.  An exception to fragmented water management is the Santa Cruz AMA, where legislation creating the AMA expressly addressed its unique hydrogeology and the inter-connection of surface and groundwater supplies.  Its management goal requires coordinated management of surface water and groundwater supplies to address seasonal and drought-sensitive conditions along the Santa Cruz River.

Environmental Protection

Restoration and preservation of riparian areas is a high priority in some AMAs.  Potential effects on these areas from ongoing groundwater pumping and surface water diversions are a concern.  These riparian areas function as natural recharge zones through streambed infiltration and can beneficially serve both environmental and water management objectives if managed appropriately.

Pinal AMA Development

Development in the Phoenix AMA

Local (Critical) Area Management

Management goals and programs currently apply to entire AMAs regardless of local conditions.  However, areas within AMAs may have specific critical concerns.  For example, hydrologic conditions can vary widely, from waterlogged areas to areas with severe groundwater overdraft that may result in land subsidence, earth fissures, and aquifer compaction.  Overdraft may affect water supply reliability for local groundwater users who lack access to renewable water supplies.

Salinity

The concentration of total dissolved solid (TDS) levels in CAP water, surface water and effluent can exceed that in native groundwater.  Typical TDS levels in Phoenix area reclaimed water range from 800 to 1400 mg/l compared to a range of 580 to 650 mg/l found in CAP water. Groundwater in the Phoenix area ranges from 200 to 5,000 mg/l (City of Phoenix, 2008). As these renewable supplies are increasingly utilized in the planning area, salinity levels will increase in both soil and groundwater.  Studies suggest there is an annual net gain of approximately 1.1 million tons of salts in the Phoenix area and about 100,000 tons in the Tucson area. (USBOR, 2003)

High salinity levels in water reduce its suitability for some uses, or may necessitate additional treatment. Salinity reduces the life of household appliances, may require water softening for some purposes, and can reduce crop yields.  Salt accumulation in agricultural area soils requires supplemental water to flush salts below plant root zones. Because salts become concentrated in wastewater, irrigation with reclaimed water may be problematic and its disposal increases salt-loading in groundwater. 

 

 

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