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Active Management Area Water Supply - Groundwater

Groundwater is an essential water supply in the planning area. It is the primary water source in the Prescott and Santa Cruz AMAs, as these AMAs lack access to CAP water.  Water supplies are managed jointly as “groundwater” in the Santa Cruz AMA due to the close hydrologic relationship of surface water, groundwater and effluent. Until relatively recently, the Tucson AMA also relied primarily on groundwater to meet demand, and it still made up 74% of its water supply during 2001-2005. Groundwater is also a vital water supply for the Phoenix and Pinal AMAs, although currently, surface water supplies surpass groundwater supplies in both AMAs.  Groundwater is a relatively abundant water supply with the median of reported well yields exceeding 1,000 gpm in the Phoenix and Pinal AMAs and exceeding 600 gpm in the other AMAs.


Y Fissure - Cave Creek, Phoenix AMA.

As a result of long term groundwater pumping in the AMAs, moderate to severe regional and localized water level declines have occurred. Over time, groundwater declines can lead to increased pumping costs, decrease in water quality, riparian damage, land subsidence and land fissuring and permanent compaction of the aquifer, all of which have occurred in the planning area.  Localized groundwater level rises have also occurred in the last two decades at some locations, due to retirement of agricultural lands, use of CAP water in lieu of groundwater and a growing number of underground storage projects.

Pursuant to A.R.S. § 45-553, groundwater may be withdrawn from the Butler Valley Basin and transferred to an initial AMA. There are no limits on the volume of groundwater that may be transported from this basin.

A.R.S. § 45-552 allows groundwater in the Harquahala Basin pumped from historically irrigated acres owned by a political subdivision of the state to be transported for use in an AMA or use by the Arizona Water Banking Authority (AWBA).6 The volumetric limit is six acre-feet per acre per year or 30 acre-feet per acre for any ten year period. The director of ADWR may establish an alternative volume as long as it will not unreasonably increase damage to basin residents and other water users. The groundwater may not be withdrawn below 1,000 feet below bls nor at a rate that causes declines of more than an average of ten feet per year during the 100 year evaluation period. The City of Scottsdale has applied to the Department to transport 3,645 acre-feet of groundwater per year from historically irrigated acres in the Harquahala Basin to the Phoenix AMA. This application is currently still under review.

McMullen Valley

McMullen Valley Basin.  Groundwater may also be withdrawn from historically irrigated acres in the McMullen Valley Basin that were owned by a city or person prior to January 1, 1988 and transported to the Phoenix AMA.

Groundwater may also be withdrawn from historically irrigated acres in the McMullen Valley Basin that were owned by a city or person prior to January 1, 1988 and transported to the Phoenix AMA. (A.R.S. § 45-552). Qualified groundwater importers include cities, towns, private water companies and replenishment districts for their use or use by the AWBA.  The City of Phoenix owns 14,000 acres of agricultural land in the McMullen Valley Basin allowing it to transport a total of 6 maf of groundwater into the Phoenix AMA. The annual volume that may be withdrawn is limited to an average of 3 acre-feet per irrigated acre.  If this water is used for an assured water supply demonstration in the AMA, only water withdrawn above 1,000 feet bls at a rate not to exceed 10 feet per year over the 100 year period will be considered.

Under A.R.S. 45-555(E), the City of Prescott can withdraw and transport an amount of groundwater not to exceed 14,000 AFA from the Big Chino Sub-basin into the Prescott AMA.  The actual volume that can be transported during a year depends on several factors listed in the statute.  In 2007, the City of Prescott applied for Modification of Designation of Assured Water Supply to include transportation of Big Chino Sub-basin groundwater.  In November 2008 the Director of ADWR issued his decision that the City was entitled to transport 8,076.4 AFA of groundwater from the Big Chino Sub-basin and that this volume should be added to Prescott’s designation provided that a pipeline to transport the groundwater is constructed by December 31, 2019. 

The City of Prescott appealed the Director’s decision to the Office of Administrative Hearings, claiming it was entitled to transport a larger volume. Subsequently, an Administrative Law Judge (ALJ) recommended the volume be increased by 500 AFA to replace the Yavapai-Prescott Indian Tribe’s CAP allocation that was sold to Scottsdale. A number of residents of the Prescott AMA also appealed the Directors’ decision, contending that pumping by Prescott in the Big Chino Sub-basin would reduce the flows of the Verde River, causing negative impacts to endangered species and surface water users.  In a November 20, 2009 decision, the Director accepted the ALJ’s recommendation to grant Prescott’s application, but upheld his previous decision, determining that Prescott was not entitled to transport the additional 500 AFA from the Big Chino Sub-basin.

In addition to the groundwater the City of Prescott is allowed to transport under A.R.S. § 45-555(E), cities and towns in the Prescott AMA are allowed to withdraw groundwater associated with historically irrigated acres in the Big Chino Sub-basin and transport the groundwater into the Prescott AMA. (A.R.S. §45-555 (A) through (D))  The Department will make a determination regarding the volume of groundwater that a city or town can transport from historically irrigated acres lands after it has finalized Administrative Rules for this process.  The allotment associated with historically irrigated acres is three acre-feet per acre per year.

The Department’s Groundwater Site Inventory (GWSI) database, the main repository for statewide well data, is available on the Department’s website.  The GWSI database consists of records for over 42,000 wells and over 210,000 water level measurements. GWSI includes spatial and geographical data, owner information, well construction and geologic data, and historic water level, water quality, well lift and pumpage records. Also included are hydrographs for Index Wells and Automated Groundwater Monitoring Sites (Automated Wells), which can be searched and downloaded for planning, drought mitigation and other purposes.

Approximately 1,700 GWSI sites are designated as Index Wells (GWSI sites are primarily wells but include other types of sites such as springs and drains). Typically, Index Wells are visited once each year by Department field staff to obtain a long-term record of groundwater level fluctuations. Approximately 200 GWSI sites are designated as Automated Wells. In these wells  water levels are measured four times daily and the data stored electronically. Automated Wells were established to better understand the water supply situation in critical areas of the state.  These devices are located  in areas of growth, subsidence, along river/stream channels, and in areas affected by water contamination or drought.

Automated well in the Prescott AMA

Automated Well in the Prescott AMA.

Volume 1 of the Atlas shows the location of Index Wells and Automated Wells. As of December 2009 there were 72 of these wells in the planning area: 35 in the Phoenix AMA; 16 in the Prescott AMA; 11 in the Tucson AMA; six in the Santa Cruz AMA; and four in the Pinal AMA. Updated maps showing the location of Index and Automated wells (including automated wells operated by non-ADWR entities) may be viewed at the Department’s website.

Information on major aquifers, well yields, estimated natural recharge, aquifer flow direction, and water level changes are found in groundwater data tables, groundwater condition maps, hydrographs and well yield maps for each AMA in Sections 8.1.6, 8.2.6, 8.3.6, 8.4.6. and 8.5.6. 


water drop  Continue to Section 8.0.5  Water Supply - Effluent and Contamination Sites


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