Water Supply of the Eastern Plateau Planning Area - Groundwater

Surface water, groundwater and effluent are important water supplies for municipal, industrial and agricultural uses in the Eastern Plateau Planning Area.  Discussed here is the largest water supply, Groundwater.

Groundwater

Groundwater is withdrawn from both large regional aquifers and from local and perched aquifers.  The location of registered exempt and non-exempt wells is shown in Figure 2.0-16. Flagstaff pumps groundwater from perched water bearing zones within the upper 500 feet or in the deeper C-aquifer (Woody Mountain and Lake Mary wellfields and inner city wells) and from shallow volcanic aquifers in the Inner Basin. Depth to water in C-aquifer wells ranges from approximately 1,200 to 1,600 feet bls. In 2005, Flagstaff purchased the Red Gap Ranch east of the city as a potential source of groundwater supplies. The USBOR (2006) reported sustainable or safe yield volumes from the city’s various groundwater supplies as follows: Woody Mountain wellfield, 3,500 AFA; Lake Mary wellfield, 2,500 AFA; inner city wells, 1,300 to 2,800 AFA; and inner basin wells, 542 AFA.

The cities of Holbrook and Winslow rely entirely on groundwater pumped from the C-aquifer.  Groundwater from the C-aquifer and from local aquifers (Bidahochi, Lakeside-Pinetop and White Mountain aquifers) is the principal water supply for municipal use in the Mogollon Rim region, including the communities of Heber, Pinetop-Lakeside, Show Low, Snowflake, Springerville, Eagar, Saint Johns and Greer.

North of the Little Colorado River, including on the Navajo and Hopi reservations, the N-aquifer, which is of good quality, is the primary water supply.  In this area the C-aquifer is generally too deep and saline to be used.  The D-aquifer underlies much of the Hopi and Navajo reservations and is utilized in some areas; however water quality is marginal due to elevated concentrations of dissolved solids.  The community of Cameron pumps highly saline groundwater from wells near the Little Colorado River and treats it for use.

Click here for the Groundwater Site Inventory (GWSI) database

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The Department’s Groundwater Site Inventory (GWSI) database, the main repository for statewide groundwater well data, is available on the Department’s website (www.azwater.gov/).  The GWSI database consists of over 42,000 records of wells and over 210,000 groundwater level records statewide. GWSI contains spatial and geographical data, owner information, well construction and well log data and historic groundwater data including water level, water quality, well lift and pumpage records.  Included are hydrographs for statewide index wells and automated groundwater monitoring sites, which can be searched and downloaded to access local information for planning, drought mitigation and other purposes.  Approximately 1,700 wells are designated as index wells statewide out of over 43,700 GWSI sites. (GWSI sites are primarily well sites but include other types of sites such as springs and drains). Typically, index wells are visited once each year by the Department’s field staff to obtain a long-term record of groundwater level fluctuations. Approximately 200 of the GWSI sites are designated as automated wells. These systems measure water levels four times daily and store the data electronically. Automated groundwater monitoring sites are established to better understand the water supply situation in areas of the state where data are lacking.  These devices are located based on areas of growth, subsidence, type of land use, proximity to river/stream channels, proximity to water contamination sites or areas affected by drought.

Volume 1 of the Atlas shows the location of index wells and automatic water-level recording sites as of January 2009.  At that time there were a total of 94 index wells and four ADWR automatic water-level sites in the Eastern Plateau Planning Area.  The automated sites are located at Flagstaff, Joseph City, east of Holbrook and south of Saint Johns. The most updated maps may be viewed at the Department’s website.

Information on major aquifers, well yields, estimated natural recharge, estimated water in storage, aquifer flow direction, and water level changes are found in the groundwater data table, groundwater conditions map, hydrographs and well yield map are found in Section 2.1.5-Groundwater Conditions.

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