Groundwater Hydrology

North/Northeastern Portion

Groundwater basins located in the north and northeastern portion of the planning area are Bonita Creek, Dripping Springs Wash, Duncan Valley, Morenci and Safford. The Safford Basin aquifers are primarily stream alluvium and basin fill, while the other basins also contain aquifers composed of volcanic rock or sedimentary rock (Gila Formation). Groundwater flow is toward the Gila River drainage and the Bonita Creek, Duncan Valley and Morenci basins contribute underflow to the Safford Basin. 

Dripping Springs Wash Basin

Dripping Springs Wash is a mountainous basin containing small sediment-filled valleys with relatively little groundwater in storage. The largest valley is north of the Gila River and drained by Dripping Springs Wash. Water producing units consist of younger alluvium and the Gila Conglomerate, with the younger alluvium along Dripping Springs Wash and its tributaries the major water producer. These deposits are reportedly less than 150 feet thick. Consolidated rocks compose the surrounding mountains and contain minor amounts of groundwater. Groundwater flow is towards the Gila River which bisects the basin (Figure 3.6-6). Groundwater recharge has been estimated at 3,000 to 9,000 AFA and groundwater in storage at less than 1maf. Well yields vary widely with a median well yield of about 394 gpm reported (Figure 3.6-6). Recent water quality data are lacking.

Surface Water Hydrology

The U.S. Geological Survey (USGS) divides and subdivides the United States into successively smaller hydrologic units based on hydrologic features.  These units are classified into four levels. From largest to smallest these are: regions, subregions, accounting units and cataloging units.  A hydrologic unit code (HUC) consisting of two digits for each level in the system is used to identify any hydrologic area (Seaber et al., 1987).  A 6-digit code corresponds to accounting units, which are used by the USGS for designing and managing the National Water Data Network.  There are portions of five watersheds in the planning area at the accounting unit level: Lower Colorado River below Lake Mead; Middle Gila River; Rio Bavispe; San Pedro River; Santa Cruz River; and the Upper Gila River (Figure 3.0-5). 

Click to view Table 3.6-6 Groundwater Data for the

Dripping Springs Wash Basin

Click to view Figure 3.6-6 Dripping Springs Wash Basin Groundwater Conditions

Click to view Figure 3.0-5 USGS 6-Digit Hydrologic Unit Code Boundaries in the Southeastern Arizona Planning Area

Middle Gila

The Middle Gila Watershed extends west from Coolidge Dam to the confluence of the Gila and Salt rivers in the Phoenix AMA.  The San Pedro River is the major tributary to this watershed in the Southeastern Arizona Planning Area.  Dripping Springs Wash, Donnelly Wash and the northernmost part of the Lower San Pedro basins are included in the Watershed.  Below Coolidge Dam, flow in the Gila River is from releases from the San Carlos Reservoir and flood flow from the San Pedro River (ADWR, 1994). Perennial streams include the Gila River, and portions of the San Pedro River and Mineral Creek in the Lower San Pedro Basin, Box Canyon in the Donnelly Wash Basin and Mescal Creek in the Dripping Springs Wash Basin (see Figures 3.8-6, 3.5-5 and 3.6-5).

Since 1936, an average of 260,000 AFA of reservoir storage and inflows have been released to the river below Coolidge Dam (ADWR, 2006).  There are three streamgages in the watershed. The highest annual flow was recorded at the Kelvin gage where a flow of 2.375 maf was measured in 1993. Annual median flow at this gage is approximately 324,300 acre-feet (see Table 3.8-2). This gage is located downstream of the confluence of the San Pedro and Gila rivers.

There are two major (10 gpm or greater) springs in the watershed, both located in the Dripping Springs Wash Basin. Both are warm springs with measured discharges of 200 gpm (Mescal Warm Spring) and 165 gpm (Coolidge Dam Warm Spring). These measurements were taken during or prior to 1982 and may not be indicative of current conditions.

Ten miles of Mineral Creek, located northwest of Kearny, are impaired due to elevated concentration of copper and selenium.

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