In the Globe-Miami area the Gila Conglomerate, composed of semi-consolidated to consolidated basin-fill sediments, forms a local aquifer. The Gila Conglomerate is up to 4,000 feet thick in this area and provides most of the area’s municipal and industrial water supply. A limestone aquifer also supplies water in the Globe-Miami area, and west of Globe several small basin-fill deposits form isolated groundwater aquifers (ADWR, 1992). Well yields are generally low in the southeast part of the sub-basin near Globe, and higher north of Globe. Granitic rocks provide small amounts of water for domestic and stock use in the sub-basin.
Mining activities in the Globe-Miami area have impacted water quality in the alluvial aquifer along Pinal Creek and Miami Wash including elevated concentrations of sulfate and metals. Drinking water standards for cadmium, chromium, fluoride, lead, other metals and for total dissolved solids (TDS) have been equaled or exceeded in a number of wells in the area.
Salt River Canyon Sub-basin
In the western portion of the Salt River Canyon Sub-basin, sedimentary and igneous rocks, similar to those in the adjacent Salt River Lakes Sub-basin, are found. The groundwater flow system is complex with disconnected recharge areas and many water-bearing zones (USGS, 2005a). The rest of the sub-basin is composed primarily of sedimentary rocks, including limestones, sandstones, siltstones, shales and thin conglomerates. These rocks are exposed along the Mogollon Rim and at other locations in the sub-basin. The Natanes Plateau, along the southern boundary of the sub-basin, is composed of volcanic rock. There is little aquifer data for the area, but based on similar rock units in other areas, there may be useable amounts of water in the Supai Formation, Redwall Limestone, Coconino Sandstone and the undivided sandstones in the sub-basin. These formations may yield moderate amounts of water, up to 100 gpm, however yields can vary widely depending on sub-surface geology (ADWR, 1992). Recharge to the sedimentary rocks occurs mainly along the Mogollon Rim.
Basin-fill and floodplain alluvial deposits are present along Cherry Creek near the western boundary of the sub-basin. The depth of basin-fill deposits in this sub-basin was estimated to be less than 400 feet thick (ADWR, 1992). The only water level change data for the 1990-’91 to 2003-’04 time-period showed a modest water level decline in a shallow well near Young. Well yield data for the sub-basin show yields of less than 100 gpm to up to 2,000 gpm in the western part of the sub-basin (Figure 5.2-9). Water quality data are lacking for this sub-basin.
White River Sub-basin
The eastern portion of the White River Sub-basin is covered with volcanic rocks and the western portion contains sedimentary rocks similar to those found in the Salt River Canyon Sub-basin. Groundwater occurs in fracture zones and the various volcanic flows, including cinder beds. Groundwater flow in the volcanic aquifer is discontinuous and well yields and water levels may vary widely over short distances. Precipitation in the area is relatively high and recharges the volcanic aquifer through infiltration into the fractured rock. Groundwater discharged from the volcanic aquifer contributes to the baseflow of the White River. Groundwater level and water quality data are lacking for the sub-basin. The only well yield data shows a yield between 100 and 500 gpm in a well between Whiteriver and Hon-dah (Figure 5.2-9).
Black River Sub-basin
The Black River Sub-basin is covered almost entirely by volcanic rocks that include basalt flows, rhyolitic ash flows, tuffs and tuffaceous agglomerates that form layers over 3,000 feet thick in some areas. Wells in this area are generally low-yield and well depths of 400 to 800 feet are common. As in the White River Sub-basin, the volcanic aquifer is recharged through infiltration of precipitation. Discharge from the aquifer contributes to baseflow in the Black River. Groundwater level data are lacking for this sub-basin. Well yield data for two wells shows yields of less than 100 gpm in the northeastern part of the sub-basin and between 500 to 1,000 gpm south of Fort Apache. A single groundwater quality measurement taken at Hannagan Meadow showed a nitrate concentration exceeding drinking water standards.