HYDROGEOLOGY
Generally, the direction of ground-water flow in the northeast flank of the Upper Verde River basin is to the southwest, toward the Verde River. Formation contracts and faults can act as impediments or conduits to flow, causing local deviations to the direction of flow. Recharge to the regional aquifer system occurs in the plateau highlands where the precipitation and aquifer permeability are greatest. The aquifer system discharges to springs and streams near the valley floor, and wells through the region (Owen-Joyce and Bell, 1983).
The principal aquifers in the study area are the Supai Formation and the Redwall Limestone. Within these aquifers, the primary source of ground water is the lower two members of the Supai Formation, and the fractures and caverns in the Redwall Limestone.
GROUND-WATER SURFACE
The elevation of the underground water table below the BPWC service area ranges from about 3,800 feet above mean sea level (ft, msl) along the northeastern edge of the service area to 3,700 ft. msl near the southwestern edge of the property. Depth to ground water ranges from approximately 300 to 450 feet below ground surface (ft, bgs). Water Resources Associates (1985) noted that although the unconfined aquifer conditions exist throughout the area, local well driller observations of ground-water levels suggest the possibility of confined and semi-confined conditions.
Historically, ground-water levels in the area have remained relatively constant. Historical water levels were available for four wells in the study area. Examination of the hydrographs reveals that water level trends increased over the period from 1975 to 1985, and decreased from 1985 to 1995. Water level trends range from a rise of 0.5 feet per year (ft/yr) to a decline of 0.3 ft/yr in two wells that cover the period from the mid 1970s to the mid 1990s.
Recent water level trends from 1993 to present, range from a rise of 0.9 ft/yr to a decline of 3.5 ft/yr. Although data for all but one of the wells show trends of declining levels over this period, water levels in most of the wells have risen since 1997. These wells are water production wells, therefore, water levels taken in them may be influenced by pumping and may not be representative of static conditions.
