Groundwater Hydrology

West Basins

The West basins include the Detrital Valley, Hualapai Valley, and Meadview basins, most of the Sacramento Valley Basin and part of the Bill Williams Basin.  Groundwater inflow and outflow are small and there is almost no stream baseflow.  These basins contain extensive areas of basin fill deposits that comprise the primary groundwater bearing unit (aquifer).

Sacramento Valley Basin

Sloping alluvial fans extend from surrounding mountains to the north-south trending valley floor of the Sacramento Valley Basin. The valley floor generally slopes to the south with elevation ranging from more than 8,400 feet at Hualapai Peak to about 500 feet where Sacramento Wash enters the Colorado River. Older basin fill is the principal aquifer in the basin. There are fractured and faulted volcanic rocks in the vicinity of Kingman that separate this basin from the Hualapai Valley Basin. Water stored in the fractures is used as part of the municipal water supply for Kingman and for domestic wells. The fractured granite aquifer beneath the community of Chloride is insufficient to meet its needs and water must be hauled from Kingman. Groundwater flow is toward the center of the Sacramento Valley and west to the Colorado River.

Groundwater recharge is from infiltration of runoff in washes and along mountain fronts, except in the vicinity of the Colorado River where infiltration of river water is the main source of recharge. Groundwater recharge is estimated at 1,000 to 4,000 AFA. Groundwater discharge is to a number of springs and from municipal and industrial well pumpage.  Groundwater in storage estimates range from 7 to 14 maf.  Recent investigations using a range of specific yield values estimated 3.6 to 9.5 maf of groundwater in storage to a depth of 1,200 feet bls (Conway and Ivanich, 2008). Median well yields are between 100 and about 170 gpm (Table 4.9-6).  Groundwater levels may be relatively deep with depths greater than 500 feet measured at several locations. Water levels declined in measured wells in the vicinity of Kingman and east of Topock between 1990-91 and 2003-04 (Figure 4.9-6).  Water-level measurements over longer time periods show fluctuating water levels in the basin with long-term declines in the Kingman area and Golden Valley area (Anning and others, 2007). 

Groundwater quality is generally good in the basin except along the base of the mountains where waters of high mineral content are common. A study conducted by ADEQ found water quality exceedences in the majority of sample sites in three areas: near the town of Chloride; in the central and southern Hualapai Mountains; and near the town of Topock (ADEQ, 1999). Concentrations of radionuclides in Chloride town wells have exceeded Safe Drinking Water Act maximum contaminant levels (City of Kingman, 2003). 

Click for Figure 4.9-6 Sacramento Valley Basin

Groundwater Conditions

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 unit code corresponds to accounting units, which are used by the USGS for designing and managing the National Water Data Network. 

Lower Colorado below Lake Mead Watershed

This watershed covers parts of two planning areas.  The northern portion is within the Upper Colorado River Planning Area (north watershed) and the southern portion is located in the Lower Colorado River Planning Area.  Groundwater basins included in the north watershed are the Lake Havasu Basin and most of the Lake Mohave and Sacramento Valley basins.  A very small portion of Detrital Valley Basin also lies within the north watershed.  Sacramento Wash, an ephemeral wash in the Sacramento Valley Basin, is the only major contributing tributary to the Colorado River in the north watershed.  Sawmill Canyon, located at the northeastern edge of the Sacramento Valley Basin, is the only intermittent stream (Figure 4.9-5).

Parker and Davis dams have created lakes that also affect groundwater conditions along the Colorado River.  Parker Dam is located in the Lower Colorado River Planning area but the lake it creates, Havasu, extends into the Upper Colorado River Planning Area.  Davis Dam, north of Bullhead City, creates Lake Mohave.  There is outflow from the river and lakes into the surrounding aquifers.  Maximum storage in Lake Mohave is about 1.8 maf (including dead storage) and average storage from 1996 to 2005 was 1.65 maf.  Maximum storage in Lake Havasu is 651,000 acre-feet (including dead storage) and average storage from 1996-2005 was about 572,000 acre-feet.

The only streamgages in the north watershed are along the Colorado River.  Streamflow is largely subject to releases from upstream dams.  A gage at Topock reports median annual flow of 8.9 maf, a gage below Davis Dam reports median annual flow of 8.5 maf, and median annual flows below Hoover Dam are 9.2 maf.

Twenty-four major springs are found in the north watershed.  These springs are located in the northern half of the Sacramento Valley Basin and in the Lake Mohave Basin along the Colorado River immediately below Hoover Dam.  Only three of the major springs have had a measured discharge rate of 100 gpm or greater.  There are a relatively large number of minor springs (42) in the Sacramento Valley Basin.  The most recent spring measurements were taken in 1979 and some measurements date to the 1940s.

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