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 (see Figure 4.0-2). 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).

Hualapai Valley Basin

The Hualapai Valley Basin trends north-northwest and is about 60 miles long, stretching from the Hualapai Mountains to Lake Mead. The basin has relatively deep, sediments divided into three units. The younger basin fill includes recent streambed deposits in Hualapai Valley and alluvium along mountain canyons.  This unit yields relatively small volumes of water to stock and domestic wells.  The intermediate basin fill, which is composed of coarse-grained sands, silts and clays, is a dependable aquifer only along the valley margins where the unit intersects the water table.  As with other basins in this category, the older basin fill is the primary water supply.  Similar to the Detrital Valley Basin located to the west, older basin fill in the northern part of the valley includes clastic sediments, limestone and basalt flows of the Muddy Creek and Chemehueve Formations.  Volcanic rocks are interbedded with the older basin fill in the southern part of the basin and yield water for municipal and domestic purposes. Groundwater flows into the central part of the basin from the south and along Truxton Wash near Hackberry (Figure 4.4-6).  Surface water collects in the Red Lake playa bear the center of the basin, whereas groundwater flows to the north underneath the topographic divide near Pierce Ferry Road (Anning and others, 2007).

Groundwater recharge comes primarily from streambed infiltration and is estimated at 2,000 to 3,000 AFA (Table 4.4-4).  Groundwater discharge is to several major springs and from relatively large volumes of well pumpage for municipal use by Kingman.  The well pumpage is are almost three times the estimated groundwater recharge rate. Groundwater in storage estimates range widely from 3 to 21 maf. Median reported well yields are relatively high at 900 gpm (Table 4.4-4). In the central and northern part of the basin groundwater levels were relatively stable or rising between 1990-91 and 2003-04 while water levels were declining in the southern part of the basin (Figure 4.4-6). Water-level measurements over longer time periods show fluctuating water levels in the basin with long-term declines found in the area northwest of Hackberry (Anning and others, 2007).  Groundwater is highly mineralized in some areas near the mountains and near Red Lake.  Chromium has been detected in some wells in the basin.

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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