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Hydrology of the Lake Havasu Basin

Groundwater Hydrology

Colorado River Basins

The Colorado River Basins include the Lake Havasu and Lake Mohave basins and those portions of the Sacramento Valley and Bill Williams basins in the vicinity of the Colorado River. In these areas the direction and occurrence of groundwater are influenced by the amount of streamflow in the Colorado River.  Infiltration of river water is the main source of inflow to aquifers in this area.  The aquifers are composed primarily of recent stream alluvium deposits that is hydraulically connected to underlying basin fill.  Groundwater occurs under unconfined conditions in both the stream alluvium and basin fill.

Lake Havasu Basin

The Lake Havasu Basin is a relatively small basin with its western boundary defined by the Colorado River. Extensive areas of the basin are covered by consolidated rock.  Basin fill, consisting of sand, silt and gravel, overlies the Bouse Formation (siltstone and fine-grained sandstone) and an underlying conglomerate unit.  These deposits decrease in thickness toward the basin margin. Most wells in the basin penetrate the upper 100-200 feet of the basin fill.  There is a direct hydraulic connection between the basin fill and the Colorado River, with groundwater occurrence and movement near the river controlled by the elevation of Lake Havasu. The lake elevation is relatively constant with a maximum fluctuation of approximately five feet during the period 1990-2008 (USBOR, 2009). 

Regional groundwater flow is north to south. Groundwater recharge is estimated at 35,000 AFA with an estimated 1.0 to 2.0 maf of groundwater in storage.  Water withdrawals from wells are primarily pursuant to Colorado River entitlements. Median well yields are relatively high at 1,500 gpm. Water level data for one public supply well showed a decline of 15 to 30 feet between 1990-91 and 2003-04.  Drinking water standard exceedences are primarily due to elevated concentrations of nitrate/nitrite and organics measured in the vicinity of Lake Havasu City.

Click to view Table 4.5-5

Click to view Table 4.5-5 Groundwater Data for the Lake Havasu Basin

Click to view Figure 4.5-6

Click to view Figure 4.5-6 Lake Havasu Basin Groundwater Conditions

Click to view Figure 4.0-5

Figure 4.0-5 Upper Colorado River USGS Watersheds

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. 

Davis Dam

Davis Dam, Lake Mohave Basin.  Parker and Davis dams have created lakes that affect groundwater conditions along the Colorado River.

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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