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Hydrology of the Upper Colorado River Planning Area - Groundwater (Highland Basins)

Havasu National Wildlife Refuge

Colorado River, Lake Mohave Basin

The Upper Colorado River Planning Area is characterized by semi-arid to arid alluvial basins with few perennial streams.  Anderson, Freethey and Tucci (1992) divided the alluvial basins in south-central Arizona into categories based on similar hydrologic and geologic characteristics.  These categories are useful in describing general hydrologic characteristics.  Although their study area does not match the Department’s groundwater basins exactly, the Upper Colorado River Planning Area is included in their study area with the exception of the Peach Springs Basin. Four basin categories identified by Anderson are represented in the planning area and are discussed: West, Colorado River, Highland and Southeast.

As shown in Figure 4.0-4, there are extensive areas of sedimentary and volcanic rocks of various ages throughout most of the planning area. Large areas of basin fill deposits are found in the western part of the planning area, primarily in the West basins.

Highland Basins

The aquifers of the Highland Basins, which generally encompass the northeastern portions of the Big Sandy and Bill Williams , consist of hydraulically connected basin fill and younger stream alluvium.   These aquifers tend to be discontinuous and limited in extent.  Groundwater inflow is from stream channels, mountain front recharge and adjacent consolidated rock aquifers.  Groundwater outflow is due to evapotranspiration and baseflow to streams (Anderson, Freethey and Tucci, 1992).

Big Sandy Basin (northeastern portion)

In this portion of the Big Sandy Basin, generally the Fort Rock Sub-basin, (see Figure 4.1-6), the primary hydrologic unit consists of sedimentary rocks composed of Redwall Limestone (a coarse-grained, massive limestone) and the Martin Formation (a fine- to coarse-grained dolomitic limestone).  The limestones form a regional aquifer that extends north and east.  There is little water development in this portion of the Big Sandy Basin and groundwater flow direction has not been reported.  Well yields in three wells varied from 100 to over 1,000 gpm.  In this area, water levels were stable in most wells measured between 1990-91 and 2003-04, with water levels ranging from about 130 to 860 feet bls (Figure 4.1-6).  Water quality measurements from three wells in the southern portion of the Fort Rock sub-basin showed drinking water exceedences of arsenic and cadmium.


Bill Williams (eastern portion)

Groundwater in the eastern portion of the Bill Williams Basin, generally the Burro Creek, Santa Maria and Skull Valley sub-basins (see Figure 4.2-6), is found in basin fill, in fractured and porous volcanic rocks and in younger stream alluvium.  In the Peeples Valley area, the stream alluvium is the main water-bearing unit.  An important water-bearing unit in the Copper Basin area east of Skull Valley is a 1,000-foot thick layer of volcanic rocks with reportedly high well yields in the upper 350 to 400 feet.  Other sources of groundwater are from faults in granite and metamorphic rocks.  Groundwater flow in the Skull Valley Sub-basin is to the southwest in the northern part, and to the northwest south of Kirkland (Figure 4.2-6). 

Santa Maria River

Santa Maria River, Bill Williams Basin

(Eastern Portion)

Groundwater recharge occurs from streamflow and mountain front precipitation. Most groundwater development is in the Skull Valley Sub-basin and at Bagdad although most of the water used at Bagdad for mining operations is transported from the Big Sandy Basin near Wikieup. Well yields in this portion of the basin are generally less than those in the western portion with a number of wells yielding less than 100 gpm (Figure 4.2-8). Median well yield for the entire basin, reported from large diameter (>10 inch) wells, is 280 gpm.  Water level measurements are available primarily for wells located in the Skull Valley Sub-basin. These show relatively shallow water levels in most measured wells (<100 feet bls). Water level change data was not available for most wells in the sub-basin for the period 1990-91 to 2003-04, but was relatively stable for the few wells measured during this period (Figure 4.2-6).  Drinking water standard exceedences in this area are generally due to elevated concentrations of fluoride, arsenic and radionuclides.



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