Groundwater Hydrology

Other Basins

Peach Springs Basin

The Peach Springs Basin was not included in the study area of  Anderson, Freethey and Tucci (1992).  This basin is characterized by an upland area to the west, the Hualapai Plateau,  composed of interbedded limestones, shales and sandstones, and by Aubrey and Truxton Valleys that are filled with recent lava flows and alluvial material (See Figure 4.8-1).  The Muav Limestone is the main water-bearing unit on the Hualapai Plateau where depths to groundwater may be as much as 1,300  feet bls.  Groundwater is limited to a few permeable layers in the basin’s two primary valleys.  In Aubrey Valley in the far northeastern part of the basin near Frazier Wells, groundwater is found in gravel beds at relatively shallow depth.  In Truxton Valley, lake-bed deposits are a local source of groundwater.  In other areas of the basin, Precambrian rocks, isolated volcanic rocks and local alluvial sands in washes provide small amounts of water. Groundwater flow is toward the north where it exits the basin at springs emanating from the Muav Limestone in the Grand Canyon.  Groundwater flow in Aubrey Valley south of Frazier Wells may be from north to south (Myers, 1987).

An annual groundwater recharge estimate is not available for the basin. The estimated volume of groundwater in storage ranges from 1.0 maf to more than 4.0 maf. Data from the southern part of the basin show well yields ranging from less than 100 gpm up to 1,000 gpm.  Water levels vary from 60 feet bls east of Truxton to over 1,300 feet bls northwest of Audley (Figure 4.8-6). Hydrographs of four wells in the basin show relatively stable water level conditions (Figure 4.8-7). Most of the water quality data shown in Table 4.8-7 is from springs, with arsenic most frequently exceeding the drinking water standards.

Click for Figure 4.8-6 Peach Springs Basin

Groundwater Conditions

Click for Figure 4.8-7 Peach Springs Basin

Hydrographs Showing Depth to Water in Selected Wells

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. 

Lower Colorado- Lees Ferry to Lake Mead Watershed

The Lower Colorado River-Lees Ferry to Lake Mead watershed is located in the Western Plateau Planning Area and in the northern portion of the Upper Colorado River Planning Area.  Included within the Upper Colorado River Planning Area portion of the watershed are the Hualapai Valley and Meadview basins, almost all of the Detrital Valley Basin, all but the far eastern portion of the Peach Springs Basin and the northernmost part of the Big Sandy Basin.

The major north-flowing tributaries to the Colorado River in the Upper Colorado River Planning Area portion of the watershed are Hualapai Wash and Detrital Wash.  These washes are ephemeral and contribute little to the flow of the Colorado River.  The other major wash is Truxton Wash in the Peach Springs and Hualapai Valley basins, which flows north to Red Lake, a dry lake.  The Colorado River is the only perennial water supply in the part of the  watershed in the planning area.  There is only one intermittent stream, a portion of Truxton Wash, located in Peach Springs Basin (AZGF, 1997 & 1993).

Lake Mead, created by Hoover Dam, has affected groundwater conditions in adjacent basins in the watershed.  There is outflow from the lake into the surrounding aquifers.  Lake Mead extends from Hoover Dam in the Lake Mohave Basin, along the planning area boundary to Peach Springs Basin.  Maximum storage in Lake Mead is 29.7 maf.  Of this, approximately 2.38 maf is “dead storage” - the reservoir capacity from which stored water cannot be evacuated by gravity.  The average storage during the period from 1996 to 2005 was 20.3 maf. 

Red (Dry) Lake, Hualapai Valley Basin.  The Colorado River is the only perennial water supply in the portion of the Lower Colorado - Lees Ferry to Lake Mead Watershed in this planning Area.

Twenty-four major springs (springs with a measured discharge rate of 10 gpm or greater at any time) are found in the watershed, primarily located in the Peach Springs and Meadview basins. Generally, springs with the greatest discharge are located in the Hualapai Plateau in the Peach Springs Basin, where discharges of 1,730 gpm at Spencer Spring and 1,233 gpm at Meriwhitica Spring have been measured.  With the exception of a number of springs measured in the early 1990s, particularly in the Peach Springs Basin, most of the spring measurements were recorded over 30 years ago and may not reflect current conditions.  For example, recent discharge measurements taken at two “major” springs in the Peach Springs Basin were less than 10 gpm. (See Springs tables in each basin section.)

There is only one streamgage in the watershed at Spencer Creek near Peach Springs.  Median flows at this gage are about 1,500 AFA.

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