Chapter 5.5, Page 2 of 3

Alluvial Aquifer

The White River alluvium generally consists of silty sand and rounded gravel and cobbles derived from sandstone, quartzite, basalt, and granite from the eastern mountains, whereas alluvium in the tributaries is finer-grained material of a local origin. Researchers report the width of the alluvial aquifer ranges from 0.1 to 1.5 miles and averages 0.5 miles (Fig. 5.5-2). The saturated thickness of the White River alluvium ranges from 0 feet at the valley edge to more than 140 feet, with an overall average of 22 feet. In the Meeker area the average saturated thickness is 54 feet. West of Meeker the saturated thickness ranges from 14 to 90 feet and averages 17 feet.

5.5-2 Geologic cross section of the White River alluvial valley near Rangely.
Modified from Van Liew and Gesink, 1985.

The Colorado Division of Water Resources well permit database identifies 75 alluvial wells of record that are completed at a depth of less than 150 feet in the White River basin. The majority of the alluvial wells are concentrated east and west of Meeker. Reported alluvial well depths ranged from a minimum of 7 feet to a maximum of 147 feet, with the majority of these wells completed at depths between 10 and 70 feet.

Water Levels/Aquifer Characteristics

For the alluvial wells of record with reported water levels, those levels ranged from a minimum of 3 feet to a maximum of 90 feet below ground surface. Though the alluvium is generally a water table aquifer, near-surface accumulations of alluvial silts and clays can produce local semi-confined conditions for the underlying coarse-grained alluvial aquifer.

Van Liew and Gesink (1985) report yields from alluvial wells generally less than 25 gallons per minute (gpm). East of Meeker, the average yield is 17 gpm, and between Meeker and Rangely the average yield is 10 gpm with a few wells able to yield 60 gpm for short periods of time. For the alluvial wells of record with the Division of Water Resources, the data indicate that nearly 90 percent of the wells produce less than 33 gpm.

A listing of reported values of transmissivity for the alluvium in the White River basin is presented in Table 5.5-1.

Table 5.5-1. Reported transmissivity values for the White River basin alluvium.

Reported Transmissivity ft2/d
Meeker municipal well field 10,000 - 93,000
West of Meeker 1,700 – 2,100
East of the confluence with Piceance Creek 3,300
Northwest of Rangely 860

From Van Liew and Gesink (1985)


Chapter 5.5, Page 2 of 3