Chapter 5.6, Page 2 of 4

Alluvial Aquifer

The alluvium of the Gunnison River basin consists of clay, silt, sand, gravel, and cobbles. Alluvial deposits are very thin or nonexistent in the canyon areas of the main stem of the Gunnison River and tributaries, for example down river of the town of Gunnison to the confluence with North Fork Gunnison River.

Alluvial deposits are essentially nonexistent in steep canyon areas
within the Black Canyon of the Gunnison.
Photo by L. Scott, CGS.

Alluvial thickness is variable in the Gunnison-Crested Butte area, ranging from less than 10 to about 140 feet, with less than 30 feet in the tributary valleys. In the lower Gunnison River basin, the thickness of alluvium is rarely greater than 200 feet and generally less than 100 feet. Well depths along the Gunnison River range from less than 10 feet to greater than 150 feet below ground surface. The Division of Water Resources well permit database contains records for approximately 1,844 wells that have been completed in the Gunnison River alluvium. Over 90 percent of these wells are completed at depths less than 100 feet below ground surface, with a mean depth of 49 feet. A listing of reported alluvial well depths along the Gunnison River and its tributaries is presented in Table 5.6-1.

Table 5.6-1. Reported alluvial well depths along the Gunnison River and its tributaries.

Stream Reach

Alluvial Well Depth (feet)

East River


Ohio Creek


Tomichi Creek


Gunnison River

20 to 103

Lake Fork Gunnison River

25 to 60

Uncompahgre River

6 to 160

From Apodaca and Bails, 2000

Chapter 5.6, Page 2 of 4