Chapter 6.2, Page 2 of 4

Hydrogeologic Units

The principal bedrock aquifers in the northern portion of the Piceance Basin are the saturated, porous members of the Uinta Formation and Parachute Creek Member of the Green River Formation (both of Tertiary age). The thickness of Tertiary-age rocks in the Piceance Basin varies from 2,000 to approximately 12,000 feet. Of lesser importance are the Fort Union aquifer and Mesaverde aquifer. Physical descriptions and hydrologic characteristics of the primary aquifers in the Piceance Basin are summarized in Table 6.2-1. South of the Colorado River, the upper Tertiary-age aquifers have largely been eroded off, exposing a thick basal confining unit of the lower Green River and Wasatch Formations. As such, most water supply wells in the southern portion of the Piceance Basin are completed in the alluvial aquifers associated with the Colorado and Gunnison River tributaries.

The Roan Cliffs expose hundreds of feet of the Green River Formation.
Photo by V. Matthews, CGS.

Table 6.2-1 Hydrogeologic Units of the Piceance Basin

Chapter 6.2, Page 2 of 4