DWR_2769958

• Title: GROUND WATER LEVELS IN THE DENVER BASIN BEDROCK AQUIFERS
• Year: 2014
• Document Type - Publications and Reports: Ground Water Levels Report

GEOLOGY OFTHE DENVER BASIN AQUIFERS
The Denver Basin i5the southern pOdjOn of much idrgerDenvepJube5burg 8d5jn that
extends northward into southern Wyoming and eastward into adjoining states (Fig. 1). For
groundwater resources administration, the Denver Basin is defined as the outcrop orsubcrop
of the base ofthe Laramie -Fox Hills aquifer, which encompasses an area ofapproximately
6,700 square miles. The administrative Denver Basin extends northward into Weld County
near Greeley, into the eastern portions of Adams, Arapahoe, and Elbert counties near Limon,
southward into Et Paso County near Colorado Springs, and is bounded on the west by the Front
Range mountains of Jefferson and Douglas counties' Figure 1 displays the geometry and
extent ofthe four main aquifers that comprise the Denver Basin aquifer system.
The Denver Basin aquifers are composed Ofsedimentary rock layers, up to 3,000 feet
thick in the deepest part of the basin. Generalized cross-sections showing the overlapping
geologic formations are shown in Figure 2. |ndescending order, the hydrogeo(oQicunits are
identified as the Dawson, Denver' Arapahoe, and Laramie -Fox Hills aquifers.
Extensive studies ofthese aquifers have been conducted for over 100 years. Water
from the aquifers has been used in the Denver area for commercial and domestic supplies
since the 188O`s' The administration of the Denver Basin aquifers is based on a detailed study
completed by the Colorado Division of Water Resources in 1985 as part of a legislatively
mandated study commonly known as Senate Bill 5' During the study, the staff 0fthe Division
collected extensive information on the nature ofthe aquifers' the occurrence of groundwater
in the aquifers, and the effects ofgroundwater pumping on surface streams throughout the
basin. The estimated amount of water contained in the aquifers is presented in Table 1'
Implementation of the South Platte Decision Support System (SPDSS) by the Colorado Water
Conservation Board also focused on updating the aquifer geometry, aquifer property, and
water level datasets of the Denver Basin. In 2011 the Colorado Geological Survey in
conjunction with the Denver Museum of Nature 6 Science produced two publications refining
our understanding of the geology of the water producing formations in the Denver Basin. Also
in 2011' the US Geological Survey published the results of a new numerical groundwater
model ofthe aquifer system.
4 brief discussion of each hydrogeo(ogic unit within the Denver Basin aquifer system is
presented below. For the purposes Ofgroundwater administration, the Division's Senate 8iii 5
study isrecognized dsthe authoritative study Ofthe Denver Basin aquifers.