DWR_2882819

• Title: GROUND WATER LEVELS IN THE DENVER BASIN BEDROCK AQUIFERS
• Year: 2002
• Document Type - Publications and Reports: Ground Water Levels Report

GEULUGY UF THE DENVER BASIN
The Den�er Basin is a structura� basin bounded by the Front Range on the west and
extends eastward to near Limon, Colorado. The basin's margin extends southward fr�m near
Greeley on the north to a location several miles to the south and east of Colorado Springs. In
total, the structural Den�er Basin includes an area of more than 6,700 square miles. The basin is
generally defined by the lower boundary of the Laramie-Fox Hills ayuifer which is the
lowermost of the four principal aquifers found in the basin. Figure 1 is a map of the Denver
Basin that identifies the lvwer boundary of each of the Den�er Basin aquifers.
The formations present in the basin that comprise the principal aquifers are composed of
sedimentary rocks that are up to 3,�00 feet thick in the deepest part of the basin. A generalized
cross-section is attached as Figure 3. In descending order, the hydrogeologic units are identified
as the Dawson, Denver, Arapahoe, and Laramie-Fox Hills aquifers.
Extensive studies of these aquifers ha�e been conducted over a period of about 100 years.
Water from the aquifers has been utilized in the Denver area for domestic supplies since the
1880's. The most recent and most detailed study of the aquifer system was completed by the
Cvlorado Division of Water Resources in 1985 as part of a legislatively mandated study
commonly known as Senate Bill 5. During the study, the staff of the Division collected
extensi�e information vn the nature of the aquifers, the occurrence of ground water in the
aquifers, and the effects of pumping ground water from the aquifers on surface streams
throughout the basin. The estimated amount of water contained in the aquifers is presented in
Figure 2.
The Colorado Division of Water Resources' study resulted in re-defining the aquifer
system into the four maj or aquifers currently recognized. For the reader to better understand the
aquifer system, a brief discussion of each hydrogeologic unit is presented below. I# should be
noted that the Division's work in this area is recognized as the authoritative study of the Den�er
Basin aquifers, and is utilized by the consulting community and governmentallregulatory
agencies.
DAWSUN AQUIFER
The Dawson aquifer is the uppermost aquifer in the basin and covers an area of
approximately 1,400 square miles. The aquifer varies in thickness, depending upon location, and
attains a maximum thickness of almos# 1,200 feet in the vicinity of Monument. The Dawson is
at or near the land surface throughout its entire areal extent. The aquifer is composed of
predominately conglomeratic, coarse-grained arkosic sandstones with minor amounts of
interbedded clay and clay shale. The northern portion of the aquifer can be subdivided into two
hydrogeologic units known as the Upper and Lower Dawson aquifers. This separation is based
on the presence of an approximately 50-foot thick shale layer that hydraulically isolates the
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