The Mountain Geologist

• Year: 2004
• Title: The Mountain Geologist
• Author: Rocky Mountain Association of Geologists
• Description: October 2004, Volume 41, Number 4
• Publications - Doc Type: Other

Aquifers of the Denver Basin, Coloradol
RALF TOPPER2
1. Manuscript received September 2, 2004; Accepted September 14, 2004
2. Colorado Geological Survey, 1313 Sherman Street, Room 715, Denver, CO 80203; e -mail: [e-mail]
ABSTRACT
Development of the Denver Basin for water supply has been ongoing since the late 1800s. The Denver
Basin aquifer system consists of the water - yielding strata of Tertiary and Cretaceous sedimentary rocks
within four overlying formations. The four statutory aquifers contained in these formations are named
the Dawson, Denver, Arapahoe, and Laramie -Fox Hills. For water rights administrative purposes, the out-
crop /subcrop of the Laramie -Fox Hills aquifer defines the margins of the Basin. Initial estimates of the
total recoverable groundwater reserves in storage, under this 6700 -mi2 area, were 295 million acre -ft.
Recent geologic evidence indicates that the aquifers are very heterogeneous and their composition varies
significantly with distance from the source area of the sediments. As a result, available recoverable
reserves may be one -third less than previously estimated. There is no legal protection for pressure levels
in the aquifer, and water managers are becoming increasingly concerned about the rapid water level
declines (30 ft /yr). Approximately 33,700 wells of record have been completed in the sedimentary rock
aquifers of the Denver Basin for municipal, industrial, agricultural, and domestic uses.
INTRODUCTION .........................145 WATER LEVELS AND WATER STORAGE ......147
LOCATION AND GEOLOGIC SETTING ........146 GROUNDWATER WITHDRAWALS ..........149
HYDROGEOLOGIC UNITS ..................146
INTRODUCTION
Once the driving force operating the elevators in the
Brown Palace Hotel and running the bellows for the Trinity
Church organ, the underground waters of the Denver Basin
have been put to beneficial use since the late 1800s (Van
Diest, 1891). To further the understanding of this resource,
evaluations of the geology and hydrology of the formations
in the Basin soon followed (Cross et al., 1884; Emmons et
al., 1896). By the early 1980s, more than 1,800 reports deal-
ing with the geology and hydrology of the Denver Basin
had been published (Robson, 1987). The importance of the
Denver Basin, as a major bedrock aquifer system, in the
State of Colorado for supplementing limited surface water
resources is well documented (Topper et al., 2003)•
This special issue of The Mountain Geologist focuses on
this tremendous and controversial groundwater reservoir.
Invited papers contained herein present the geology and
hydrology of the Denver Basin, the regulatory framework
established for the administration of water rights, structural
and stratigraphic relationships influencing the basin's
hydrogeology, recharge /discharge considerations, and
innovative technologies available to optimize groundwater
withdrawals. This introductory paper establishes the frame-
work for understanding the hydrogeology of the aquifers
in the Denver Basin and the demands placed on this
resource. Much of the information presented here is
derived from the Denver Basin chapter of the recently
published Groundwater Atlas of Colorado by the Colorado
Geological Survey (Topper et al., 2003). That atlas is a
comprehensive, map -based publication that presents the
location, geography, geology, water quality, and hydro-
logic characteristics of the state's major aquifers in an artis-
tic, understandable manner.
7heMountain Geologist, Vol. 41, No. 4 (October 2004), p 145 -152 145 The Rocky Mountain Association of Geologists