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

Vertical Hydraulic Conductivity Measurements in the Denver Basin,
Coloradol
PETER E. BARKMANN2
1. Manuscript received September 1, 2004; Accepted September 17, 2004
2. Colorado Geological Survey, 1313 Sherman, Room 715, Denver, CO 80203; e-mail: [e-mail]
ABSTRACT
The Denver Basin is a structural basin on the eastern flank of the Rocky Mountain Front Range, Col-
orado, containing approximately 3000 ft of sediments that hold a critical groundwater resource supplying
many thousands of households with water. Managing this groundwater resource requires understanding
how water gets into and moves through water - bearing layers in a complex multiple - layered sedimentary
sequence. The Denver Basin aquifer system consists of permeable sandstone interbedded with imperme-
able shale that has been subdivided into four principle aquifers named, in ascending order, the Laramie -
Fox Hills, Arapahoe, Denver, and Dawson aquifers. Although shale can dominate the stratigraphic
interval containing the aquifers, there is very little empirical data regarding the hydrogeologic properties
of the shale layers that control groundwater flow in the basin. The amount of water that flows vertically
within the basin is limited by the vertical hydraulic conductivity through the confining shale layers. Low
vertical flow volumes translate to low natural recharge rates and can have a profound negative impact on
long -term well yields and the economic viability of utilizing the resource.
To date, direct measurements of vertical hydraulic conductivity from cores of fine - grained sediments
have been published from only five locations; and the data span a wide range from 1x10-3 to 1x10-11
cm /sec. This range may be attributable, in part, to differences in sample handling and analytical meth-
ods; however, it may also reflect subtle differences in the lithologic characteristics of the fine - grained
sediments such as grain -size, clay mineralogy, and compaction that relate to position in the basin. These
limited data certainly call for the collection of additional data.
INTRODUCTION .........................169
THE DENVER BASIN AQUIFER SYSTEM ........171
GROUNDWATER FLOW WITHIN THE
DENVER BASIN AQUIFER SYSTEM ...........173
VERTICAL HYDRAULIC CONDUCTIVITY
MEASUREMENTS ........................176
SaintVrain Core ..........................177
Castle Pines Core .........................177
INTRODUCTION
The Denver Basin is a structural basin on the eastern flank
of the Rocky Mountain Front Range. In eastern Colorado,
approximately 3000 ft of section within this structural basin
holds a critical groundwater resource that supplies hundreds
Kiowa Core . ............................177
Parker Core . ............................179
SPDSS Core . ............................180
DISCUSSION . ............................180
RECOMMENDATIONS FOR ADDITIONAL
DATA COLLECTION ......................182
REFERENCES . ............................183
of thousands of households with water. Extending south
from Greeley to Colorado Springs and east from Golden to
Limon, the Denver groundwater basin covers an area of
nearly 6700 mil (Fig. 1). Encompassing much of the Denver
metropolitan region, the water resource within these basin -
fill sediments is being increasingly exploited, particularly
The Mountain Geologist, Vol. 41, No. 4 (October 2004), p 169 -183 169 The Rocky Mountain Association of Geologists