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Groundwater-Level Elevations in the Denver Basin Bedrock Aquifers and Upper Black Squirrel Creek Alluvial Aquifer, El Paso County, Colorado, 2021–24

Scientific Investigations Report 2024-5123
Prepared in cooperation with Upper Black Squirrel Creek Ground Water Management District
By: , , and 
https://doi.org/10.3133/sir20245123

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Abstract

El Paso County is the second-most populous county in Colorado and is projected to grow another 15 percent by 2030. Within El Paso County is the Upper Black Squirrel Creek Designated Groundwater Basin (Black Squirrel Basin), an area where surface water is scarce and water users rely primarily on groundwater from five different aquifers (the Upper Black Squirrel Creek alluvial aquifer and four bedrock aquifers within the Denver Basin aquifer system: the lower Dawson, Denver, Arapahoe, and Laramie-Fox Hills aquifers) to meet their needs. Currently (2024), land within the Upper Black Squirrel Creek Basin is primarily used for rural grazing and agriculture; however, municipal development is ongoing.

In 2021, the U.S. Geological Survey, in cooperation with the Upper Black Squirrel Creek Ground Water Management District, began a study to establish a baseline dataset and assess the groundwater resources of the aquifers within the Black Squirrel Basin. A network of 39 wells was established in 2021; discrete groundwater-level measurements were made bimonthly. Nine of the 39 wells were equipped with pressure transducers to record hourly groundwater-level data. Seven wells had statistically significant seasonal trends, and trends at 3 wells were negative. For the discrete data, 16 wells had a significant trend for the study period, and 4 wells had negative trends. For the time-series data, 8 wells had significant trends, and 3 wells had negative trends.

Potentiometric surface maps were created for this study using discrete, static groundwater levels measured in April 2023. These maps showed the estimated groundwater flow direction from the north-northwest to the south-southeast in the alluvial aquifer and from the northwest to the east-southeast for the lower Dawson and Denver aquifer wells.

This study indicates the potential benefit of monitoring wells in the areas near municipal pumping. Additional monitoring could lead to a better understanding of connectivity between aquifers and be an important tool for assessing long-term sustainability of groundwater use.

Suggested Citation

Kisfalusi, Z.D., Hennessy, E.K., and Sharp, J.B., 2025, Groundwater-level elevations in the Denver Basin bedrock aquifers and Upper Black Squirrel Creek alluvial aquifer, El Paso County, Colorado, 2021–24: U.S. Geological Survey Scientific Investigations Report 2024–5123, 49 p., https://doi.org/10.3133/sir20245123.

ISSN: 2328-0328 (online)

ISSN: 2328-031X (print)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Study Methods
  • Groundwater-Level Elevations in Aquifers in the Upper Black Squirrel Creek Designated Groundwater Basin
  • Additional Research
  • Summary
  • References Cited
  • Appendix 1. Groundwater Well Measurement Diagram
  • Appendix 2. Hydrographs Showing Groundwater-Level Elevation Through Time for Wells in the Upper Black Squirrel Creek Designated Groundwater Basin, El Paso County, Groundwater-Level Monitoring Network
  • Appendix 3. Descriptions and Equations of Mann-Kendall Test, Seasonal Mann-Kendall Test, and Theil-Sen Slope Estimate
Publication type Report
Publication Subtype USGS Numbered Series
Title Groundwater-level elevations in the Denver Basin bedrock aquifers and Upper Black Squirrel Creek alluvial aquifer, El Paso County, Colorado, 2021–24
Series title Scientific Investigations Report
Series number 2024-5123
ISBN 978-1-4113-4591-1
DOI 10.3133/sir20245123
Year Published 2025
Language English
Publisher U.S. Geological Survey
Publisher location Reston VA
Contributing office(s) Colorado Water Science Center
Description Report: vii, 49 p.; Database
Country United States
State Colorado
County El Paso County
Online Only (Y/N) N
Google Analytic Metrics Metrics page
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