Generalized Potentiometric Maps of the Fort Union, Hell Creek, and Fox Hills Aquifers within the Standing Rock Reservation

Scientific Investigations Map 3516
Prepared in cooperation with the Standing Rock Sioux Tribe of North & South Dakota
By:  and 



Generalized potentiometric surfaces of the Fort Union, Hell Creek, and Fox Hills aquifers were constructed to assess the groundwater resources of the Standing Rock Reservation. Additionally, this information can provide water managers with tools and data to effectively manage water resources in the future. Previous studies that mapped the geology and hydrogeology of the area at differing scales were used to confirm in which aquifer the study wells were completed. Water-level data from wells are provided by the U.S. Geological Survey Groundwater System Inventory database, the South Dakota Department of Agriculture and Natural Resources, and the North Dakota Department of Water Resources. Hydrographs were constructed for five selected observation wells to evaluate historical water-level fluctuations and trends. Hydrographs for the Hell Creek aquifer showed a flat trend with a rise in 2020. Hydrographs for the deeper Fox Hills aquifer showed that water levels fluctuated in response to climatic conditions and demonstrated an increasing trend in water-level elevations starting in 2010. Hydrographs were not constructed for any wells completed in the Fort Union Formation because none of the wells had continuous long-term measurements.

Generalized potentiometric surfaces, constructed from interpolating water-level elevations, gave insight into groundwater flow directions. Groundwater in the Fort Union aquifer likely flows radially outward from the northwest part of the study area to the northeast and south-southeast parts. Groundwater in the Hell Creek aquifer generally flows from higher elevations in the northwest towards lower areas, where surface-water tributaries have incised into the aquifer. Groundwater in the Fox Hills aquifer likely flows from higher elevations in the west, southwest, and central parts of the study area towards the valleys of the Grand River and Missouri River.

Most wells used for constructing potentiometric maps had only one recorded water-level measurement from drillers at the time of well construction. These measurements are often subject to error because the well is still recovering and because of spatial limitations of data availability. Also, because single water-level measurements were recorded at different points in time, additional uncertainty is introduced by fluctuating climatic conditions effect on water levels. Potentiometric map interpretation limitations are a result of areas with sparse data. Limitations also arise from potentiometric surfaces generalizing a complex and dynamic hydrogeologic system; however, the generalized potentiometric surface maps can be used to assist water managers and can help prioritize locations for future monitoring in areas with high uncertainty from sparse existing data.

Suggested Citation

Anderson, T.M., and Lundgren, R.F., 2024, Generalized potentiometric maps of the Fort Union, Hell Creek, and Fox Hills aquifers within the Standing Rock Reservation: U.S. Geological Survey Scientific Investigations Map 3516, 4 sheets, includes 13-p. pamphlet,

ISSN: 2329-132X (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Data and Methods
  • Data and Interpretive Limitations
  • Summary
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Generalized potentiometric maps of the Fort Union, Hell Creek, and Fox Hills aquifers within the Standing Rock Reservation
Series title Scientific Investigations Map
Series number 3516
DOI 10.3133/sim3516
Year Published 2024
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Dakota Water Science Center
Description Pamphlet: vii, 13 p.; 4 Sheets: 42.00 x 36.00 inches or smaller; Data Release
Country United States
State North Dakota, South Dakota
Other Geospatial Fort Union, Hell Creek, and Fox Hills aquifers, Standing Rock Reservation
Online Only (Y/N) Y
Additional Online Files (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details