By Joyce E. Williamson and Janet M. Carter
Water-Resources Investigations Report 01-4194
Prepared in cooperation with the
South Dakota Department of Environment and Natural Resources and the West Dakota Water Development District
This report summarizes the water-quality characteristics of ground-water and surface-water in the Black Hills area. Differences in groundwater quality by aquifer and differences in surfacewater quality by water source are presented. Ground-water characteristics are discussed individually for each of the major aquifers in the Black Hills area, referred to herein as the Precambrian, Deadwood, Madison, Minnelusa, Minnekahta, and Inyan Kara aquifers. Characteristics for minor aquifers also are discussed briefly. Surface-water characteristics are discussed for hydrogeologic settings including headwater springs, crystalline core sites, artesian springs, and exterior sites.
To characterize the water quality of aquifers and streams in the Black Hills area, data from the U.S. Geological Survey National Water Information System water-quality database were examined. This included samples collected as part of the Black Hills Hydrology Study as well as for other studies within the time frame of October 1, 1930, to September 30, 1998. Tables of individual results are not presented in this report, only summaries. Constituents summarized and discussed include physical properties, common ions, nutrients, trace elements, and radionuclides. Comparisons of concentration levels are made to drinking-water standards as well as beneficial-use and aquatic-life criteria.
Ground water within the Black Hills and surrounding area generally is fresh and hard to very hard. Concentrations exceeding various Secondary and Maximum Contaminant Levels may affect the use of the water in some areas for many aquifers within the study area. Concentrations that exceed Secondary Maximum Contaminant Levels (SMCL’s) generally affect the water only aesthetically. Radionuclide concentrations may be especially high in some of the major aquifers used within the study area and preclude the use of water in some areas. The sodiumadsorption ratio and specific conductance may affect irrigation use for some wells.
High concentrations of iron and manganese are the only concentrations that may hamper the use of water from Precambrian aquifers. The principal deterrents to use of water from the Deadwood aquifer are the high concentrations of radionuclides as well as iron and manganese. Iron, manganese, and hardness may deter use of water from the Madison aquifer as well as dissolved solids and sulfate in downgradient wells (generally deeper than 2,000 feet). Iron, manganese, and hardness may also deter use of the Minnelusa aquifer. Water from the Minnekahta aquifer generally is suitable for all water uses although it is hard to very hard. High concentrations of dissolved solids, iron, sulfate, and manganese may hamper the use of water from the Inyan Kara aquifer. In the southern Black Hills, radium-226 and uranium concentrations also may preclude use of water from the Inyan Kara aquifer. Suitability for irrigation may be affected by high specific conductance and sodium-adsorption ratio for the Inyan Kara.
Surface-water quality within the Black Hills and surrounding area generally is very good but the water is hard to very hard. Concentrations of some constituents in the study area tend to be higher exterior to the Black Hills, primarily due to influences from the Cretaceous-age marine shales, including dissolved solids, sodium, sulfate, selenium, and uranium. Headwater springs have relatively constant discharge, specific conductance, dissolved solids, and concentrations of most other constituents.
Concentrations at crystalline core sites are very similar to those found in samples from Precambrian aquifers. Some high nitrate concentrations greater than the Maximum Contaminant Level (MCL) of 10 mg/L (milligrams per liter) have occurred at Annie Creek near Lead, which have been attributed to mining impacts. Trace elements generally are low with the exception of arsenic, for which 60 percent of samples exceed the proposed MCL of 10 µg/L (micrograms per liter) and one sample exceeds the current MCL of 50 µg/L. The SMCL’s for iron and manganese also have been exceeded in some samples. Artesian springs have very constant discharge and specific conductance at each site but show some variability between sites. Dissolved solids concentrations exceeding the SMCL of 500 mg/L and sulfate concentrations exceeding the SMCL of 250 mg/L are common for these sites.
Low dissolved oxygen concentrations in surface waters only occur at sites exterior to the Black Hills where high temperature and low flow occasionally are problematic. About 66 percent of the samples from sites exterior to the Black Hills exceed 1,000 mg/L sulfate. Concentrations exceeding the arsenic MCL, the selenium aquaticlife criterion, and the iron and manganese SMCL’s occasionally occur at these sites. Radionuclide data are limited, but higher uranium concentrations are found for the areas exterior to the Inyan Kara Group outcrop.
Occasionally very low pH levels are recorded immediately downstream from abandoned mine sites but generally are within acceptable ranges once they mix with additional stream water. Changes in specific conductance, sodium, and sulfate in Bear Butte Creek occurred after additional mining activities in a tributary basin. Bear Butte Creek also had exceedances of the acute and chronic copper aquatic-life criteria for several samples between 1992-94. Within-basin changes for Rapid Creek follow the general trend of increasing concentrations for most constituents. Nutrient levels are low but do show an increase, indicating that land-use practices, both urban and agricultural, may be affecting the stream.
Download the PDF version of the report (8.8MB).
Sections available in pdf:
Cover Titlepage TOC 65KB
Purpose and Scope
Description of Study Area
Physiography and Climate
Sampling Sites and Methods
Water-Quality Characteristics of Selected Aquifers
Inyan Kara Aquifer
Inyan Kara Aquifer
Inyan Kara Aquifer
Summary for Aquifers in Relation to Water Use
Water-Quality Characteristics of Selected Surface-Water Sites
Summary for Surface-Water Groups in Relation to Water Use
For additional information write to:
U.S. Geological Survey
1608 Mt. View Road
Rapid City, SD 57702
Copies of this report can be purchased from:
U.S. Geological Survey
Box 25286, Federal Center
Denver, CO 80225-0286
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Last modified: Thursday, September 01 2005, 02:03:45 PM