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Open File-Report 2014-1022

Prepared in cooperation with the U.S. Air Force

Groundwater Level and Nitrate Concentration Trends on Mountain Home Air Force Base, Southwestern Idaho

By Marshall L. Williams

Thumbnail of and link to report PDF (3.1 MB)Abstract

Mountain Home Air Force Base in southwestern Idaho draws most of its drinking water from the regional aquifer. The base is located within the State of Idaho's Mountain Home Groundwater Management Area and is adjacent to the State's Cinder Cone Butte Critical Groundwater Area. Both areas were established by the Idaho Department of Water Resources in the early 1980s because of declining water levels in the regional aquifer. The base also is listed by the Idaho Department of Environmental Quality as a nitrate priority area.

The U.S. Geological Survey, in cooperation with the U.S. Air Force, began monitoring wells on the base in 1985, and currently monitors 25 wells for water levels and 17 wells for water quality, primarily nutrients. This report provides a summary of water-level and nitrate concentration data collected primarily between 2001 and 2013 and examines trends in those data.

A Regional Kendall Test was run to combine results from all wells to determine an overall regional trend in water level. Groundwater levels declined at an average rate of about 1.08 feet per year.

Nitrate concentration trends show that 3 wells (18 percent) are increasing in nitrate concentration trend, 3 wells (18 percent) show a decreasing nitrate concentration trend, and 11 wells (64 percent) show no nitrate concentration trend. Six wells (35 percent) currently exceed the U.S. Environmental Protection Agency's maximum contaminant limit of 10 milligrams per liter for nitrate (nitrite plus nitrate, measured as nitrogen).

First posted February 19, 2014

For additional information, contact:
Director, Idaho Water Science Center
U.S. Geological Survey
230 Collins Road
Boise, Idaho 83702
http://id.water.usgs.gov

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Suggested citation:

Williams, M.L., 2014, Groundwater level and nitrate concentration trends on Mountain Home Air Force Base, southwestern Idaho: U.S. Geological Survey Open-File Report 2014-1022, 49 p., https://dx.doi.org/10.3133/ofr20141022.

ISSN 2331-1258 (online)



Contents

Overview

The Problem

Study Area in Context

Monitoring Well Locations

Purpose of the Study

Background

Past Analysis and Studies

Trend Analysis

Criteria

Years of Water-Level Monitoring

Key Findings

Nitrate Concentration by MW Location

Summary Tables

Summary of Findings

Supplementary Information

References


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