Methods for evaluating potential sources of chloride in surface waters and groundwaters of the conterminous United States

Abstract

The purpose of this report is to provide information about potential sources of chloride, water and solute budgets, and methods for collecting water-quality data to help identify potential sources of chloride in the surface waters and groundwaters of the conterminous United States. This study was done by the U.S. Geological Survey (USGS), in cooperation with the Federal Highway Administration (FHWA), because scientists, engineers, regulators, and decisionmakers need this information for the evaluation of potential sources of chloride in areas where chloride may have adverse ecological effects or may degrade water supplies used for drinking water, agriculture, or industry. Knowledge of potential sources can help decisionmakers identify the best mitigation measures to reduce the total background chloride load, thereby reducing the potential for water-quality exceedances caused by superposition on rising background concentrations. Also, knowledge of potential sources may help decisionmakers identify the potential for the presence of contaminants that have toxic, carcinogenic, mutagenic, or endocrine-disrupting effects at concentrations that are lower by orders of magnitude than the chloride concentrations in the source water.