The U.S. Geological Survey (USGS) and the Federal Highway Administration (FHWA) are currently cooperating in a national project to evaluate Chloride in the Nations Waters. The Chloride (Cl) ion is receiving increasing attention as population growth makes increasing demands on available water resources and anthropogenic activities increase solute loads in natural waters. Cl is a growing concern because anthropogenic inputs may increase Cl concentrations to the USEPA taste criterion for potable waters (250 mg/L) and to the USEPA suggested limits of 230 mg/L for chronic aquatic life exposure and 860 mg/L for acute aquatic life exposure in surface waters. The Cl ion is ubiquitous in natural waters, has a wide variety of sources, readily moves through surface and groundwaters, and is difficult to remove from runoff and water supplies. Cl concentrations in natural waters range from less than 1 mg/L in pristine water bodies without atmospheric or geologic Cl sources to about 275,000 mg/l in continental brines. This national synthesis is a cooperative effort between the USGS and Federal Highway Administration designed to provide the information necessary for watershed managers to assess all potential sources of Cl in a given watershed as part of a total water and solute budget. This will include information necessary to develop a localized water budget; to develop water-quality transport curves; to estimate natural, agricultural, and anthropogenic sources of Cl; to examine interrelationships among water-quality constituents and to use the National Water Information System Web to identify and interpret available groundwater, surface-water and water-quality data. This effort also will provide a summary of field methods including geophysical techniques and automated monitoring of runoff, streamflow, and groundwater.

FHWA Natural Environment Web Page

This effort is an offshoot of the National Highway Runoff Water-Quality Data and Methodology Synthesis

For questions, comments, additions or suggestions contact:
Gregory Granato