Introduction to SWQAs

In 2002, the National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey (USGS) implemented Source Water-Quality Assessments (SWQAs) to characterize the quality of selected rivers and aquifers used as a source of supply to community water systems (CWS) in the United States. These assessments are intended to complement drinking-water monitoring required by Federal, State, and local programs, which focus primarily on post-treatment compliance monitoring.

The primary objective of SWQAs is to determine the occurrence of about 280 primarily unregulated anthropogenic organic compounds in source water used by community water systems. Source water is the raw (ambient) water collected at a supply well or surface-water intake prior to water treatment used to produce finished water. A secondary objective is to understand occurrence patterns in source water and determine if these patterns also occur in finished water prior to distribution.

The NAWQA program is planning as many as 30 surface-water and 30 ground-water assessments through 2013.

Surface-water assessments will monitor raw and finished water monthly to characterize seasonal variability in water-quality conditions. In addition, samples will be collected during critical timeframes when water-quality conditions may change quickly and (or) when larger concentrations of contaminants most likely will occur. Similarly, each ground-water assessment will monitor raw and finished water of 15 supply wells. Wells that have no treatment associated with them will be avoided.