ABSTRACT
To date, the Water Quality Assessment (WQA) mandated by national legislation (the Clean Water Act) is the most comprehensive dataset summarizing water quality on a national and statewide level. The assessment is the principal means by which the U.S. Environmental Protection Agency (EPA), Congress, and the public evaluate water quality, the progress made in maintaining and restoring water quality, and the extent of remaining problems. The procedures for developing the assessment database 334 and the methods for evaluating and reporting assessment results are being improved to facilitate better rep011ing of water quality conditions. Here we present the results of our work with the WQA in California (CWQA) for Sierra Nevada rivers and streams. By attaching assessment database records to the EPA River Reach File, we have developed a more usable form of the statewide assessment. The CWQA spatial database is a Geographic Information System (GIS) which will enhance resource managers’ ability to visually depict water quality conditions associated with specific rivers and to analyze these conditions to evaluate possible sources of impairment. An analysis of the resultant CWQA for the Sierra Nevada demonstrates the strength and weaknesses of the spatial dataset in its current format. In addition, a preliminary regional comparison of water quality problems and restoration project locations and issues illustrates how the CWQA spatial database can be incorporated into regional analyses that support watershed management decisions.
