chapter  4
30 Pages

Candidate Reference Conditions

Our nation’s need to improve the condition of streams is mandated by Congress in the Federal Water Pollution Control Act and as modified as the Clean Water Act (CWA, 33 U.S.C. Section et seq.). The objective of both acts is “to restore and maintain the chemical, physical and biological integrity of the nation’s waters.” (CWA, Section 101(a), 33 U.S.C., 1251(a), 1999). To meet these objectives, the law requires states to develop and enforce water quality criteria based on biological assessment (bioassessment) in accordance with methods published by the Environmental Protection Agency (EPA), whenever numerical criteria for toxic pollutants are unavailable (CWA, Section 303(c) (2)(B), 33 U.S.C., Section 1313(c)(2)(B), 1999). The law also requires streams to be assessed for nonpoint source pollution (NPS; CWA, Section 319, 33 U.S.C., Section 1329, 1999), and that the current quality of surface waters and the extent that they will support wildlife be reported to the EPA (CWA, Section 305(b)(1)(B), 33 U.S.C., Section 1313(c)(2)(B), 1999). To support these requirements the EPA has published guidelines on developing bioassessments, the Rapid Bioassessment Protocols for Use in Streams and Wadeable Rivers: Periphyton, Benthic Macroinvertebrates, and Fish (Barbour et al. 1999); and biocriteria, Biological Criteria: Technical Guidance for Streams and Small Rivers (Gibson et al. 1996). Bioassessments, and their resulting

Background of Bioassessment and the Reference Condition .................................. 35 Characterizing Reference Conditions: Selection of Regional Reference Sites........36 Assessing Anthropogenic Impact on Stream Quality Using the Synoptic

Approach .............................................................................................................40 Data Sources and Preprocessing .............................................................................. 42 Data Analysis ...........................................................................................................44 Assessment of Reference Sites ................................................................................ 47 Geographic Information System (GIS)-Selected Reference Sites or Best

Professional Judgment (BPJ)? ............................................................................. 51 Conclusions .............................................................................................................. 59 References ................................................................................................................ 62

way of integrating the chemical, physical, and biological effects on water quality by directly measuring biologic integrity and indirectly measuring physical and chemical integrity. This indirect measurement of chemical integrity may actually be more representative of the true integrity of the stream than base flow chemical data since chemical composition varies widely over time, both seasonally and during storm flows (Bolstad and Swank 1997; Johnson et al. 1997).