Clark County Assessment of Wadeable Streams, Clark County Clean Water Division

This project generates county-wide stream health data at a subwatershed scale appropriate to stormwater management efforts. Criteria for these determinations include the comparison of benthic macroinvertebrate and habitat data to aquatic life criteria.

Benthic Macroinvertebrate
The primary objective is to assess current stream conditions and trends using biological indicators. Results indicate whether significant water quality or habitat limitations are present, characterize baseline conditions, and can help describe changes in condition over an extended time period.

Benthic macroinvertebrate samples are collected following procedures described in the Washington State Department of Ecology Standard Operating Procedures and Minimum Requirements for the Collection of Freshwater Benthic Macroinvertebrate data in Wadeable Streams and Rivers (Washington State Department of Ecology, 2010).

Benthic macroinvertebrates are good indicators of stream health because of their potentially high numbers, known pollution tolerances, limited mobility, wide range of feeding habits, varied life spans, and dependence on the land environment around the stream. The species and number of macroinvertebrates present in a stream segment are used to calculate a Benthic Invertebrate Index of Biological Integrity (B-IBI) score (Karr, 1998; Karr and Chu, 1999) or other appropriate metrics.