Selecting Reference Condition Sites - An Approach for Biological Criteria and Watershed Assessment

This talk describes the Oregon Department of Environmental Quality's approach to selecting reference condition sites. The purpose of selecting reference condition sites is to establish an objective and systematic method for finding water bodies minimally disturbed by human activities for a given region. The approach consists of using geographic information systems (GIS) and site specific information to characterize human disturbance. Selected reference sites are then used to describe "reference condition" for a specific region for the purposes of stream and watershed assessment. Site selection involves three steps: 1.) Pre-screening, which involves selecting a region, identifying the primary natural gradients, and using GIS information and best professional judgment to identify watersheds with minimal human disturbance. 2.) Site visits which are used to record reach level human disturbance and together with delineated watershed geographic information is used to score a Human Disturbance Index (HDI). 3.) Site verification involves reviewing the disturbance information and sampling data. While reference site selection is not based on in-stream conditions, final verification includes an evaluation of the biological, physical habitat, and water quality data for outliers that might indicate unidentified problems. Verification is completed with the assignment of a "site classification" grade.