Monitoring the effects of forestry on streams: variable selection and the development of an expert system

An expert system, PASSSFA, has been developed to help select the most appropriate variables for monitoring the effects of extensive land use activities, particularly forestry, on streams. PASSSFA was initially developed for headwater streams in the northwestern U.S. and Alaska, but the consistency of the underlying principles make it much more broadly applicable. The selection process is based on the designated beneficial uses of concern, the type of management activity, accessibility during high flows, frequency of sampling, and the costs for equipment, data collection, and sample analysis. A total of thirty potential monitoring variables are considered, and these were selected because of their sensitivity to land management activities and their effects on key designated uses. Problems in developing PASSSFA and the use of expert systems are discussed.