ASSESSING GLOBAL RIVER WATER-QUALITY - CASE-STUDY USING MECHANISTIC APPROACHES

Rivers, like the atmosphere and oceans, are integrative and reflect conditions within their boundaries. Critical to an understanding of the role of human activity in environmental change is an understanding of the impact of human activity an river quality and how river quality may be used as an indicator of environmental change. Current data collection practices, based largely on the traditional parametric or ambient fixed-station network approach, do not generally provide the information necessary to relate human activity to quality of river water or to utilize water quality data as an indicator of global environmental change. What is needed is an alternative approach which permits development of valid cause and effect relationships. This strategy, one involving intensive surveys, is referred to here as mechanistic. The Willamette River, Oregon, USA, is used as a case study to illustrate quantitative, semi-quantitative and qualitative approaches to mechanistic assessment of river water quality using, respectively, dissolved oxygen depletion, erosion/deposition and potentially toxic trace elements as examples.