The Columbia River Estuary and the Columbia River Basin Fish and Wildlife Program Independent Scientific Advisory Board

The Northwest Power Planning Council (Council) requested the Independent Scientific Advisory Board (ISAB) to undertake a review of the impacts of estuarine conditions on the Council's mission to " protect, mitigate and enhance " fish and wildlife in the Columbia River as affected by development and operation of the hydroelectric system. The ISAB agreed to undertake the review but cautioned that it was unlikely that it could quantify the impact of changes in the estuary relative to specific program or management actions taken in the upper river. The ISAB could, however, provide a historical perspective and qualitative assessment of impacts, identify potentially useful collaborations, and provide recommendations concerning future efforts needed to more quantitatively address this issue (letter to Council, Jan. 26, 2000). While conducting this review the ISAB became aware that there was extensive overlap between a study by the National Marine Fisheries Service (NMFS) and this ISAB assignment. The ISAB expects the NMFS study will add significantly to an informed response to the Council. Consequently, this report has been prepared as a preliminary reply, with additional detail possible following publication of the NMFS study. Before human influence, the Columbia River estuary was a high-energy environment dominated by physical forces, with extensive sand-beds and highly variable river flows. Several authors have suggested that the biological processes in this environment may have been unique on the Pacific coast. The estuary of today, however, has been extensively modified in terms of physical and biological processes. The development and operation of the hydroelectric system have contributed significantly to these changes. Direct effects have been through changes in seasonal flow rates, reduced sediment discharge, and resultant changes in the estuary's energy balance. There is extensive documentation about changes in the estuary over the past century. The major changes resulting from development of peripheral wetlands and their isolation from the estuary, development and deepening of the Federal Navigation Channel, and regulation of upper Columbia River flows for hydrosystem needs and flood control. The effects of these changes do not function discretely. The estuary is a complex interaction of physical features (predominated by the energy balance between river flow and tidal forces), resultant changes in circulation, salinity intrusion, sediment processes, and ultimately the biological consequences of these changes. Superimposed on this dynamic environment have been changes in water quality, introduction of exotic species, and the enormous investment in hatchery production of salmonids to mitigate for …