ABSTRACT:
Many state and federal agencies have adopted a “watershed approach” for water quality assessment and management, and the U.S. Environmental Protection Agency (EPA) recommends using hydrologic units for this purpose. Watershed are important spatial units for studies of land-water relationships, but most hydrologic units are not watershed. More importantly, watersheds, basins, or hydrologic units do not correspond to the spatial patterns of regional characteristics, such as physiography, soils, vegetation, geology, climate, and land use that influence the physical, chemical, or biological nature of water bodies. For effective management strategies regarding protective water quality standards or restoration goals, these regional differences in ecological potentials should be considered. An ecoregion framework is an appropriate and necessary complementary tool for watershed assessment and management. Reference watersheds within ecoregions can be used to help set expectations, standards, and management practices. National, regional, and state examples illustrate the need to recognize the limitations of water quality assessments conducted solely within watershed or hydrologic unit frameworks.
Footnotes
Glenn E. Griffith is a geographer with the USDA Natural Resources Conservation Service; James M. Omernik is a research geographer with the U.S. Environmental Protection Agency National Health and Environmental Effects Research Laboratory; and Alan J. Woods is a geographer at Dynamac Corporation, all in Corvallis, Oregon. The research described in this manuscript has been partially funded by the U.S. EPA, and through contract 68–C6–0005 to Dynamac., It has been subjected to the Agency's peer and administrative review and approved for publication. The comments and views do not necessarily reflect official positions of the authors' current or former employers.
- Copyright 1999 by the Soil and Water Conservation Society
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