thinking about watersheds, which are fairly obvious, understandable landscape units. Ecosystems are far harder to draw on a map with any precision and even federal agencies have drawn different lines in dividing the nation into ecoregions (GAO, 1994). As Adler (1996) points out:
. . . ecological boundaries often cannot be identified with precision, and depending on the aquatic resources of greatest concern, a variety of potential aquatic ecosystem boundaries exist— ''salmonsheds" versus "ducksheds," for example. After adding terrestrial ecosystems, the situation becomes even more complex. should programs focus on the boundaries of aquatic ecosystems (watersheds, ducksheds, or salmonsheds), on plant ecosystems (forestsheds), or on the ring of key terrestrial species (bearsheds).
Of course, neither ecosystem boundaries nor watershed boundaries are matched to the political boundaries that are the most common basis for resource management decisionmaking, which leads to many difficulties in implementing such approaches. In fact, rivers were often used as boundaries in creating political divisions, thus actually cutting watersheds in half. Political boundaries are important in delineating the areas by which much of the demographic, cultural, and economic data are collected and analyzed in the nation. They also set the limits of political and legal authority, and set the policies by which natural resources of the area are governed. Awareness of boundaries—political and physical—is thus essential for both understanding the advantages and disadvantages of a watershed approach to decisionmaking and for overcoming barriers to implementation of such approaches.
The notion of watersheds as the basic unit for management of water resources is not new and a watershed approach is being used in many places in the United States to protect and enhance natural resources. However, watersheds are rarely the primary unit used for management because neither national nor local decisionmaking infrastructures are designed to address the complex biophysical, sociological, and economic interactions that occur within watersheds.
Over the past 20 years, the nation's greatest achievement in the field of water management has been enormous reduction in pollution from point sources, with some notable water quality improvements. Yet major portions of our lakes, rivers, wetlands, estuaries, and coastlines do not meet current water quality standards. The unfortunate results of continued impairment can be seen in the decline of fisheries, loss of biodiversity, and curtailment of commercial and recreational activities in watersheds across the country (Wayland, 1993). Programs focused on addressing particular problems, contaminants, or types of activities can be helpful, but are by definition limited. Lasting solutions to many remaining water quality and environmental problems require an integrated management approach