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Watershed urbanization and managing stream habitat for fish
| Author: |
Imhof, Jack G.; Planck, R. John; Johnson, Fred M.; Halyk, Larry C. |
| Date: |
1991 |
| Periodical: |
In: Transactions of the 56th North American Wildlife and Natural Resources Conference; 1991 March 17-22; Edmonton, Alberta, Canada |
| Abstract: |
Rivers have been for many years used as sources of hydraulic power, irrigation, convenient conduits for waste water and human effluent, and transportation. Modification and deterioration of the aquatic environment, habitat and fish communities is not simply the result of development along a river but rather the cumulative changes of land use within the watershed of the river. Conventional urbanization appears to be the endpoint in a continuum of change that began in most watersheds with the modification of land that resulted from the first human settlements. Alteration and degradation of rivers has occurred through the modification of the hydrologic cycle of the river's watershed. Changes in the hydrologic character of a watershed acts to decouple the aquatic ecosystem from the terrestrial ecosystem by severing or impairing interactive biophysical pathways. To protect, manage and rehabilitate rivers and fish habitat in urbanizing watersheds requires a knowledge of the attributes of historically productive rivers, and understanding of river ecosystem theory and ecosystem stress theory. The complexity of issues dealing with the surface waters within an urban area often overwhelms the planners, engineers, biologists and ultimately the decision makers. Faced with a depressing array of seemingly contradictory goals such as flood protection, drainage, health, odor, safety, recreation, domestic water demands and natural environmental amenity, each discipline has responded by a simplification process. By simplification within each discipline the overall problems become partitioned into a set of sub-issues which allow a feeling of satisfaction within each discipline or interest group. The results are that engineers channelize, naturalists protect specific sites, and developers develop uplands. This fragmented approach has resulted in conflicts that arise continuously resulting in great environmental, economic and societal costs. Historically, biologists and naturalists acting within the planning and policy framework have focused upon the relatively small minor sites within a watershed that contain wetland or forested subsystems. While each of these areas may be important, they may have varying degrees of importance to the overall watershed ecosystem. Unfortunately the strong focus towards these sites, has deflected attention from ecosystem components which may be critical to the sustainability of the total system. These critical areas include recharge areas or areas which should be reinstated as biotic corridors coupling the terrestrial and aquatic systems. An ecosystem approach using the watershed as the logical geographical/ecological planning unit is recommended. By managing water as the integrator of biophysical processes within a watershed, ecosystem targets can be developed to balance the requirements for healthy, stable and productive rivers and terrestrial environments while still meeting human needs. |
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