High -elevation watershed characterization and sensitivity analysis: Science as a basis for watershed protection *policy.

摘要

Water resource managers in the mountainous western U.S. must address water quality problems caused by rapid economic and population growth, but are hampered by a lack of scientifically-based management tools. The sensitivity of high elevation catchments to ecological stressors compounds management challenges. Furthermore, outdated institutional frameworks conflict with the realities of watersheds adding to difficulties in effectively managing water resources.;The watershed protection project in San Miguel County of southwest Colorado was an example of innovative new approaches to watershed management in the New West. The San Miguel River watershed faces typical western water management problems including acid mine drainage and reduction of in-stream flows. San Miguel County is typical in its influx of new residents and rapid increase in recreational tourism. County planners sought to implement policy based on science to prevent future degradation of headwater catchments while allowing reasonable economic and recreational activities.;During the summer of 1997, I studied high-elevation catchments in the San Miguel River Basin to assess sensitivity to water quality degradation, and develop a scientifically-based tool for water resources management. I mapped landscape types and associated water quality parameters with those types, enabling sensitivity assessment at the landscape unit scale, and so addressing catchment heterogeneity. Landscape type maps and derived sensitivity maps were entered into a geographic information system (GIS). The maps proved effective visual tools in policy decisions and public presentations.;Water quality issues addressed were sensitivity to acidification and sensitivity to nutrient enrichment. Landscape types with associated surface waters having acid neutralizing capacity (ANC) < 50 mueq L-1 were considered sensitive to acidification, and included talus and mining related areas. Landscape types sensitive to nutrient enrichment were those with associated surface waters having average growing season nitrate (NO3-) concentrations >9. 0 mueq L -1, and included tundra, talus, and rock glaciers.;Using the results of my study, San Miguel County commissioners adopted regulations for restricting development in sensitive high-e1evation areas, including limits on building footprints and bans on septic systems. Adoption of these regulations lays the foundation for future application of this approach to headwater catchments in other western U.S. locations.