A study of high-elevation catchments in the San Miguel River Basin of southwest Colorado was conducted during the summer of 1997 to develop a scientifically based tool for water resources management. The authors mapped landscape types and associated water quality parameters with those types, enabling sensitivity assessment at the landscape unit scale, thus addressing catchment heterogeneity. Landscape-type maps and derived sensitivity maps were entered into a geographic information system (GIS). They proved effective visual tools for use in policy decisions and public presentations. Water quality issues addressed were sensitivity to acidification and nutrient enrichment. Landscape types associated with surface waters having growing season acid neutralizing capacity (ANC) < 50 μeq/L were considered sensitive to acidification and included talus and mining-related areas. Types sensitive to nutrient enrichment were those having average growing season NO₃⁻ concentrations > 9.0 µeq/L, and included tundra, talus, and rock glaciers. Using the results of this study, San Miguel County commissioners adopted regulations for restricting development in sensitive high-elevation areas, including limits on building footprints and bans on septic systems. The adoption of these regulations lays the foundation for future application of this approach to headwater catchments in other western US locations.