Atmospheric emissions of sulphur and nitrogen outside national park and wilderness area boundaries in the western US threaten the ecological integrity of highly sensitive ecosystems. Based largely on the results of Environmental Protection Agency’s Western Lakes Survey, National Acid Precipitation Assessment Program concluded that many high-elevation western lakes were extremely sensitive to acidic deposition effects. Topographic relief is also a contributing factor to acidic deposition sensitivity in the West because the mountainous terrain contributes to major snowmelt events that may cause episodic pH and Acid neutralizing capacity depressions. Geology, soils, aquatic systems, vegetation, and fauna are highly variable at both large and small spatial scales owing to the complex mountainous topography of this region. The Rocky Mountains are rugged glaciated mountains with many peaks up to 4,500 m in elevation. Mountainous topography is generally highly dissected with intervening valleys and plateaus.