Temporal and Spatial Analysis of Climate Driven Deterioration of Acid Mine Drainage Impacted Watersheds Across Colorado

Mining in pyrite-rich host rock in Colorado has produced a legacy of acid rock and acid mine drainage, including toxic metal concentrations in affected watersheds. Localized observations in specific tributaries in Colorado indicate a 100-400% (400-2,000 μg/L) increase in zinc and other metals between 1980-2013. This study aggregates stream quality data from across the entirety of the Colorado Mineral Belt from 1970-present to examine spatial and temporal patterns in intensifying acid rock drainage at base-flow conditions. Preliminary results indicate increasing sulfate and metal concentrations are restricted to low-order, low-flow mountain streams above pre-existing mines and streams up-gradient of recent bulk-head installations. A climate change driven increase in acid rock drainage in Colorado headwaters will exacerbate challenges associated with water quality remediation of the mining legacy. Worsening acid rock drainage signals in high-order streams may be diluted by mine drainage inputs from abandoned adits and tunnels which obfuscate the climate-driven trends. This study is ongoing.