Downstream water quality impacts persist despite mountaintop coal mine reclamation in the Canadian Rocky Mountains

Reclamation is a requirement of mountaintop coal mines. Many jurisdictions require a return to predevelopment condition or to equivalencies based on unimpacted (i.e., upstream) reaches. Here we summarize decades of government and industry water quality monitoring and research spanning the onset, operation, closure, and reclamation of three Rocky Mountain coal mines in Alberta, Canada. The mines all occur within the McLeod River basin, offering opportunities to examine cumulative inputs and impacts. Selenium concentrations remain elevated and above guidelines for the protection of aquatic life decades after mine closure and reclamation despite regulatory requirements for the opposite. But the water quality impacts extended beyond selenium. Higher concentrations of a broad suite of both solutes and particle-bound heavy metals were noted downstream of all three mines, with impacts most obvious in Luscar Creek and Gregg River - tributaries to the McLeod River. After decades of coal extraction, changing regulatory requirements, and near complete reclamation of one coal mine, water quality remains negatively impacted with higher concentrations of ions, nutrients, and metals downstream of coal mines. These results suggest current reclamation practices and regulatory requirements for water quality and aquatic ecosystems are not meeting the desired objectives.