From the Summit Daily News (Janice Kurbjun):
Nearly 2,000 miles of waterways in Colorado are affected by acid rock drainage, said Diane McKnight, who co-authored the study. “Spring runoff is happening longer,” Shaw said, which means the water runs slowly into the ground instead of along its surface in one spring melt. It passes over mineralized rocks, leeching the minerals into the streamflow as it moves. Crouch said the earlier snowmelt also means drier streambeds in September and October, which could increase metal concentrations. It’s a smaller scale of what was observed during the 2002 drought, in which prolonged dry conditions allowed the harmful chemical reactions to occur in areas where water once was, and will be again.