The international waterways found along the U.S-Canadian border that feed into the Milk and St. Mary river basins provide important water resources for the Chippewa Cree Indians, Blackfeet, Assiniboine and Sioux Tribes who live downstream. These rivers also support agriculture, urban use, and fisheries trans-nationally. The possibility of a warmer future making droughts more severe and frequent has left resource managers concerned about changes in water availability in the region. A better understanding of future drought risks in the Milk and St. Mary river basins will better prepare managers to address these changes.  

However, the streamflow records to study the effects of drought in this area are limited. To address this lack of information, North Central CASC-supported researchers, including the USGS Northern Rocky Mountain Science Center scientists Greg Pederson and Justin Martin, reconstructed historical streamflow data through tree rings to explore how drought has impacted the river basins over time. The research team found that not only were the lower elevation prairies more sensitive to changes in temperature, but the period from 2000 to 2010 was one of the driest periods on record for these prairies. The data collected by the team will inform resource managers in developing adaptation strategies to protect crucial water resources in the Milk and St. Mary river basins.  

This work is supported by the North Central CASC project, “Characterizing Historic Streamflow to Support Drought Planning in the Upper Missouri River Basin”.