The Chilkat River Basin of Alaska is characterized by glaciers, highly dissected mountains with steep-gradient streams, and braided rivers in broad, alluvium-filled valleys. Orographic effects and a wide seasonal range in temperature cause variations in the amount and distribution of precipitation, and thus in the resulting runoff and streamflow. Seeps and springs flowing from alluvial fans contribute to streamflow year round. Infiltration of water from the Tsirku River and its distributary channels is the most important source of groundwater recharge on the river 's alluvial fan, 20 mi north of Haines. Groundwater discharge along the toe of the fan maintains open leads in a reach of the Chilkat River downstream from the fan. This ice-free reach provides spawning habitat for a late run of salmon, which in turn attracts the world 's largest concentration of bald eagles (more than 3,000 birds). Both surface and groundwater are a calcium bicarbonate type. Stream samples had dissolved-solids concentrations < 115 mg/L; values for groundwater were slightly greater. The glacier-fed Chilkat, Tsirku, and Klehini Rivers carry large concentrations of suspended sediment during periods of high flow.
