Storm Response and Water Balance of Temperate Rainforest Karst Watersheds: Tongass National Forest, Alaska

The Tongass National Forest in southeast Alaska contains 2,176 square kilometers of karst. As part of the evolving Tongass Land Management Plan, research into the function of karst systems is crucial in understanding how forest management affects not only karst areas but also surrounding ecosystems. Dye trace and water balance results in two watersheds on the north end of Prince of Wales Island demonstrate the difficulty in containing the effects of management, as water can enter karst catchments from unknown sources at different flow regimes. A dye trace was conducted in Windgate and Canyon Block watersheds. Two sinking streams were traced to one resurgence spring in Canyon Block, and four sinking streams were traced to one resurgence spring in Windgate. Water balance data calculated for the entire study period and individual storm events suggests that Windgate has been sufficiently delineated. Data from the study period and storm event water balance calculations for Canyon Block suggest that at high flow discharge is pirated into Canyon Block from another system. High resolution monitoring in each catchment show that there is no significant delay between the increase in discharge and the arrival of direct runoff, as evidenced by the quick decrease in specific conductance. This could result in a quick transmission of sediment and contaminants through the karst system into downstream salmon habitat