Stream Temperature Monitoring Network for Alaska's Salmon Streams

Water temperature plays a critical role in all phases of the salmonid lifecycle, especially in freshwater systems where fish spawn. High stream temperatures stress fish making them increasingly vulnerable to pollution, predation and disease.  Yet despite the links between warm water temperatures and reduced salmonid survivorship in other regions, there is little consistent, long-term temperature data for salmon streams in Alaska.   Through this multi-year project, we are implementing a Stream Temperature Monitoring Network to identify thermal impacts in coastal salmon habitat in the Cook Inlet basin of Southcentral Alaska.  Beginning in the summer of 2008, continuous water and air temperatures were taken in 48 non-glacial salmon streams. Maximum stream temperatures ranged broadly among sites and between years: 9.2 – 22.0 degrees C (2008), 13.1 – 24.5 degrees C (2009), and 11.0 – 20.4 degrees C (2010). The highest temperatures were recorded in streams that drain lakes or lowland areas west of the Susitna River. We used regional climate projections from Scenarios Network for Alaska Planning (SNAP) to better understand how air temperatures are likely to change as an indicator of future stream temperatures. These projections predict that air temperatures and, to a lesser degree, precipitation will increase across the landscape over the next 100 years. July air temperatures may increase as much as 5 degrees C in the Susitna River valley and increasing winter air temperatures may reduce snow accumulation, especially on the lower Kenai Peninsula and west side of Cook Inlet.  With a 5-year data collection goal to capture recent annual variation, this NGO-driven project will play an important role in identifying the most temperature-sensitive salmon streams in Cook Inlet. With this information, state and federal resource managers can prioritize habitat protection and restoration efforts to ensure Alaska wild salmon endure as thermal change continues.