The upper Nooksack River basin in northwest Washington State covers about 1,500 square kilometers, about 40% of which retains an annual snowpack that is expected to decrease as climate change brings warmer winters. Additionally, about half of the forested landscape in the upper Nooksack River basin has the potential to be harvested, which could intensify climate-induced changes to streamflow and water temperature in the river.

Gap openings in forests — small gaps in the forest canopy created by harvesting or other disturbances — have been shown to accumulate more snow that produces more meltwater into the river, cooling the water temperature and boosting streamflow in warmer months when streamflow is lowest. However, harvested areas can produce more runoff during heavy rain and rain-on-snow events, resulting in higher winter streamflow and flood risk, and increased sediment carried by the river. These changes in streamflow, sediment and water temperature threaten critical salmon habitat and restoration efforts and jeopardize river management infrastructure and communities in the lowlands. 

Although several watershed modeling studies have been performed in the Nooksack basin to examine its response to climate change, none have explored how forest harvest practices influence snow accumulation and melt and how these processes are linked to both low and peak streamflows, both now and in the future. To address this research gap, Kristen will use a distributed hydrology model to examine how possible forest management strategies will affect low-summer flows and winter-peak flows in the upper Nooksack River basin in response to projected warming climate conditions. A primary stakeholder in this project is the Nooksack Indian Tribe, which is concerned about how forest harvesting and projected warming climates will impact streamflows and valuable salmon habitat in the Nooksack River. Through this project, Kristen will work with the Washington State Department of Natural Resources and Whatcom County scientists in designing forest harvest scenarios. The modeling outcomes will inform both the Nooksack Tribe and Whatcom County River flood managers in designing climate resilience strategies to preserve salmon habitat and infrastructure in the Nooksack River basin.