Wetter Winters and Drier Summers: The Effects of River Flow Extremes on Algae and Aquatic Plant Growth in a Degraded River

  • Karuk Tribe
  • Yurok Tribe
  • Klamath Tribal Water Quality Consortium
In Progress

Primary productivity, which describes the growth of algae and aquatic plants, is a central ecosystem function supporting aquatic food webs and influencing water quality and fisheries health. Land use and direct alterations to rivers are associated with widespread increases in primary productivity, which can lead to degraded water quality. Despite expectations of substantial changes in Pacific Northwest river flows with climate change, the effects of water stress and changing flow patterns on primary productivity in rivers are poorly understood. 

 This project will investigate the effects of changing streamflow patterns associated with climate change on ecosystem rates of primary productivity in the Klamath River, where excessive algae growth degrades water quality. Using a 14-year data set of high-frequency dissolved oxygen data, the research team will calculate daily rates of primary productivity during times of high algae growth and water quality impairment, which occur in the summer and fall. Using water quality data collected by the Yurok and Karuk Tribes, this research will test hypotheses about how the magnitude and length of summer low flows determine rates and patterns of primary productivity, as well as how preceding winter floods influence productivity the following summer. Understanding how rates of primary production differ under changing flow patterns will inform predictions about ecosystem change associated with the drier summers and wetter winters expected to occur with climate change. These relationships can inform river flow management in association with dam removal, nutrient reductions and restoration of environmentally-significant flows, which are aimed at improving water quality, fisheries health and the health of local communities who rely on the river for cultural practices and subsistence.