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RIPARIAN SHADE CONTROLS ON STREAM TEMPERATURE NOW AND IN THE FUTURE ACROSS TRIBUTARIES OF THE COLUMBIA RIVER, USA
Citation:
Fuller, M., N. Detenbeck, P. Leinenbach, R. Labiosa, AND D. Isaak. RIPARIAN SHADE CONTROLS ON STREAM TEMPERATURE NOW AND IN THE FUTURE ACROSS TRIBUTARIES OF THE COLUMBIA RIVER, USA. Society for Freshwater Science (SFS) Annual Meeting, Detroit, MI, May 20 - 24, 2018.
Impact/Purpose:
This work is contributing significant information for Region 10's Coldwater Refugia project. The Coldwater Refugia project was established in response to challenges to EPA's approval of Oregon's water temperature standards. On November 3, 2015, NOAA’s National Marine Fisheries Service (NMFS) issued a biological opinion pursuant to section 7(a)(2) of the Endangered Species Act on EPA’s approval of Oregon’s water temperature standards, and NOAA concluded that Oregon’s narrative cold water refugia provision of the state’s 20○C migration corridor criterion had not been implemented effectively to avoid jeopardy for certain salmonids; salmonids need sufficient coldwater refuges to pass safely through the Columbia and lower Willamette Rivers during migration to spawning grounds. As a result, EPA Region 10 and NMFS have entered into an agreement to work with the state of Oregon to map cold water refugia and determine areas needing protection and/or restoration. EPA is leading development of a plan for the Columbia River.
Description:
Future climates may warm stream temperatures altering aquatic communities and threatening socioeconomically-important species. These impacts will vary across large spatial extents and require special evaluation tools. Statistical stream network models (SSNs) account for spatial autocorrelation in rivers and are suited to evaluate stream parameters affected by climate change. SSNs predicted mean August stream temperature for tributaries of the mainstem Columbia River (downstream of Snake River) under three climate scenarios (present, 2040, 2080). These climate scenarios were crossed with three channel shading levels including (1) topographic – no riparian vegetation, (2) present vegetation shade, and (3) potential vegetation shade – maximum height of riparian vegetation to evaluate the use of riparian restoration to offset forecast climate changes. The mean August temperature of all 191 tributary outflows was below the minimum cold water refugia (CWR) threshold of 20°C for three scenarios (present climate/present shade, present climate/potential shade, 2040 climate/potential shade); other scenarios were 1-2°C above. Relative to the present climate/shade scenario, the percent of tributaries below the CWR threshold in 2040 drops 35%, while 2040 climate with potential shading drops only 6%. This suggests riparian shading regionally could maintain Columbia River CWR in 2040.