Cover: The lower McKenzie River (Photograph by Leslie Bach, The Nature Conservancy) Summary Report: Environmental Flows Workshop for the McKenzie River, Oregon By John C. Risley1, Leslie Bach2, and J. Rose Wallick1 1 U.S. Geological Survey, Oregon Water Science Center 2 The Nature Conservancy, Oregon Chapter This page is intentionally blank ii Contents Introduction .................................................................................................................................................................... 1 Background ................................................................................................................................................................ 1 McKenzie River .......................................................................................................................................................... 1 Workshop ....................................................................................................................................................................... 2 Agenda ....................................................................................................................................................................... 2 Results ....................................................................................................................................................................... 5 South Fork McKenzie River .................................................................................................................................... 5 Fall flows for channel habitat maintenance and fish outmigration ....................................................................... 5 Winter high flow for reconnecting off-channel habitat ......................................................................................... 7 Small spring flows for fish outmigration ............................................................................................................... 7 Spring bankfull flow for flushing and scouring ..................................................................................................... 7 Summer low flow for vegetation development and fish rearing ........................................................................... 8 Middle McKenzie River ......................................................................................................................................... 10 Fall flows to protect Chinook redds and benefit fish outmigration ..................................................................... 10 Winter bankfull flow for off-channel habitat maintenance and fish outmigration ................................................ 10 Winter high flow for reconnecting off-channel habitat ....................................................................................... 12 Winter flood for channel/floodplain habitat enhancement ................................................................................. 12 Small spring flows for juvenile fish outmigration and riparian vegetation enhancement .................................... 12 Spring bankfull flow for flushing and scouring ................................................................................................... 13 Summer low flow for vegetation development and fish rearing ......................................................................... 13 McKenzie River through EWEB canal reaches ..................................................................................................... 15 Fall flows to protect Chinook redds and benefit fish outmigration ..................................................................... 15 Winter bankfull flow for gravel movement ......................................................................................................... 15 Winter high flow for reconnecting off-channel habitat ....................................................................................... 17 Winter flood for channel/floodplain habitat enhancement ................................................................................. 17 Small spring flows for fish outmigration and riparian vegetation enhancement ................................................. 17 Spring bankfull flow for flushing and scouring ................................................................................................... 18 Summer low flow for vegetation development and fish rearing ......................................................................... 18 Lower McKenzie River .......................................................................................................................................... 20 Fall flows to protect Chinook redds and benefit fish outmigration ..................................................................... 20 Winter bankfull flow ........................................................................................................................................... 20 Winter high flow for reconnecting off-channel habitat ....................................................................................... 22 Winter flood to rejuvenate Oregon chub habitat ................................................................................................ 22 Small spring flows for fish outmigration and riparian vegetation enhancement ................................................. 22 Spring bankfull flow for flushing and scouring ................................................................................................... 23 Late spring flow for fish outmigration ................................................................................................................ 23 Late spring flow for Oregon chub spawning ...................................................................................................... 23 Recommendations for future monitoring and evaluation .............................................................................................. 25 iii Off-Channel Habitat ................................................................................................................................................. 25 Gravel Bars and other Alluvial Features ................................................................................................................... 26 Riparian Vegetation .................................................................................................................................................. 27 Aquatic Biology ........................................................................................................................................................ 28 Recommendations for Future Studies .......................................................................................................................... 29 Channel Morphology and Streamflow ...................................................................................................................... 29 Streambed Incision .................................................................................................................................................. 29 Sediment Budget ...................................................................................................................................................... 29 Geomorphic Assessment and Mapping.................................................................................................................... 29 References Cited ......................................................................................................................................................... 30 Appendix A. Workshop agenda ................................................................................................................................... 31 Appendix B. List of workshop attendees ...................................................................................................................... 32 Figures Figure 1. Map of the McKenzie River basin, showing study reaches. ......................................................................... 2 Figure 2. RPT generated plot of flow recommendations for the South Fork McKenzie River (Reach 3). .................... 6 Figure 3. Dam flow release and ecology linkages for the South Fork McKenzie River (Reach 3) ............................... 9 Figure 4. RPT generated plot of flow recommendations for the Middle McKenzie River (Reaches 4–7) .................. 11 Figure 5. Dam flow release and ecology linkages for the Middle McKenzie River (Reaches 4–7) ............................ 14 Figure 6. RPT generated plot of flow recommendations for the EWEB canal reaches (Reaches 8–10) ................... 16 Figure 7. Dam flow release and ecology linkages for the EWEB canal reaches (Reaches 8–10) ............................. 19 Figure 8. RPT generated plot of flow recommendations for the lower McKenzie River (Reaches 11–12) ................ 21 Figure 9. Dam flow release and ecology linkages for the Lower McKenzie River (Reaches 11-12). ......................... 24 Tables Table 1. River reach assignments for the workshop breakout groups. ........................................................................ 3 Table 2. McKenzie River streamflow statistics for the four workshop study reaches based on estimated and observed unregulated daily-mean streamflow data from 1936 to 2004. ...................................................................................... 4 iv Summary Report: