PANELISTS LEROY POFF PROFESSOR OF BIOLOGY COLORADO STATE UNIVERSITY
Effect of NISP on the Poudre River Ecosystem N. LeRoy Poff, PhD Department of Biology Colorado State University BizWest Water Conference, 18 July 2019
Ecological Health of Poudre River Ecosystem Physical Chemical Biological
River Health Indicators by Section
River Health Assessment River is impaired and sensitive to further degradation How will Glade Reservoir affect Poudre?
City of Fort Collins - ERM Flow Scenarios Key Reach Scale Drivers (physical, chemical) Indicators of River Condition Channel Aquatic Functioning Algae Structure Insects Riparian Zone Rejuvenating Riparian Native Fish Trout Mosaic Wetlands
Poudre River Hydrograph: Key to Sustaining Ecosystem Functions Floodplain inundation - maintain channel width and heterogeneity - riparian tree and wetland habitat - shallow groundwater Floodplain Cobble movement - bed rejuvenation River flow - fish/insect habitat Rate of Recession Gravel movement - spawning habitat - cottonwood seedling survival - groundwater discharge rate - insect habitat Silt flushing Reduced Baseflow - Insect habitat Average - brown trout spawning and Peaks overwinter survival Dry Streambeds Dry Streambeds Fish/insect wetted habitat; Brown trout egg and fry survival
Projected changes in flows with NISP Historic and Current Poudre Hydrograph River flow
Full bypass 2,800 cfs 1,200 cfs 0 cfs 2,200 cfs 1,600 cfs 3 days 2 days 3 days 1 day 1 day
Reduced overbanking flows will lead to … • Direct gradual narrowing • Thresholds: switch to upland or dominated by non-natives/pond like system • Vegetation moving into the channel, smaller river (with increased flood hazard?)
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