CLBMON-15a Mid-Columbia River Physical Habitat Monitoring Project, 2017

Author: E. Plate, M. Zimmer, A. Duncan, Y. Bychkov, E.Smith, N. Wright

The focus of CLBMON-15a was to provide empirical information on the response of key physical habitat variables to the implementation of minimum flow releases from Revelstoke Dam and operation of REV 5. To gather the necessary data, stage and temperature were monitored continuously at six stations in MCR and two tributaries complimented by seasonal monitoring of water quality. The main objectives of CLBMON-15a were: 1) Measure differences in the daily and seasonal river water temperature regimes between pre- and post- implementation of the 142 m3/s minimum flow regime, 2) Measure spatial and temporal differences in the daily and seasonal range of river level fluctuations between pre- and post- implementation of the 142 m3/s minimum flow regime, 3) Collect seasonal nutrient and electrochemistry data at the reach scale to spatially characterize water quality conditions and 4) Estimate changes in the quantity and spatial distribution of permanently inundated river channel resulting from 142 m3/s minimum flow releases.

Management Question 1: How does the 142m3/s minimum flow and the increased flow based on REV 5 affect water temperature in the flowing reach of the MCR?
Based on continuous temperature data sampling, diel variation of water temperature following implementation of the new flow regime was 0.1-0.4 °C smaller than before. The ecological significance of such a small change is questionable. The seasonal pattern of mean water temperatures does not appear to be affected by the new flow regime.
Management Question 2: How does the 142m3/s minimum flow and the increased flow based on REV 5 affect the range and variability in river level fluctuations in the MCR?
Based on continuous stage logger measurements from 2008 to spring of 2015, diel variation in water levels following the new flow regime was larger following the new flow regime while the seasonal pattern of mean river fluctuations did not appear to be affected.
Management Question 3: Does the 142m3/s minimum flow and the increased flow based on REV 5 affect water quality in terms of electrochemistry and biologically active nutrients?
Based on three individual annual samples from 2008 to spring of 2015 for nutrients, physical parameters and electrochemistry the sampling frequency was deemed to be too low to determine any differences between the pre- and post-new flow regime conditions. This decision was made as part of a a discussion during a RFMP (Revelstoke Flow Management Plan) workshop in February of 2014. Little to no difference before /after new flow regime was found in the MCR stations (within and among years).
A subsequent literature search on on the effects of flows on water quality did not yield any comparable study.
Management Question 4: How does the 142m3/s minimum flow and the increased flow based on REV 5 affect total area of river channel that is permanently wetted and are there biologically significant differences in velocity and depth, if so where do these occur
The estimates based on Golder 2014 and the HEC-RAS model show that the wetted riverbed area at minimum flows increased by 32% after implementation of the new flow regime, but only when Arrow Lake Reservoir is below 425 m ASL.
When ALR is higher, the effect is lessened in the reaches close to REV where the MCR is backwatered by high Arrow Lakes elevations, and non-existent in the MCR reaches further from REV and below the elevation of Arrow Lakes Reservoir.

Management Question 1: How does the 142m3/s minimum flow and the increased flow based on REV 5 affect water temperature in the flowing reach of the MCR?
Based on continuous temperature data sampling, diel variation of water temperature following implementation of the new flow regime was 0.1-0.4 °C smaller than before. The ecological significance of such a small change is questionable. The seasonal pattern of mean water temperatures does not appear to be affected by the new flow regime.
Management Question 2: How does the 142m3/s minimum flow and the increased flow based on REV 5 affect the range and variability in river level fluctuations in the MCR?
Based on continuous stage logger measurements from 2008 to spring of 2015, diel variation in water levels following the new flow regime was larger following the new flow regime while the seasonal pattern of mean river fluctuations did not appear to be affected.
Management Question 3: Does the 142m3/s minimum flow and the increased flow based on REV 5 affect water quality in terms of electrochemistry and biologically active nutrients?
Based on three individual annual samples from 2008 to spring of 2015 for nutrients, physical parameters and electrochemistry the sampling frequency was deemed to be too low to determine any differences between the pre- and post-new flow regime conditions. This decision was made as part of a a discussion during a RFMP (Revelstoke Flow Management Plan) workshop in February of 2014. Little to no difference before /after new flow regime was found in the MCR stations (within and among years).
A subsequent literature search on on the effects of flows on water quality did not yield any comparable study.
Management Question 4: How does the 142m3/s minimum flow and the increased flow based on REV 5 affect total area of river channel that is permanently wetted and are there biologically significant differences in velocity and depth, if so where do these occur
The estimates based on Golder 2014 and the HEC-RAS model show that the wetted riverbed area at minimum flows increased by 32% after implementation of the new flow regime, but only when Arrow Lake Reservoir is below 425 m ASL.
When ALR is higher, the effect is lessened in the reaches close to REV where the MCR is backwatered by high Arrow Lakes elevations, and non-existent in the MCR reaches further from REV and below the elevation of Arrow Lakes Reservoir.