CLBMON-47 Lower Columbia River whitefish spawning ground topography survey: Year 3 data report

Author: Golder Associates Ltd

This monitoring program was initiated in 2011 and was carried out over three years. This project completed in 2015; however, recent discussions regarding the Mountain Whitefish Spawning Protection Flows resulted in a request from the regulatory agencies to have an independent review of the Mountain Whitefish Egg Loss Model that was updated as a part of this study. The review is in progress in 2018 and will be reported out to the Columbia Operations Fish Advisory Committee (COFAC) this fall. The report review will be provided to the CWR in the 2019 Annual Report. A key data gap identified by the water use plan Consultative Committee was the low quality and quantity of topographic data to describe characteristics of whitefish spawning locations, contributing to reduced confidence in the degree to which existing data represented the habitats of concern, and overall reliability of egg loss estimates. This monitoring program addresses these uncertainties by understanding how changes in dam releases influence the wetted channel area at key whitefish spawning locations.

MQ: What are the topographic characteristics of the key spawning locations for Mountain Whitefish in the lower Columbia and Kootenay rivers?
At the CPR Island spawning area, topographic features include steep gradient banks along the RDB, a channel between the LDB and CPR Island that remains wetted at higher water elevations, and shallow depths in the downstream portion of the spawning area.
In the downstream portions of the Kootenay River, topographic features include Kootenay Eddy along the RDB, a large point bar that deflects and constricts the Kootenay River flow creating a deep channel along the LDB adjacent to the eddy, and a ridge between the eddy and the channel. The middle section is dominated by low gradient banks, a relatively wide thalweg with consistent depth, and a large backwater area downstream of two islands along the LDB. Topographic features of interest in the upstream portion include a shallow shoal and a bedrock outcrop along the RDB.
The upstream section of the Kootenay expansion area is dominated by a large boulder garden in the mid-channel and along the LDB. Downstream of the boulder garden, multiple benches and ridges are present. In the mid-channel portion of the confluence section of the expansion area, the river bottom is relatively uniform. Along the LDB, the gradient gradually decreases, while along the RDB, gradients were typically steeper. The downstream section of the expansion area consists of steep gradients along both banks, while the mid-channel portion of the river bottom is relatively uniform.
MQ: What is the hydraulic response of the river to discharge fluctuations at these key spawning locations? How do changes in river discharge influence river stage, and how does river stage relate to wetted channel area at these key spawning locations?
Updated topographic data were collected for the Kootenay River and Upper Reach of the Columbia River. The original HEC-RAS model was then updated and calibrated. The River2D models allowed quantification of changes in river stage (water elevation) with changes in combined discharge of BRD and HLK. River stage within these spawning areas also depended on the particular discharge levels of HLK and BRD that comprised the total discharge. At CPR Island, predicted water elevations and wetted area were higher if discharge from HLK made up the larger portion of combined discharge. At Kootenay, this pattern was observed if BRD discharge accounted for the larger portion of the combined discharge.
As HLK discharge increased, the influence of BRD on wetted area at CPR Island decreased dramatically. Increases in water elevation resulted in a nonlinear increase in wetted area at both areas. Over the range of discharge documented in this study, the wetted area in the Kootenay River spawning area was typically 3 to 5 times higher than at CPR Island. As it is the larger of two spawning areas, the range of wetted area in relation to water elevation was substantially larger in the Kootenay River.
MQ: How do daily flow changes contribute to cumulative channel dewatering in key spawning areas over the whitefish reproductive period?
The ELM was updated and redesigned as an R-based model. The updated version includes modeling of stranding across the entire River2D surface, rather than individual transects, and incorporates time, depth, and temperature effects on egg deposition and incubation. In addition, the model incorporates uncertainty of these effects and yields confidence intervals around the stranding estimates. The model is undergoing further refining, and will be included in its final form with the finalized version of this document. Egg loss estimates for CPR Island were slightly higher and less variable than estimates for the Kootenay River. At CPR Island, egg loss estimates were above 20% in all years examined (2007 to 2012), while the Kootenay River estimates were below 20% in all years. Inter-annual egg loss estimates did not appear to be correlated to the flow stabilization index
Recommendations to refine the River2D and Egg Loss models include: calibration of the River2D models at high flows, incorporating BC Hydros substrate mapping data (when completed) into the ELM, field tests of the ELMs accuracy, and conduct more egg developmental experiments to refine ATU-to-hatch estimates. Recommended adjustments to how the flow stability index is calculated in the future were also presented.

MQ: What are the topographic characteristics of the key spawning locations for Mountain Whitefish in the lower Columbia and Kootenay rivers?
At the CPR Island spawning area, topographic features include steep gradient banks along the RDB, a channel between the LDB and CPR Island that remains wetted at higher water elevations, and shallow depths in the downstream portion of the spawning area.
In the downstream portions of the Kootenay River, topographic features include Kootenay Eddy along the RDB, a large point bar that deflects and constricts the Kootenay River flow creating a deep channel along the LDB adjacent to the eddy, and a ridge between the eddy and the channel. The middle section is dominated by low gradient banks, a relatively wide thalweg with consistent depth, and a large backwater area downstream of two islands along the LDB. Topographic features of interest in the upstream portion include a shallow shoal and a bedrock outcrop along the RDB.
The upstream section of the Kootenay expansion area is dominated by a large boulder garden in the mid-channel and along the LDB. Downstream of the boulder garden, multiple benches and ridges are present. In the mid-channel portion of the confluence section of the expansion area, the river bottom is relatively uniform. Along the LDB, the gradient gradually decreases, while along the RDB, gradients were typically steeper. The downstream section of the expansion area consists of steep gradients along both banks, while the mid-channel portion of the river bottom is relatively uniform.
MQ: What is the hydraulic response of the river to discharge fluctuations at these key spawning locations? How do changes in river discharge influence river stage, and how does river stage relate to wetted channel area at these key spawning locations?
Updated topographic data were collected for the Kootenay River and Upper Reach of the Columbia River. The original HEC-RAS model was then updated and calibrated. The River2D models allowed quantification of changes in river stage (water elevation) with changes in combined discharge of BRD and HLK. River stage within these spawning areas also depended on the particular discharge levels of HLK and BRD that comprised the total discharge. At CPR Island, predicted water elevations and wetted area were higher if discharge from HLK made up the larger portion of combined discharge. At Kootenay, this pattern was observed if BRD discharge accounted for the larger portion of the combined discharge.
As HLK discharge increased, the influence of BRD on wetted area at CPR Island decreased dramatically. Increases in water elevation resulted in a nonlinear increase in wetted area at both areas. Over the range of discharge documented in this study, the wetted area in the Kootenay River spawning area was typically 3 to 5 times higher than at CPR Island. As it is the larger of two spawning areas, the range of wetted area in relation to water elevation was substantially larger in the Kootenay River.
MQ: How do daily flow changes contribute to cumulative channel dewatering in key spawning areas over the whitefish reproductive period?
The ELM was updated and redesigned as an R-based model. The updated version includes modeling of stranding across the entire River2D surface, rather than individual transects, and incorporates time, depth, and temperature effects on egg deposition and incubation. In addition, the model incorporates uncertainty of these effects and yields confidence intervals around the stranding estimates. The model is undergoing further refining, and will be included in its final form with the finalized version of this document. Egg loss estimates for CPR Island were slightly higher and less variable than estimates for the Kootenay River. At CPR Island, egg loss estimates were above 20% in all years examined (2007 to 2012), while the Kootenay River estimates were below 20% in all years. Inter-annual egg loss estimates did not appear to be correlated to the flow stabilization index
Recommendations to refine the River2D and Egg Loss models include: calibration of the River2D models at high flows, incorporating BC Hydros substrate mapping data (when completed) into the ELM, field tests of the ELMs accuracy, and conduct more egg developmental experiments to refine ATU-to-hatch estimates. Recommended adjustments to how the flow stability index is calculated in the future were also presented.