Science Advisory Report 2018/048

Assessment of the Instream Flow Needs for fish and fish habitat in the Saskatchewan River downstream of the E.B. Campbell Hydroelectric Station

Summary

• The natural flow regime in the Saskatchewan River system is highly altered due to the cumulative effects of several reservoirs (e.g., Lake Diefenbaker, Abraham Lake, Brazeau Reservoir), agricultural water withdrawal in Alberta and Saskatchewan, and water diversions to the Milk and Qu’Appelle rivers. The water management upstream directly affects the availability of water for the E.B. Campbell Hydroelectric Station (EBC), and its reservoir, Tobin Lake; thus, complicating the isolation of the effects directly due to the EBC hydropeaking facility on fish downstream.
• Returning to the natural hydrograph without a barrier would be preferential for fish and fish habitat, however, understanding that EBC will remain operational, science advice focused on instantaneous minimum flows and ramping rates to reduce risks to fish and fish habitat and discussed as a series of mitigation options.
• Rather than the use of absolute values of instantaneous minimum flows, the use of percentages of inflow to EBC as criteria for downstream releases may be more valuable to maintain the temporal and seasonal patterns of the natural hydrograph.
• It is recommended that the minimum flow downstream of EBC at any time should not be lower than the natural 95% exceedance flow rate for the 1912-1963 flow record.
• Higher minimum flows in BSP2 and 3 (i.e., April 30–July 24) will help protect spawning periods for the majority of fish species in the Saskatchewan River. Increasing the minimum flows will lead to a reduction in the ramping limits and consequently a decrease in the hydropeaking potential. Reduced hydropeaking will likely increase successful egg incubation and larval drift during BSP2 and 3 and reduce the stranding risk during all BSPs.
• Lake Sturgeon (Acipenser fulvescens) is a species of significant cultural importance. It is currently designated as endangered under COSEWIC and is under consideration for listing under the Species at Risk Act. To protect recruitment of Lake Sturgeon, absolute values of the instantaneous minimum flow of >700 m³·s-1, mean daily discharges of >800 m³·s-1 (not a percentage), and a reduction of daily peaking in the two week spawning window (first two weeks of BSP3) are recommended. Given the long life span of Lake Sturgeon, successful recruitment is not necessary every year to maintain a sustainable population structure. Therefore, the above mentioned instantaneous flow releases do not have to occur every year but in years when flows of these magnitudes are possible and the timing should coincide with Lake Sturgeon spawning.
• Hydropeaking leads to much higher flow variations than would naturally occur in a given day. Under the current peaking and minimum flow rules fish stranding is occurring on a daily basis downstream of EBC. Rapid down ramping due to hydropeaking increases fish stranding risk close to the dam (Figure 2). Flows <500 m³·s-1 result in the largest Wetted Useable Area changes. Gradual down ramping procedures (beginning at 500 m³·s-1) over an extended period of time is recommended to mitigate fish stranding. Specific research and monitoring should be conducted to provide further guidance on strategies to reduce the stranding risk.
• Flows >1,000 m³·s-1 provide flooding and connectivity in the Saskatchewan River Delta and potentially increase fishery productivity. Consequently, these high flows should not be avoided by storing water in upstream reservoirs.
• Lake Diefenbaker, Codette Reservoir, and Tobin Lake function as sediment traps leading to sediment starvation downstream of EBC and ultimately in the Saskatchewan River Delta. The starvation of sediment causes armoring and down cutting of the riverbed and perching of tributaries and side channels (e.g., Old Channel). Consequently, both water quantity and water quality (including nutrients) must be considered for fish and fish habitat. Mitigations for sediment replenishment may be considered.
• Water storage along the Saskatchewan River system alters the water temperature from the natural temperature regime. Limited temperature data was available for the review; however, EBC has turbine intakes that release surface waters and not cold waters from the reservoir bottom, therefore, water temperatures up- and downstream of EBC are not very different.
• BSPs were developed during a workshop held in 2005 in Prince Albert, SK with a group of experts using the Delphi method. Although the BSPs are thought to be acceptable, the potential to modify them by linking their start dates to measured water temperatures could be further explored.
• Information on surface ice cover, ice dynamics, frazil or anchor ice formation was not reviewed but was considered a data gap. In addition to this, a considerable number of uncertainties due to the lack of monitoring and field studies conducted on the Saskatchewan River system were identified.
• A holistic water and sediment management scheme for the Saskatchewan River system is necessary to protect the ecological significance of the Saskatchewan River Delta.
• It was recommended to improve the documentation of Traditional Ecological Knowledge to obtain more valuable information on fish and fish habitat in the Saskatchewan River Delta.

This Science Advisory Report is from the May 9–10, 2018 regional peer review on the Assessment of the Instream Flow Needs for fish and fish habitat in the Saskatchewan River below the E.B. Campbell Hydroelectric Station. Additional publications from this meeting will be posted on the DFO Science Advisory Schedule as they become available.

Complete document (PDF, 828 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.