Brilliant Fall Flow Reduction and Fish Stranding Monitoring

Author: Columbia Power Corporation

To further protect fish, CPC has also implemented a slow ramping rate at BRX. This is intended to meet Owner’s Commitment #99R: “low ramping rates will be used during the initial change in October from the 18,000 to 16,000 cfs target minimum flows to mitigate stranding effects.” This is achieved by reducing the flow in 500 cfs increments every 15 minutes. CPC has also extended this slow ramping rate of 2,000 cfs/hr to all reductions in base flow (defined as the minimum flow in the past 48 hours) at all times of the year as described in the Canal Plant Agreement (CPA) Operating Procedure 10 (OP 10).

The BRX environmental assessment concluded that sufficient flows would usually be available during the fall period to meet the target minimum flows and that load shaping above the target minimum would often be possible. However, operational experience has shown that this time of the year has become a very low flow period due largely to changes in the operations of upstream storage reservoirs (e.g., Libby and Duncan reservoirs). As a result, it has become a challenge to meet the target minimum flow during this period. Flows are kept stable to the best extent possible and at levels that best meet the intent of the target minimum flows. This is done to minimize the impact to downstream aquatic productivity, while also considering the impact on upstream fisheries (particularly shoal spawning Kokanee in Kootenay Lake). The Columbia Operations Fisheries Advisory Committee (COFAC) is consulted on the scheduled flows when there is a flow reduction planned for the beginning of October.

The Stranding Protocol has defined an “effect” at any particular stranding location as an average of greater than 100 fish stranded at a site per survey under similar water temperature and river stage conditions (this also varies depending on the species). An effect is not considered to have occurred if fewer than 100 fish have been stranded at any particular site. This criterion was used when evaluating the results from the three years of fall reduction stranding monitoring work carried out at BRX. From summary Table 1 we can see that the total number of fish affected by the October flow reduction was N=19 in 2007, N=40 in 2008, and N=94 in 2009. If we were to refer to the Stranding Protocol when gauging the level of risk presented by the October 01 flow reduction at BRX and whether or not any effects have occurred, this criterion was not met at any of the sites examined during stranding surveys conducted between 2007 and 2009. The results suggest a low likelihood that significant numbers of fish (i.e., N>100) are likely to be stranded following future target minimum flow reductions during the October/November period. The low level of fish stranding identified during the 2007, 2008, and 2009 surveys supports the initial assessment of low stranding risk that was reported in the BRX PAC application document.

To further protect fish, CPC has also implemented a slow ramping rate at BRX. This is intended to meet Owner’s Commitment #99R: “low ramping rates will be used during the initial change in October from the 18,000 to 16,000 cfs target minimum flows to mitigate stranding effects.” This is achieved by reducing the flow in 500 cfs increments every 15 minutes. CPC has also extended this slow ramping rate of 2,000 cfs/hr to all reductions in base flow (defined as the minimum flow in the past 48 hours) at all times of the year as described in the Canal Plant Agreement (CPA) Operating Procedure 10 (OP 10).

The BRX environmental assessment concluded that sufficient flows would usually be available during the fall period to meet the target minimum flows and that load shaping above the target minimum would often be possible. However, operational experience has shown that this time of the year has become a very low flow period due largely to changes in the operations of upstream storage reservoirs (e.g., Libby and Duncan reservoirs). As a result, it has become a challenge to meet the target minimum flow during this period. Flows are kept stable to the best extent possible and at levels that best meet the intent of the target minimum flows. This is done to minimize the impact to downstream aquatic productivity, while also considering the impact on upstream fisheries (particularly shoal spawning Kokanee in Kootenay Lake). The Columbia Operations Fisheries Advisory Committee (COFAC) is consulted on the scheduled flows when there is a flow reduction planned for the beginning of October.

The Stranding Protocol has defined an “effect” at any particular stranding location as an average of greater than 100 fish stranded at a site per survey under similar water temperature and river stage conditions (this also varies depending on the species). An effect is not considered to have occurred if fewer than 100 fish have been stranded at any particular site. This criterion was used when evaluating the results from the three years of fall reduction stranding monitoring work carried out at BRX. From summary Table 1 we can see that the total number of fish affected by the October flow reduction was N=19 in 2007, N=40 in 2008, and N=94 in 2009. If we were to refer to the Stranding Protocol when gauging the level of risk presented by the October 01 flow reduction at BRX and whether or not any effects have occurred, this criterion was not met at any of the sites examined during stranding surveys conducted between 2007 and 2009. The results suggest a low likelihood that significant numbers of fish (i.e., N>100) are likely to be stranded following future target minimum flow reductions during the October/November period. The low level of fish stranding identified during the 2007, 2008, and 2009 surveys supports the initial assessment of low stranding risk that was reported in the BRX PAC application document.