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Local authorities endorse plan to work toward a more flexible weir
At a recent Cowichan Watershed board meeting, Craig Sutherland of the KWL engineering firm gave an interesting comparison between the current rigid “rule curve” weir management rules and the proposed new flexible “rule band” approach.
The rule curve is strict approach to water levels in the lake. It essentially keeps the lake at certain prescribed level, regardless of precipitation or other lake inflow conditions.
The proposed rule band protocol allows much more flexibility. It will allow the operating group to compensate for changing inflows and take advantage of any summer rainfall by keeping it until it is needed late in the summer.
Both protocols have the weir at zero storage at the end of the summer management period.
Summer water inflows have dropped by thirty five percent since the mid eighties. It is clear the flexible rule band would have resulted in considerable improvement in river conditions in many years.
It is also clear summer inflow conditions are decreasing quickly and that just managing our current weir as well as possible may not be enough to ensure sufficient late summer water in the future. If this trend of decreasing summer precipitation continues, as many in the scientific community expect, we may need to store more water than our current weir can provide.
CWB member Tim Kulchyski indicated Cowichan Tribes supports immediate movement to the Rule Band approach but would consider this to be a temporary measure. He did not want to prejudice any other options to store more water in the summer and to get more local control.
There was also discussion from CVRD board members regarding what would have happened this year if we had applied the rule band. It was confirmed we would have had enough water with rule band protocol to have had the minimum seven cubic meters per second flow rate required for salmon migration, plus extra 24 hour pulses to encourage the fish to go up the river.
There would have been no low flow crisis and we would not have been trucking salmon this year if we had used the rule band.
There was a sense of urgency about getting control of our water quickly in order to mitigate climate change effects on our watershed in the future.
Both the Cowichan watershed board and the CVRD board voted to support adoption of the rule band, as an amendment to the Catalyst water license. Pending Catalyst approval, the next steps will be taken in January with public meetings.
It is very encouraging that the provincial government has taken notice of the crisis we had this fall and is willing to help us to facilitate the changes necessary for us to better manage our water resources.
We can now see what must be done this winter to ensure we start to manage our weir much more efficiently next summer and into the future.
Parker Jefferson is a member of the Cowichan River protection lobby group Once Cowichan.