This has been a very challenging winter for the Cowichan watershed. The prolonged spell of cold and dry weather we experienced in February and into March put a lot of stress on the riparian ecosystems. We probably lost a large portion of the salmon and steelhead eggs that were laid in the fall and early winter.
The water flow in the Cowichan River got as low as 15 cubic metres per second in March when the “normal” range for winter is about 80 to 100 cms. The lake level got down to about 20 per cent of the height of the weir at the head of the river, when water should have been flowing over the top.
The spring rains we have seen so far have helped, but the storage capacity of the weir is still not full, so unless the rains continue for some time, we could again be in trouble for water this fall.
This situation is going to be typical for our watershed, according to climate-change predictions from the University of Victoria’s Pacific Climate Impacts Consortium. In fact, these effects are going to get worse, and it will be very challenging for the fish and all other species that depend on our watershed ecosystem for their existence.
We can expect increasingly drier and warmer summers. Our driest summers now will be the wettest ones in the near future. Our total annual precipitation should stay about the same, but it will be concentrated in heavy rainfall events in the fall and early winter. Late-winter precipitation will decrease. Our snowpack will also decrease steadily and will likely disappear entirely in a few decades.
In the fall, we require high flows to allow the salmon to reach their spawning beds. Winters are usually no concern, as we expect lots of rain and the river usually stays high, covering the incubating eggs. The next critical time is in the early spring, starting in March, when the salmon eggs start to hatch.
We need a minimum flow of 25 cms in the Cowichan River for April and May, when the weir is in operation so the hatching fry have suitable habitat and shelter from predators.
Last fall, when the salmon were spawning, the typical heavy rainfall events had the river full and running at 100 to 150 cms. All of the good spawning beds were accessible and used by the salmon. Then we experienced a long, cold dry spell, just when the salmon eggs started to hatch. Many of the side channels and near-shore spawning beds dried out completely and most of the eggs deposited in them have been lost.
Salmon are resilient creatures. They have evolved to adapt to bad-flow years similar to what we just experienced. They have a typical life cycle in which most fish return after a certain number of years, but all species have a number of fish that don’t follow the rules and return a year or two early. This ensures that a bad year of river conditions will not wipe out a year-class of fish. But if we have three or four bad years in a row, as climate projections promise, there will be serious consequences.
The work First Nations and the wider community have done restoring habitat and carefully managing river flows has helped. We have been counting returning chinook salmon in the Cowichan River since 1988. Back then, the run was about 6,000, but it steadily declined to a low of 500 in 2009.
We responded to this urgent decline with projects such as the Stoltz Bluffs remediation project that kept heavy winter rains from silting the river and smothering salmon eggs.
Since 2009, we have had steady increases in chinook returns, with more than 20,000 returning fish for the past two years. That is by far the most salmon we have counted since 1988 and against the trend of other Salish Sea rivers.
We have a new Cowichan Water Use Plan (cowichanwup.ca) that was created last year by local first Nations, all levels of government, NGOs, industry and other stakeholders. In the plan, we reached a consensus that we need to rebuild the weir and add 70 cm to the height to increase water storage. One centimetre of water stored will run the river for 24 hours, so this additional storage will help to provide steady flows during our annual summer droughts. We also need to have much greater flexibility in the operation rules that allow us to hold water back when we can to try to even out the flows and provide critical flows when necessary for fish health.
This is in part a climate change adaptation strategy backed by science and overwhelmingly supported by our community. The biggest obstacle is the legalities of who will hold the licence and the liabilities of the new weir. We are hoping the provincial government will help by taking out or otherwise facilitating a conservation water licence to help our Heritage River survive and thrive for future generations to enjoy.
Even though the situation is already urgent, higher levels of government and particularly the province have been slow to help work this through. Our community stands ready to help fish in the face of climate change, and we hope the powers that be join us before it’s too late.
Parker Jefferson is co-chair of the Cowichan Stewardship Roundtable, a group consisting of First Nations, all levels of government, NGOs and private citizens.