Water issues are always a hot topic in the Cowichan Valley.
Summertime water shortages are an ongoing concern. Should we raise the weir at Cowichan Lake in the winter to store more water for summer use?
A number of our creeks and river drainages are suffering from a succession of ill-conceived channel modifications and bad management decisions. What has been forgotten time and time again is that you cannot change a drainage channel without affecting what happens downstream.
For example, when you smooth out a curve in or straighten a river’s course, you cause its flow speed to increase, which gives it more energy to scour the river bottom and pick up more gravel and debris.
As the water gets closer to the river’s mouth, where the land tends to flatten out, the flow spreads out and its energy declines causing material it is carrying to be deposited.
Local examples of this transfer of gravel and debris from further upstream are Bonsall Creek, Richards Creek and, most notably, the Cowichan River.
Old-timers to the area will be able to tell you stories of when they were kids jumping off the Black Bridge, just near Allenby Rd., into deep water. You cannot do that anymore. Gravel and boulders from further upstream, where well-meaning souls have straightened the river course, have now filled in the riverbed closer to town. No fun.
Here are two important impacts. First, the lower reaches of the Cowichan River and the Bonsall are now more prone to flooding. Second, upstream gravel beds have been scoured so there are fewer spawning beds for returning salmon and trout.
And problems with environmental management do not seem to end with the Cowichan and Bonsall drainages, as a similar situation exists on the Richards Creek outfall.
On Richards Creek, beaver activity has reduced outflow to the point where farmland and seasonal wetlands further upstream are now in semi-permanent flood, no longer viable for cultivation and less attractive for migrating bird life.
Perhaps of greatest concern is the Somenos drainage, right at the entrance to our town. Outflow from the creek into Cowichan Bay is so restricted that Somenos Lake has become a sewage lagoon with the tides flushing back and forth, and organic debris building up in the bottom of the lake.
Reports show that this organic buildup, in the absence of oxygen, is leading to bacterial activity along the lake bottom, which is poisoning the environment. In the case of the Somenos, what used to be an important spawning ecosystem for salmon and trout has been killed off. To correct this problem, the lake needs to be dredged and the Somenos outflow brought back to its original state.
We cannot make changes to our rivers and streams in isolation. We must consider the whole impact up and downstream, over the course of all four seasons for years, even decades.
And be willing to correct our mistakes, and making changes to these systems that might have short-term negative impact but, in the long run, will allow these environments to recover.
It seems that until we do, our fisheries and drainages are in danger of further degradation; not be much of a legacy for our children and grandchildren.
Laurie Thomson is a retired geologist living in Maple Bay enjoying life after a busy life inthe mining industry.