Is It Really Getting Drier in The Cowichan Valley?


There’s always talk of how dry, or wet, or cold, or hot things have been lately. It’s human nature to talk about the weather and, because the weather happens on relatively short time spans, that makes sense. We are talking about our experiences and perceptions. Makes for something to talk about with the neighbours.

It’s when the talk of the weather turns into changing public policy,¬† think about raising or lowering the weir up at Lake Cowichan for example, that our human limitations in accurately remembering¬† make for a dangerous situation. The amount of rain, for example, has been much talked about lately. Global warming they say, or something bigger anyway, must be happening.

Except, based on the simple observations and record-keeping, the cornerstone of actual science, nothing is actually happening. Things are more or less as they have always been. The precipitation records for the Cowichan Valley in fact demonstrate a small increase in rainfall over the last century. It’s actually not drier, but wetter.

The key thing is the huge yearly and decadal variations that fool our much shorter recollections into seeing trends where they are not. Of course if one fervently believes something, science and facts won’t matter. When a new piece of information disagrees with our deeply held belief, we have two choices. One, we can change our belief to incorporate new facts or, two, we can change the facts to fit our current beliefs.

Unfortunately, the history of human knowledge and science is littered with the skeletons of beliefs that were held onto far too long, often at a cost of great misery to many.

Does the chart below challenge or confirm your beliefs?


  1. I have to say that this and the solar PV articles were the closest thing to factual unbiased presentation of information that I have ever seen in this publication. Having said that, I am sure that it is no accident that the full story about our Cowichan Valley precipitation patterns was left untold. In my 11 years on the Cowichan Watershed Board, I have seen a multitude of briefings and updates on precipitation and NOT ONE of them has suggested that our annual precipitation has decreased, or that any models suggest it will decrease. What the models HAVE predicted and what is being confirmed by measurement is that rainfall patterns are changing. More precipitation in the winter months and less of that falling and lingering as snow pack. This is what is resulting in longer, drier, hotter summers and droughts AND reduced summer inflows from snow melt and summer rain into the watershed. This is why more storage is needed in Lake Cowichan and why a raised weir is required to keep the river alive. But I am sure that you already know all of that.

    • You may well be correct. I would suggest that the reduced snowpack does not create a longer or hotter summer though possibly drier, but snowpack isn’t correlated to subsequent summer rainfall, is it?. What is the long term data on snowpack, run-off, river levels if you have it from your many briefings? River levels are certainly one thing but ultimately all that water feeds the underlying water table, which is what feeds at least part of our water needs, and I wonder what the data on that is. Finally, the weir needs to be raised. I recall debate around this many decades ago and the amount they raised it was in the inches. How many gallons in an inch of Lake Cowichan water ? Quite a lot I think.

      The real point was, though, to point out that our perceptions and memories are quite fallible in regards to long term trends that might shape public policy and we should be careful about that, as you might well agree. We need to look at ALL of the data.

      Thanks for the input!

      • Snow pack is not related to summer rainfalls, but when more of the annual precipitation falls in winter months, by extension less falls in summer months. And because less falls and sticks around as high elevation snow pack, summer inflows are greatly reduced.
        The weir is to be raised 70 cm. One cm of water in Lake Cowichan is conveniently almost equal to 24 hrs of river flow as 7 cms (cubic meters per second). So the extra height should give 70 days a the “minimum desired” flow for fish friendly river conditions.

  2. Good article Nick. It is important that we look at the long term data and not be persuaded to take actions based on short term trends and fear based analysis.
    The thing I am concerned about is the distraction from the very real damage we are doing to our local waterways and ocean.


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