Precipitation in the Cowichan Watershed in winter has historically been in the form of rain and snow. In higher mountain areas surrounding Cowichan Lake, the snowpack that builds through the winter is a reservoir of water that augments the capacity of the lake, and contributes significantly and critically to the lake in spring and summer.


Groundwater is water which is stored underground - not surprisingly. It can be confined, which means that a deposit of water is surrounded by nonpermeable rock, typically in aquifers or unconfined, in which case it is surrounded by permeable rock, gravel, soil, and other materials. Around 20% of the world's freshwater is groundwater, and groundwater makes up a significant portion of the potable water consumed worldwide, with up to 50% of some populations relying on groundwater.

Supply and Demand

Water in the Cowichan Basin

The Cowichan Watershed can be characterised as having high precipitation/recharge, high storage, and low population/demand in the western and upper half of the watershed, contrasted with low precipitation, low storage, and high population/demand in the eastern and lower half. Supply and demand are not matched regionally, nor seasonally, and the supply-demand gap is pushed to extremes in the late summer and early fall.

Watershed Videos

Many videos are available online which introduce the hydrological/water cycle and watersheds. Here are four from YouTube. Even the ones aimed at children are informative - and fun. Enjoy.

For kids: music, no words

Watersheds and the Hydrologic Cycle in 90 seconds.

For kids: music, no words

Fish in the Cowichan Watershed

FishSpeciesInCowichanWatershedThe Cowichan Watershed is home to many fish species. This is a function of both the size of the watershed and its incredible ecological richness as habitat and in terms of nutrients.

The ecological health of the watershed is reflected in the health of its fish. It's a mutual relationship. Healthy fish make a healthy watershed, and vice versa.

Click here for a table listing the fish in the Cowichan Watershed. The table shows fish presence recorded in a number of streams and three lakes in the watershed, and indicates whether they are exotic/introduced species, and shows their BC Conservation and COSEWIC status.

On this page we look at a few representative fish of the Cowichan Watershed, including some "Salmonids", which are the most abundant and ecologially and economically the most important fish, at "Exotic/Introduced" species, and a couple of "Rare or Endangered" fish.

"Anadromous" is the term used to describe fish which spend some part of their lives in fresh water and some in salt water. Salmon are anadromous.


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