Ice-Age About 29,000 years ago, precipitation in the form of snow and a cold climate resulted in a period of glaciation that, upon its retreat about 10,000 years ago, formed the deep depression of Cowichan Lake, the much shallower depressions of Somenos Lake and Quamichan Lake, the channels of the Cowichan River and its tributaries, and the gravels, sands, and clays in the Cowichan Estuary.
Plants return As the climate began to warm, plants recolonized the land, watered by winter rain and snow. Up to five metres of water fell yearly on the peaks west of Cowichan Lake. Much of this precipitation would percolate into forest soils, where it would slowly flow into streams and enter aquifers. Annual floods carried soil into the flatter reaches of the Cowichan River, where it accumulated in fertile pockets.
Fish and other Animals Gradually, animals began to fill the ecological niches of the Basin. Salmon came to spawn in the gravels deposited in the Cowichan River. Juvenile fish found excellent rearing habitat in the lakes and channels of the Basin. The web of life in the Basin became complex and resilient.
Aboriginal people reached the Cowichan Valley not long after the glaciers receded. The people adapted themselves to the seasonal pattern of weather, fish, and plants, and a rich culture flourished in the Cowichan Basin for centuries.
In the mid 1800s, Euro-Canadian settlers arrived, bringing a different view of the Cowichan Basin. The new residents made big changes to the hydrologic system in the Basin.
Dykes were constructed to control winter floods that threatened roads, railroads, and settlement. Water was extracted from waterbodies and aquifers to meet increasing human demand. Farmers took advantage of the rich soils in the lower Basin and began to straighten and deepen streams to hasten drainage, drill wells, and extract water for irrigation. With settlements came pavement, storm drains, septic fields, and sewage treatment plants, all affecting water in the Basin.
Industry also needed water, and in the 1950s the government issued a water license to a pulp mill at Crofton to divert substantial volumes of water from the Cowichan River. A weir was built at the outlet of Cowichan Lake to store water for the mill.
In the past 150 years, the face of the Cowichan Basin has changed more than in the preceding 5,000. As the population and development increases in the Basin, so does the rate of change to the hydrologic cycle. Forestry, settlement, agriculture, recreation and tourism, industry, and cultural values compete for water in the Basin, often not leaving enough for healthy ecosystems.
Human impacts The old growth forests are nearly gone and forest soils are thinner, their water-holding capacity reduced. Wishing to be near the water, people build houses on the banks of rivers and lakes, removing riparian vegetation to improve access and views. More than 530 licences have been issued to extract water from streams and lakes in the Basin, and more than 1,300 wells have been drilled to pump water from the aquifers. Thousands of visitors come to the Basin each year to kayak, inner tube, swim, and fish in the lakes and streams and to hike and camp along the shores.
Catalyst Paper continues to withdraw water from Cowichan River for mill operation in Crofton.
Changing precipitation Seasonal fluctuations and unpredictable amounts of annual precipitation create water management challenges in the Basin. The Basin can experience floods in winter and spring and droughts in summer and fall, when water demand is at its peak. In recent dry years, low summer water levels in the Cowichan River system have put fish populations at risk and caused concerns about possible suspension of operations at the Catalyst Paper mill. Droughts also meant falling water levels in the streams and aquifers that supply many people with drinking water, and less water to dilute treated effluent discharges to the River. Water-based recreation, such as boating, swimming, and fishing, has also been affected by low flows in the River. These problems are likely to get worse in the future as climate change alters the hydrologic cycle of the Basin, bringing more intense winter rainstorms, less snowpack and earlier melt, and warmer summers.
A new relationship between people and water needs to be established to ensure that there will be reliable water supplies available for human use, thriving ecosystems, and a healthy economy in the Cowichan Basin, both now and in the future.
The Cowichan Basin Water Management Plan was published in March 2007
Cowichan Basin Water Management Plan, March 2007
Westland Resources Group
Water Facts, October 2005
Westland Resource Group
Water Issues, October 2005
Westland Resource Group