Cowichan LakeLake Level
A weir at Cowichan Lake stores water so that it is available for users downstream. Catalyst withdraws water from the Cowichan River for delivery to the Pulp and Paper Mill and the community of Crofton. Water is withdrawn about a kilometer upstream of the Allenby Road bridge in Duncan. Cowichan Lake is also the water supply for the Town of Lake Cowichan which withdraws water directly from the Lake. The Cowichan Lake level graph shows the change in lake level over the course of 2017 (black line).
The available water storage calculation is based on 100% storage corresponding to the crest of the weir and 0% corresponding to the lake level that can sustain the minimum flow of 7 m3/s. The lake can store water above the crest of the weir, however water stored above the weir is not released into the river at a controlled rate and so it is not considered “available storage”. Prior to July 1st, the target water storage is the crest of the weir. After July 1st, the target for water storage is a regulated rule curve. For Cowichan Lake, the rule curve is the regulated limit set by the Province for the maximum amount of water that can be stored during the Summer and early Fall.