| Abstract/Description or Keywords |
The Cowichan Lake weir is used to store water in Cowichan Lake to regulate flow in the Cowichan River during the spring and summer period. The weir is usually operated from April 1st or but not earlier than March 1st in dry years until lake levels start to rise as a result of increased inflow in the fall. The operation of the weir is guided by a set of operational protocols that have been developed based on past experience and knowledge of the system. The primary purpose of these protocols is to maintain minimum flow in the river of 25 m3/s from April 1st to April 30th, 15 m3/s from April 1st to June 14th and 7 m3/s from June 15th until the end of the control season when lake levels rise as a result of increased inflow in the fall (typically before Nov 4th). The purpose of this study was to assess these protocols using hydrological analysis and recommend changes to improve the reliability of the system. An operational model of the Cowichan Lake Weir has been developed to assess impacts of changing the weir operation protocol on the ability to maintain lake levels at or above the weir crest during the early control season (prior to July 9th) and to maintain lake levels above zero storage before the end of the control season (when lake levels rise due to increased inflow typically before Nov 4). In addition, an assessment of how changing the weir operation impacts peak lake levels has also been completed. This project was co-funded by Living Rivers-Georgia Basin/Vancouver Island (2006-11), a program of the BC Living Rivers Trust Fund. |
