One of the biggest concerns I hear are to do with lake levels, particularly in the winter at peak water levels or often referred to as the High Water Mark (HWM).
As is turns out the Government of Canada has been recording lake levels and river flows for decades. This can be found on their website at http://www.wateroffice.gc.ca and look for station 08HA009 where it will show you current water levels and you can search historical data as well. The graph is referenced as: Real-Time Hydrometric Data Graph for COWICHAN LAKE NEAR LAKE COWICHAN (08HA009) [BC]
This data shows us that before the existing weir was constructed in 1957 the HWM averaged 164.16m from 1953 to 1956 and has since averaged 164.01m for the 61 years from 1957 to 2018. The lowest HWM was 162.33m in 1978 and the highest HWM was 165.39m in 1968.
The current weir crest height is at 162.37m. With an average HWM of 164.01m you can see that the weir is actually submerged (by 1.6 meters or 5 feet) during the high water season. I took a few photos a couple of weeks ago and the flow over the weir is hardly noticeable as the water flows completely over it, across the weir island and around the south side. The flow control shifts downstream to the natural river valley close to the Greendale Trestle and it is the river valley that then controls the HWM as the valley narrows and the river bottom rises. Similarly the new weir (at 163.07m) will be submerged during the high water season and shouldn’t impact annual High Water levels.
With longer, hotter and dryer summers becoming the new norm it will be important to hold back some more of these winter waters for release through the summer months.
There has been a lot of interest and questions regarding paddling, kayaking, surfing and general whitewater types of recreation in connection with this project. I did not answer each of the questions that have come through individually – instead I thought I would address it here. Although not a paddler of any sort I can certainly understand the attraction of using this heritage river and all of it’s surrounding beauty and to want to ‘play’ in it.
This project and the associated grant from the BC Salmon Restoration and Innovation Fund (BCSRIF) is targeted towards the improvement of environmental/fish flows and doesn’t have the mandate to design integrated whitewater recreational features. This work is to inform the eventual water license holder who would also become the owner and operator of the new weir. This ownership entity is still unknown. Quite frankly, we are not even sure an integrated water feature would be feasible given the hydraulics, landforms and land ownership issues in this immediate area. Having said that, a feasibility study could be taken on (by others) and could take into consideration our current preliminary design and it’s hydraulic outputs. Perhaps there is opportunity to consider something immediately downstream of the weir or even further downstream throughout the entire reach of the river. People with expertise in this area of study would need to evaluate those different scenarios.
The whole notion of another form of recreation is important in my estimation, however it needs to be brought forward in a planful way and start fitting into strategic plans for local communities such as the CVRD and the Town of Lake Cowichan. Strategic plans usually look ahead 5 or more years and these new ideas need to be integrated into those systems for long term support and success.
I certainly appreciate your energy and enthusiasm and coming forward with such a strong and cohesive voice. I suggest keep your agenda moving forward by integrating your ideas into the local governments planning processes.
I just wanted to thank everyone for making the December 10 virtual presentation regarding the Weir Preliminary Design a success. Most importantly we had over 100 participants and you really added value with all of your great questions. Under the ‘Weir Design’ TAB on this website you can see the presentation and hear the Q&A session. Although we ran out of time, we did address most of the questions and I am hoping it addressed yours. If not, please send me your question through this site. I will do my best to respond over the next couple of weeks.
I would also like to apologize for those who did not receive enough notice regarding this meeting. Apparently some of the letters were delivered well after the meeting date. I take responsibility.
The primary reason for raising the weir is for environmental flows to support fish habitat and create a better environment for salmon in particular. Our Heritage Cowichan river has seen much degradation in it’s fish bearing capability over the past 100 years primarily due to development and climate change. This project is just one of the ways we can help protect one of our finest assets in the Cowichan Valley.
Although not required for fish health or fish passage, items like a walkway over the weir, hydroelectric power, lighting, and recreation are items of interest to people in the area. I agree we need to find the balance between a basic functional design and a design that is pleasing, educational and supports the local community. We will continue with the design in the new year and consider what we have heard.
Stay safe, take care and Best of the Holiday Season to you! Leroy.
The current ‘Weir’ actually has several distinct and unique elements making it the WEIR as we commonly describe it today. From north to south it is a collection of a boat lock, a concrete dam, a concrete sill across the weir Island, a gate structure with 4 independent gates, a fish ladder and finally a concrete sill into the south abutment. Only the gates control the flow during the control period (from April to October). During the winter months (November to March) the gates are laid down and are considered fully open. The concrete dam and sills give us the elevated water supply for us to control but they do not control the flow volume.
As we design a new elevated weir one of the questions is whether or not any of the existing structures can be reused. We have determined that we cannot reuse the concrete dam, the concrete sills nor the fish ladder. They have deteriorated over the past 63 years but most importantly they are at the wrong elevation. It appears that both the boat lock foundation and the gate foundation can be reused and would save considerable costs of demolition and rebuilding new. The health of those concrete structures will be verified over the next couple of weeks.
The design is becoming clearer as we near our Preliminary Design deadline. We will share that information with you on December 10. Stay tuned.
While I am not the right person to give you all the facts and figures on why a new weir is necessary, I can point you to few places to get all the information you need at the end of this posting. Essentially the weir is needed to support environmental (i.e. fish) flows due to climate change which has resulted in greatly reduced precipitation (including snow) in our valley. A new weir is not required to ensure water supply to Crofton’s pulp and paper mill. Their existing water license and the current weir have secured that supply since 1957 and that will continue into the future, regardless of a new weir.
I can tell you that the current structure, built in 1957, does not meet todays engineering standards or Dam Safety requirements. That doesn’t mean it isn’t safe, it just means that it requires regular reviews, inspections and that maintenance is necessary. It also means that it is not as robust as it would be if we apply today’s standards. Data of precipitation, flooding, earthquakes, seismic activity are much more robust now than 65 years ago. The understanding of science, geology, engineering, material technology has also progressed substantially over the past several decades. One would certainly expect changes to engineering and design standards over time particularly as populations have increased around water bodies.
The following are a couple of links to websites with much more information on why we need the weir: