Without environmental approval, and in contravention of the Muskoka River Water Management Plan, the proponent’s construction plans include an upstream cofferdam which would block all flow in the Bala north channel for the ten months from June through March.
Not only would this create stagnant water at the base of the Bala north falls (which would harm the critical Walleye habitat there), but flow through the Bala north channel is also needed for high flow events which occur outside of the traditional spring freshet period of April to May.
Analysing the available Moon River flow data from Environment Canada’s Water Office shows that in the ten months from June through March, flows exceeded the 252 m³/s capacity of the Bala south channel twelve times. The table below shows the specific dates and flow which the Bala north channel would have needed to carry on these dates.
For example, on December 12, 1966, the total flow through Bala was 337 m³/s, which is 85 m³/s more than the Bala south channel’s capacity, so the Bala north channel would have had to handle 85 m³/s to prevent flooding of Lake Muskoka.
|June to March peak date||Peak flow
|Exceeded 252 m³/s
(south channel capacity) by …
|1||December 12, 1966||337||85|
|2||November 7, 1967||293||41|
|3||March 19, 1967||274||22|
|4||September 9, 1981||298||46|
|5||December 9, 1982||268||16|
|6||June 1, 1984||261||9|
|7||January 4, 1985||275||23|
|8||November 18, 1992||333||81|
|9||November 18, 1995||256||4|
|10||November 22, 2003||282||30|
|11||January 15, 2008||291||39|
|12||December 5, 2010||273||21|
Based on the last 49 years of data, to ensure their construction plans do not cause flooding of Lake Muskoka, the proponent must ensure that the Bala north channel can handle a flow of at least 85 m³/s throughout their proposed construction. As detailed here, the proponent’s current plan to handle such a flow by quickly removing their proposed upstream cofferdam is not feasible.