While flooding of Lake Muskoka could be reduced if the MNRF began earlier to draw-down the water level of Lake Muskoka, the MNRF’s ability to do this is constrained as the downstream flow is controlled by Ontario Power Generation. It appears that any flow down the Moon River greater than about 72 m³/s requires that OPG direct this excess flow to bypass their generating stations. Therefore, OPG would not earn any revenue from this excess flow.
After passing through Bala, the water from Lake Muskoka gets to Lake Huron either through the Moon River (the north branch) or the Musquash River (the south branch). Ontario Power Generation’s Ragged Rapids and Big Eddy generating stations are both on the south branch, so water flowing down the Musquash River earns OPG money twice, first by going through the Ragged Rapids generating station, then a few km later, through the Big Eddy generating station.
This is shown on the map below, which is a section of Figure 2.2 from the Muskoka River Water Management Plan (click on it to see the entire map).
OPG controls the flow through the Musquash River by the amount of water they pass through their generating stations. OPG also owns and operates the Moon Dam, which controls the flow through the north branch of the Moon River. Any water OPG allows through their Moon Dam is money lost, as this water gets to Lake Huron without going through OPG’s two generating stations. OPG desperately needs money to pay their employees’ high salaries, so OPG is incentivized to open their Moon Dam as late as possible and only as much as they feel absolutely necessary. The winter is a peak electrical demand time, so OPG would not want to waste the power generation opportunity, or the revenue.
As shown below (click on it for a larger view), this year OPG opened their Moon dam about January 1. Unfortunately we don’t know when OPG removed all the stop-logs from the Moon Dam, as the flow through it also depends on the upstream water level.
Therefore, the MNRF’s ability to draw-down the water level of Lake Muskoka in preparation for the spring freshet depends on when OPG removes stop-logs from the Moon Dam.