Summary
The proponent would be increasing the water level of Lake Muskoka in order to increase their profits. Which would be fine, except this increases the risk of flooding Lake Muskoka when unexpectedly heavy rains occur.
Detail
The proponent’s 2009 Environmental Screening report detailed the changes the proponent would request to the Muskoka River Water Management Plan.
The dashed line in this diagram shows the “Target Operating Level” for Lake Muskoka, which is the water level (in metres above sea level) the proponent would be attempting to maintain for Lake Muskoka. As you see, it varies throughout the year for various reasons (for example, it is lowered in advance of spring freshet to allow for the rapid increase when the snow begins to melt), and this is the same water level the Ministry of Natural Resources currently attempts to maintain.
However, the proponent proposes a “Best Management Zone”, shown in more detail in the inset image, which would allow the proponent to raise the water level of Lake Muskoka by 4 cm during August, and by 5 cm during September.
In addition, the proponent would be allowed to cycle the operation of the proposed generating station, for example, by stopping flow through the generating station during the night and morning (increasing the water level of Lake Muskoka), and running it at up to ⅓ capacity during the afternoons (decreasing the water level of Lake Muskoka). This cycling would change the water level of Lake Muskoka by perhaps 2 cm each day. As detailed in Section 9.12, the required water level is reported as a 24-hour average, so the actual water level could be 1 cm lower than the top of the Best Management Zone at night, and 1 cm higher in the afternoon (so, 5 cm higher during August and 6 cm higher during September), and it would still be considered in compliance.
But as shown by the green band, the proponent could raise water levels even further and still be in the “Compliance band”, which would normally be to allow delays while staff get to the dams to insert and remove stop-logs. But the proposed generating station would be automatically- and remotely-operated, and is now said to have a higher capacity (96 m³/s) than originally-proposed (79 m³/s). So the output could change more rapidly to try to not exceed the Complaince Zone, which would increase even more the danger to those in the water at the base of the Bala north falls.
This higher water level would be at the times power is generated (and higher water levels mean greater power generated and greater profits to the proponent), but only during the months that the proposed generating station would have the least flow and therefore least profits. So this appears to be only for the purpose of generating more revenue for the proponent. Which is fine, except higher water levels also result in less margin to allow for heavy rains, which as we’ve seen, seem to be occurring more often lately.
So there would be more shoreline erosion and more risk of flooding just so the proponent can increase their revenue.