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February 28, 2018
What's happening this year?

Your water level task force has returned for another season to keep watch on lake levels, interpret what is happening and keep you informed.  We will be sending you communications monthly unless we start to experience higher levels and then we will increase our communications to weekly.

The water levels in the Muskoka Lakes are controlled by the Muskoka River Water Management Plan (MRWMP) that sets seasonal operating levels for each of the lakes.  Over the winter, the lakes are gradually drawn down to the bottom of the winter operating zone and this year they made it to the target.  This provides space in the lake for the spring melt to be stored until it can pass downstream into the Moon River at Bala.

The winter has abruptly come to an end with the mild temperatures and rain fall. There was 
heavy rain [40 mm – 1.6”] last week in Muskoka. This caused the Upper Lakes – Rosseau and Joseph - to rise by 9 cm and Lake Muskoka to rise by 14 cm.  Despite these increases in lake level, Lake Muskoka water elevations are well below normal summer lake levels and below the MRWMP target operating level for this time of year. Upper Lakes levels are below summer levels but slightly higher than the target operating level for this time of year. See below for more detail.

 
Lake Muskoka Status:

In Figure 1 [below] lake levels are shown for the past year. The right-hand side of the graph shows that water levels have been drawn down consistently from early November through the first week of January, and from early February until last week’s rain event on the 20th. Water levels rose slightly in January as warmer temperatures and rain melted the snow.

As stated above, lake levels are well below the MRWMP target for this time of year and well below normal summer levels. Looking back at this time last year shows comparable lake levels. Barring major rain events, the lake is at less risk of damaging high water this year as the snow levels in the watershed are lower.
Figure 1 : LAKE MUSKOKA – 2017/18 WATER LEVELS
[meters above gauge 02EB018 Beaumaris]
Situation: Lakes Rosseau and Joseph:

For Lakes Rosseau and Joseph Figure 2 [below] shows lake levels are about 0.25m [10”] below summer levels. The current water level is 0.05m [2”] above the normal drawdown level for this time of year. As snow level is below normal, keeping these lakes a bit on the high side may be prudent to ensure enough water for summer.  The situation on these lakes is less sensitive to rainfall and sudden snow melt than Lake Muskoka for three reasons: (1) snow is closer to normal levels; (2) there is still the normal 0.6m [2 ft] head difference at Port Carling so these lakes continue to drain at their normal pace [about 45 m3/s], and (3) unlike Lake Muskoka, only the immediate area drains into these lakes – not the entire 5,000 km2 watershed.
Figure 2: LAKE ROSSEAU/JOSEPH WATER LEVELS 2017-18
[meters above gauge 02EB020 Port Carling]
Do It Yourself: 

Members are encouraged to keep themselves appraised of changing water levels and how these compare to their personal waterfront structures. To access current water levels on your lake please click here and select either Lake Muskoka or Lake Rosseau under the heading "Checking Water Levels on Your Lake". If you are able to get a measurement of dock height above ice, you can know your own dock elevation for reference. If not, use the normal summer levels on Figures 1 and/or 2 to guesstimate your level.
Winter Construction:
Both the big lock at Port Carling and the Bala North Hydro plant have been under construction this winter. Figure 3 shows the big lock dewatered and repairs underway to the lock walls. Most drainage for the Upper Lakes goes through the small lock channel. Unless there is very high water, the big lock does not come into play.
Figure 3: Construction at big locks Port Carling 
Figure 4 shows construction of the intake channel for the Bala North hydro plant a week ago. A temporary cofferdam had been in place, blocking three of the North Dam sluices, until the end of last week. With the intake construction complete, we are informed that the temporary upstream cofferdam has now been removed. With this blockage removed and there is no longer any impediment to normal water operations at Bala during the upcoming freshet. 
Figure 4: Upstream cofferdam for Bala North hydro plant
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