WLTF Report to MLA Members Issue 2017-3

Cooler weather and continued water level drawdown by MNRF have reduced the risk of flooding for this week…. water levels are still above the required drawdown level for this time of year but long term weather forecast - daytime highs just above freezing but overnight below freezing - should allow for continued drawdown of the water levels. 

Lake Muskoka Update:
The graph below shows Lake Muskoka water levels peaked about March 12th. Since then water level has dropped about 10 cm [3.9”] over five days. If this rate of 2 cm /day can be sustained through this week the lake level will drop 0.14m [5.5”] lower and will approach where it was before the rains at end of February sent it higher. Further drawdown in subsequent weeks, weather permitting of course, might allow the normal drawdown level of 8.95m to be reached ahead of freshet. Discharge through the Bala Dams is slightly lower than last week’s 240 m3/s and flow constrictions around Bala Park Island continue to cause a backup. As reported last week, this is nearly the highest discharge rate at Bala without risking damage to structures in the downstream Bala Reach/ Moon River area. Note that the slope of the drawdown is steeper than earlier in the year, so drawdown is proceeding faster, which is a good sign.

For reference, Normal Summer levels: 9.35m to 9.65m; Normal Drawdown level 8.95m; Flood Level 10.05m on following figure.

Figure 1: LAKE MUSKOKA – 2017 WATER LEVELS [meters above gauge 02EB018]

Lakes Rosseau and Joseph Update:
The graph below shows water levels for Lakes Rosseau and Joseph peaked about March 11th and have dropped about 6 cm [2.4”] since then. The water level difference at Port Carling appears to be preserved so drainage into Lake Muskoka is still taking place at approximately 1cm/day. This rate, if continued over the next week, will return levels to about 8.65m and if continued for two weeks could allow normal drawdown level of 8.58m to be reached. Stay tuned for next week’s update.

For reference, Normal Summer levels 8.88m to 9.03m; Normal Drawdown level 8.58m; Flood Level 9.28m on following figure.

Figure 2: LAKE ROSSEAU/JOSEPH WATER LEVELS 2017 [above gauge 02EB020]

Snow Core information
Snow core data just received from MNRF for March 15th shows average snow water content was 41% above normal. Snow core information as of March 15th is used to inform MNRF whether to trigger lower than normal drawdown levels. This amount of snow water content indicates that lower than normal drawdown levels are likely triggered. Additional information is that the recent cold weather has converted much of the ground snow to ice. Despite the high snow levels, the condition of the snow is good news as ice will be slower to melt and runoff than comparable amounts of wet snow.

Weather Information
Over the coming week, daily temperatures are expected to remain below zero and only minor precipitation with little rain is forecast [per The Weather Network]. This weather is favourable as it allows time for drawdown to occur and storage capacity to be increased to accommodate spring flooding.

Summary
Water levels are still high on the Muskoka Lakes but are starting to drop. Cool, mostly dry weather over the next week should allow an appreciable amount of the early year drawdown to be restored. There is still a high level of snow in the bush, so higher than normal drawdown is required. Fortunately, the cold weather has converted this snow to ice, decreasing the risk of flooding from rapid temperature rise. Continued cold dry weather will need to persist for desired drawdown levels to be achieved. While not expected within the next week, significant rainfall is now the main concern and could trigger high water.

Members are encouraged to keep themselves appraised of changing water levels and how these compare to their personal waterfront structures. Please refer to previous advice on how to access current water levels on line [wateroffice.ec.gc.ca]. 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 communicated in our last issue to guesstimate your level.

So please prepare your property for what looks like another year of spring flooding in Muskoka.