WLTF Report to MLA Members Issue 2017-10

May 5th – 12:00pm: ……Spring Freshet is not over. Heavy rainfall at the end of last week has partially reversed recent lake level reductions for Lake Muskoka and completely reversed them for Lakes Rosseau and Joseph. Levels are again at or above Spring high and projected to rise significantly again with major 40 to 70mm rainfall forecast for Friday.  MNRF has issued a Flood Warning for entire Muskoka River watershed in advance of this rain.  Members are advised to act to mitigate damage from submergence and wave action. Also, if travelling by boat, go slow to avoid adding wake damage to already fragile shorelines and waterfront structures.  Care is also advised to avoid contacting floating debris if travelling by boat.

What does this mean to you?
The level of each property owner’s docks relative to lake level is unique to individual circumstances.  The MLA strongly encourages property owners to relate their docks/boathouses to the nearest Environment Canada water level gauge [Beaumaris for Lake Muskoka; Port Carling for Lake Rosseau; Bala for Bala Bay].  If possible, measure distance from top of dock to water level and obtain water gauge elevation from muskokawaterweb.ca website under “checking water levels on your lake”.  Alternatively, the level can be guesstimated from summer levels provided below.  The MLA appreciates that normal Spring level may be higher than some docks and that current water levels may allow wave action to wash over some docks now.

How we got here:
Please see earlier newsletters for this winter’s water level history.  Click here.

Lake Muskoka Update:
Figure 1 below shows Lake Muskoka water levels crested at 9.96m on April 22nd and then dropped 27 cm [11”] to April 29th.  A major rain event April 30/May1 of 50mm has raised levels by 9 cm [3-1/2”] to gauge elevation 9.78m.  With weather forecasting services issuing rainfall warning for May 5 and 6, calling for 40 to 70mm of rain, another water level rise on the order of 9 cm is probable. MNRF has issued a flood warning for this lake in advance of the heavy rain.  A pattern of stabilization and cresting by late next week, similar to this week, can be achieved if the rains cease for a while.

Property owners are advised to take action to mitigate high water effects on their property.

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

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

FIGURE 2 – Historic Water Levels for Lake Muskoka 2002 – 2016

Average [2002-2016] - blue solid line       2016 actual – red line    Maximum [2002- 2016] – green line

MRWMP Flood Level = 10.05 m             Top NOZ = 9.8 m for Mar 27 to May 16th

Lakes Rosseau and Joseph Update:
The graphs below show Lake Rosseau and Joseph water levels crested at 9.17m on April 22nd and then dropped 6 cm by April 27th.  High rainfall of 50 mm at month end raised water levels by 10 cm to a new peak level for this year of 9.21m gauge.  The forecast of 40 to 70mm of rain could raise levels another 10cm and place this lake above Water Management Plan flood level.  This level could be quite close to the level experienced last year. MNRF has issued a Flood Warning for these lakes in advance of the heavy rains.  With dry weather and the usual draw down rate of about 1 cm/ day, returning these lakes to normal levels could take over two weeks.

Property owners are advised to take action to mitigate high water effects on their property.

Figure 3: LAKE ROSSEAU/JOSEPH WATER LEVELS 2017 [above gauge 02EB020]

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

Figure 4 - Historic Water Levels for Lakes Rosseau & Joseph 2002 – 2016

Average [2002-2016] - blue solid line       2016 actual – red line    Maximum [2002- 2016] – green line

MRWMP Flood Level = 9.28 m  Top NOZ = 9.13 m April 1 to May 20th

Bala Reach/ Moon River Update:
Prior to last weekend’s rain, flows into the Bala Reach had declined to 290 cms, which is still above the flood level of 280 cms.  Flow has since increased, post the recent rain, and further flow increases at least equal to last weekend will likely follow after the heavy rain expected this weekend May 5 and 6th.  A Flood Warning was re-issued by MNRF and remains in effect.  These conditions are expected to last for as long as Lake Muskoka remains above “normal levels”. Members are advised to take action to mitigate effects of ongoing flooding.

MNRF Statements
On Thursday, May 4th MNRF issued a “Flood Warning” for entire Muskoka River watershed.

Ice Damage
Although the ice is now out, members are advised that damage did occur over the winter due to ice expansion.  Please see earlier communications for details.

Summary
Heavy rain last weekend undid the previous weeks’ water level declines.  Another major rainfall, predicted for this weekend is expected to push lakes into the flood zone.

Shoreline property owners are advised to take action to mitigate flood effects on their shoreline structures and personal property.