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News, Energy Supply, Environment
Apr 15  Comment

April update: Peak water level forecast for Marsh Lake and other hydro basins

HYDRO PLAYS A KEY ROLE IN YUKON’S ELECTRICITY MIX.  In 2021, we expect to use water to generate about 94% of the electricity needed by Yukoners connected to the grid.  We own and operate three hydroelectric generation facilities in the territory – one in Whitehorse, one in Mayo and one in Aishihik. Lots of rain last summer and heavy snowfall this winter has resulted in high snowpack levels in each of these areas near our hydro reservoirs.  what high snowpack levels mean for water levels  On their own, snowpack levels don’t paint the full picture of how much water will flow into lakes this year. Three sources of water contribute to reservoir inflows and water levels:  Snowpack Rain Glacier melt (for Whitehorse only; not Aishihik or Mayo) The timing of each of these inflows also plays an important part in determining water levels, as does the natural limits to the amount of water that can flow into a hydro dam (i.e., Miles Canyon).  April 2021 snowpack levels forecasted summer peak water levels  Marsh Lake – 656.79 m  Forecast: Above Full Supply.  Assumes a wet spring.  Assumes we receive approval from the Yukon Water Board to draw down Marsh Lake 10 cm lower than its permitted Low Supply Level.  3 cm lower than the peak water level forecasted in March 2021.  55 cm lower than peak water levels during the 2007 flood.  Mayo Lake – 665.84 m  Forecast: At Full Supply.  Aishihik Lake – 914.82 m  Forecast: Below Full Supply.  what we have done, and continue to do, to drawn down Marsh Lake Every spring, we make room in Marsh Lake for rain and spring melt by lowering water levels on the lake close to its Low Supply Level (653.796 m) – the lowest level allowed under our water use licence.  This spring, because of high snowpack levels in the area, we have taken the following steps to increase flows through the Whitehorse dam and to lower levels on Marsh Lake:  Opened up the gates at the Lewes River Control Structure. All 30 gates have been open since March 19, 2021.  Lowered water levels on Schwatka Lake by 40 cm.  Submitted an emergency amendment to our Whitehorse Rapids Generating Station water use licence to the Yukon Water Board on April 1, 2021. The Yukon Water Board is currently deliberating our request.  To date, we’ve had success in lowering water levels on Marsh Lake. Between March 1, 2021 and April 15, 2021, levels on Marsh Lake have dropped 91 cm. Conditions downstream of the Whitehorse dam have also remained typical of this time of year.  Over the next several months, we’ll continue to keep a close eye on lake levels on Marsh Lake and downstream of the dam. As conditions change and our inflow forecasts become clearer, we’ll look at which additional options exist within our control to draw down lake levels even further, if needed. We will always keep the potential effects to the Southern Lakes, to neighbourhoods downstream of the dam, and to the land and environment top of mind. 

News, Safety
Mar 31  Comment

Yukoners asked to avoid going on the ice on Schwatka Lake

Ice breaks and fast-flowing water possible as Yukon Energy continues to lower Marsh Lake levels. Yukon Energy is asking Yukoners to avoid going on the ice on Schwatka Lake starting today. Water levels on Schwatka Lake will fall over the next week as Yukon Energy continues to increase the amount of water flowing through Miles Canyon and the Whitehorse dam, in an effort to lower water levels on Marsh Lake. Yukoners are being warned that lower water levels on Schwatka Lake may cause ice along the lake’s shorelines to break and for there to be unpredictable ice conditions. Water flowing under the ice surface is also likely to move faster than before. Yukon Energy started increasing flows at the Whitehorse dam earlier this month after Yukon government’s March 2021 Snow Survey Bulletin highlighted snowpack levels in the Southern Lakes region to be 172% of normal. At the time, Yukon Energy also forecasted that in case of a wet spring, water levels on Marsh Lake could peak at 656.82 m – similar levels to those reached in 2004, but 52 cm below water levels reached during the 2007 flood. On March 19th, Yukon Energy opened all 30 gates at the Lewes River Control as an initial measure to lower levels on Marsh Lake. As of 8:00 this morning, Marsh Lake levels were at 654.61 metres above sea level and 60 centimetres lower than lake levels on March 1, 2021*. Every spring, Yukon Energy draws down lake levels on Marsh Lake by generating hydroelectricity at the Whitehorse dam. This makes room in the lake for rain and spring melt. Water levels in Marsh Lake typically reach their lowest level in late May when they fall to around the Low Supply Level of 653.796 m – the lowest level allowed under Yukon Energy’s current water use licence. This spring, because of high snowpack levels, Yukon Energy plans to apply for an emergency amendment to its water license to draw Marsh Lake levels down 10 cm lower than the existing low supply level. Yukon government will release their next Snow Survey Bulletin in April. Yukon Energy will provide an updated peak water level forecast for Marsh Lake shortly thereafter. *Corrected. A previous version stated March 1, 2020. Media contact: Megan Yakiwchuk Corporate Secretary Yukon Energy 393-5337 megan.yakiwchuk@yec.yk.ca

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