Our Latest Summer Forecast for Marsh Lake

Energy Supply, Environment

Jul 24, 2012  Comment

While property owners and residents in the Southern Lakes continue to watch the water rise around their homes, we too are keeping a close eye on the levels. Our latest forecast for peak levels on Marsh Lake shows a range. The darker dotted line shows the 'worst case' scenario, with levels reaching 40 cm (16 inches) below 2007 peak levels. The lighter dotted line shows the 'best case' scenario, with levels below the 2004 peak.

We continue to get questions about why we are keeping water levels so high this year. In fact we have no ability to control the lake levels at this time of year. Here are a few points that we hope will explain how we are allowed to operate.

1. Today's lake level (July 24) is 656.368 metres above sea level. That is about 16 cm higher that our current Full Supply Level in our water licence, which is 656.23 metres.

2. Our water licence says that we must have all our gates open by May 15th each year, and the gates must remain open until at least August 15th. Even then, we can only close them if the water has dropped to below our Full Supply Level (FSL). That means there are some years when we don't actually start to close gates until late September (typically that happens in higher-than-normal water years such as this one). It also means that during the summer, Yukon Energy does not have the ability to control lake levels. The level you see now is the natural level.

3. Marsh Lake goes to our Full Supply Level elevation naturally every year, and often it goes well above this level.

4. Lake levels today appear to be typical of other high water years. High water years occur about 25 percent of the time.

We are also asked what will happen with lake levels if we get permission to go to a new Full Supply Level, as we are looking at in the Southern Lakes Enhanced Storage Concept.

1. The new Full Supply Level that we are considering is 656.53 metres, which is 30 cm (1 foot) higher than the current Full Supply Level.

2. The flood level is 656.79, which is the 2004 water level. That is .26 of a metre (26 cm or close to a foot) HIGHER than the proposed Full Supply Level. "Flood level" is a bit of an arbitrary term, but essentially it's a level where people start to experience some flooding issues.

3. In 2007 Marsh Lake peaked at 657.34. That is .81 of a metre (81 cm) above the proposed Full Supply Level and is more than a metre above today's lake level.

4. Marsh Lake reaches 656.53 (the proposed new FSL) naturally one out of every three to four years. In the last 26 years, the lake has reached this level naturally 10 times: in 2009, 2007, 2004, 2000, 1994, 1993, 1992, 1989, and 1986.

5. Today the lake is approximately 13 cm below the proposed new Full Supply Level.

We know this can be a complicated subject, so please don't hesitate to send us a note if you have questions or comments.


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