2011 Spring Precipitation Model

As we near the first day of spring, here's an update on water conditions and what Ontario Power Generation is doing to manage its regulated river systems in Northeastern Ontario.

OPG conducts snow surveys throughout the region. These surveys are conducted to assess the water content in the snow (snow depths themselves do not provide much information in managing river systems - what's important is how much water is contained in that same snow). As of March 15th, snow surveys throughout the region are once again showing lower than normal water content. However, water content is still above last year's record setting lows.

With that in mind, the winter drawdown (the practice of lowering water levels in the winter to create storage capacity for spring inflows to mitigate flooding downstream) has ended at water control dams further south of the region, and is approaching an end at those further north. Most dams will ultimately close approximately 2 to 4 weeks earlier than normal, as was the case last year, in light of the snow survey data collected, provided conditions remain the same.

However, the majority of inflows required to fill area reservoirs comes in the form of spring precipitation. Since the ground is usually frozen or saturated in the spring, March, April and May showers make their way quickly into reservoirs as they cannot be absorbed by the ground or dormant vegetation. This is the primary reason for the drawdown. Once rain arrives in the summer, it generally gets absorbed by surrounding vegetation and has little impact on inflows. In other words, even in a year where a single snow flake wouldn't fall on the area, reservoirs would still need to be drawn down to make room for rain.

To put things into perspective, on an average year, snow in Northeastern Ontario should contain 5 to 7 inches of water or 127 to 177mm at this time. Last October, in one single day, we received 70mm of rain in some areas and more in others. Two days of heavy rain or even a week of steady rain can provide as much water as what we have at this time, after an entire winter of snowfall. Once again, contrary to popular belief, area reservoirs are drawn down primarily to accommodate spring rainfall, not snow.

Environment Canada's latest model, which I've attached, is predicting normal to above normal precipitation for Northeastern Ontario and normal temperatures for the period of April to June. Taking into account current snow conditions and weather models, water levels should reach their respective summer minimum elevations by Victoria Day weekend.

If you have any questions regarding area regulated river systems managed by OPG or if you would like more information, please do not hesitate to contact me.

Please feel free to forward this information or my contact information to anyone who shares your concern and your passion for area regulated waterways.

I will continue to provide updates as conditions evolve.

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Precipitation Model.pdf

Marcel Pelchat
Public Affairs Officer
Ontario Power Generation
Tel.: (705) 267-7033 ext. 3303
Cell: (705) 262-2381