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Water levels discussion

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in Blog
on 06 March, 2012

Robert Caldwell, an Environment Canada water resources engineer, knows his phone might ring any minute with a request from the Montreal Port Authority to allow a bit more outflow from Lake Ontario so a ship can safely float to its berth in the Port of Montreal.
The 2012 summer’s heat and drought has caused water levels to recede to lows not seen in decades on Lake Ontario and near and at the Port of Montreal. There’s no reason for commercial navigators to panic, he says. Not yet, anyway.

 “We have enough water to release as necessary for the rest of this navigational season,” he said from the Great Lakes-St. Lawrence Regulation Office in Cornwall, Ont. “But if we experience consecutive years of this kind of drought, it would be awful.”

Caldwell supplied Marine Matters with the provisional values/estimates for July with six days left in the month.
At 183.3 metres, Lake Superior is slightly higher than last year as a result of wetter conditions in the region, but expected to fall below chart datum by January.
Michigan and Huron are comparable to 2007 levels, which aren’t unusual but relatively low at 176.04 metres. They’re expected to fall below chart datum by September, and possibly sooner.

St. Clair, at 194.94 metres, is higher than in 2007 by 2 centimetres but still relatively low. The same goes for Lake Erie, which at 174.13 metres is again comparable to 2007. Both lakes are expected to remain above chart datum but below average.
Lake Ontario will likely remain above chart datum, but significantly below average. A hot, dry summer in most of southern Ontario has lowered the water level to 74.79 metres – the lowest July level since 1965. The last time it approached being so low was in 1999, at 74.81 metres, but the current level is still within the normal range.

“The International St. Lawrence River Board of Control is closely monitoring the situation to continue to restore water to Lake Ontario, while maintaining adequate levels for commercial navigation downstream of Cornwall,” Caldwell says.

 As a result, the St. Lawrence Seaway is 74.27 metres on average. The board has a directive to keep its levels at a monthly mean of no lower than 74.15 metres from April to November (even though a warmer clime has vessels sailing as early as March and as late as the end of December).

While the level is for the most part meeting the needs of commercial shipping, it’s causing misery to marinas and recreational boaters.

Lake St. Louis, along the shores of Montreal’s West Island, has dropped to 20.68 metres – the lowest level for July since 2001. Fixed docks are too high in many cases to use with the lower levels. Many boats already have been pulled out of the water to avoid them becoming stuck in mud. Boasters still using their craft are running a much greater risk of hitting rocks or bottom in the shallower conditions.

“It’s necessary for us to look ahead at the risk of the water getting too low on Lake Ontario for commercial navigation and other key stakeholders towards the fall if we don’t keep some of it in reserve now,” Caldwell says.

“We’re already seeing record lows at the Port of Montreal and Lake St. Louis and have come off the regulation plan to release small quantities of water downstream to float certain vessels into the port.”

The need has arisen twice so far this summer. “In each case it was done for an overseas container ship that prepared its cargo according to the information available on water levels at the time of loading at its homeport,” says Yves Gilson, communications manager at the Montreal Port Authority. “These forecasts were done up to 35 days earlier and the situation changed by the time each vessel arrived near Montreal.

“For the vast majority of vessels, the levels aren’t posing a problem because they have the most up-to-date information and load accordingly. The radar-tracking systems aboard most ships also ensure that vessels sail within sufficient depths.”

Ships are loading lighter, but it could also be as a result of softer destination markets in the current economic climate.

If the Montreal Port Authority’s harbour master perceives a tight squeeze, a call is made to the Canadian Coast Guard. It transmits to the Cornwall regulation office the port authority’s request to briefly increase Lake Ontario’s outflow.

“We first have to determine whether there’s enough water to do the job,” Caldwell says. “Then, if we think we can help, we contact six other agencies in Canada and the United States representing hydroelectric and other interests and must reach a consensus on whether the anticipated increase in water velocity will be alright.  
“If the water travels too fast, the levels through the upper reaches of the St. Lawrence can become too high and could cause ships to ground. We also have to avoid the gradients in the river upstream from Cornwall from getting so high that the water levels in that region drop too dramatically.”

Usually everything is considered and a decision made within the hour.

“A minimum of 20.6 metres – 25 centimetres above chart datum – is necessary for vessel transit on Lake St. Louis,” Caldwell says. “So we’ve consistently maintained the water above that level on a daily mean basis by releasing some water a few times in recent weeks.”

In Montreal, where the measurements are taken at Jetty 1 (upstream from where most of the commercial activity in the port occurs), the water level was about to set a record monthly mean for July at approximately 5.27 metres. It would be the lowest level since records starting being kept for the present regulation regime that began in 1967. The previous record low for July was 5.46 metres in 2010. The water is significantly deeper where commercial ships dock and was at -.37 metres relative to chart datum on Aug. 1.

Lake Ontario’s usual outflow has been within the normal range. The dramatically lower levels in and around Montreal are being caused by a reduced flow out of the Ottawa River (called Rivière des Outaouais in Quebec) into the St. Lawrence.

The largely unregulated Ottawa River doesn’t have dams that can store water for release during shortages. Snowmelts and downpours run their course in one big hurry. The dams that do exist are run-of-river hydroelectric installations that make power from the water naturally pouring over them.

A totally separate arm of Environment Canada – the Ottawa River Regulation Secretariat – monitors the river’s water levels for hydroelectric interests, and the way it collects and presents its data can make it tricky at times to figure out the impact on the St. Lawrence.

While the idea of further regulating the Ottawa River to control its output into the St. Lawrence during times of drought or potential flooding has been raised, it is not being considered at present.

The Port of Montreal will likely remain below chart datum until ice forms in the St. Lawrence, and may remain at record low elevations through the end of the year if dry conditions persist.

As for next year, it’s too early to tell. “We took 15 centimetres off Lake Ontario’s wake this past spring to reduce the risk of flooding,” Caldwell notes. “But it would take significant, persistent above-average precipitation over several months – or some other climate factor such as a heavy snowmelt – to restore the system to average levels, which I think is unlikely to happen.”

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