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Seaway Shipping Navigates Back-to-Back High and Low Water Extremes

eisenhower locks
Eisenhower Locks, St. Lawrence Seaway (File image)

Published Jun 20, 2021 5:24 PM by Harry Valentine

The international regulatory agency that oversees water levels on Lake Ontario and downstream along the St. Lawrence River is working to manage the effects of lower than normal water levels in their jurisdiction resulting from drought conditions. This drought follows two years of extremely high water levels in Lake Ontario and along the St. Lawrence River.

Introduction

The governments of Canada and the USA have kept long-term records on water levels in the Great Lakes and along some major rivers. For two successive previous summers, water levels in Lake Ontario and along the St. Lawrence River had reached record levels. Some officials speculated that such levels might represent a new norm caused by changing climatic conditions. Now the same officials are expressing concern over record low water levels caused by a drought that affects the watershed area of the Great Lakes. Presently, excess water from previous years is beginning to flow from the Upper Great Lakes.

Lake Ontario presently measures 14 inches below the long-term average water level. According to long-term projected weather forecasts, that level is expected to continue for several months. A 12-month period in 1966 was the last time when water levels in Lake Ontario dropped to such low levels. Reduced water levels in Lake Ontario have affected water levels in the Lower St. Lawrence River on the upstream approach to the Port of Montreal. As a result, captains of the deepest draft vessels that sail to Montreal have been urged to sail at reduced speed.

Hydroelectric Power

 There are two large hydroelectric power dams located along the Upper St. Lawrence River between Montreal and Lake Ontario, with Lake St. Francis being the holding reservoir for the lower dam operated by Hydro Quebec and Lake St. Lawrence for the upper dam that is jointly operated by New York Power Authority and Ontario Power Generation. The operation of air conditioners increases over the hot summer months, increasing demand for power that occasionally pushes the power grid to its limits.

A reduction in hydroelectric power generation along the Upper St. Lawrence River would reduce water volume flowrate into the Lower St. Lawrence River and the Port of Montreal. The drought has reduced rainfall over watershed areas of numerous rivers that flow into the St. Lawrence River, including the Ottawa River, which has a hydroelectric power dam located northwest of Montreal. Hydroelectric power dams are located along many other rivers that flow into the St. Lawrence River, which also provide numerous municipalities with drinking water and sustain some agricultural production through irrigation.

Ship Traffic

At the present time, ship traffic on the Upper Great Lakes involving large bulk carrier ships has so far been essentially unaffected by the drought, the result of excess water volume left over from the previous two years of excess precipitation. The smaller than maximum Seawaymax dimensions of container ships that currently sail upstream of Montreal to Lake Erie allows for their continued operation. The majority of bulk carriers that are built to near maximum Seawaymax dimensions usually carry agricultural produce on this route, and they sail toward the approach of winter.

The drought has sufficiently reduced water levels along sections of the Lower St. Lawrence River between Quebec City and Montreal to require sailing speed reductions for deep draft vessels. There is the possible option of partially offloading the largest container vessels at either Port of Quebec City or Port of Halifax so as to sufficiently reduce draft to assure sailing to the Port of Montreal. However, water levels in Lake Ontario and along the Upper St. Lawrence later this year would determine the sailing strategy of ships along the Lower St. Lawrence River. 

Long Term Weather Patterns

The combination of two years of record high water levels across the Great Lakes and St. Lawrence River followed by drought and record low water levels raises concern as to whether climate change is causing such swings. Measurements taken over the period of a decade or longer could determine whether climate change would affect the frequency of record low and record high water levels in the Great Lakes. Climate change will likely cause ocean levels to rise and potentially increase sailing depth along the eastern section of the Lower St. Lawrence River.

During previous low water level occurrences along the Upper St. Lawrence River, concerns were raised about the need to maintain navigation depth along the Lower St. Lawrence River. While the option of installing navigation locks on the Lower St. Lawrence River had been raised for such a purpose, it was rejected. However, severe future drought could require reconsideration for such locks, perhaps east of Lake St. Pierre and under the bridge at Quebec City to maintain sufficient navigation depth for deep draft container ships to sail to the Port of Montreal.

Future Planning

Numerous scientists and environmentalists have repeatedly issued warnings about possible future outcomes of climate change. The outcomes include rising sea levels, increased occurrences of drought in some regions along with increased and more severe precipitation in other regions. There is also the possibility of the same region experiencing alternating occurrences of severe drought during some seasons and excess precipitation in other seasons. The long-term future weather patterns that will occur over the watershed regions of the Great Lakes and St. Lawrence River will determine the nature of future water management along the waterway.

The Lower St. Lawrence River downstream of Montreal is under the jurisdiction of the Government of Canada, which has the authority to decide as to whether or not to install navigation locks along the river to assure sufficient water levels during future drought. Officials may be motivated to maintain the “status quo,” hoping for the return of traditional long-term weather patterns. They will need to establish strategy by which to manage future excess high water levels on Lake Ontario and along the Seaway in a way that prevents excess flooding around the City of Montreal.

Future Electric Power

It is presently unknown as to whether climate change is causing alternating periods of record low water levels and record high water levels in Lake Ontario and the St. Lawrence River. Reducing hydroelectric output along the St. Lawrence River between Lake Ontario and Montreal to conserve water would reduce the volume of water flowing into the Lower St. Lawrence River and affect shipping. Undertaking such strategy would require the installation of navigation locks along the Lower St. Lawrence River to both conserve water and assure continued ship navigation to the Port of Montreal.

During future periods of record low water levels in Lake Ontario, reducing power generation along the St. Lawrence River would require that available power be sourced from elsewhere. Such strategy may even require the construction of new power stations elsewhere at suitable locations. Future periods of record high water levels would likely warrant reduction of hydroelectric power generation and resulting reduction in water volume flowrate downstream along the St. Lawrence River to prevent flooding at Montreal. Governments would likely be reluctant to build new navigation locks and new power stations to deal with changing climate.

Conclusions

Over the past three successive years, record levels of high water and low water have occurred on Lake Ontario and along the St. Lawrence River. It is presently unknown as to whether such unusual weather patterns are a rare occurrence or the start of a long-term trend of severe alternate swings between drought and excess precipitation over the watershed areas of the Great Lakes and St. Lawrence River. An ongoing continuation of these weather patterns would likely require navigation locks along the Lower St. Lawrence River to assure continued large ship navigation to the Port of Montreal.

Long-term future severe weather patterns would require reexamining plans for the Port of Quebec City, especially in the absence of installation of locks along the Lower St. Lawrence River. Future low-water conditions could limit big container ships to sail only as far inland to the Port of Quebec City. It might take a decade or longer to observe weather patterns to decide future navigation strategy between the Atlantic Ocean and Great Lakes.

The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.