Impact of Water Level Changes on Commercial Navigation in the Great Lakes and St. Lawrence River

Article excerpt

This paper estimates the impact on commercial navigation of, first, the implementation of proposed water level regulation measures for the Great Lakes and St. Lawrence River and, second, a doubling of atmospheric carbon dioxide. The impetus for the development of new water level regulations was the high water levels experienced on most of the Great Lakes in the mid 1980s. These levels resulted from almost two decades of above normal precipitation and below normal evaporation in the Great Lakes-St. Lawrence River basin. They were a major cause of flooding, erosion, and shoreline damage. The International Joint Commission was asked to examine and report on measures to alleviate the adverse consequences of fluctuating water levels. The Commission established a Levels Reference Study Board which, in proposing ways of reducing the impacts of varying Great Lakes-St. Lawrence water levels, developed a number of new water level regulation measures.

Changes in the Great Lakes and St. Lawrence River levels are important to commercial navigation. Most vessels in the Great Lakes are constructed to take advantage of maximum allowable depths; their under-keel clearances in locks, harbours, and connecting channels are often less than one metre. Thus, even small decreases in water depths can reduce vessel carrying capacities and increase unit transportation costs. The impacts of water level changes are examined by simulating a recent year's (1989) pattern of shipments in the Great Lakes and St. Lawrence River with each of the proposed water level regulation measures in place and determining the changes in variable shipping costs resulting from each measure. A similar simulation is done using the water levels resulting from a doubling of atmospheric carbon dioxide. All impacts are compared to a benchmark reflecting historic hydrologic conditions and current water management structures and procedures

The next three sections review commercial navigation in the Great Lakes-St. Lawrence system, related past research, and the water level regulation measures evaluated. Thereafter the methodology is presented, followed by sections on the results and conclusions.

Commercial Navigation

The Great Lakes-St. Lawrence River system provides a strategically placed and efficient transportation system for Canada and the United States. Stretching 4,000 kilometres from the head of Lake Superior to the Gulf of St. Lawrence the system is a convenient and low-cost means of transporting commodities through a heavily industrialized part of North America. Navigation has been facilitated by the construction of locks at Sault St. Marie, the Welland Canal, and the St. Lawrence Seaway together with various water control structures.

Bulk commodities dominate the freight moved in the system as water transport is attractive for bulk commodities while other modes compete effectively for package freight. (1) Grain is moved from the upper lakes to lower St. Lawrence ports for transshipment to export markets. A backhaul of iron ore is available from the Quebec-Labrador region to mills in Ontario. The major movement of coal is from American Lake Erie ports to Ontario generating plants and steel mills. Other traffic includes domestic shipments of grain, petroleum products, salt, limestone, pulpwood, and other crude materials.

Ships of the Great Lakes fleet are usually built specifically for operation in the Great Lakes-St. Lawrence system. Most Canadian vessels are built to the dimensions of the locks in the Welland Canal and Seaway. The 1989 Canadian fleet was made up of 119 ships; 56 bulk commodity carriers (bulkers), 34 bulk commodity carriers with self-unloading capability (self-unloaders), 25 tankers, and 4 others. Bulkers are primarily engaged in long-haul grain and ore movements; self-unloaders are used more for short hauls of coal, salt, and limestone; and tankers for petroleum products. Canadian ships carry most of the Great Lakes-St. …