FINAL REPORT - International Joint Commission

FINAL REPORT
• Shore protection maintenance on Lake Ontario is the aspect most affected by changes in a regulation
plan. Even small differences in levels and the timing of levels can impact the overtopping and
undercutting of shore protection.
• By comparison with some of the other interests, flooding on the lower St. Lawrence River does not
represent huge economic damages, but the differences between plans can be significant, especially for
the lower portion of the River downstream of Montreal around the Sorel/Lac St. Pierre area.
• Erosion on the lower river is not a major economic issue since most of the developed properties are
already protected.
• Shore protection maintenance on the lower river does not vary much regardless of the plan evaluated.
Recreational Boating
• It is possible to develop a plan that results in increased boating benefits for all regions, with water
stored on Lake Ontario providing extra depth for Lake Ontario boaters and extra supply to help river
boaters during droughts.
• A key issue raised by recreational boaters throughout the system is the desire to maintain higher levels
until later in the fall to extend the boating season and to make for easier boat haul-out.
Commercial Navigation
• The main difference between plans lies in the costs induced by shipping delays on the Seaway. There
is usually enough water on Lake Ontario to keep ships fully loaded, and none of the plans is significantly
better than the others in terms of avoiding shallow depths in the Seaway above the Moses-Saunders
dam. The plans do differ in how well they maintain minimal acceptable levels on Lac St. Louis and at
the Port of Montreal, especially during extended droughts.
Hydropower
• The operators of hydropower facilities benefit from high flows through their turbines, minimal spillage
and higher operating heads, but also from predictable and stable flows. The less releases changes
from month to month and from week to week, the better the plans are for hydropower.
• Hydropower benefits are greatest when releases are similar to what would occur without regulation
(assuming regulation to limit ice jams in the winter and early spring). Natural releases create a higher
average head at Moses-Saunders, result in very little spillage, and tend to be the most stable and
predictable.
Municipal and Industrial Water Uses
• Municipal, industrial and domestic water use is generally not vulnerable to water level changes.
The Study found that the Montreal system could be at risk later in the century, assuming that climate
change induces the dry, hot scenario modeled in the Study.
• Other exceptions are the Russell and Ginna power generating stations and the County of Monroe potable
water pumping and treatment plant on the south shore of Lake Ontario in New York State. The two
power generating facilities report critical low water elevations for their cooling water intakes at levels
within the historical record under the current regulation regime. However, the Study Board was
informed that Russell is closing and Ginna would take measures to deal with this design flaw.
• The Monroe water pumping and treatment plant experiences flooding problems at Lake Ontario
elevations within the historical maximum range.
• Shoreline wells, groundwater contamination and sewage overload were evaluated in terms of the
recurrence of water levels likely to induce such problems, but not in economic terms, since impacts
were either small relative to other categories or could not be estimated by plant operators.
20 Options for Managing Lake Ontario and St. Lawrence River Water Levels and Flows