Lake Ontario St. Lawrence River Plan 2014

Commercial Navigation

Comment Received

IJC Response

Plan 2014 could dramatically impact commercial navigation because it increases the frequency of extreme low-water conditions.

Overall, Plan 2014 will provide about the same benefits for commercial navigation as Plan 1958DD. In the historical supply series simulation, Plan 2014 Lake Ontario water levels are noticeably lower than 1958DD levels in the 1930s and again in the 1960s. Some ships that operate only on Lake Ontario will have to reduce their drafts (and loads) during rare low-water years.   These rare low water years are predicted to occur 2.5 percent of the time, which is a slight increase from the 1.8 percent probability of the extreme low water occurring under Plan 1958DD.  However, because annual minimum Lake Ontario levels during the shipping season are a bit higher under Plan 2014 about 75 percent of the time, these same ships may be able to carry larger loads in other years. For ships traveling across Lake Ontario to or from the Upper Lakes, the low Lake Ontario levels may not make any difference in loading because the controlling clearance will often be on Lakes Michigan-Huron or Superior, which are below chart datum about five times more often than Lake Ontario. For the Montreal to Lake Ontario section of the St. Lawrence Seaway, the lower levels on Lake Ontario are more than compensated by less frequent low levels on Lake St. Louis which results in more consistent higher drafts on the entire route.

Plan 2014 would increase the risk of commercial navigation delays in the Seaway because the frequency of Lake Ontario outflows above 9,900 cubic meters per second increases by 40 percent during the navigation season.

The frequency of extremely high flows is very low under either plan. While Plan 2014 increases the frequency of flows above 9,900 cubic meters per second in the historical scenario by 40 percent compared to Plan 1958DD, the frequency of such flows during the navigation season is less than one percent under either plan.