Summary for Week Ending 21 February 2018
Lake Ontario outflow is expected to be 8600 m3/s to start the week. Outflows were adjusted throughout the past week to maintain Lake St. Lawrence levels around the Plan 2014 minimum level (I-limit) that applies at this time of year to protect municipal water intakes. Outflows will continue to be adjusted over the coming week according to conditions in the St. Lawrence River.
  Week Ending: Average this time
  Wed, 21 Feb 2018 of the year (c)
Lake Ontario -    
Actual end of week level: 74.90 m (245.73 ft) 74.61 m (244.78 ft)
Computed Plan 2014 Level (a): 74.90 m (245.73 ft)  
Computed Preproject Level (b): 75.54 m (247.83 ft)  
Weekly Mean Outflow: 8630 m/s (304800 ft/s) 7010 m/s (247600 ft/s)
Weekly Total Supply: 9620 m/s (339700 ft/s) 7100 m/s (250700 ft/s)
Lake St. Lawrence at Long Sault Dam 71.75 m (235.40 ft) 72.50 m (237.86 ft)
Weekly Mean Level:
Lake St. Louis at Pointe-Claire Weekly 21.73 m (71.29 ft) 21.34 m (70.01 ft)
Mean Level:
Montreal Harbour at Jetty #1 Weekly Mean 7.09 m (23.26 ft) 6.87 m (22.54 ft)
Ottawa River at Carillon Weekly Mean 2080 m/s (73500 ft/s) 1830 m/s (64600 ft/s)
Preliminary Lake Ontario Outflow for Week 8600 m/s (303700 ft/s) 7120 m/s (251400 ft/s)
Ending Fri, 02 Mar 2018:
Levels are in metres (feet) IGLD 1985. Supply and flows are in cubic metres (feet) per second m/s (ft/s).
(a) Levels that would have occurred with strict adherence to Plan 2014.
(b) Levels that would have occurred had there been no Lake Ontario regulation.
(c) For comparison purposes, Lake Ontario water level data since 1918 are used to be consistent with those published in the US and Canadian Great Lakes bulletins ( Other averages are for the periods as follows: Lake Ontario outflows and levels at Long Sault and Pointe-Claire since 1960; Montreal since 1967; and Ottawa River outflow at Carillon since 1963.
The regulation plan for Lake Ontario specifies a weekly average outflow from Saturday through the following Friday, inclusive. To provide timely information for the coming week to the hydropower and Seaway operators, and our readers, we complete the regulation plan calculations each Thursday. Our calculations use the data available at the time, which are from the previous seven days (Thursday through Wednesday). Since the two time periods do not exactly coincide, their data are usually slightly different.
The table shows the actual flow for the week ending Wednesday. It also gives the preliminary flow for the coming week ending Friday. We emphasize that this is the preliminary flow, since unforeseen flow changes may occur after we have issued our notice. When these flow changes occur, they are reflected in the subsequent week's notice.
Information in this report is compiled from provisional data provided by: Environment & Climate Change Canada, Fisheries and Oceans Canada, Hydro Quebec, Ontario Power Generation Inc, the New York Power Authority, and the U.S. National Ocean and Atmospheric Administration.