Weekly Regulation Summary
Summary for Week Ending 20 January 2021
Mild temperatures in December and January delayed ice formation in the critical sections of the St. Lawrence River. With colder weather arriving, ice is expected to begin forming in the Beauharnois Canal. This may require outflows to be temporarily reduced during the coming week.
|Week Ending: Wed, 20 Jan 2021||Average this time of the year (c)|
|Lake Ontario -|
|Actual end of week level:||74.60 m (244.75 ft)||74.59 m (244.72 ft)|
|Computed Plan 2014 Level (a):||74.67 m (244.98 ft)|
|Computed Preproject Level (b):||75.55 m (247.87 ft)|
|Weekly Mean Outflow:||9280 m³/s (327700 ft³/s)||6400 m³/s (226000 ft³/s)|
|Weekly Total Supply:||8340 m³/s (294500 ft³/s)||7000 m³/s (247200 ft³/s)|
|Lake St. Lawrence at Long Sault Dam Weekly Mean Level:||71.79 m (235.53 ft)||72.96 m (239.37 ft)|
|Lake St. Louis at Pointe-Claire Weekly Mean Level:||21.86 m (71.72 ft)||21.31 m (69.91 ft)|
|Montreal Harbour at Jetty #1 Weekly Mean Level:||7.08 m (23.23 ft)||6.74 m (22.11 ft)|
|Ottawa River at Carillon Weekly Mean Outflow:||2480 m³/s (87600 ft³/s)||1950 m³/s (68900 ft³/s)|
|Preliminary Lake Ontario Outflow for Week Ending Fri, 29 Jan 2021:||9200 m³/s (324900 ft³/s)||6540 m³/s (231000 ft³/s)|
Levels are in metres (feet) IGLD 1985. Supply and flows are in cubic metres (feet) per second m³/s (ft³/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 (https://www.waterlevels.gc.ca/C&A/bulletin-eng.html). 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.