The following map displays the sub-basins that drain into the Lake Ontario-St. Lawrence River system, managed by the International Lake Ontario - St. Lawrence River Board. The coloured circles indicate locations of water level gauges. Click on the Legend, at the top left of the map, for more information. You may also click on any of the coloured circles to obtain information and data from the water level gauge.
We are currently rebuilding our story map.
In the meantime, you can learn more about Lake Ontario—St. Lawrence River regulation and the creation of the Lake Ontario—St. Lawrence River Board. Visit our FAQ page for more information about the board and the Lake Ontario—St. Lawrence River system.