Dive Conditions Oct 12, 2020

Weather and water temps have been pretty much the norm for the middle of October: sunny, cool days punctuated by regular rain and thunderstorms and the river dipping below 15C/60F.

The main event of this Thanksgiving weekend has been the International River Board’s raising of the water level in Lake St. Lawrence (the area between the upstream Iroquois dam and the downstream Cornwall dam) for this weekend only; this has allowed local boaters to safely remove their boats for the season.

Here are excerpts from the Board’s most recent news releases. If you click either link, you’ll get the full news releases and more.

September 03, 2020
The Board will temporarily decrease outflows over the second weekend of October to raise Lake St. Lawrence levels significantly and provide a brief, final opportunity for residents of Lake St. Lawrence to remove their boats and other equipment prior to winter.

Last week, the Board agreed to let Lake St. Lawrence levels slowly decline following the 7 September long weekend. Lake Ontario water levels remain above their long-term average value for this time of year. Regulated outflows from Lake Ontario, as prescribed by Plan 2014, will remain high in response to persistent, high supplies into the lake, specifically from Lake Erie.

April 28, 2020
Water levels throughout the Lake Ontario – St. Lawrence River system in 2020 are expected to peak well below the record-highs of 2017 and 2019, according to the latest projections from the International Lake Ontario-St. Lawrence River Board. While Lake Ontario’s water level is currently well above average, improving conditions are the result of much more moderate weather and water supply conditions this year, as well as actions taken by the Board to increase Lake Ontario outflows and help the system recover faster following extreme water level periods.

The Board has been able to continue increasing Lake Ontario outflows (see Lake Ontario tab), in part, because the Ottawa River has been declining and conditions downstream can now handle additional flow.

The result for those divers at Lock 23 this weekend has been an overnight increase in depth of over a foot and a corresponding dramatic slowing of current and eddies around Lock 23. Divers yesterday noted that current was mild and visibility greatly improved if you cared to venture into the chilly water. By tonight, levels had dropped again. (As an aside, I find it mind-boggling that water levels can be artificially raised and lowered to such a degree in a single day across this enormous expanse of water.)

This answers (hopefully) a question I’ve pondered all summer: Why has the visibility been so bad and unchanging? Why has it been the same with or without storms or heavy rains? Surely it’s not simply because the zebra mussels have “gone”. I’ve wondered if perpetually low waters and high current had some hand in it. It seems it has.

On this site I have regularly commented at how the landscape has changed since 2017. Last year the Board kept the water level low for most of the summer. This year it kept it lower yet. Back-eddies in the locks have been consistently strong and visibility consistently awful. Seasonal weed growth has done little to “trap” silt. I now reinforce the idea that the site is an “advanced” dive rather than an “intermediate” dive, and one that should only be done with buddy divers who know the site well. I have steered novice divers completely away.

While the International Board sounds optimistic about water levels next year, none of us can say what weather events the winter and spring will bring and how they will affect dive conditions. However a number of us have been in active discussions on how to assist divers of all levels with enjoying this wonderful site in whatever conditions we find ourselves exposed to, perhaps with a better understanding of why.

Good diving to you!