FINAL REPORT - International Joint Commission

ANNEX 3
The three adjustments based on the moving average NTS take precedence; hence, if one of these
adjustments is triggered, the annual NTS forecast adjustment is not applied.
Step 2 – Flow smoothing: Since each quarter-month has its own rule curve, Plan A + can produce releases
that vary somewhat erratically from quarter-month to quarter-month. In order to prevent this, a simple
smoothing rule is applied which slows down the rate at which Plan A + can vary releases. This rule
averages the last two releases and the current release produced in Step 1 above, giving the Step-1 release
double weight.
New Releases = [2 x (Step-1 Release) + (Release @ t-1) + (Release @ t-2)]/4
Where: Step-1 Release = the release adjusted for NTS moving average and forecast,
Release @ t-1 = the final release made in the previous quarter-month,
Release @ t-1 = the final release made 2 quarter-months ago.
This rule is only applied if the current Lake Ontario level is ≤ 75.55 m (247.87 ft). If the Lake is higher
than 75.55 m (247.87 ft), then the smoothing rule is not applied so that releases can be increased fast
enough to avoid flooding.
Step 3 – J limit: A J limit is also applied. This limits flow changes from quarter-month to quarter-month
based on the current Lake Ontario level.
Table B-6: J-Limit based on Lake Ontario level
Lake Ontario Level
Plan A + J Limit
> 75.5 meters (247.7 ft) 2100 m 3 /s (74,200 ft 3 /s)
≤ 75.5 meters (247.7 ft)
700 m3/s (24,700 ft 3 /s)
Note that because the rules are applied after the J limit, two other factors can result in violation of the
J limit: 1) flow reductions for ice conditions, and 2) flow reductions to avoid flooding downstream.
Step 4 – Downstream flood prevention: Adjustments to the release are made to prevent downstream
flooding. For simulation purposes, these adjustments are applied using the freshet perfect forecast
indicator developed by David Fay. The release is limited to keep Lake St. Louis from rising above certain
levels, depending on the Lake Ontario level as shown in Table B-7.
Table B-7: Adjustments to prevent downstream flooding
Lake Ontario Levels
Lac St Louis Limit
< 75.4 meters (247.38 ft) 22.3 meters (73.16 ft)
≥ 75.4 (247.38) and < 75.5 meters (247.7 ft)
22.4 meters (73.49 ft)
≥ 75.5 (247.7) and < 75.6 meters (248.03 ft)
22.6 meters (74.15 ft)
≥ 75.6 (248.03) and < 75.7 meters (248.36 ft)
22.7 meters (74.48 ft)
≥ 75.7 meters (248.36 ft)
22.8 meters (74.80 ft)
180 Options for Managing Lake Ontario and St. Lawrence River Water Levels and Flows