FINAL REPORT - International Joint Commission

FINAL REPORT
Interest-specific short-term deviations have mixed support on the Study Board. Each of the above-mentioned
examples of interest-specific deviations has been implemented by the Control Board in past years.
These actions are open to varied interpretations, and the Control Board may not always be aware of other
interests that might be harmed by these actions. The Study Board cannot reach a consensus view in
support of or against short-term, interest-specific deviations or on the details concerning how such
deviations might be applied. It is suggested that the Commission decide whether deviations for these
purposes should proceed at all, or proceed only with Control Board assessment of effects and/or prior
Commission approval.
In all potential short-term deviation cases, the intent of the regulation plan rules should be maintained.
Consideration should also be given to balancing the effect of short-term deviations within the week.
To minimize the effect that short-term deviations might have on Lake Ontario, all interest-specific deviations
if allowed, should be limited. For example, the Study Board suggests the following: (1) deviations should
be limited to no more than 323 cubic metres per second (11,400 cfs) equivalent to 1 centimetre (0.4 inches)
on a weekly basis on Lake Ontario levels; (2) the total of these accumulated deviations at any time should
be limited to no more than +/- 5 cm (2 inches) over a calendar year on Lake Ontario; (3) no increase in the
Lake Ontario level should be permitted if levels there are approaching the extreme high-water-level threshold
listed in Table 11; and (4) conversely, no decrease should be permitted if Lake Ontario levels are approaching
the extreme low-water-level thresholds as listed.
Long-term discretionary deviations from plan flows have been an increasingly frequent practice of the
St. Lawrence River Board of Control in recognition of changing conditions and priorities in the system and
as a means of meeting the criteria in the existing Orders of Approval when water supplies are outside the
range for which Plan 1958-D was developed. An example of such a deviation is the “storing” of water on
Lake Ontario in the springtime, during expected lower-than-average upstream water supply conditions, for
the purpose of maintaining higher Lake Ontario levels into the fall and enabling additional late fall releases
of water down the St. Lawrence River.
All of the proposed candidate plans have been designed in recognition of the current Lake Ontario-
St. Lawrence River water level and flow interests. The plans have also been designed to respond to and
accommodate a wide range of water supply conditions reflective of 50,000-years of stochastic hydrology
as well as potential climate change conditions. Therefore, deviations from candidate plan flows when
water levels on the Lake or River are high or low will act to nullify the benefits of the plans.
The Study Board is of the opinion that long-term discretionary deviations from plan flows are not generally
justified because such actions change the performance of the plans as designed and the benefits that flow
from them. This position is conditional on ensuring that performance indicators upon which the regulation
plan is based are verified and updated in an adaptive management process.
During extreme low- or high-water level and flow conditions on Lake Ontario or the St. Lawrence River,
consideration should be given, however, to implementing Criterion (k) type plan deviations after examination
of the impact of plan flows on interests and processes in the Lake Ontario-St. Lawrence River system and
with the express concurrence of the Commission.
86 Options for Managing Lake Ontario and St. Lawrence River Water Levels and Flows