FINAL REPORT - International Joint Commission

FINAL REPORT
Plan Evaluations and Comparisons
Plan evaluation is the process of measuring and assessing the expected outcomes of newly designed
regulation plans. The Shared Vision Model was used to estimate the outcomes in terms of the water levels
and flows and the economic and environmental changes the plans would produce. The results were displayed
in the “Board Room,” a series of Excel spreadsheets that integrated the results of the components of the
Shared Vision Model.
In addition to the evaluation of plans using the historical supply sequence, all of the candidate plans along
with 1958-DD and Plan E were run through the full 50,000-year sequence of stochastic water supplies.
This stochastic analysis is very important in terms of obtaining the most reliable economic evaluation of
the plans. This is particularly significant for the coastal erosion and shore protection maintenance
performance indicators since these have serial dependence, and damages cannot be completely avoided,
only delayed. The best way of assessing plans, then, is to determine which one delays or postpones
coastal damages to a later time. The damages are then discounted to a present value. Impacts were
analyzed over a thirty-year period using a 4% discount rate as recommended by the economic advisors.
Plan rankings did not change when different discount rates and evaluation periods were used. In terms of
choosing plans, the Study Board decided that the only legitimate comparative analysis of economic
benefits and costs among the various plans should be based on the stochastic hydrologic sequence alone,
rather than the historical record. The environmental results are based on the historical sequence because
the Integrated Ecological Response Model had not been adapted to run through the 50,000-year sequence.
However, the environmental results are available for the four 101-year stochastic scenarios. In addition the
Environmental Technical Work Group ran an adapted wetlands model through the 50,000-year stochastic
series and found plan rankings to be consistent with the historical results.
The Importance of the Stochastic Analysis
We know the future will not be a repeat of the past; especially when it comes to the weather that drives the
water supplies in the Great Lakes–St. Lawrence River system. Even without the effects of increased
greenhouse gases in the atmosphere, we can be confident that there will be periods of higher and lower
supplies sometime in the future due to the natural variation in climate. The challenge in developing a new
plan is to devise tests for candidate plans that prove whether they will work well whatever the future
climate brings. To make sure the candidate plans would perform well, the Study Board tested them using
a stochastically generated supply sequence to evaluate their hydraulic range and economic benefits.
Wetland type extents were also calculated over this range for all candidate plans.
When Plan 1958-D was designed and tested, its authors measured its performance using the water
supplies that had been experienced from 1860 to 1954. Almost as soon as it went into effect, it became
apparent that it would not perform well because the test had been too limited. Had Plan 1958-D been
strictly adhered to during the drought of the early 1960s and the wet periods since, Lake Ontario levels
would have been lower and higher than they would have been without regulation, and in the late 1980s,
they would have destroyed many houses along the shoreline.
40 Options for Managing Lake Ontario and St. Lawrence River Water Levels and Flows