FINAL REPORT - International Joint Commission

FINAL REPORT
Coastal damages occur regardless of the regulation plan and none of the candidate plans creates significant
benefits relative to what would be expected under 1958-DD. The biggest problems result from increased
shore protection maintenance on Lake Ontario under Plan B + and downstream flooding under Plan A + .
Environment
Plan B + is the best of the candidate plans for the environment above the Moses-Saunders Dam, but no
plan is significantly better than any other below the Dam. Plan B + is judged best above the Dam on the
strength of its performance indicator scores, especially for Meadow Marsh, Virginia Rail, Black Tern and
Muskrat house density scores. Plan B + creates more natural variation in Lake Ontario water levels and
preserves the natural timing of the seasonal rise and fall.
The table of plan performance below (Table 10) shows a subset of the 32 key environmental performance
indicators that together tell a coherent story about species habitats, seasonal and life cycles and whether a
plan partially restores natural long-term variability. For the results of all 32 key performance indicators,
refer back to Table 8.
Table 10: Priority Performance Indicators Identified by Members of the Environmental Technical
Work Group based on Historical Analyses
Priority Performance Indicators Plan A + Plan B + Plan D + Plan E
Lake and Upper River
Meadow Marsh 1.02 1.44 1.17 1.56
Black Tern - Reproductive index 1.03 1.12 1.01 1.16
Virginia Rail - Reproductive index 0.96 1.11 0.99 1.15
Muskrat - House density 1.42 4.39 1.73 37.25
Northern pike – Young-of-Year (YOY) 1.05 1.03 1.01 1.06
recruitment and net productivity 4.02 2.08 1.17 4.08
Largemouth Bass - YOY 0.99 1.00 1.00 1.00
Fish Guild (High-veg 24 C) 1.03 1.01 1.02 1.02
Lower River
Golden Shiner - Suitable feeding habitat area 1.00 1.00 1.00 1.03
Virginia Rail - Reproductive index 0.94 0.97 1.06 1.00
Migratory Wildfowl - Productivity 1.06 1.00 1.00 1.03
Northern Pike - Reproductive area 0.97 0.94 0.94 0.94
Bridle Shiner - Reproductive habitat surface area 1.00 0.97 1.03 1.03
Muskrat - Surviving houses 1.04 0.88 0.96 0.80
Notes to Table 10:
1. Figures reflect the impact relative to Plan 1958-DD expressed as ratios, where 1 represents no change from 58-DD,
>1.00 an improvement relative to 58-DD, and < 1.00 a deterioration relative to 58-DD.
2. Run using the historical supply sequence because the Integrated Ecological Response Model component of the
Shared Vision Model could not be adapted to run the full 50,000-year sequence.
3. Aqua shading identifies species at risk.
4. Yellow shading indicates essentially no change from 1958-DD (within 10% difference). Anything above 1.10 is
marked in blue and anything below 0.90 is marked in red.
The Environmental Technical Work Group has suggested from the beginning of this Study that the best
plan for the environment is the natural flow plan. Plan E produced the closest to natural flows that can be
achieved while still maintaining a smooth ice cover on the St. Lawrence River. But while Plan E simulates
more natural conditions, it does not represent the natural condition before regulation. The system,
especially on the lower St. Lawrence River, has changed dramatically since the Moses-Saunders Dam was
built. For example, much of the tributary mouth wetlands on the lower river have been converted to
farmland. What might have once been good for the environment in terms of levels and flows may no
longer be the case. The environment on the lower river is responding to a different set of conditions than
68 Options for Managing Lake Ontario and St. Lawrence River Water Levels and Flows