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Potential for multi-lake regulation to address extremes is limited

The potential for multi-lake regulation to address extreme water levels in the Great Lakes - St. Lawrence River system is limited by the uncertainty regarding future climatic conditions and NBS, very high costs, environmental concerns and institutional requirements. Some key points included: - Multi-lake regulation plans involving the existing structures as well as new control points on both the St. Clair and Niagara rivers, or plans involving the existing structures and a new control point on only the Niagara River, could be designed to reduce the frequency of occurrence of extreme water levels across multiple extreme net basin supply scenarios and at all evaluation points in the system; however, plans involving the existing structures and a new control point on the St. Clair River only could not be designed to achieve this objective. - Additional control points on the connecting channels require both the construction of adjustable control structures, such as a dam, to restrict flows during dry conditions, as well as excavation to increase channel conveyance so as to increase flows during wet conditions. The cost of excavation is significant, and is normally much greater than the cost of the control structures themselves. This is particularly true for the St. Clair River, where the gradual slope of this channel would require extensive excavation costing several billion dollars to allow for the increases in flows required by the various plans developed in this analysis. - Multi-lake regulation plans must be developed with consideration given to the impacts on water levels throughout the system, including the lower St. Lawrence River. Though not assessed directly in this analysis, extensive mitigative measures costing several billion dollars would be necessary in the lower St. Lawrence for any multi-lake regulation plan developed. - Environmental considerations related to new control structures and excavation in the connecting channels would be significant, as such activities would disrupt important fish habitat, such as that of the Lake Sturgeon in the St. Clair River, and also cause issues with suspended sediment. - Institutional considerations would also be significant. Finally, the analysis indicated that while system-wide multi-lake regulation could reduce the frequency and magnitude of extreme events at all evaluation points (with the exception of the lower St. Lawrence River), it could not eliminate such events entirely. Extreme water levels in the future may be unavoidable, even with additional regulation capabilities. Therefore, additional adaptive measures may be required.
Related Projects
Environmental Impacts of Structures in the St. Clair River
Regulation and Compensation Literature Review
Multi-Lake Regulation
Institutional & Governance Analysis