Where water control works or other measures appeared to be economically and environmentally practicable, the Commission was asked to determine the full costs and benefits, and indicate how the various interests on either side of the boundary would be affected. The Commission was also asked to determine the need for, and costs of, remedial or compensatory works or measures to offset costs to the interests that may be adversely affected by any proposed regulatory measure.

Fluctuating flow and water levels in the St. Lawrence River, whether natural or human-induced, are of concern to the various stakeholders (government organizations, research scientists, industries and the general public) that have been involved for several years in managing water resources and their use, and in maintaining the physical chemical and biological integrity of the ecosystem. Such concerns are particularly justified in the current context of climate change, which is likely to significantly influence socio-economic and environmental policy decisions. In recent years, Environment Canada research scientists have been studying the problem of fluctuating flows and water levels in the fluvial portion of the St. Lawrence. Much of their research has been carried out in the context of the work of the International Joint Commission and, more specifically, the International Lake Ontario-St. Lawrence River Study Board, which has a mandate to evaluate the procedures and criteria used to regulate outflows from Lake Ontario and manage water levels in Lake Ontario and the St. Lawrence River. This document is the product of the work of several of the above-mentioned Environment Canada research scientists. It is a synthesis of the current state of knowledge and of certain recommendations relating to the possible impacts of fluctuating flows and water levels on various environmental and socio-economic factors.