RUNOFF REGULATION FOR HYDRO-POWER AND ITS EFFECT ON THE OCEAN ENVIRONMENT / Régularisation d'écoulement pour obtenir l'énergie hydro-électrique et son impact sur le milieu marin

Abstract

Abstract It has not yet been recognized that modification of the natural seasonal discharge of rivers might result in significant consequences to the ecology of the adjacent marine environment. An example of such regulation is the St Lawrence system, where, in order to optimize power production, large quantities of water from the spring runoff are retained in storage lakes and returned to the river during the low natural discharge period of autumn and winter. It has been estimated that under present conditions the spring and summer runoff at the entrance to the Gulf of St Lawrence has been reduced by between one-third and one-half. This drastic alteration of the natural pattern of runoff has caused significant changes in the physics and dynamics of the waters of the Estuary, Gulf and adjacent coastal region. It is argued that such modifications produce a profound impact on the biological balance of the whole ecosystem, as well as changes in the seasonal heat budget.