Probable Effects of Proposed Passamaquoddy Power Project on Oceanographic Conditions

Abstract

The proposed Passamaquoddy power project involves the construction of a series of dams across the mouth of Passamaquoddy and Cobscook Bays. Passamaquoddy Bay, the proposed high pool, will be filled near high water by 90 filling gates, and Cobscook Bay, the proposed low pool, will be emptied near low water by 70 emptying gates. Water will flow continuously from the high pool to the low pool, through a 30-turbine powerhouse. Tidal range will be reduced to approximately 4 and 8 ft in the high and low pools respectively. The effect of this proposed installation on oceanographic conditions in the region has been considered. It is concluded that currents, within the impounded bays and in the area lying inside the Bliss Island–Head Harbour region, will be altered markedly. In the outer Quoddy Region, tidal stream directions will be altered only slightly, while the changes in speed will probably not exceed 20% of their present value. No significant change in residual flow is expected outside the Quoddy Region. Not more than a 1% increase in tidal range is anticipated for the entire Bay of Fundy. Inside the impounded bays, there will be increased stratification. Seasonal variations in temperature of the surface layer will be increased. The summer maximum is expected to reach 20 °C and the winter minimum will be less than 0 °C. Ice cover is expected to occur over part of the impounded waters. Salinities at the surface will be reduced. Only minor changes in temperature and salinity of the deep layer are anticipated. No significant changes are expected in temperature or salinity in the outer Quoddy Region.