Impact of construction of a hydroelectric project on the water quality of five lakes in Nova Scotia

Abstract

In February, 1975, a [Formula: see text] year study of five highland lakes (Big, Cheticamp, Gisborne, Long, and Surge Lakes) in the Wreck Cove area of Nova Scotia was initiated to determine the limnological effects of construction of a hydroelectric project. Almost 600 lake-water samples were used to monitor water-quality changes resulting from tunnelling, dam construction, reservoir clear-cutting, slashing, and burning, and establishment of access roads.The impact on Surge Lake was much more pronounced than on the other four lakes. Evidence strongly suggests that the significant water-quality changes in Surge Lake can be attributed to clear-cutting operations and construction activities (of longer duration and higher intensities in the vicinity of Surge Lake area in comparison with other areas) resulting in accelerated soil erosion, nitrification, and soil leaching. Also, the Surge Lake watershed had steeper slopes, and different vegetative cover.Nitrate, ammonia nitrogen, total and ortho phosphorus, calcium, magnesium, sodium, potassium, chloride sulfate, total solids, conductance, pH, suspended solids, and turbidity increased significantly in the lower-most lake (Surge) but only moderately in the remaining lakes. The relative rates and amounts of revegetation of exposed soils were also considered key factors in influencing the magnitude of changes in water quality of these highland (elevation 400 m) lakes.