Characterization of a ground water flow system influenced by pumped storage reservoir seepage losses, Niagara Falls, Ontario

A hydrogeologic field study and the development of a 3-dimensional finite difference flow model are used to characterize a large scale anisotropic ground water flow system influenced by reservoir seepage loss. The reservoir is the Sir Adam Beck pumped-storage reservoir associated with the Sir Adam Beck hydroelectric power plant. This reservoir was suspected of contributing to excessive groundwater seepage at a nearby quarry. The 7 km2 flow system is comprised of a variable thickness of glacio-lacustrine sediment and till overlying the Middle Silurian Lockport Formation, a regional carbonate bedrock aquifer. Discretization of the flow domain was supported by hydraulic field testing, which employed slug and constant head step injection testing, continuous water level monitoring, and simulation of transient ground water responses and point dilution experiments to estimate physical flow system properties. Calibrated model results indicate that the hydraulic head perturbations created by reservoir losses (1050-1080 m3/d) and routine daily cycling are naturally attenuated 200-250 m from the reservoir perimeter. Three dimensional numerical flow analyses provide an attractive means to derive effective hydraulic conductivity values necessary for analysis of large scale ground water flow systems. 70 refs., 29 figs., 9 tabs