A three-dimensional model was developed through a parameter-estimation method based on nonlinear regression to simulate ground-water flow in the Lockport Group, a fractured dolomite aquifer near Niagara Falls, N.Y. Horizontal fracture zones within the Lockport Group were represented by model layers, and connections between the zones were represented by vertical leakage between the layers. Results of steady-state simulations were compared with (1) the observed potentiometric surface of the weathered bedrock surface, (2) average heads measured by piezometers in underlying fracture zones, (3) low-flow measurements of springs and streams, and (4) measurements of discharge from tunnels and excavations. Results indicated that (1) measured flow into the Falls Street tunnel, an unlined storm sewer excavated in bedrock, exceeds the amount that can be sustained by the aquifer, and, therefore, a connection between the tunnel and the Niagara River can be assumed; (2) recharge within the urban parts of the modeled area is greater than in rural areas, possibly because of losses from the municipal water supply or infiltration from unlined storm sewers that intersect the bedrock; and (3) lowlands near the Niagara River might contain widespread areas of upward flow that discharge ground water through evapotranspiration and surface drainage.
