At night, two tunnels divert a substantial fraction ( per second) of the water in the Niagara River to the forebay. Electricity generated in the Moses plant powers the pumps to push water into the upper reservoir behind the Lewiston Dam. The water is pumped at night because the demand for electricity is much lower than during the day. In addition to the lower demand for electricity at night, less water can be diverted from the river during the day because of the desire to preserve the appearance of the falls.