Demand in a water distribution system is determined by the steps of measuring the volume of water flowing into the water distribution system through an input during a predetermined interval of time, measuring the change in the volume of water stored in the storage reservoir during the same time interval, measuring the volume of water flow exiting the water distribution system through an output during the same time interval, calculating an adjusted input measurement by subtracting the measured flow of water exiting the water distribution system from the measured volume of water flow into the water distribution system, and adding a measured increase in the volume of the water in the storage reservoir to the adjusted input measurement or subtracting a measured decrease in the volume of water in the storage reservoir from the adjusted input measurement to determine the demand.