Theoretically, the rate of water loss should be equal to the flow rate of water from the make-up tank, which can be represented by the overall water mass balance, L_(return ) +G_inlet (H_inlet )=G_outlet (H_outlet ) (1) where L_(make-up) is the mass flow rate of the water from the make-up tank, G_inlet is the mass flow rate of the air at the inlet, H_inlet is the humidity of the air at the inlet, G_outlet is the mass flow rate of the air at the outlet and H_outlet is the humidity of the air at the outlet. The amount of make-up water needed by the system can be calculated by determining the loss of water due to evaporation. Using a mass balance of the air flow in the tower, the mass flow rate of the water leak, L_loss, can be represented by L_loss=G_outlet-G_inlet (2) The mass flow rate of the air at the inlet and outlet of the cooling tower can be calculated