Cooling water supply system and method

A method for supplying cooling water to a condenser under conditions where an evaporation rate of the cooling water is a low value during a certain period of time in each day and is higher than the low value during other periods of time in each day, comprising the steps of:

• providing a water reservoir within a basin underlying a cooling tower;
• delivering the cooling water from the water reservoir to the condenser for cooling working fluid of a facility;
• controlling a height of the cooling water in the water reservoir, during the certain period of time when the evaporation rate of the cooling water is low, to be a variable water level that is varied based on ambient temperature conditions, such that a temperature of the cooling water in the water reservoir throughout said other periods of time will assure a predetermined condensate temperature of the working fluid, or a temperature lower than the predetermined temperature, in the condenser throughout said other periods of time;
• and
• controlling the height of the cooling water in the water reservoir during the other periods of time at a value for maintaining a concentration of a dissolved solid and ions that is lower than a predetermined value.