Abstract: A method and system for treating water, and using the treated water for the cooling of industrial processes is disclosed. The water is treated and stored in a large container or artificial lagoon, has high clarity and high microbiological quality. A system of the invention generally includes a containing means, such as a large container or artificial lagoon, a coordination means, a chemical application means, a mobile suction means, and a filtration means. The coordination means monitors and controls the processes in order to adjust water quality parameters within specified limits. The large container or artificial lagoon can act as a heat sink, absorbing waste heat from the industrial cooling process, thus creating thermal energy reservoirs in a sustainable manner, which can be later used for other purposes. The method and system can be used in any industrial cooling system with any type of water available, including fresh water, brackish water, and seawater.