A comprehensive hydro-scheduling system, HYSS, was developed for the Pacific Gas and Electric Company to produce optimal release policies for each of the 86 hydropower plants in the 23 river-basin hydroelectric system. HYSS has become the basic tool used to operate the utility’s complex hydro-generation system efficiently. The use of HYSS has helped increase production of hydropower, resulting in a reduction of revenues required from ratepayers of an estimated $10 million to $45 million each year. Also, the improved schedules for hydropower result directly in better resource planning throughout the company.