Forty miles east of Turlock, Don Pedro Dam was built in 1923 when Turlock and Modesto Irrigation Districts joined together to build the dam which had a storage capacity of 289,000 acre feet. That dam was small and barely held enough water to provide irrigation needs for one growing season.  In 1967 they decided to build a new Don Pedro Dam which took until 1971 to build and cost $105 million. That reservoir had a capacity of 2,030,000 acre feet, increasing TID’s water storage on the Tuolumne River. This dam was 580 feet high and 855 feet above sea level.

Don Pedro Lake helps provide flood protection for the valley below it. The huge capacity is able to absorb rushes from the Sierra storms and protect the properties and farmlands in the valley. It is required for the spillway to be opened when Don Pedro reaches its elevation of 830 feet.

Opening Don Pedro’s spillway in February of 2017 will be the second time in the dam’s history that the gates will have been opened. The gates were opened in 1997 which caused massive flooding and damage in Stanislaus and San Joaquin Counties. In 1997 when the gates were opened it gushed out 55,800 cubic feet per second causing the Tuolumne River in Modesto to raise to more than 70 feet.

On February 20, 2017 at 3:00 p.m. the spillway was opened, and it will remain open for about four days. The water will flow through at 18,000 to 30,000 cubic feet per second. The water will take 23 hours to travel before it will reach Modesto in Stanislaus County. According to weather reports, the Tuolumne River is expected to peak at 62 feet by Tuesday night.

Further in the valley on Monday night there was a levee breach on the San Joaquin River which caused residents in Manteca to evacuate and many roads to close.