Soon after completion, sediment-accumulation threatened the benefits of the dam.
The Yellow River carries more sediment than any other in the world.
During the 18 months after the river was closed, 1.8 billion metric tons of sediment had accumulated in the reservoir.
Only 7% of the sediment-load was released downstream and the reservoir lost 17% of its capacity below a 335 m (1,099 ft) ASL elevation.
Navigation and farmland were threatened upstream along with the relocation of an additional one million people.
Despite the dam's 12 deep-sluices and alterations in the release of water, silt continued to build in the reservoir, particularly in the back waters.
Responding to the potential crisis, a meeting was held in December 1964 with Premier Zhou Enlai.
At the meeting, it was decided to reconstruct the dam's outlet works for improved discharges and silt control.
The renovation was carried out immediately and in two stages.
The first stage included the installation of two tunnels on the dam's left bank at an elevation of 290 m (951 ft) ASL along with converting four penstocks into flushing pipes.
The flushing pipes began operating in 1966 and the tunnels in 1967 and 1968.
In the second stage, eight bottom sluices were added to the left side of the dam which became operational between 1970 and 1971.
Silt balance was achieved in 1970.
Two more bottom sluices began operating in 1990 along with another in 1999 and the final in 2000.
Soon after completion, sediment-accumulation threatened the benefits of the dam. The Yellow River carries more sediment than any other in the world. During the 18 months after the river was closed, 1.8 billion metric tons of sediment had accumulated in the reservoir. Only 7% of the sediment-load was released downstream and the reservoir lost 17% of its capacity below a 335 m (1,099 ft) ASL elevation. Navigation and farmland were threatened upstream along with the relocation of an additional one million people. Despite the dam's 12 deep-sluices and alterations in the release of water, silt continued to build in the reservoir, particularly in the back waters. Responding to the potential crisis, a meeting was held in December 1964 with Premier Zhou Enlai. At the meeting, it was decided to reconstruct the dam's outlet works for improved discharges and silt control. The renovation was carried out immediately and in two stages. The first stage included the installation of two tunnels on the dam's left bank at an elevation of 290 m (951 ft) ASL along with converting four penstocks into flushing pipes. The flushing pipes began operating in 1966 and the tunnels in 1967 and 1968. In the second stage, eight bottom sluices were added to the left side of the dam which became operational between 1970 and 1971. Silt balance was achieved in 1970. Two more bottom sluices began operating in 1990 along with another in 1999 and the final in 2000.
Sanmenxia Dam