The first stage of the reconstruction of the Sanmen Gorge dam was carried out from 1965 to 1968. It involves cutting; two tunnels 900 meter in length and eleven meters in diameter through a rock cliff on the left bank of the dam to discharge silt and turning four of the eight huge steel pipes, originally designed to lead water, for power generation into new water and sand discharge channels. From 1970 to 1973 the builders opened the eight water outlets at the bottom which were used during the construction of the dam to increase flood discharging capacity. The remaining four steel pipes for power generating and one that had been turned into a sand discharging tube were lowered by 13 meters and low water head hydroturbine generators resistant to sand abrasion were installed to replace the high water head generating sets. Dam has the following advantages. 1. Relieving from big floods. 2. lifting the threat of ice floes; many dyke breaches were caused by jamups during the ice floe season from Dec. to Feb., when thawing began in the upper reaches while the lower reaches remained ice bound, now the dam is able to regulate the water and lessen the pressure on the dyke during floe jam. 3. Providing abundant water for irrigation, urban consumption and industrial use. 4. The reconstructed Sanmen Gorge power station can drive turbine by natural river flow.