Study on the issues of Tongguan elevation and Sanmenxia reservoir operation modes

Analysis has been made for variation of Tongguan elevation since the operation mode of “storing clear water and releasing the muddy of Sanmenxia Reservoir. The main cause of the continuous rising of Tongguan elevation in recent years is the rapid reduction of the incoming runoff during flood season. To control Tongguan elevation, it is necessary to adjust the operation mode of Sanmenxia Reservoir to suit new inflow condition. In non-flood season, the water level at the dam should be controlled below 318m. In flood season, the flow-rate limit of opening all outlets to discharge sediment should be reduced to 1000～1500m 3/s,. The beginning water level prior to ice-melt flood should be lowered to 313m. In the first ten-days period of June, the water level should be lowered to 310m.