The incoming sediment from upstream of Tongguan is the unique source to leading the Tongguan river bed rising,but it is the only source of silt body to balance the impact on Tongguan river bed between the incoming water and reservoir operation mode.

The authors analyzed the data and problems of Sanmenxia reservoir operation since 1974 and demonstrated the capacity of sediment transport of the lower reaches downstream of Tongguan station when practicing the mode of "impounding clear water and releasing muddy water".

The conclusions are as follows: a) the two-reservoir operation has changed the annual runoff distribution of inflow and outflow of the reservoir and the runoff proportion of the flood season reduced from 60% before the reservoir to about 40%;the duration of big outflow discharge has reduced and the duration of small discharge increased;the o.

The operation model of Xiaolangdi reservoir is different from others.

Discussion on the operation mode of Xiaolangdi Reservoir in the late sediment-trapping phase;

Progress of studying the Xiaolangdi Reservoir operation mode and several main alternatives are reviewed, and the operation mode of “gradually raising reservoir level and slightly regulating water” is extensively analyzed.