Delayed Response of Tongguan's elevation to the sedimentation in Sanmenxia Reservoir

This paper presents a study of the reservoir sedimentation and the variation of Tongguan's elevation in response to changes in flow and pool level of the Sanmenxia dam.The hysteresis phenomenon occured in the fluvial processes of the reservoir was thoroughly studied.Research found that the accumulated sediment deposition and the elevation of Tongguan were affected not only by the current year's flow and pool level conditions,but also by the previous years' flow and pool level conditions.This was demonstrated by the 2 years of time delay in Tongguan's elevation compared with the sediment deposition in the reservoir area downstream Tongguan.And the sediment deposition in the reservoir area was closely related to the 5 years' superimposed pool level.In addition,under the operational conditions of controlled release adopted since 1974,the elevation of Tongguan was closely related to the six continuous years' weighted-average runoff.Also the channel bed slope from Tongguan to Guduo is related to the 7 years' moving average pool level.