Study On Methods Of Hydrograph Forecasting Of Sediment Concentration For The Yellow River Reach From Huayuankou To Jiahetan

The Yellow River is reputed the cradle of the Chinese. But since ninetieth era, twentieth century, it has provoked the people's attention again because of stream breaking in lower reach, ecological environment deteriorating, water contamination aggravating, and rapid channel shrinkage. Facing the condition in which people get along with the river deteriorating gradually, they realized that they must adopt some measures to change this situation in order to make people get on well with the river. Less water and more sediment therefore unbalanced relationship between water and sediment is the ultimate reason that the Yellow River silts, so people put forward some measures as impounding clear water while discharging muddy water, holding up coarse sand while letting fine particle off, releasing water in good time to regulating sediment and silting flood plain while scouring major trough. All these measures could fail to work well unless the water and sediment conditions fit. if the hydrograph of sediment concentration or sediment discharge rate can be predicted in advance, it should be advantageous to control water and sediment change factitiously therefore to get the aim of harmonizing the relation of water and sediment of the Yellow River so that people and river gets along well.Because of some reasons, there have been no the suitable models or methods of sediment concentration forecasting that can be applied in practice. To research at the methods of sediment content forecasting and proposal a adaptive forecasting one is a work not only of important practical meaning and prospect but also of significant scientific sense in the middle and downstream rich of the Yellow River for reservoir operation, flood into resource transforming and contents of the related knowledge enriching and developing.This thesis associated with a part of the special Yellow River regulating project issued byYRCC—study on the forecasting methods of maximum sediment concentration at majorhydrometric station on main steam of middle and down reach of the Yellow River, taking the river course from Huayuankou to Jiahetan as a study object, analyzes the characteristics of the water and sediment concentration change firstly and then builds the different three kinds of models from river dynamics theory, hydrological theory and hydrological theory combined with river dynamics theory respectively for the lower reach of the Yellow River. All these three models are verified by observations from the course and compared with each other. The bestone in the terms of performance is recommended. The major contents and studying results ofthose works are listed as follow.(1) Based on the theory of river dynamics and hydrology, nonequlibrioum transforming models for steady and unsteady flow and response function model are built respectively, meanwhile the methods for parameter calibration and practical forecasting operation are given as well. Simulating forecasting has been carried out, which looked as a verification of the three models in forecasting performance. The results of the verification indicate that the two latter forecasting models are available and definitely effective. Specially, the forecasts from the response function model are satisfying.(2) Through the analysis and comparison, the conclusion is drown to be that the method based on hydraulics has clear physical bases and describes the things subtly. Because of this, more factors that affect each other obviously are considered and high quality data are needed. Therefore the precision of forecasts from these models is hard to be improved due to the unsatisfied observations and inadequate knowledge referring to some behaviors of muddy water.(3) Response function model probes into mainly the statistic laws of water and sediment change in macroscopic view without seeking the mechanism seriously so the requirement of the model to observed data is easily met. Another advantage of this model is to be applied conveniently in practice. The results of verification indicate that the response function model is good in forecasting precision. However, this happens only under the condition of normal case. If the mechanism of muddy water movement is introduced in the model construction, the model will have better precision.(4) In view of the characteristics which the hydraulics model has good physical base and the response function model can be applied conveniently in practice, it is worth to advocate the combination of those two ways to forecast sediment concentration hydrograph.