| In recent years,under the change of climate and the influence of human activities, the conditions of water and sediment and the evolution of river channels have changed. Studying the conditions of water and sediment matching in watersheds under changing conditions and exploring the trend of the river bed may occur under the new river channel boundary conditions have a guiding significance for governancing river, alleviating the flood pressure and ensuring the harmonious coexistence of rivers and human beings. In this paper, we take the lower reaches of the Wei River as a research object to predicting the evolution trend of the river bed by collecting and analyzing water and sediment data, sedimentation volume and cross-section data of this reach.In order to studying and forecasting the river bed. we analyze the sedimentation and scouring conditions of the lower reaches of the Wei River by using sediment transport method and section method. Finally, according to current boundary conditions of the river channel, the trend of river bed is predicted by combining the forecast of water and sediment in the next five years.The following conclusions are drawn from this paper:(1) The time series analysis method and statistical analysis method were used to analyze the trend and persistence of runoff and sediment. The analysis showed that the runoff showed a tendency to decrease significantly, and this trend will continue to be maintained in the next period of time. And the same as sediment, the amount of sediment transport maintain the history of the lowest state lasted about 10 years from 1993 to 2003. After 2003, it has linmited increased, yet the current amount of sediment is still small. And compared to the reduction in the amount of sediment, the amount of water is more obviOous.(2) The change of sediment transport rate of the hydrological stations in the lower reaches of the Wei River Basin also showed a significant decreasing trend, which was basically at the lowest level in history after entering the 21 st century. The value of incoming sediment coefficient in the mid-1990s to the mid-21st century showed a relatively chaotic phenomenon with the magnitude of the change. It is in line with the lowest level of history at present.(3) After the comprehensive river regulation, the flood control capacity has been improved compared with the historical period in the lower reaches of the Wei River, and the river regime has little change. At present, the low water level slope is at a low level. And Tongguan elevation with the completion of the Sanmenxia reservoir and the adjustment of the operation has taken place a certain change, the current level is 327.63m, which is still high. Above river boundary conditions are not conducive to the river erosion and sediment transport.(4)The flood season and annual critical sediment coefficient of each hydrological station is determined through establish the relationship between the incoming sediment coefficient and sedimentation volume. For the critical to the sediment coefficient changes, the flood season is always less than the whole years for single station, the Xianyang station is less than the Lintong and Huaxian station.(5) On the prediction of the coming water and sediment conditions of Huaxian hydrological station in the next five years (2015 -2019). Firstly, we predict the amount of runoff and the possibility of probability through the ensemble forecast model. Then we obtain sediment transport capacity and incoming sediment coefficients in the same year by the recent water and sediment collocation relation. And then we contrast these data with critical sediment coefficient value. The results show that water and sediment conditions conducive to the riverbed stay balance and stable.(6) Based on the analysis of the river bed stability index and the boundary condition of Tongguan elevation, we predict that the evolution trend of river will maintain balance in the future. |
