| Under the dual influence of climate and human activities,the water and sediment in Inner Mongolia section of the Yellow River have decreased significantly.The change of water and sediment not only affects the industrial,agricultural and domestic water use of the people along the Yellow River,but also makes the sediment deposition of the river more serious,which increases the difficulty of river regulation,flood control and ice prevention,and also seriously affects the ecological environment health of the river basin and the development and utilization of water resources in the reach.Based on the measured water and sediment data of four representative hydrological stations in Inner Mongolia Section of the Yellow River from 1973 to 2017,this paper analyzed the non-uniformity coefficient,variation coefficient,trend,catastrophe and periodicity of water and sediment by various mathematical methods.The main factors affecting the change of water and sediment were identified by the improved cumulant slope change rate comparison method,the weight of each factor was detennined,and the variation of water and sediment was discussed.Based on the differential autoregressive moving average model,the runoff and sediment processes of hydrological stations are simulated,and the following conclusions are drawn:(1)Water and sediment inhomogeneity exists in the Inner Mongolia section of the Yellow River,in which the annual inhomogeneity degree of sediment transport is relatively high and the dispersion degree is large.After the abrupt change year,runoff and sediment transport amount show a decreasing trend,and the variation period of water and sediment sequence is 5 and 12 years respectively.(2)In addition to precipitation,air temperature and wind speed,which are important natural factors causing the change of water and sediment,the establishment of reservoirs,the implementation of water and soil conservation measures,and the increasing water diversion along the Yellow River and other human activities are also the main driving factors leading to the decrease and abrupt change of water and sediment.The average contribution rate of human activities to water and sediment reduction in the Inner Mongolia section of the Yellow River was 50.59%and 64.48%respectively.(3)After 1985,the channel silting in the Inner Mongolia section of the Yellow River intensified.Through analyzing the relationship between the runoff and sediment content of the inlet section of the Inner Mongolia section of the Yellow River(shizuishan)and the erosion and silting volume of the downstream section,it was concluded that the runoff volume of shizuishan station was about 29.985 billion m3 and the sediment content was about 2.15kg/m3 when the downstream section reached the erosion and silting balance.(4)The differential autoregressive sliding average model(ARIMA)was established based on the monthly water and sediment data,and the monthly water and sediment volume was predicted from January to June in 2017.The results show that the fitting effect of monthly runoff is better,and the qualified rate of predicted monthly runoff is 67%-83%,under the influence of different sources of water and sediment,the qualified rate of predicted monthly sediment transport volume is only 17R-67%.The research results in this paper can provide some reference for the rational allocation of water resources in Inner Mongolia section of the Yellow River,the comprehensive management of river courses and the optimal operation of reservoirs. |
