Research On Anti-icing Flow In Ningxia-inner Mongolia Reach In The Upstream Of Yellow River Based On Ice Condition Changes

The Ningxia-Inner Mongolia Reach is the section with the most ice flood disasters on the Yellow River.Under the background of global warming,the characteristics of Ningxia-Inner Mongolia Reach have changed greatly.In response to the change in climate caused by climate change,humans can adapt it by continuously adjusting the reservoir anti-ice dispatching scheme.Therefore,fully understand the law of the evolution of ice status under the changing environment,do a good job forecasting the ice status,calculate the adaptive climate anti-ice flow of Liujiaxia Reservoir,and provide a reference for the formulation of future ice prevention and disaster reduction policies,which has important practical significance for the sustainable development of the Yellow River.In this paper,the Ningxia-Inner Mongolia Reach and the reservoirs in the upstream of Yellow River are taken as the research objects.Firstly,the spatial changes of the main ice impact factor are analyzed.Secondly,a piecewise multivariate linear regression model of ice forecasting is established and a set of temperature rise scenarios are constructed.Finally,Freeze-up Time and Break-up Time of Ningxia-Inner Mongolia Section in the upper reaches of the Yellow River and the climate-adaptive flow control plan are estimated.The main research results are as follows:(1)Select temperature and flow as the main ice impact factors,analyze the trend,abrupt change and continuity with time change and analyze the trend of change of Break-up Time and Freeze-up Time in the different period of Ningxia-Inner Mongolia reach.The results show that the average temperature of Ningxia-Inner Mongolia Reach in ice prevention period is rising.there was a sudden jump in the late 1980s;after the Liujiaxia Reservoir was put into use in 1968,the flow of Ningxia-Inner Mongolia Reach of the Yellow River in ice prevention period increased significantly,indicating human activities,especially reservoir scheduling had a significant impact on the change of flow in Ningxia-Inner Mongolia Reach in ice prevention period;Under the rising tempeatrure conditions of Ningxia-Inner Mongolia Section in the late 1980s,the Freeze-up Time of the river showed a tendency to push back,and the Break-up Time of the river showed an earlier trend(2)Based on the analysis of the law of the main ice factors with the time change,it takes the abrupt change point of the average temperature of each hydrological station as the time cutoff point,a piecewise multiple linear regression model of the ice forecasting is established and the prediction accuracy of the model is analyzed.The results show that the accuracy of the ice prediction model based on the ice status data after the catastrophe point is better than other models,and it can be used to study the impact of climate change on the future freeze-up date,break-up date and the change in the ice prevention flow(3)Construct the temperature increase scenario set of Ningxia-Inner Mongolia Reach by assuming the climate scenario method and the GCMS model output scenario method(BCC-CSM1.1).based on the model for ice forecasting,the freeze-up date,break-up date and the change range of the ice prevention flow limit is estimated.At the same time,according to different temperature increase scenarios and anti-icing scheduling principles,the climate-adaptive anti-icing flow plan of the Liujiaxia Reservoir is determined.The results show that the future freeze-up and break-up date of the Ningxia-Inner Mongolia Reach has different degrees of postponement and advancement under different temperature increase scenarios.At the same time,the effect of warming on the freeze-up date of the Ningxia-Inner Mongolia Reach is greater downstream than upstream,but the impact of break-up date change is greater upstream than downstream;the climate-adaptive ice prevention flow scheme of Liujiaxia Reservoir under different temperature-increasing scenarios is deduced.In general,it is necessary to increase the Liujiaxia ice prevention flow in November,December and January,and to reduce February and March.The range of change changes with the temperature increase.