Reconstruction Of Hydrometeorological Sequence In The Lower Yellow River And Response Of Runoff To Climatic Factors In A Changing Environment

In order to study in depth the reconstruction of hydrometeorological sequences and quantify the contribution of climate factors to runoff changes in changing environments,this paper uses 7 hydrological stations and 35 meteorological stations in the lower Yellow River from 1979 to 2015.Based on ArcGIS software,the precipitation of the lower Yellow River Spatial interpolation of temperature,temperature and sunshine hours series to make up for missing areas;use Mann-Kendall mutation test and sliding sample entropy method for consistency analysis of hydrometeorological series;use gray correlation method to identify runoff influencing factors in the lower Yellow River.Budyko's hypothesis of coupled hydrothermal balance is based on the water balance method as the main theoretical basis to reduce runoff in the lower Yellow River.Climate change is attributed to changes in hydrothermal conditions.Cumulative slope change rate comparison method and multiple regression model are used to separate meteorological elements.Contributions to changes in runoff and potential evapotranspiration.The main research conclusions are as follows:1.The warming and drying characteristics of the lower Yellow River have been obvious in the past 40 years.The annual precipitation and the average daily sunshine hours show a significant downward trend(p<0.05),and the average temperature of the four seasons shows a significant upward trend(p<0.05),and both have periodic changes.Among them,the Huayuankou station has three main periods of annual change:22a,15a and 5a;the Jiahetan(21a and 5a)and Lijin station(21a and 6a)have two main periods of change;and the Aishan station has 15a periods;In the lower reaches of the Yellow River,there is a 21a first main period change in the average temperature and annual average sunshine hours in spring,autumn,and winter,and a 20a first main period change in the summer and annual average temperature.2.The inverse distance weighting method has the highest accuracy in the spatial interpolation of precipitation;the spline function method is more suitable for the spatial interpolation of temperature;the kriging method can better reflect its spatial distribution in the spatial prediction of sunshine hours.On the whole,the annual precipitation and the average annual temperature show a gradually decreasing distribution pattern from the southwest to the northeast;the annual average sunshine hours show a spatial characteristic that gradually increases from the southwest to the northeast.3.The mutation test based on the sliding sample entropy method showed that the annual precipitation in the lower reaches of the Yellow River changed abruptly in 1995;the average temperature of spring,summer,autumn,and winter changed abruptly in 2001?2000?2004 and 1987,respectively;Mutations occurred in the year.Non-uniform changes in hydrometeorological sequences.4.Based on the Budyko hypothesis,runoff simulations on the monthly and annual scales of the lower Yellow River were performed with low accuracy(NSE<0);the Zhang model based on the improved Budyko hypothesis was used to perform annual-scale runoff simulations with good simulation results(NSE>0.7)and monthly scale The runoff simulation accuracy is low(NSE<0);the improved Zhang model based on the Budyko assumption is more suitable for the annual runoff simulation of non-consistent hydrometeorological sequences in the lower Yellow River.5.The annual average runoff showed a significant downward trend(p<0.05),and a sudden change occurred in the 1990s.Human activities and potential evapotranspiration have a positive driving effect on runoff changes in the lower Yellow River,while changes in precipitation,temperature,and sunshine hours have a negative driving effect on runoff changes.Runoff responds to climatic factors under changing circumstances.The research results in this paper can provide continuous hydrometeorological sequences for the lower Yellow River,provide data support for hydrological model parameter calibration,and provide a certain theoretical basis for the rational development and utilization of water resources in the river basin.