Spatio-temporal Evolution And Its Non-stationary Diagnostic Of Surface Runoff In The Upper And Middle Huaihe River Basin

The characteristics of runoff changes have important theoretical and practical significance for agricultural irrigation,water resources allocation and management of river basins.The Upper and Middle Huai River Basin is an important agricultural area in China.Therefore,the study on the characteristics and mechanism of the runoff process in the Huaihe River Basin highlights its importance.Based on the runoff data of 9 hydrological stations in the basin from1956 to 2016,the paper analyzes the annual distribution interannual variation,trend,mutation,and periodic changesof runoff in the Upper and Middle Huai River Basin by non-parametric Mann-Kendall trend test and wavelet transform.Secondly,using Pettitt nonparametric test,GAMLSS model and flood frequency analysis model to reveal the evolution law of flood frequency in the Upper and Middle Huai River Basin,analyzing the flood intensity and the effects of flood disasters which based on stationary and non-stationary conditions.Finally,M-K nonparametric test method and wavelet analysis were used to study the temporal of the average flow(low water flow)of the first to last days of the Upper and Middle Huai River Basin at 1d,7d,15d and 30d.The analysis results are as follows:(1)The runoff in the Upper and Middle Huai River Basin is mainly concentrated from May to September,accounting for 70.37%of the total annual runoff,the variation coefficient is between 0.16 and 0.85,and the interannual extremum ratio is between 1.7 and 23.9.The interannual variation of runoff is severe;the runoff in Upper and Middle Huai River Basin decreases generally,especially in April and May,and the seasonal change is not obvious;the annual runoff of the stations in the Upper and Middle Huai River Basin shows a significant cyclical change in 2000s,Bantai,Wangjiaba,Lutaizi and Bengbu stations have a small period of 2.0-3.4a on this scale,and Xixian,Huangchuan and Jiangjiaji stations are in high energy areas.The significant periods of the seasons and flood seasons and non-flood periods are concentrated in 1960s,1980s and 2000s.(2)The annual runoff of Huangchuan Station has the most obvious response to climatic factors,and its response to MEI and PDO index passed the95%and 99%significance tests respectively.The teleconnection of PDO on the monthly runoff of each site was most significant,and it was mainly concentrated in June,with a prominenet negative correlation,most obvious for Bantai hydrological station,which passed the 95%significance test in January,April and June respectively.The SOI,NAO and Nino3.4 indices have significant lags in the response of the monthly runoff in the study area.The impact of Nino3.4on the lag period of the monthly runoff in the study area mainly occurred in Huangchuan and Jiangjiaji stations,while the AO and PDO indices have no hysteresis response.(3)There was no obvious variation in Huangchuan,Hengpaitou and Bengbu hydrological stations,and the other 6 hydrological stations showed mean or variance variation,and the variation time was mainly concentrated in2000.The optimal fitting distribution function of the Upper and Middle Huai River Basin is Weibull;Bantai,Jiangjiaji and Hengpaigtou hydrological stations are suitable for non-stationary models,and the rest of the stations choose stationary models.The design flow value under the non-stationary condition of per 10 and 20 years of each station have small difference quantity with the Pearson III type design flow value that under thestationarity condition,but the design flow of once in 30 years,once in 50 years,and once in 100 years difference gradually become larger.The flood amplification factor of Hengpaitou Station are greater than 1,and has increased with time,and the return period of one hundred years is less than 80 years.The annual maximum flood peak flow of each site and the flood area of the Upper and Middle Huai River Basin and Anhui Province all passed the 95%or 99%significant test.(4)The variation coefficient of low water flow in the Upper and Middle Huai River Basin is between 0.23-1.34,and the annual minimum dry water flow is between 0.002-24.5m~3/s,and the dry water flow varies greatly from year to year.The variation time of each site occurred mostly in the early phase of 1960s and 21st century.The change trends of the Xixian,Huangchuan,Bantai and Wangjiaba hydrological stations in Q1,Q7 and Q15 are basically the same,and the overall trend is oscillating.In the spatial distribution,the upstream dry water flow showed an increasing trend,while the middle reach showed a downward trend.The 5 hydrological stations of Xixian,Bantai,Fuyang,Bengbu and Lutaizi all had significant cycles in 1960-1977 years.Huangchuan,Bantai,Wangjiaba,Jiangjiaji,Hengpaitou and Bengbu hydrological stations had a significant period change of 2.0-4.6a during 1997-2012 years.