| With the climate change and the intensification of human activities,more and more drastic changes in water and sediment in the middle reaches of the Yellow River.For the problem of water and sediment changes in the sediment laden and coarse sand area of the middle reaches of the Yellow River.in this paper,hydrological statistics,principal component analysis,principal component regression analysis,GAMLSS model and quantile attribution analysis are adopted to study the main influencing factors of water and sediment variation in WuDing River basin,analyzed the variation trend of meteorology and water sediment in WuDing river basin,and clarifying the impact of climate change and human activities on water and sediment changes in the watershed.The contribution rate of the main factors affecting the Wwater and sediment changes in WuDing river basin is analyzed and calculated by the method of cumulant slope change rate comparison method,the elastic coefficient method and the quantile attribution analysis method.The main achievements of this paper are as follows:(1)Clarified the change trend of meteorological and hydrological series in WuDing river basin.There is no significant increase in annual precipitation in WuDing river basin;The annual potential evaporation has a significant decreasing trend,and the year of mutation is 1982;Annual runoff and annual sediment discharge both have a significant decreasing trend,and the abrupt year is all 1971;The GAMLSS model and the preferred GAMMA function were used to analyze the change trend of the mean and variance of annual precipitation,annual potential evaporation,annual runoff and annual sediment discharge series in WuDing river basin,the results shows that the mean value of annual precipitation series has no significant change trend,but its variance has changed significantly with time t.The mean values of annual potential evaporation and annual sediment discharge series have a significant change trend with the extension of time,but there is no significant change in variance.The mean and variance of annual runoff series have a significant change trend with the extension of time.(2)The contribution rate of climate change and human activities to water and sediment variation in the duling river basin is quantitatively identified by cumulant slope change rate comparison method and elastic coefficient method,the results shows that the contribution rates of annual precipitation,annual potential evaporation and human activities to annual runoff in WuDing river basin were 12.50%,21.68%and 65.82%,respectively,based on the cumulative slope change rate comparison method.The contribution rates of annual precipitation,annual potential evaporation and human activities to annual runoff in wuding river basin were 14.64%,21.62%and 63.74%,respectively,based on elastic coefficient method.The contribution rates of annual precipitation,annual potential evaporation and human activities to annual sediment discharge in wuding river basin were 3.56%,6.18%and 90.25%,respectively,based on the cumulative slope change rate comparison method.The contribution rates of annual precipitation,annual potential evaporation and human activities to annual sediment discharge in wuding river basin were 0.99%,9.77%and 89.24%respectively,based on elastic coeff-icient method.The contribution rate of human activities to annual runoff and annual sediment discharge in wuding river basin is greater than that of climate change to annual runoff and annual sediment discharge.Moreover,the contribution rate of human activities to the change of annual sediment discharge in wuding river basin is significantly greater than that of annual runoff.(3)The rationality of calculation results based on single covariates and multiple covariates is compared.Based on the GAMLSS model,it is established that the fitting relationship between annual precipitation,annual potential evaporation,annual cumulative dam area,annual cumulative level of terraced field area,annual cumulative woodland area and annual cumulative grass area,and the relationship between the six covariate combinations and runoff and sediment load.The fitting relation between single covariate and runoff and sediment transport is established,it can be seen that the annual potential evaporation of the fitting equation is positively correlated with runoff,it contradicts the actual situation,moreover,the result of the positive correlation between the annual sediment discharge of the wuding river basin and the annual cumulative level terraced field area and annual accumulated grass area is also in contradiction with the actual situation.By comparing the relationship between the covariates,the combinations of the six covariates and runoff,sediment discharge,it can be obtained that the fitting relationship and uncertainty interval between the annual runoff,the annual sediment discharge and the covariate established by six covariables is obviously better than the relationship between the annual runoff,the annual sediment discharge established by a single co variable.Compared with the result based on the single factor fitting formula,the simulation results of annual runoff and annual sediment discharge process line are obtained by using the multi-factor annual runoff and annual sediment discharge fitting formula established in this paper,it is more consistent with the actual interannual variation of water and sediment in wuding river basin.(4)The contribution rate of different covariates to the change of water and sediment.Compared with the result based on the single factor fitting formula,the process line simulation results of annual runoff and annual sediment discharge are derived from the multi-factor annual runoff and sediment transport fitting formula is more in line with the actual interannual change of water and sand in wuding river basin.The contribution rate of annual precipitation,annual potential evapotranspiration,annual cumulative dam area,annual cumulative level terraced field area,annual accumulated forestland area and annual accumulated grass area to annual runoff decrease in the 1988?1998 period in wuding river basin is 18.89%,0.24%?28.74%?52.04%?-4.74%and 4.83%,respectively,and the contribution rate in the 1999?2009 period is 2.60%?-0.06%?41.73%?40.87%.29.24%and-9.19%,respectively.The contribution rate of annual precipitation,annual potential evapotranspiration,annual cumulative dam area,annual cumulative level terraced field area,annual accumulated forestland area and annual accumulated grass area to annual sediment discharge decrease in the 1988-1998 period in wuding river basin is 26.75%?7.90%.22.84%?33.73%?-3.44%and 12.22%,respectively,and the contribution rate in the 1999?2009 period is 4.85%?21?39%?46.57%?38.80%?31.36%and-3 3.27%,respectively. |
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