Study On Relationship Between Water And Sediment In Wuding River Basin Based On Energy Theory

Climate change and human activities have been the driving forces behind the inconsistent characteristics of water and sediment changes in the watershed.In the past few decades,research on water and sediment changes in the watershed has achieved rich research results.Statistical models can achieve efficient and concise water and sediment forecasting,and provide necessary support for water resources planning and water and soil erosion control in river basins,but there are also shortcomings that lack clear physical processes.The watershed sediment model based on the physical process has become an important technology to make up for the shortcomings of the statistical model,but the redundancy and complexity of the parameters have caused many obstacles to the mechanism simulation of truly realizing the watershed sediment process.Therefore,it is of great theoretical significance to achieve a balance between these two models and find a response parameter of water and sediment based on the energy theory.This study took the Wuding River Basin as the research area,and analyzed the inconsistent characteristics of water and sediment changes in the four sub-basins controlled by Baijiachuan,Dingjiagou,Zhaoshiyao,and Suide Hydrological Stations in the Wuding River Basin.Based on the energy theory,the relationship between water and sediment changes in the Wuding River Basin was analyzed,the calculation formula of the runoff sediment energy in the basin was deduced,the indicators of the annual runoff sediment energy in the basin were identified.At last,contributes of the climate change and human activities to the annual runoff,annual sediment load,and annual runoff sediment energy were calculated quantitatively,and the effects of climate change and ecological construction on annual runoff,annual sediment load,and annual runoff sediment energy were analyzed.The main research results obtained are as follows:(1)There were no significant trends and significant change-points in the annual precipitation of the four sub-basins of the Wuding River Basin from 1960 to 2015.There was obviously a main period oscillation of about 40 years and small periodic changes of about 24 years and about 3 years.The annual variation of annual precipitation in the four sub-basins showed consistency.There was a significant downward trend in annual runoff and annual sediment laod in the four sub-basins(p<0.05).There were significant change-points in annual runoff and annual sediment laod at 70s,80s,90s,and 00s(p<0.05).Annual runoff and annual sediment load had 40-year and the main period oscillated for about 30 years.The annual precipitation and annual runoff,annual precipitation and annual sediment load,annual runoff and annual sediment load showed obvious inconsistent relationships.(2)From 1960 to 2015 in the four sub-basins of the Wuding River Basin,the coupling degree of runoff and sediment load,and the coupling degree of runoff energy and sediment load all showed a significant downward trend(p<0.05).Annual runoff and annual runoff energy generally had the strongest impact on annual sediment load under larger conditions,and the relationship between runoff energy and sediment load was more closely related.When the parameters Q1 and Q2 of the annual runoff sediment energy of Baijiachuan,Dingjiagou,Zhaoshiyao and Suide Hydrological Stations of Wuding River were taken as the 1 and 0.885 quantiles,1 and 0.985 quintiles,0.995 and 0.86 quintiles,0.99 and 0.935 quantiles of the daily flow series during the year,respectively,the linear relationship between annual runoff sediment energy and annual sediment load was optimal,and R2 reached 0.85,0.78,0.87,0.87,respectively.Runoff sediment energy was the energy that effectively played a role in sediment transport in runoff energy.Its general index form was closely related to the large flow in the river basin.The runoff sediment energy was always highly consistent with the sediment load in the river basin.(3)Compared with the first stage(base period),the contribution of human activities to the reduction of annual runoff,annual sediment load,and annual runoff sediment energy in the Wuding River Basin during the second stage are 84.60%,105.62%,and 114.57%,respectively,and the contribution during the third stage reached 105.75%,117.60%,and 126.92%,respectively.Human activities played a leading role in reducing annual runoff,annual sediment load,and annual runoff sediment energy in the Wuding River Basin,and this dominant role was constantly being strengthened.Annual precipitation and the construction of the check dam from 1960s to 1970s mainly reduced the annual runoff,annual sediment load,and annual runoff sediment energy.The construction of terraces played an important role in reducing annual runoff,annual sediment load,and annual runoff sediment energy during the 1960s.The increasing significantly area of the annual vegetation coverage accounted for 85.38%of the total area in the Wuding River Basin from 2000 to 2015,90.92%of the total area of the vegetation coverage risk level was moderately low.Before the policy of returning farmland to forest was implemented,the increase in natural vegetation would not cause a significant reduction in annual runoff,annual sediment load,and annual runoff sediment energy.