The Relationship Between Precipitation And Land Use Measures Change On Runoff And Sediment Yield In Anding District

Climate change and human activities have led to major changes in river runoff and sediment load.This paper takes the Anding District of Dingxi City as the research area,and the research period during 1957~2016.Based on the discharge,sediment transport and precipitation,land use measure and GF-1 image data.With the object-oriented classification method,the land use information were extracted by us in the verification period(2016).The Mann-Kendall trend analysis and mutation test and Morlet wavelet analysis were used to analyze the annual precipitation,runoff,sediment transport evolution and periodic changes.The relationship between annual precipitation and land use measures(non-controlled and control area)changes on river runoff and sediment yield was analyzed via single factor and multi-factor regression analysis.The main conclusions of this study were as follows:(1)Characteristics of runoff and sediment variation.During the study period scale,the annual precipitation,runoff modulus and sediment transport modulus showed a decreasing trend.The annual precipitation was smaller,and the runoff modulus and sediment transport modulus decreased to a very significant level(P<0.01).Both runoff and sediment transport are characterized by water and sediment synchronization.The annual precipitation,runoff and sediment transport changes have the following rules.On the 22~24a,8a,and 4a time scales,there are obvious oscillation periods,and the average time period is approximately 15a,5a,and3a.The amplitude appears to decrease from large to small throughout the time series,especially after 2001,the amplitude of runoff and sediment decreased sharply.(2)The changing characteristics of land use measures.Due to the different intensity of soil and water conservation work,the distribution intensity of non-controlled area that contains sloping land,unused land and other land use is decreasing;The distribution intensity of the land control which are construction land,terrace,arbor,shrub,economic forest,grass planting wasteland,returning farmland to grassland,enclosure control and dam is increasing.However,the types of soil and water conservation measures implemented are different at different periods,and the rate of change of different measures are distinct.The distribution intensity of non-controlled area decreased from 99.76hm~2/km~2 in 1957 to 23.58hm~2/km~2 in 2016.The land control increased from 0.05hm~2/km~2 in 1957 to 76.18hm~2/km~2 in 2016,and the annual treatment rate was 1.27%.(3)Analysis of the correlation between annual precipitation(runoff),land use measures and water and sediment changes.In terms of linearity model,logarithm model,power function model and exponential model,it has positive correlation that the precipitation and runoff,runoff and sediment transport,non-controlled area and runoff,non-controlled area and sediment transport.The land control is negatively correlated with runoff and sediment transport,and the nonlinear relationship between land use measures and runoff and sediment transport is greater than linear.Correlation of between different non-soil and water conservation measures and runoff and sediment transport modulus,from R value of highest to lowest are ranked,as follows:sloping land>unused land and other land>construction land;Correlation of between different soil and water conservation measures and runoff:terrace>returning farmland to grassland>economic forest>shrub>arbor>enclosure control>dam>grass planting wasteland;The tendency of the R values of correlation between different soil and water conservation measures and sediment transport are as follows:enclosure control>dam>terrace>economic forest>returning farmland to grassland>shrub>arbor>grass planting wasteland.(4)Impaction and contribution share analysis of annual precipitation(runoff)and land use measures on water and sediment.Under the conditions of yearly and different periods(3a,5a,15a),with the increase of precipitation,the annual discharge and runoff rate are rapidly increasing.With the increase of runoff modulus,the sediment load increased rapidly,however the sediment load rate decreased.As the distribution intensity of the non-controlled area decreases,the discharge and sediment load decrease rapidly,and the runoff rate and sediment load rate become gradually small.With the distribution intensity of the land control increases,the discharge decrease,and the sediment load augmnet slightly,and the runoff rate and sediment load rate decrease gradually.The standardized residuals basically match to the normal distribution in different periods,but the runoff modulus is superior to 5a,the sediment transport modulus is better at 3a.It was extremely significant by constructing multivariate efficacy function(P<0.001),this function constructed by precipitation(runoff),distribution intensity of the non-controlled area and the land control with water and sediment change.The amount of precipitation,non-controlled area and land control have effect on the contribution rate of runoff modulus are 23.08%~-0.21%,84.62%~101.86%and-7.69%~2.34%,respectively;The amount of runoff modulus,non-controlled area and land control have influence on the contribution rates of sediment transport modulus are 37.35%~115.87%,35.42%~76.29%and 20.58~23.84%,successively.