Study On The Flood Runoff Response In Jinghe River Basin Under Changing Environment

Human activities have changed the underlying surface conditions of runoff and confluence to different degrees,which have influenced the regional hydrological cycle and its response pattern.In this article,the Jinghe River basin is used as the research object to analyze the variation characteristics of underlying surface conditions and hydrometeorological factors in the Jinghe River basin.This study can provide theoretical reference for water resources management and soil and water conservation in Loess Plateau of Shaanxi Province.The main outcomes of the study are as below:(1)The interannual variation characteristics of meteorological elements in the Jinghe River basin between 1960 and 2015.The Jinghe River basin was generally characterized by a change in decreasing precipitation,increasing temperature,and growing evaporation between 1960 and2015.Among them,the maximum valueof mean annual precipitation happened in 1964 with789 mm,and the minimum value was 338 mm in 1997.Meanwhile,the minimum value occurred in 1964,and the maximum value was in 1997.The average annual temperature in Jinghe River Basin was 9.1℃,with an overall increasing trend.(2)The analysis of NDVI and land use change in Jinghe River basin.In accordance with the time-series data of the NDVI in the Jinghe River basin during 1998-2018,the change characteristics of its spatial and temporal distribution were analyzed by using the Theil-Sen Median trend and Mann-Kendall test.Based on the six phases of land use remote sensing data in the Jinghe River basin between 1980 and 2015,this paper investigated the composition of land use in the basin in diverse phases and the pattern of land change and transfer type of land.The outcomes revealed that the distribution of multi-year NDVI in the basin regularly increased in a stepped manner from northwest to southeast.The overall improvement of vegetation coverage,with 92.15% of the significantly improved area.The main land use types in the basin are cropland and grassland.The relationship between the multiple land-use types was:grassland > cultivated land > forest land > construction land > water area > unused land..(3)The construction and application of the flood simulation model of the conceptual river basin.The flood data of 54 floods between 1964 and 2013 were chosen for simulation.The flood simulation model of the Muskingum method and the combined flood simulation model of the three water sources of Xin’an River and the Muskingum method were executed.Based on the simulation results,the response characteristics of flood characteristic values to land use change were analyzed.The results show that the peak discharge was smaller and the peak time was later before the 1980 s.Since the 1980 s,human activities have had a large impact on the subsurface of the basin.vegetation coverage was diminishing.In this phase,the flood peaks was more prominent in the same magnitude flood process.(4)A distributed hydrological model based on grid was established and flood process simulation was carried out.The data of 32 flood processes with good rainfall-flood relationships were chosen to build a distributed hydrological model(MCDRM)based on grid,and using Monte Carlo algorithm to machining parameter optimization to analyzed the influence of anthropogenic modification of subsurface conditions on flood processes in the basin.The outcomes indicated that the model was applicable in the Jinghe River basin and simulated peak present time and flood flow better.The flood peak and flood volume under the simulated subsurface production and confluence conditions after 1996 generally decrease compared with the land use before 1996,and the degree decreases with the rise of flood volume.