Analysis Of Sub-flood Retreat In Chabagou Basin And Its Response To Underlying Surface Changes

Due to the change of climatic conditions and human activities in the Yellow River Basin,the hydrological cycle of the basin has changed significantly.The ecological environment of the basin is facing great challenges due to the sharp reduction of river runoff and the reduction of groundwater levels in the region.Therefore,it is of practical significance to study the evolution of the underground runoff process in the Yellow River Basin under changing circumstances.This article takes the Chabagou watershed in Yulin area as an example to analyze the change trend and sudden change of rainfall and flood in this basin.Based on quantum genetic algorithm and multi-source time-varying gain model,the underground runoff is divided into multiple measured floods in the watershed,and the watershed is simulated.The underground runoff process of the flood during the base period and the underlying surface change period.The response degree of the underground runoff process to the underlying surface change was analyzed quantitatively and qualitatively.The main research contents are as follows:(1)Based on the remote sensing data of the four phases of land use in the Chabagou Basin in 1986,1995,2000,and 2008,the area and spatial evolution of multiple land use types in the basin during the period from 1986 to 2008 were analyzed.The analysis shows that the area of land use types in the watershed did not change significantly during this period,as long as the change in characteristics was a shift in the spatial distribution of the watershed.(2)In this paper,the rainfall process corresponding to the maximum flood discharge in Chabagou watershed from 1960 to 2010 is selected.Linear trend regression and MK nonparametric rank correlation test were used to analyze the change trend of multiple rainfall statistical parameter time series.The results showed that the intensity of secondary rainfall decreased significantly,and the rainfall process line gradually changed from sharp and lean type to short and fat type process;The ordered year clustering method,sliding T test and anomalous cumulative test were used to diagnose the mutation year.The results showed that the secondary rainfall intensity and the rainfall process line parameter mutation year were both 1970.(3)The trend and catastrophe analysis of the flood hydrographs corresponding to the maximum flood peak discharge in Chabagou watershed from 1960 to 2010 was conducted.The results show that there is a significant downward trend in flood peak flow and sub-flood,the flood hydrographs line gradually changes from a sharp and lean type to a squat type process,the flood increase process is more flattened and the rate of withdrawal is slower;The year of sudden change of flood surge and backwater parameters is also 1970.(4)Based on the quantum genetic algorithm,the parameters of the flood underground runoff and backwater in the watershed base period(1961-1970)and underlying surface change period(1971-2010)were deduced,which were 4.310h and 6.211h,respectively.The rate of flood retreat is slower than that of the secondary flood in the reference period.Based on the evaluation of the algorithm accuracy and the rationality verification of the backwater parameters,the subsurface runoff water sources are divided by the subsurface runoff backwater parameters.(5)Select multiple flood processes before and after the underlying surface changes,and use the multi-source TVGM model for model parameter calibration and applicability verification.The results show that the model has good effects in simulating flood processes and sub-flood and retreat processes.It is considered that the model is suitable for basin floods And simulation of underground runoff processes.From the simulation results of the sub-flood process and the underground runoff process,it can be seen that the sharp and thin sub-flood process has a larger value of the underground run-off depth and the total run-off depth than the chubby sub-flood process,and the sub-flood process during the basin change period is compared with the baseline During the secondary flooding process,the values of underground runoff depth and total runoff depth generally increased.The sub-flood processes of different magnitudes are divided according to the recurrence period,and the flood process and underground runoff process are simulated based on the two sets of confluence parameters before and after the underlying changes.The results show that the change of the underlying surface conditions in Chabagou watershed leads to the reduction of flood peaks and the amount of secondary floods in the watershed.The underground runoff depth Rg and the ratio of the underground runoff depth to the total runoff depth Rg/R in the secondary floods have different degrees.Increase.