Research On Flood And Drought Pattern And Runoff Simulation Of Ling River Basin

Ling River basin is located in the typical semi-humid of the north China. For a long time, flood and drought disaster occur frequently in the basin, and soil and water loss seriously. The ecological environment of the basin is fragile. The shortage of water resources is also serious. All about these affect the economic development of the basin seriously. So it is important to analysis and research on the impacts of meteorological and hydrological regulations in the basin.The paper uses daily rainfall data from 1961 to 2010 in 50 years of precipitation station in Ling River basin to analysis the changes in rainfallcharacteristics, including the annually and interannual variations. Analysis result shows that rainfall reduced gradually from the south to the north of the research area, the interannual changes greatly, that is obvious in the south than in the north part; annual rainfall mainly concentrated in the flood season, focuses in the middle of July, and in recent years, flood season precipitation is reducing, the concentrationratioshows a trend of decrease. Interannual variability of evaporation changes in a small range, the highest evaporation occurs in May, and the lowest occurs in December and the following January, in other months, its distribution doesn’t vary greatly, so the concentrationratio is not so high. Parameters and non-parametrictest results both show that the it is significant correlation when annual rainfall and relative sunspot number is 0.05.At the same time, the paper uses the Z index and SPI index of drought and flood in typical years to divide the spatial distribution of flood and drought in Ling River basin, the results show that SPI index reflects more sensitive for extreme drought conditions and Z index reflects more sensitive to floods.Secondly the data of 12 main hydrometricstations of Daling River basin and Xiaoling River basin are used to analysis the runoff’s annual and interannual variability, searching for the evolution law of annual runoff. Result shows, in Daling River basin and Xiaoling River basin, runoff in July and August occupies the largest percentage; the most unequally annual distribution occurs in 1960s, after 2000 annual distribution difference is minimal. And interannual variations have a tendency of descendâ†'significantly descendâ†'riseâ†'significantly decend. From the trend test results of the typical stations, runoff of Daling River has an obvious decrease trend. LingHai station on main stream’s break point is 1980, and Habaqi station on the branch locals in confidenceinterval, but also has a break. The two stations on main stream of Xiaoling River have the same variationtendency, but both show a trend of decline. Periodicity analysis shows that LingHai station on main stream, Habaqi station on the branch of Daling River, and Gangyaokou station have the same primaryperiod of 26 a, periodicity is apparent. Analysis of hydrological drought of Ling River basin shows that,1960s were primary wet years,1970s were primary normal years,1980s especially after 2000 were primary dry years in Daling River basin. And Xiaoling River basin’s 1980s were primary dry years, after 2000 dry years increase obviously.The paper uses the coupling of distributed hydrological model MIKE SHE and the hydrodynamic model of MIKE 11 to establish the Xiaoling River flow yield and concentration model. Based on the DEM grid, different land uses, topographical features, weather, vegetation, geological and soil conditions as input data simulation of hydrological processes in XiaoLing river basin. Through the sensitivity analysis, the soil parameters of overland flow, the roughness of river runoff roughness value, riverbed leakage coefficient are set as the main parameter. The results showed that the daily runoff simulation, Nash-Suttclife coefficient in the rate of regular (1990-1994/Jinzhou station) and the validation period (1995-1999/Jinzhou station) were 0.636 and 0.582, the correlation coefficient reached 0.839 and 0.788,the rate of regular Ens and R was 0.794,0.863;0.961,0.960 of month scale simulation; verification period of two stations Ens and R for 0.740,0.820;0.911,0.917, which shows the model in Xiaoling River basin is practical, reliable calibration parameters. Model calculation results uncover that correlation coefficient of the simulation model of long sequences and Nash efficiency coefficient can meet the accuracy requirements in the model. The normal flood has a better simulation in the model, duration of flood, peak flow and measuredvalue match well. But when the runoff is max flow, the simulation has some deviation. That will underestimate the peak flow of maximum. Analysis shows, runoff and ground storage capacity and precipitation have a strong correlation, but when the precipitation comes to maximum, the correlation reduces.