Study On Distributed Hydrological Simulation And Drought Evaluation Method In Luanhe River Basin Based On SWAT Model

With the effects of human activities and climate change, the water resources shortageand frequently occurring hydrological extremes have been the serious worldwideproblems. Based on distributed hydrological simulation and geographical informationtechnology, stdudy on hydrological processes and drought response to land use/coverchange is of great important to exploit and use water and land resources reasonably,social economy sustainable development.As one of the four first order zoning areas of Haihe river basin, Luanhe river basinis one of the most important water resources areas of economic circle around BohaiSea, and it is one of the places where water resource system is most vulnerable andhave more frequent droughts. Therefore, the paper established the distributedhydrological simulation and drought evaluation model, and the hydrolgical responseto land use/cover change were simualted and evaluated from two aspects of normalhydrological processes and drought characteristics, and formed a evaluation methodabout drought evaluation and response to land use/cover change. Besidies, theattribution of climate variablity and human activities for runoff decrease wasquantitatively assessed in Luanhe river basin. Through the above researches, wemainly obtained the following conclusions:(1) The spatial distribution of precipitation has an important impact on distributedhydrological simulation. Aiming at precipitation records incompleteness of gauges inthe Luanhe river basin, the paper established the time scale extend method forprecipitation, thus estimating the precipitation data of gauges and providing datafoundation for distributed hydrological simulation in the long time scales. Comparedwith the directly utility of precipitation data of meteorological station, the method can increase the accuracy of runoff simulation to some extent. On that basis, the SWAT(Soil and Water Assessment Tool) distributed hydrological model was established inLuanhe river basin.(2) Based on the establised distributed hydrological model, the paper analyzed thehydrological processes response to1985and2000land use conditions, and landuse/cover scenarios. Compared that land use condition in1985, the land use changesfrom forest to farmland and grassland would led to increase of runoff and peak flowbetween1985and2000land use. The change of average annual surface runoff hadsignificantly spatial variability, and other land use/cover change scenarios also haddifferent effects on hydrological processes.(3) Given that the exsiting drought indices evaluated drought only from oneforming factor (precipitation) or characteristic(soil moisture), and the shortage ofreflecting the spatial heterogeneity of regional drought. Referring to Pamler droughtseverity model, the paper proposed a drought evaluation model combined thesimulation results of hydrological components based on SWAT model. On that basis,drought response to land use/cover change were analyzed from drought infulenceregions, frequency, duration and severity, thus form a evaluation method aboutdrought and response to land use/cover change. Results indicated that the droughtregions, frequency, duration and severity would be increased under the2000land use.(4) On the basis of the improved attribution analysis method of water resourcesevolution, the attribution for runoff decrease was quantitatively assessed in theLuanhe river basin. The SWAT model was calibrated with hrdro-meteorological datain the natural period (1971-1979). Then using the same model parameters andmeteorological data in the impacted period (1980-2000), the natural streamflow in theimpacted period could be reconstructed by hydrological model. Therefore, thecontribution of climate variability and human activities to runoff change could bequantitatively estimated. Results indicated that the decrease of runoff from1980-2000could be attributed to26.5%and73.5%from climate variability and human activities,respectively. Human activities were main reasons of runoff reduction in Luanhe riverbasin. Then combined the restored runoff through added the social and economic water uses including the water storage of the reservoirs, industrial and agriculturalwater use to measured runoff, the paper further analyzed the attribution of differenthuman activities for runoff reduction, and the contribution of social economicfactor(reservoirs, industrial and agricultural water use) was47%. Compared withunderlying surface condition (land use/cover etc.), the social economic factor hadsignificant effect on runoff reduction.