Eco-hydrological Response Of Small Watershed To Land Use Change And Climate Variation

The Loess Plateau has experienced long time of drought and severe soil erosion. With the proceeding of afforestation and reforestation in the region and the trend of climate warming, it is important to explore the eco-hydrological response to land use change and climate variation. We aim to provide the water resource management, plannging, and eco-environment restoration with theoretical foundation by understanding the various eco-hydrological responses for different catchment system.On the basis of the understanding of the deficiency of empirical model applied in the research of effects of land use change and climatic fluctuation, we built the models of Lv'ergou watershed in the Loess plateau and Seitengraben catchment of Austria, respectively, with the MIKESHE model code. With the validated models, we discussed the potential effects of land use change and climate variation by the simulation of "extreme land use scenarion", "spatial deployment land use scenario" and climatic scenarios which decreased 20% of precipitation and raise the temperature of 2℃. Furthermore by couping MIKESHE modeling results and MUSLE equation we have performed evaluation of spatial distribution of soil erosion of Lv'ergou watershed and scenario simulation.Hydrological effect analysis by Zhang model has shown that the impact of land use change can not been detected with empirical model as much of model error occred with the prediction. With either Zhang model or Budyko model, hydrological response of both watersheds has displayed consistent sensitivity to climate change. However, the attempt of explaning the inter-annual runoff anomy with the climate variation was failed, which indicate the existence of the impact of land use change in the runoff observation to some degree.MIKESHE has generally represent the runoff process of Lv'ergou watershed with the correlationcoefficient of 0.833 and 0.630, and F_Bal of -40% and -17.9%, respectively for calibration and validation period. And the performance of MIKESHE in the application of Seitengraben catchment was well, with R of 0.711 and 0.785, and F_Bal of-1.97% and -3.56%, respectivelly for calibration andvalidation period.Scenario analysis has demonstrated that eco-hydrological response of Seitengraben catchment was more sensitive than that of Lv'ergou watershed. Conversion between various land uses for Lv'ergou watershed would cause the potential maximum change of 2.97% in evapotranspiration and 3.46% in total streamflow, and 10.14% for Seitengraben catchment in evapotranspiration and 12.6% in streamflow. The 20% of increase of forest cover for lv'ergou watershed has reduced the total water yield by 14mm (around 18%), but the conversion from either sloping filed or grass land to forest didn't shown significant impact. While for Seitengraben catchment it was found that every 10% of increase of forest cover would reduce the total water yiled by 9.5mm. Both lv'ergou watershed and Seitengraben catchment has shown similar response to precipitation change. With the decrease of 20% of precipitation, simulation of evapotranspiration, overland, as well as total streamflow was found decreased by 6.16% tol2.4%,74.69% to 95.16%, and 66.59% to 89.40%, respectively. Hydrological response of lv'ergou waterhed to temperature rise was more sensitive than that of Seitengraben catchment. With 2 degree of temperature rise, simulation of evapotranspiration for lv'ergou watershed was decreased by 6.4% to 8.7%, runoff by 42.82% to 51.82%, and total streamflow by 41.69% to 49.38%. On the contrary, for Seitengraben catchment, evapotranspiration was decreased by 0.84% to 1.04%, runoffby 4.78% to 10.53%, and total streamflow by 3.69% to 8.04%.The coupling of MIKESHE and MUSLE has displayed that the channel of lv'ergou watershed accounted for 90% of the total sediment yield. 33% of sediment yield was attributed to village and non-agricultural land use, and 27% and 24% to sloping field and grass land, respectively. Scenario simulations for various land use has indicated that the conversion to timber forest has most significant effect on controlling soil erosion with 70 to 1398t/km² of decrease in sediment yield, which was followed by the conversion to grassland. While the conversion to shrub or orchard has shown the least effect with 70 to 517t/km2 of decrease in sediment yield.