Attribution Study Based On Ensemble Simulation Of The Evolution Of Water Resources In Luanhe River Basin

The water circular system is an important part of the climate system, and climate change can certainly cause water resources change in temporal and spatial. With the continuous growth of the population and social-economic development, the impacts of climate change and human activities on hydrology and water resources are becoming increasingly prominent. It is of important significance to quantify the influences of climate change and human activities on the cognition of evolution law and sustainable development of water resources. In this paper, Luan River Basin was taken as the study area, and research of the evolution of the hydrological cycle was carried out by the water balance model and the SWAT model. Partial quantization of climate change and human activities, as well as the uncertainty in the water resources simulation results was also studied. The main research achievements are listed as follows:There was a decreasing trend of natural runoff in Luan River Basin from1957to2000, as well as precipitation and potential evaporation. The5-year moving average lines of runoff and precipitation process showed good consistency, which showed that precipitation change was an important factor to affect runoff change. The natural runoff sequence (from1957to2000) was detected for catastrophe point by the precipitation-runoff double mass analysis and moving t-test. The whole basin natural runoff sequence displayed a significant mutation in1979, thus the whole period was divided into the base period (from1957to1979) and change period (from1980to2000). The runoff series from1972to2000was divided into two stages:1972to1988and1989to2000.This paper described the structure and principles of the SWAT model, and then displays the database construction for hydro-meteorological, land use and soil. The SWAT model could be applied in the Luan River Basin by case study verification. Meanwhile, the water balance model based on Fu’s formula was built by hydro-thermal coupling theory, based on energy balance and water balance principle for any closed basin. And it can be a good applicability in the Luan River Basin. In order to reduce the uncertainty of the hydrological modeling, an ensemble simulation study of multi-mode and multi-model was launched. By comparison, the simulation accuracy of SWAT model was higher than that of water balance model for the runoff simulation in Luanxian hydrological station. The simulations of natural runoff were applied by combining forecasts model in Luanxian hydrological station from1972to2000, which was based on set pair analysis, entropy method and multiple linear regression, respectively. The simulation curve and the measured curve based on the multiple linear regression model were consistent with the highest degree, and its simulation is the best.In terms of water cycle of a basin, to identify the impact of climate change and human activities indirectly from the runoff change is reasonable and feasible. Runoff was the terminal of hydrological cycle, so it could be observed conveniently and could intuitively reflect the influence change that climate change and human activities have on water resources. This research fixed climatic factors and land use/cover change and import simulation context into SWAT model and water balance model. The multiple linear regression model was applied to simulate the natural runoff under the corresponding simulation context. The results were then used to calculate the influence degree that climate change and land use change have on natural runoff. The results showed that climate change was the leading factor that caused the decrease of natural runoff of Luanxian hydrological station from1972to2000.