The Evolution Mechanism And Attribution Analysis Of River Basin Water Resources Based On SWAT Model

With the rapid development of climate changes and socio-economic development,water resources in river basins have also gradually changed.At the same time,people's demand for water resources is also changing,so the contradiction between supply and demand increased accordingly.The analysis of evolution mechanism of basin water resources,the quantitative analysis of climate,underlying surface and water withdrawal and other factors on the water resources of the basin have become the hotspots of hydrological and water resources research in the current river basin.Under such circumstances,analyzing the basin's water resources evolution mechanism and attribution analysis has important implications for alleviating the contradiction between supply and demand,establishing a reasonable water resources management system,and promoting the sustainable development of water resources.This paper takes the upstream of the Daqing River as the research area,based on the basin Water Cycle theory and the SWAT model,analyzes the basin water resources evolution mechanism,quantitatively analyzes the climate factors,underlying surface conditions and the degree of influence of artificial water withdrawal on runoff changes,it used the formula based on Budyko Hypothesis of Fu Baopu-Coupled Water Energy Balance model to verify the results,and based on the sensitivity analysis to predict the evolution of future water resources.The main results of this study are as follows:(1)Analysis of on the variation tendencies of hydrological and meteorological elements in river basins.The Mann-Kendall non-parametric trend test,mutation test and wavelet analysis were used to analyze the trends,abrupt changes and periodicity of the hydrological and meteorological elements in the basin.The results showed that the runoff in the upstream of the Daqing River showed a significant decrease from 1981 to 2015;There is no obvious trend on the time scale,but the average annual precipitation varies greatly before and after 1998;both temperature and potential evapotranspiration show a significant upward trend.The mutation analysis showed that 1999 was the beginning year of the mutation,and though as the accordance to which the study period was divided into the reference period from 1981 to 1998 and the change period from 1999 to 2015.In order to exclude the effects of abundance,the sub-reference period was set from 1985 to 1998 based on the wavelet analysis results,and its sub-variation period was from 2000 to 2013.(2)Analysis of the characteristics of underlying surface changes.From 1980 to 2015,it's 3.54%for changing area out of the total area.By analyzing of the transfer matrix,it shows that the main type of land-use conversion changing from low-coverage grassland to high-coverage grassland,which occurs mainly in the eastern part of the studied area.In addition,there has been a decrease in woodland,an increase in urban and residential land use,a decrease in reservoir pits and beaches,and a decrease in paddy fields and drylands.(3)Analysis of artificial water withdrawal on runoff changes.Artificial water consumption has been decreasing year by year,water used in agriculture and industry has decreased,and environmental water usage has increased.Agricultural water accounted for the largest proportion and peaked in 2011.(4)Construct the SWAT model in the upstream of the Daqinghe River and the Coupled Water Energy Balance based on Fu's formula,and simulate the monthly runoff process and the annual runoff process in the upstream of the Daqing River.The SWAT model has a better simulation effect.Based on the two models,the Hydrological Model Simulation Method and the Conceptual Model Method were used to attribute the evolution of water resources in the upstream of the Daqing River.The hydrological modelling method was used to obtain climate change,land use,and artificial water consumption for runoff changes during the sub-reference period and the sub-variation period.The contribution rates were 40.33%,30.60%,29.07%(Zijingguan Station)and 39.24%,42.56%,18.20%(Daomaguan Station);and the conceptual model method obtained precipitation,evaporation,land use and artificial water withdrawal.The contribution rates to runoff were 29.79%,13.49%,26.24%,30.48%(Zijingguan Station)and 29.84%,16.82%,27.38%,25.96%(Daomaguan Station),respectively.Both methods show that climate change is the dominant factor that caused the reduction of runoff in the upstream of Daqing River from 1981 to 2015.(5)Future water resources forecast.In 2016-2030,the future runoff calculation based on the SWAT model will increase by 3.46 mm(Zijingguan Station)and 2.09 mm(Daomaguan Station),which imainly dues to climate change;while the results of future runoff changes calculation based by the Coupled Water Energy Balance are in two type.The site performance was inconsistent.Zijingguan station showed an increase in runoff(2.00 mm),mainly due to the increase in precipitation,while the inverted horse station showed a decrease in runoff(-6.71 mm),mainly due to land use changes.