Study On Water Resources Assessment Based On SWAT Model

Karst water resources are an important basis for living demand and economic development in Lijiang River Basin,Guilin,Guangxi.With the development of economy and society and the aggravation of human activities,the frequent occurrence of hydrogeological environmental geological problems and the uneven spatial distribution of precipitation have seriously affected the water security of local residents.At the same time,it also restricts the further development of economy,making it urgent to solve the problem of water resources development and utilization in this area.Because of the unique hydrogeological structure in the karst area of Lijiang River basin and the construction of many reservoirs in the upper reaches of Guilin Hydrological Station,it is difficult for traditional hydrogeological methods to describe the hydrological cycle in the basin.It is urgent to find effective methods to find out the relationship between surface water and groundwater in the area,and to evaluate the water resources scientifically and reasonably for water resources management,in order to provide scientific basis for water resource evaluation.In this paper,SWAT model that a distributed hydrological model widely used in the world is adopted.Based on the characteristics of runoff generation and concentration in karst area and the special spatial structure of aquifer,the open source SWAT model is improved to make it have the function of recharge and storage of groundwater in surface karst zone.At the same time,the Muskingum method is used to restore the outflow data of the reservoir,and finally a hydrological model consistent with the hydrological process of the basin is established.By collecting meteorological and hydrological data and geospatial data of Lijiang River Basin,a distributed hydrological model is established by using SWAT model.The total area of the study area is 10889.13 km~2,of which the clastic rock area is 5419.4 km~2 and the karst area is 5469.73 km~2,and the two lithologies are cross-distributed.The study area is divided into 138 sub-basins and875 hydrological response units.Monthly and daily runoff simulation were carried out respectively,and the simulation period was January 2008 to December 2016.In this paper,SWAT-CUP is used to identify and validate the model.Through the simulation analysis of daily and monthly measured runoff of hydrological stations in the basin,the model can meet the accuracy of hydrological cycle research in this area.Through the comparison of runoff simulation before and after reservoir inversion,it can be concluded that the simulation of daily runoff after reservoir inversion is closer to the real hydrological process than that before reservoir inversion,and the simulation accuracy is effectively improved.Moreover,the daily runoff simulation evaluation factors R~2 and NS of Guilin Railway Station increased from 0.73 and 0.66 to 0.87 and 0.86.The improved SWAT model of combined with the characteristics of karst basin reflects the regulation and storage characteristics of surface karst zone by comparing the changes of base flow before and after the improvement.There is a lag of about 30 days before the improvement of base flow,and groundwater recharge in each sub-basin increases in varying degrees.According to the results of model operation,distribution characteristics of hydrological parameters such as runoff yield coefficient,runoff depth,runoff modulus and runoff coefficient were obtained.The total water resources in the study area are 117.59×10~8 m~3,of which the groundwater recharge resources are42.73×10~8 m~3.The groundwater runoff modulus is 10.88L/s·km~2 in karst area and5.24L/s·km~2 in clastic rock area during dry season.The groundwater exploitable amount is 3.53×10~8 m~3 calculated by runoff modulus method in extremely dry years.