| Hailun City which is Located in the northeast of the Songnen Plain,is an important commodity grain base in China,as well as an old revolutionary base area of Class II and a state-level poverty-stricken county.Since the reform and opening up,with the population growth and economic development,groundwater resources have been developed with high intensity,and the ecological and geological environment has been destroyed.Problems such as water and soil pollution and black soil loss are showing an increasing trend,which have become a serious constraint on economic and social development.Although the surface water in Hailun City is very rich,the heavy use of pesticides and fertilizers,the improper disposal of livestock breeding waste and human domestic waste in recent years have led to a decline in surface water quality,which has affected food security and water supply security.Therefore,this study carried out research work on water resources in the upper reaches of the Tongken River,the purpose of which was to find out the quantity and quality of water resources in the basin,the quality of water environment,and environmental geological problems related to water ecology,and to propose an optimized allocation plan for water resources development and utilization.The research work also provides a scientific basis for the restoration and treatment of the ecological environment and the solution of drinking water problems.This study takes the upper reaches of the Tongken River Basin,a typical agricultural area in the arid-semi-arid region of Hailun City,as the research object.Based on the analysis of the characteristics of the spatial and temporal changes of various hydrological elements in the watershed,the impact of climate change and human activities on water resources in the watershed was studied.Establish a coupling model of surface water and groundwater in the Tongken River Basin,analyze the interaction process of surface water and groundwater,calculate the ecological environment water demand of the watershed,and construct a new model of rational allocation of water resources based on water quality,water quantity,and ecological water demand,so as to provide a watershed Provide technical support for efficient development,utilization and protection of water resources.The main results obtained in this study are as follows:?1?Combined with GIS technology,the SWAT model is used to simulate the surface runoff process in Hailun City.Based on the collection of hydrometeorological,land use,and soil type data in the study area,a soil attribute database was established.Based on the digital elevation model,ArcSWAT software was used to complete the steps of river network generation,sub-watershed division,watershed boundary determination,and hydrological response unit generation.Finally,a surface runoff model in the study area was constructed.The model was calibrated using runoff observation data from 2008 to 2009,and the model was verified using runoff observation data from 2010 to 2016.The correlation coefficient during the verification period is 0.895 and the Nash coefficient is 0.87,indicating that the model can truly reflect the actual trend of runoff in the study area.?2?According to the surface water movement characteristics and groundwater recharge,runoff,and discharge conditions,a coupling model of SWAT-Visual MODFLOW was constructed.Through the analysis of hydrogeological data in the study area,the groundwater recharge,runoff and discharge conditions in Hailun City were ascertained,and the groundwater numerical model in the study area was constructed using Visual MODFLOWF Flex6.1 software.After adjusting the model using the water level data of 11 groundwater monitoring wells,the correlation coefficient can reach 0.99,and the residual water level can be controlled at 0.84m.The results show that the model can truly reflect the groundwater movement in the study area.Using ArcGIS software,the data fusion of minimum calculation unit?HRU and Cell?between SWAT model and Visual MODFLOW model is realized.?3?Taking into account the impact of climate change,the SWAT model was used to predict the surface runoff in 2030 in the upper Tongken River Basin.The Hurst index calculated by the R/S method shows that rainfall has a reverse trend in the time series.Wavelet analysis shows that the annual precipitation changes periodically in the period of 4-5a,10-15a,17-23a,and 25-35a.Among them,the periodic trend of 4-5a is more obvious,which runs through the entire observation period.The calculation results show that the average runoff from 2010 to 2030 in the Tongken River Basin is 3.1513×108m3/a.The average runoff from 2017 to 2030 was 3.2215×108m3/a.The average runoff from 2025 to 2030 is 3.0552×108m3/a.Due to the impact of climate change,especially rainfall,the surface runoff has decreased significantly.Analysis of surface water quality shows that the surface water quality in Hailun City ranges from Class II to Class V,with good water quality during flood season and poor water quality during low-flow period.?4?Considering the impact of climate change and human activities,the coupled model is used to predict the groundwater quantity and quality in the upper Tongken River in 2025 and 2030.The total inflow of groundwater resources in the Tongken River Basin in 2025 is 38430.85×104m3,of which,the storage of groundwater is9368.82×104m3,the amount of leakage recharge of the river is 2252.30×104m3,and the amount of recharge of rainfall is 26811.07×104m3;The groundwater extraction volume is 13028.31×104m3?agricultural irrigation 10960.95×104m3,centralized water supply well extraction is 2067.36×104m3?,the groundwater discharge volume is6942.30×104m3,and the evaporation volume is 18462.06×104m3.The total inflow of groundwater resources in the Tongken River Basin in 2030 is 37609.60×104m3,of which,the storage of groundwater is 8272.36×104m3,the amount of leakage recharge of the river is 2281.61×104m3,and the amount of recharge of rainfall is 27055.99×104m3.The groundwater extraction is 12992.90×104m3?agricultural irrigation10990.98×104m3;centralized water supply well extraction 2001.92×104m3?,the groundwater discharge is 6648.53.30×104m3,and the evaporation is 18149.26×104m3.Compared with 2025,the amount of groundwater resources has not changed much,mainly due to the small changes in meteorological conditions and human exploitation.According to the characteristics of the agricultural area,four typical ions,such as nitrate?NO3-?,nitrite?NO2-?,ammonium?NH4+?,and chloride?Cl-?,which are greatly affected by human activities,were selected for solute transport simulation.According to the solute transport simulation results,by the end of 2025,According to the results of the solute migration simulation,by the end of 2025,the area of the four ions with high concentration has been expanded.In the profile view,the vertical migration is obvious,and it runs through the entire confined aquifer.The leakage of farmland fertilization water and the discharge of domestic sewage are the main reasons for the changes in groundwater quality.?5?Based on the analysis of the influencing factors of ecological environmental water demand in Hailun City,a mathematical model of ecological environmental water demand is established.According to the established mathematical model,the eco-environmental water demand of Hailun City in the upstream area of the Tongken River Basin was analyzed and calculated,and the value of the terrestrial eco-environmental water demand of Hailun City was 0.3431×108m3;The value of river ecological water demand in Hailun City is 1.8881×108m3;The value of the ecological environment water demand of wetland and reservoir in Hailun City is 0.1211×108m3;The value of the ecological environment water demand in Hailun City is 2.3523×108m3.The mathematical model is simple and practical,and can meet the quantitative analysis and research of ecological environment water demand of Tongken River Basin.?6?Taking the sustainable use of water resources as the goal,and using grey forecasting and multi-objective planning models,the reasonable allocation of water resources in Hailun City has been studied.The model is based on the current cultivated land area,population size development trend,agricultural modernization development,and ecological environment in Helen City,while taking into account economic benefits,social benefits,efficiency rationality,water resources development and utilization efficiency,and ecological environmental benefits.Based on the SWAT-Visual Modflow Flex model and the grey model,the prediction results of water resources in the river basin are shown.The results show that the water resources allocation plan is the best in2025,followed by the plan in 2020. |
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