Impact Of Land Use And Land Cover Change On Groundwater Recharge In The Hongjiannao Basin

The earth's surface is an important interface connecting underground and atmospheric processes,and it is strongly influenced by human transformation.On the global scale,the earth's surface is experiencing the most drastic and complex environmental changes in history,and human activities are increasingly involved in the process of the earth system,especially in the hydrological process.The most typical form of the earth surface change is land use and land cover change(LUCC).Correct understanding of the impact of LUCC on underground hydrological process is of great significance to regional groundwater resource evaluation,rational land use and research on impact of human activities on hydrological cycle.Hongjiannao basin is located in semi-arid area,and groundwater resources play an important supporting role in the process of economic and social development.Taking Hongjiannao basin as an example,this paper studies the impact of LUCC on groundwater recharge by combining in-situ monitoring with numerical simulation,point intensive research with regional research,centralized parameter model with distributed parameter model,field investigation and indoor analysis.The following research results were obtained:(1)The land use and land cover characteristics of the study area in different years were analyzed by the method of variation amplitude.From 2005 to 2017,the most severe change of land use type in the study area is impervious,reflecting the significant impact of urban construction in recent years;the area of cultivated land and grassland has increased significantly during this period,the wetland has been seriously degraded,and the water area has continued to decrease;Driving force analysis shows that public policy,economic development,temperature and precipitation are the main driving forces.(2)The influence of LUCC on groundwater recharge was discussed based on the in-situ monitoring data and numerical model.The water transport model of the one-dimensional profile under bare soil conditions was established based on Hydrus-1D software.The hydraulic parameters of the profile were obtained after model calibration and validation.The groundwater recharge was calculated based on this model.Results show that the groundwater recharge will be reduced by 15% after bare land?grass transformation.(3)The every unit of WetSpass(WM)and Groundwater model(GM)are unified and the spatial distribution of water flow parameters in the area were obtained by using the WetSpassgroundwater flow model coupling method.The results of this coupled model show that the groundwater recharge of grassland,bare land and cultivated land accounted for 61.61%,19.77%,and 14.21% of the total groundwater recharge in 2005,and the average recharge intensity of groundwater was 112 mm and the average recharge coefficient of infiltration was 0.60 in 2005.The groundwater recharge of grassland and cultivated land accounts for 75.46% and 20.27% of the total groundwater recharge in 2018,the average recharge intensity of groundwater is 134 mm,and the average recharge coefficient of infiltration was 0.461 in 2018.(4)The effects of groundwater recharge by LUCC under three land use scenarios are predicted using the coupled model of the WM-GM.Based on the land use and land cover in 2018,the WM-GM is used for recharge prediction of bare land?grassland(scenario I),bare land?forest land(scenario II),and the impervious surface linear growth(Scenario III)in 2028.The prediction results show that the increase of surface coverage in the study area will lead to a decrease in groundwater table and a decrease in groundwater recharge.The groundwater recharge under the three land use scenarios will be reduced by 1.30%,1.36% and 10.30% and groundwater table in specified area will be reduced by 3m,1m and 10 m,respectively,compared with 2018.These change will have a significant impact on the ecological environment of the Hongjiannao Basin.These researches above can provide demonstration and scientific basis for groundwater resource evaluation,rational development and utilization of land resources,ecological engineering and nature reserve construction in semi-arid basins such as Hongjiannao.