Numerical Simulations Of Groundwater Flow And Resource Recovery In Baotou City

The groundwater exploitation intensity of Baotou City keeps increasing in order to meet the needs of industry,agriculture and domestic water since the 1950s,resulting in continuous expansion of cone of groundwater depression and over-exploitation of groundwater resources.At the same time,Baotou is suffering a very serious groundwater pollution,which,together with over-exploitation of groundwater,has significantly affected the sustainable development of ecological and socio-economic of Baotou City.Researches and management works to recover the water table and to remediate the contaminated groundwater is of great significance for the sustainable development and ecological civilization construction of Baotou CityThe groundwater resources recovery program is developed based on the collection of a great number of data and the analysis of characteristics of the hydrogeology and the movement of groundwater of Baotou City.A three-dimensional non-steady groundwater flow model in the region is developed based on MODFLOW to simulate the flow and circulation law of groundwater under mining conditions in this area,the model was then identified and validated using the measured data.The feasibility of groundwater resources recovery in Baotou City is firstly analyzed in the aspects of the groundwater’s origin,storage conditions and dynamic characteristics etc.The model of aquifer structure and the conceptual simulation of groundwater flow is established,identified and validated then.The fitting results groundwater level so good that the water level fitting errors of observation wells are all less than 1 meter during the model identification process and less than 2m during the model validation.The calculation of water balance shows a negative balance of both unconfined water and confined water,which reflects the real situation of Baotou’s groundwater.Therefore,the identified and validated model can be used to predict the future trends of groundwater flow field in Baotou City.Six different groundwater restoration programs are then developed considering the actual situation of the city,by which the response of groundwater flow field in the next 35 years is simulated.The results show that the groundwater levels of confined aquifer is experiencing a continuous decline while the cone of depression is experiencing a continuous expansion under the current exploitation conditions,which can be significantly slowed down by the prohibition of industrial or agricultural use of confined groundwater.When the industrial and agricultural use of confined groundwater are prohibited at the same time,the cone of depression will no longer expand and the water level will recover slowly.When the annual artificial recharging of 36 million m~3 is adopted at the same time together with the implementation of the prohibition of the industrial and agricultural use of confined groundwater,the groundwater level shows a significantly faster recovery and the cone of depression area is reduced significantly.The depth of the cone center can reach to 36.57m by 2050,7.00m shallower than the one in 2013.While the area of the cone can reach to 408.5 km~2,141.9 km~2 smaller than the one in 2013.The simulation results show that engineering measures to develop the artificial groundwater recharging must be applied in order to ensure the sustainable use of groundwater resources of Baotou City.