Study On Groundwater Resources And Simulation Of Groundwater Age Distribution In Ordos Cretaceous Basin

Wei Ning Plain is located in arid areas of northwest China,which is drought and rain,with intense evaporation and relatively poor water resources.At the same time,as an important economic development zone in Ningxia and the main grain producing areas,Wei Ning Plain has serious water shortage.With the development of urbanization,water supply contradiction has become increasingly prominent in here.In order to achieve the coordinated development of social economy and resources and environment,understanding the occurrence of groundwater and reasonable evaluation of groundwater resources and recognition of groundwater cycle characteristics in Wei Ning Plain,it is of great practical significance to rational allocation and efficient utilization of water resources in Weining area.Based on the above research significance,this paper clarifies the composition of groundwater resources in Wei Ning Plain by numerical model,analyzes the characteristics of groundwater circulation and age distribution in the area,and provides scientific basis for the development and utilization of groundwater resources in Wei Ning area.Based on the numerical calculation of the amount of groundwater resources in the study area.,havingestablished a three-dimensional model of groundwater steady flow and unsteady flow numerical model by GMS software.,and.fitted and corrected by actually observing the pore water level.The simulated results show that the total groundwater recharge in the area is 3.092×108m3/a,The main source of recharge is field irrigation infiltration,canal leakage and rainfall infiltration recharge,account the total recharge of 82.8%;The total discharge is 3.106×108m3/a,mainly include drainage ditch excretion,evaporation and excretion to the Yellow River-based.The study area showed a weak negative balance.In order to reveal the groundwater circulation system and its characteristics in the study area,two-dimensional numerical simulation of the profile profile was selected.Through the simulation results show that the distribution of local,regional and regional circulation system three levels of groundwater circulation system.The local and intermediate circulation systems are mainly in the section,and the boundary between the different cycles is not obvious.And thelocal and intermediate circulation system of groundwater seepage rate and water cycle strength is greater than the deep regional circulation system.In the section,the seepage velocity reaches the maximum at the boundary between the Yellow River and the hilly and the plain,and the groundwater circulation mainly concentrates the local and intermediate circulation system.Based on the understanding of the characteristics of the section flow system,the 14 C solute transport model was established on the basis of the two-dimensional flow model,and the distribution of groundwater age in the study area was simulated.The simulation results show that in the shallow and middle part of the section,the groundwater age is light,and the age of 14 C is several hundred to 2000 years,which is modern water.Andin the deep section of the section,14 C as the age of about 15,000 years,localized more than 30000 years of the region,the performance of ancient groundwater.