Study on distribution law of TDS and main ion concentration in groundwater in the Ordos Cretaceous Artesian Basin

The distribution law of TDS and main ion concentration in groundwater with three circulating depths of shallow,middle and deep level has been studied in the Ordos Cretaceous Artesian Basin by 1124 hydrochemical samples.On the whole,TDS and main ion concentration in groundwater in the north of the basin are lower than those in the south of the basin.And fresh water is more rich in the north of the basin than that in the south.Fresh water in the north of the basin distributed mainly in shallow and middle level groundwater in both sides of ground watersheds and in Wuding River-Wulanmulun River groundwater regime in east of Anbian-Dongsheng-Sishili beam while in the south of the basin,except that groundwater in Luohandong aquifer is mainly fresh water,groundwater in Huanhe and Luohe aquifers is mainly brackish water and saline water.