by the local government, has relocated more than 1 million people from the contiguous poverty-stricken areas of the Liupanshan Mountains to the areas along the Yellow River. The Ningxia ecological migration project is a process of population spatial reconstruction under the response of ecological pressure in the ecologically fragile area and the extremely poor area of Liupanshan Mountains.

Owing to the relatively high prevalence of endemic fluorosis in China, the fluorine distribution, origin, and other factors responsible for the disease have frequently been investigated. Liu and colleagues demonstrated in 1980 that endemic fluorosis was mainly concentrated in 3 regions within China: an east-to-west belt in the northern deserts, a region along the northern coast, and a region in the south, with a number of localized smaller areas elsewhere. Groundwaterrainfall and water supply is limited. In the south-central area, the annual rainfall is about 300 mm, mostly occurring during the wet season from July to October, whereas annual evaporation exceeds 2300 mm. Local populations often use untreated spring and well water as sources for drinking water despite its poor quality. The Qingshui River system is the only first tributary of the Yellow River in central and southern Ningxia. Qingshui River basin is the main area where the Qingshui River and the shallow groundwater in the basin resupply and transform each other.Fig. 1Map of location and fluorine concentrations

The local geography surrounding the river basin is characterized by mountains with thick strata deposited during the Jurassic, Cretaceous, and Tertiary Periods. These strata are rich in water-soluble salts such as gypsum (CaSO~4~)