Study On Recharge And Evolution Of Groundwater In Ulan Buh Desert

The recharge and evolution of groundwater in Ulan Buh Desert is studied on the basis of hydrogeological and geological data and water chemical tracer technique, hydrogeochemical modeling and multivariate statistical methods. We have got several conclusions as follows:First, There are several major recharge sources consisting precipitation, shallow water in Bayan Ul Mountain, Helan Mountain, Yellow River water and irrigation field water for the shallow water in Ulan Buh Desert on the basis of hydrogeological data. In the southwest of the desert, the shallow water serves as one source for the Jilantai Salt lake. When it comes to the deep groundwater, Yellow River water, the Jilantai Salt lake deep groundwater, Bedrock fissure water of Bayan Ul Mountain and deep buried phreatic water on the north piedmont of Helan Mountains are the main recharge sources for the deep groundwater in the desert. And the deep groundwater in the desert recharges the shallow groundwater within the scope of the artesian area.Second, along the flow path(Yellow River to Ulan Buh Desert), the water types of water changes from HCO3-�'HCO3--Cl- to Cl--HCO3- and eventually into a Cl- type water. However from Bayan Ul Mountain to the desert, the water type evolves from HCO3--Cl- to Cl--SO42-,and finally into a Cl- type. Similarly from Helan Mountain to the desert, the water type evolves from HCO3- to HCO3--Cl- and then into Cl--HCO3--SO42-, and in the end into a Cl- type water. However the water type of the deep groundwater of the Jilantai salt lake and the desert are of the same type (HCO3--Cl-、HCO3--Cl--SO42-). When the Yellow River water recharges the deep groundwater in the Ulan Buh desert the water type evloves from HCO3- into HCO3--Cl- type. The water types of the deep and shallow groundwater in the desert are of the same type(HCO3--Cl-). The calcite deposits and the CO2(g) separates out from the water and the dissolution of the dolomite、gypsum and halite occurs when the shallow groundwater flows. All the probable minerals dissolute when the deep groundwater flows. Compared with the reactions of the flowing shallow groundwater, similar reactions happen when the deep groundwater supplies the shallow groundwater in the desert.Finally, HCO3- in the water is mainly controlled by carbonate dissolution. Cl-mainly comes from the the dissolution of halite, and in local area, it is also under the influence of human activities. The major source for SO42- is sulfate(such as gypsum, glauber’s salt). The possible source for the NO3- is nitrogenous fertilizer and excrement of animals(for example camels, cattle, sheep). There are various sources including(carbonate, sulfate, silicate) for Ca2+. And there are also some complicated mechanisms(such as common ion effect、cation exchange) controlling the Ca2+ content in the study area. The content of Na+ is also controlled by the dissolution of evaporite consisting halite and glauber’s salt and silicate including albite. It is also under the inpacts of reverse cation exchange and cation exchange. K+ principally comes from the dissolution of potassium chloride and potassic fertilizer. Mg2+ mainly comes from the carbonates comprising dolomite and marlstone.