Chemical Characteristics And Factors Affecting Groundwater Chemistry From The Yellow River Irrigation Area In Tumochuan Plain In The Middle And Upper Reaches of The Yellow River Basin

The Yellow River irrigation area in Tumochuan Plain is one of the primary grain production areas in the middle and upper reaches of the Yellow River Basin (YRB). The groundwater in the area is bitter and salty, which significantly influences drinking water safety of residents. To investigate its chemical characteristics and material sources, we collected 12 groundwater samplings, 3 irrigation water samplings, and 1 precipitation sample during the winter irrigation period (WIP) in November 2016 and the spring irrigation period (SIP) in April 2017, respectively. We then analysed the hydrogen and oxygen stable isotopes and hydrochemical characteristics of the shallow groundwater in the study area and investigated their affecting factors by using environmental isotopes, Gibbs diagrams, Schoeller diagrams, and ion proportionality coefficient analysis. Next, we qualitatively analysed the material sources. The results show the followings: (1) The concentrations of major ions in groundwater in the SIP are generally higher than in the WIP, which may be recharged by snow melting water in the spring. (2) The average values of δD and δ18O for the groundwater are -78.0‰ and -10.3‰, respectively, in the WIP and -77.4‰ and -10.3‰, respectively, in the SIP. However, the characteristics of hydrogen and oxygen isotopes in the groundwater are almost identical in the WIP and SIP. (3) The formation of groundwater chemical constituent are controlled by evaporation concentration and lixiviation, and dissolution of evaporite and mirabilite is the most important factor. Synchronously, the formation of groundwater chemical constituent is also influenced ion exchange and human activities. The study provides effective guidance for groundwater resource development in arid and semi-arid regions.