Hydrochemical Evolution Process Simulation Of Unconfined Aquifer In Jinghuiqu Irrigation District Of Shaanxi Province

Jinghui Irrigation District is a large surface-groundwater Irrigation District, located in the middle of the Guanzhong Plain of Shanxi province, bring surface water from Jing River. It is also an important Production Base of grain,vegetables,eggs and milk in Shanxi province. According to the result of phreatic water survey in irrigation area in 1990,2008 and 2009, it is indicated that groundwater was polluted on a large scale, contaminant exceed standard on a large scale, groundwater quality continuous deterioration and have a large threaten to the agricultural development and human health in Irrigation District. This article studies the process of phreatic hydrochemistry evolution and gets the dynamic situation of groundwater pollution by hydrogeochemical simulation in Irrigation District. It can offer scientific basis for controlling groundwater pollution and promoting all-round development of irrigation district.In this paper, we studied chemical types of the groundwater according to common ions distribution in the irrigation district using the Aquachem4.0 software. All the research based on relevant literatures, hydro-geological data of the irrigation district, groundwater recharge, runoff and discharge conditions. The main processes of chemical characteristics of groundwater are leaching, cation exchange, mixing and evaporation-concentrating. In order to reveal the chemical evolution of groundwater irrigation mechanism, using inverse hydrogeochemical simulation Preeqc software in 3 typical flow paths of groundwater to simulate the chemical evolution mechanism of groundwater in the irrigation district and analyzed the results based on the water-rock interaction theory and hydrogeochemical modeling theory.Based on this study, Get following conclusions:1. The TDS value of groundwater in irrigation has significant correlation with Na++K+ and SO42- concentration, the correlation coefficients are 0.94 and 0.97, the concentrations of Na++K+,Ca2+,Mg2+,Cl-,SO42- and HCO3- present general trend from high to low along the groundwater flow direction.2. By analyzing and calculating the chemical type of groundwater of irrigation with Aquachem 4.0, it indicated that the main types of groundwater were Na-Mg-SO4-HCO3 and Na-Mg-SO4-HCO3-Cl. 3. The main hydrochemistry formation processes of the Jinghui Irrigation District groundwater are leaching, cations exchange, mixing and evaporation-concentrating. Leaching is the main effect in the process of groundwater chemical composition formation.4.The results of groundwater flow simulation indicate that:in pathâ… , calcite and mirabilite dissolve, dolomite,gypsum,halite precipitate, and Na-Ca exchange, hydrochemistry type transforms from Na-Mg-SO4-Cl to Na-Mg-SO4-HCO3-Cl. In pathâ…¡, calcite and mirabilite dissolve, dolomite,gypsum,halite precipitate, and Na-Ca exchange, hydrochemistry type transforms from Na to Mg. In pathâ…¢, mirabilite dissolve, calcite,dolomite,gypsum,halite precipitate, and Na-Ca exchange, hydrochemistry type transforms from Mg-Na-HCO3-Cl to Na-Mg-SO4-HCO3.