Spatial And Temporal Evolution Of Groundwater Quality In The Plain Area Of Jungar Basin

Junggar Basin is a complete closure arid inland basin, which is temperate continentalarid, semi-arid climate zone in the northern hemisphere. Groundwater resources are animportant part of the domestic, production, ecological water of the Junggar Basin. Due tolarge-scale human activities in modern times, the tendency of groundwater qualitydeterioration is becoming increasingly obvious. To solve environmental issues such asgroundwater quality deterioration and to use groundwater rationally became the key to ourwork. It is important to study groundwater evolution characteristics, hydrogeochemicalprocesses and groundwater quality in the plain area of Junggar Basin. At the same time, it canbe a demonstration and reference to other inland basins in arid areas and urban rationalexploitation of groundwater resources to ensure sustainable economic development.This paper comprehensively utilizes hydrochemistry, isotope data， inverse hydro-geochemical modeling, groundwater quality and pollution evaluation and unconfined watervulnerability assessment，combining the hydrogeological conditions and groundwater spatialand temporal evolution information of the plain area of Jungar Basin to study the chemicalcharacteristics，the hydro-geochemical processes, the spatial and temporal evolution ofgroundwater and the groundwater vulnerability of the6prefectures (cities) including UrumqiCity, Kelamayi City, Changji Hui Autonomous Prefecture (referred to as Changji), AltayPrefecture, Bortala Mongol Autonomous Prefecture(referred to as Bortala) and TachengPrefecture as well as Shihezi City-municipalities of Xinjiang Uygur Autonomous Region-which located in the plain area of Junggar Basin. The main results and innovation of thispaper listed as below:(1) This paper reveals the chemical characteristics of groundwater in plain area ofJunggar Basin from the basin, river basin, typical city–Shihezi–and a typical profile–Manas River Basin–level. pH value of unconfined and confined water is7.1~8.9and6.6~9.0. Mostof the groundwater is alkaline water. TDS of unconfined water is0.11~6.79g/L, which is highin Northeast and Southwest while low in Northwest and Southeast of study area. TDS ofconfined water is0.13~1.27g/L, which is high in the center while low in East and West ofstudy area. Hydrochemical type of unconfined water is SO4·HCO3-Na·Mg, which ofconfined water is HCO3·SO4-Na·Ca.(2) Distribution law of groundwater quality of study area in the horizontaland verticalwas comprehensively analysed. Emin and the middle Tianshan Mountains river basin is thebest. Groundwater quality of East Tianshan Mountains and Aibi Lake River basin are betterthan Irtysh River basin, Jimunai various river basins and Wulungu lake basin. The averageion content of unconfined water is increasing from south to north, while which in confinedwater is increasing from west to east. Content of hydro-chemical components in confinedwater is lower than unconfined water.(3) Inverse hydrogeochemical modeling was carried out on a typical profile in JunggarBasin to simulation the hydrolysis process occurring in groundwater systems which decidedthe chemical characteristics of the plain area of Jungar Basin including hydrolysis process,evaporation, ion exchange and oxidation-reduction process. Ion exchanging graduallyincreased from south to north.(4) Variation of groundwater quality in different periods (in2011and2003in basin, from2001to2013in the typical district, January,April,July and October1992in the typical district)and at different levels (basin, typical district) in study area are analysed. Relative to2003, thegroundwater quality of Irtysh basin and Ebinur basin was significantly worse in study area in2011, while which of Wulungu Lake Basin and North Tianshan Mountains middle river basinwas getting better. Type Ⅳ and Ⅴ groundwater percentage in Altay region and KaramayCity both above average percentage(45.3%) in the study area. Type Ⅲ groundwater isdominant in Bortala, Changji and Tacheng. Type Ⅱgroundwater is dominant in Urumqi andShihezi City.The average ion content of unconfined water is increasing from south to north. (5) First proposed VDEAL model that suitable for unconfined water vulnerabilityassessment evaluation in basin scale in inland arid areas. Unconfined water vulnerability ofJunggar Basin is evaluated use this model. The results show that: Very high vulnerability zonelocates in small part of Altay, Bortala, Changji, Shihezi and Tacheng. High vulnerability zonelocates in Kuitun and most area of Shihezi. Medium vulnerability areas locate in most area ofAltay, Bortala and Karamay. The rest rigon are low vulnerability zone.