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Exploring the Hydrochemical Characteristics and Controlling Processes of Groundwater in Agricultural Lower Reaches of a Typical Arid Watershed on Tibetan Plateau

Zhen Zhao, Gongxi Liu, Guangxiong Qin (), Huijuan Chen, Huizhu Chen, Wenxu Hu, Shaokang Yang, Jie Wang, Yuqing Zhang, Dongyang Zhao, Yu Liu and Yong Xiao ()
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Zhen Zhao: Bureau of Qinghai Environmental Geological Prospecting, Xi’ning 810007, China
Gongxi Liu: Faculty of Geosciences and Engineering, Southwest Jiaotong University, Chengdu 611756, China
Guangxiong Qin: Bureau of Qinghai Environmental Geological Prospecting, Xi’ning 810007, China
Huijuan Chen: Bureau of Qinghai Environmental Geological Prospecting, Xi’ning 810007, China
Huizhu Chen: School of International Studies, Chengdu College of Arts and Sciences, Chengdu 610401, China
Wenxu Hu: Faculty of Geosciences and Engineering, Southwest Jiaotong University, Chengdu 611756, China
Shaokang Yang: Bureau of Qinghai Environmental Geological Prospecting, Xi’ning 810007, China
Jie Wang: Faculty of Geosciences and Engineering, Southwest Jiaotong University, Chengdu 611756, China
Yuqing Zhang: Faculty of Geosciences and Engineering, Southwest Jiaotong University, Chengdu 611756, China
Dongyang Zhao: Bureau of Qinghai Environmental Geological Prospecting, Xi’ning 810007, China
Yu Liu: Xiamen Institute of Environmental Science, Xiamen 361006, China
Yong Xiao: Faculty of Geosciences and Engineering, Southwest Jiaotong University, Chengdu 611756, China

Sustainability, 2025, vol. 17, issue 5, 1-20

Abstract: Groundwater is crucial for domestic, agricultural, and ecological uses, particularly in the lower reaches of arid basins, where its quality often limits availability. A total of 26 phreatic groundwater samples were collected from a typical endorheic watershed on the Tibetan Plateau to assess the hydrochemical characteristics of phreatic groundwater in the lower reaches of arid inland watersheds. The hydrochemical characteristics, quality, and formation mechanisms of groundwater were analyzed using the Entropy-Weight Water Quality Index (EWQI), irrigation water quality indexes (such as sodium adsorption ratio, soluble sodium percentage, and permeability index), hydrochemical diagrams, and correlation analysis. The findings indicate that phreatic groundwater in the lower reaches is slightly alkaline, with a substantial TDS variation from 252.58 to 1810.41 mg/L. Groundwater is predominantly characterized by fresh hydrochemical facies of HCO 3 -Ca and HCO 3 -Na types, with a few saline Cl-Na types present. The concentrations of NO 3 − , NO 2 − and NH 4 + , in groundwater range from 0.32 to 100.00 mg/L, 0.00 to 0.48 mg/L, and 0.00 to 0.20 mg/L, respectively, and 3.59%, 26.92%, and 7.69% of the samples exceeding the permissible drinking limits recommended by Chinese guideline and World Health Organization. Groundwater is classified as fresh at 80.8% of sampling sites and brackish at 19.2%. Approximately 96.2% of the sampled groundwaters is rated as excellent to medium quality according to EWQI assessments, suitable for domestic use, while 3.8% is of extremely poor quality and should be avoided for direct consumption. Groundwater from all sampling sites is suitable for agricultural irrigation and does not pose permeability hazards to the soil. Most groundwaters are suitable for long-term irrigation in terms of sodium hazards, with only 3.8% and 7.7% of samples falling into the “Permissible to Doubtful” and “Doubtful to Unsuitable” categories, respectively. Salinity poses the primary threat in long-term irrigation, with 38.5%, 53.8%, and 7.7% of sampled groundwaters exhibiting moderate, high, and very high salinity risks, respectively. Groundwater chemistry is primarily governed by water-rock interaction and evaporation, with additional impacts from agricultural inputs of nitrogen contaminants and chemicals. Agricultural practices contribute to elevated groundwater salinity in the study area, while natural evaporation drives salinity accumulation in the lower parts. In managing and utilizing groundwater resources in the study area and similar arid regions globally, attention should be paid to salinity caused by agricultural activities and natural evaporation, as well as nitrogen pollution from farming.

Keywords: hydrochemistry; groundwater salinity; nitrite contamination; agricultural pollution; arid basin (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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