Sources and hydrogeochemical processes of groundwater under multiple water source recharge condition

Heng Gao; Lihu Yang; Xianfang Song; Minli Guo; Binghua Li; Xu Cui

doi:10.1016/j.scitotenv.2023.166660

Sources and hydrogeochemical processes of groundwater under multiple water source recharge condition

Sci Total Environ. 2023 Dec 10:903:166660. doi: 10.1016/j.scitotenv.2023.166660. Epub 2023 Aug 31.

Authors

Heng Gao¹, Lihu Yang², Xianfang Song³, Minli Guo⁴, Binghua Li⁴, Xu Cui⁵

Affiliations

¹ Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: gaoheng001x@igsnrr.ac.cn.
² Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: yanglihu@igsnrr.ac.cn.
³ Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: songxf@igsnrr.ac.cn.
⁴ Beijing Water Science and Technology Institute, Beijing Engineering Technique Research Center for Exploration and Utilization of Non-Conventional Water Resources and Water Use Efficiency, Beijing 100048, China.
⁵ Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.

PMID: 37657547
DOI: 10.1016/j.scitotenv.2023.166660

Abstract

Ecological water replenishment (EWR) is an essential approach for improving the quantity and quality of regional water. The Chaobai River is a major river in Beijing that is replenished with water from multiple sources, including reclaimed water (RW), the South-North Water Transfer Project (SNTP), reservoir discharge (RD). The effects of multiple water source recharge (MWSR) on groundwater quality remain unclear. In this study, hydrochemical ions, isotopes (δ²H-H₂O, δ¹⁸O-H₂O, δ¹⁵N-NO₃^-, and δ¹⁸O-NO₃^-), mixing stable isotope analysis in R (MixSIAR), and hydrogeochemical modeling were used to quantify the contributions and impacts of different water sources on groundwater and to propose a conceptual model. The results showed that during the period before reservoir discharge, RW and SNTP accounted for 38 %-41 % and 54 % of the groundwater in their corresponding recharge areas, respectively. The groundwater in the RW recharge area contained high levels of Na⁺ and Cl^- leading to the precipitation of halite, and was the main factor for the spatial variation in groundwater hydrochemical components. The surface water changed from Na·K - Cl·SO₄ type to Ca·Mg - HCO₃ type which was similar to groundwater after reservoir discharge. RD accounted for 30 % of the groundwater; however, it did not change the hydrochemical type of groundwater. Dual nitrate stable isotopes and MixSIAR demonstrated that RW was the primary source of NO₃^- in groundwater, contributing up to 76-89 %, and reservoir discharge effectively reduced the contribution of RW. δ¹⁵N-NO₃^- or δ¹⁸O-NO₃^- in relation to NO₃-N suggests that denitrification is the main biogeochemical process of nitrogen in groundwater, whereas water recharge from the SNTP and RD reduces denitrification and dilutes NO₃^-. This study provides insights into the impact of anthropogenically controlled ecological water replenishment from different water sources on groundwater and guides the reasonable allocation of water resources.

Keywords: Groundwater; Hydrogeochemical process; MixSIAR; Multiple water sources recharge; Water and nitrate stable isotopes.