Resources Science ›› 2020, Vol. 42 ›› Issue (12): 2419-2433.doi: 10.18402/resci.2020.12.13

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Impacts of reclaimed water recharge to a river channel on ambient water bodies: A case study of the Chaobai River in Beijing

JIANG Ruixue1,2(), HAN Dongmei1,2(), SONG Xianfang1,2, YANG Lihu1, LI Binghua3   

  1. 1. Key Laboratory of Water Cycle & Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
    2. College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
    3. Beijing Water Science and Technology Institute, Beijing 100048, China
  • Received:2019-12-31 Revised:2020-05-26 Online:2020-12-25 Published:2021-02-25
  • Contact: HAN Dongmei E-mail:jiangrx.18s@igsnrr.ac.cn;handm@igsnrr.ac.cn

Abstract:

Reclaimed water is used primarily for replenishing rivers and lakes in Beijing, but the impact of reclaimed water on ambient water environment has also been a concern. This research monitored the water quality of the reclaimed water, surface water, and shallow groundwater in the Chaobai River in Beijing from 2015 to 2017. This study used mathematical statistics and hydrochemical analysis to investigate the characteristics of the ambient water bodies under long-term reclaimed water recharge to the river. The results show that the total nitrogen in surface water exceeded the quality standard at all monitoring points because the reclaimed water had a high nutrient content. The concentration of nitrogen and phosphorus decreased and the pH value increased along the river, which was more significant in the summer. This is related to photosynthesis and denitrification. The surrounding shallow groundwater level showed seasonal variation only. The hydrochemical type of shallow groundwater was mainly HCO3·Cl-Na·Ca type, which was similar to the reclaimed water. But the main ion concentrations in different water bodies were different due to cation exchange and absorption during the infiltration process and mixing. The maximum distance of the reclaimed water impact on shallow groundwater quality was about 425 m away from the center of the river course. Of the 140 water samples, 120 met the class Ⅱ to IV groundwater quality standard, and the groundwater quality tended to get better along the groundwater flow direction. The ammonia nitrogen concentration of 19 water samples exceeded the quality standard. It mainly occurred near the Henan Village dam. Nitrogen might have come from soil nitrogen, irrigation, and fertilization input in the surrounding agricultural and forestry lands. This study provided important references for improving the water quality of the ambient water bodies in the Chaobai River and increasing the utilization of reclaimed water.

Key words: reclaimed water, surface water, groundwater, water quality, water level, Chaobai River