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Research Article
Ruixue Jiang
Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences
Corresponding Author
ORCiD: https://orcid.org/0000-0003-3469-1842
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Reclaimed water (RW) has been widely used as an alternative water resource to recharge rivers in mega-city Beijing. At the same time, the RW also recharges the ambient aquifers through riverbank filtration, and modifies the subsurface hydrodynamic system and hydrochemical characteristics. To assess the impact of RW recharge on the unconfined groundwater system, we conducted a 3D groundwater flow and solute transport model based on 10 years of sequenced groundwater monitoring data to analyze the changes of the groundwater table, Cl- loads, and NO3-N loads in the shallow aquifer after RW recharge to the river channel. The results show that the groundwater table around the river channel elevated by about 3~4 m quickly after RW recharge from Dec. 2007 to Dec. 2009, and then remained stable due to the continuous RW infiltration. However, the unconfined groundwater storage still declined overall from 2007 to 2014 due to groundwater exploitation. The storage began to recover after groundwater extraction reduction, rising from 3.76×108 m3 at the end of 2014 to 3.85×108 m3 at the end of 2017. Cl- concentrations varied from 5~75 mg/L before RW recharge to 50~130 mg/L in two years (2007–2009), and then remained stable. The zones of the unconfined groundwater quality-affected by RW infiltration increased from 11.7 km2 in 2008 to 26.7 km2 in 2017. Cl- loads of the unconfined groundwater increased from 1.66×104 t in 2008 to 3.8×103 t in 2017, while NO3-N loads decreased from 29.8 t in 2008 to 11.9 t in 2017 annually in the zones. We determined the maximum area of the unconfined groundwater quality affected by RW, and groundwater outside this area not affected by RW recharge keeps its original state. The RW recharge to the river channel in the study area is beneficial to increase the groundwater table and unconfined groundwater storage with lesser environmental impacts.
Keywords
Reclaimed water, Unconfined aquifer, Groundwater table, Groundwater storage, Nitrate loads, Numerical model
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This preprint is under consideration at Environmental Science and Pollution Research. A preprint is a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Learn more about In Review
Research Article
Ruixue Jiang
Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences
Corresponding Author
ORCiD: https://orcid.org/0000-0003-3469-1842
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
Peer Review Timeline
CURRENT STATUS: Under Review
Version 1
Posted 03 Nov, 2021
No community comments so far
First submitted
On 02 Oct, 2021
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
Subject Areas
Environmental Chemistry
License:
This work is licensed under a CC BY 4.0 License. Read Full License
Reclaimed water (RW) has been widely used as an alternative water resource to recharge rivers in mega-city Beijing. At the same time, the RW also recharges the ambient aquifers through riverbank filtration, and modifies the subsurface hydrodynamic system and hydrochemical characteristics. To assess the impact of RW recharge on the unconfined groundwater system, we conducted a 3D groundwater flow and solute transport model based on 10 years of sequenced groundwater monitoring data to analyze the changes of the groundwater table, Cl- loads, and NO3-N loads in the shallow aquifer after RW recharge to the river channel. The results show that the groundwater table around the river channel elevated by about 3~4 m quickly after RW recharge from Dec. 2007 to Dec. 2009, and then remained stable due to the continuous RW infiltration. However, the unconfined groundwater storage still declined overall from 2007 to 2014 due to groundwater exploitation. The storage began to recover after groundwater extraction reduction, rising from 3.76×108 m3 at the end of 2014 to 3.85×108 m3 at the end of 2017. Cl- concentrations varied from 5~75 mg/L before RW recharge to 50~130 mg/L in two years (2007–2009), and then remained stable. The zones of the unconfined groundwater quality-affected by RW infiltration increased from 11.7 km2 in 2008 to 26.7 km2 in 2017. Cl- loads of the unconfined groundwater increased from 1.66×104 t in 2008 to 3.8×103 t in 2017, while NO3-N loads decreased from 29.8 t in 2008 to 11.9 t in 2017 annually in the zones. We determined the maximum area of the unconfined groundwater quality affected by RW, and groundwater outside this area not affected by RW recharge keeps its original state. The RW recharge to the river channel in the study area is beneficial to increase the groundwater table and unconfined groundwater storage with lesser environmental impacts.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
This is a list of supplementary files associated with this preprint. Click to download.
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