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Jinan, China, is famous for its springs. However, societal and economic development over the past decades has detrimentally altered the natural water cycle in the spring area. Managed aquifer recharge (MAR) is an effective measure to ensure the normal gushing of springs. Balancing water resource utilisation, ecological effects, and water quality risks is not always easy to implement. This study focused on the potential effects of MAR projects that divert water from multiple local surface water sites, e.g., the Yellow River and South-to-North Water Diversion (SNWD) Project. A numerical simulation model for the entire spring area was built using MODFLOW and MT3DMS. The SNWD Project diverts water with relatively high total dissolved solids (TDS) to the Yufu River, which consequently recharges groundwater and poses a potential risk to the downstream karst water in the Jinan Spring area. Different simulation scenarios were set, and the results showed that the 90% recovery ratio scheme yields the highest TDS reduction efficiency as well as the largest karst water extraction volume. In addition, the water table remains stable as a whole. The benefits of the designed scheme are multifold, including improving water quality up to Standard III groundwater quality and meeting the water needs of the economy. The study provides a novel method of addressing the groundwater quality risks posed by artificial recharge. [ABSTRACT FROM AUTHOR]

The use of stormwater for managed aquifer recharge (MAR) has become one of the most important ways to deal with water shortages and the corresponding environmental geological problems, especially in the north of China. The Fe (III) clogging of porous media is a common and significant problem that influences the effect of the infiltration rate. This paper focuses on the migration characteristics and clogging mechanisms of iron hydroxides in sand columns. The results indicate that the permeability of porous media significantly decreased at the inlet of the fine sand column and inside the coarse sand column. We demonstrated that, when the Fe (III) concentration was higher, a smaller infiltration medium size was produced more rapidly, and there was more significant clogging. More than 80% of the injected Fe (III) remained in the sand column, and more than 50% was retained within 1 cm of the column inlet. The mass retention increased with the decrease in the size of the infiltration medium particles and with the increase in the injected Fe (III) concentration. The main material that caused Fe (III) clogging was iron hydroxide colloids, which were in the form of a granular or flocculent membrane coating the quartz sand. The mechanisms of clogging and retention were blocking filtration and deep bed filtration, adsorption, and deposition, which were strongly affected by the coagulation of Fe (III) colloidal particles. [ABSTRACT FROM AUTHOR]

• Groundwater in Beijing Plain has been severely depleted. • A pilot MAR indicates great potential to restore depleted storage. • A large-scale MAR is designed and simulated with multi-scale models. • Sustainable groundwater development can be achieved with the MAR operation. Intensive groundwater exploitation has depleted groundwater storage and led to a series of geo-environmental problems in Beijing Plain, China. Managed Aquifer Recharge (MAR) has been endorsed to mitigate the groundwater storage depletion and achieve groundwater sustainability. A pilot MAR has been tested in the Chaobai River catchment since 2015. An innovative large-scale MAR consisting of 9 cascade terraced infiltration ponds was proposed and its effectiveness was assessed in this study using an integrated modelling approach. The integrated model coupled the regional and local transient flow and transport processes. The transient regional flow model simulated historical groundwater level declines and storage depletion in the Beijing Plain from 1995 to 2018. The coupled regional and local flow model was used to simulate the pilot MAR test in the Chaobai River from 2015 to 2018. A significant groundwater level increase was observed nearby the pilot MAR since 2015. The transport model results indicate that approximately 40% of the infiltrated water was captured by pumping wells in the No.8 well field. The models were further used to assess the long-term effects of the large-scale MAR from 2020 to 2050. The simulation results show that the groundwater system will reach a new equilibrium state under the implementation of the large-scale MAR scheme. Almost 91% of the abstracted water in the No. 8 well field will come from the MAR infiltration. The proposed large-scale MAR is very effective in restoring the depleted aquifer storage and maintaining the groundwater abstraction in the No.8 well field. However, with the increase of the groundwater level, the infiltration rate of several ponds will decrease. Therefore, it is important to maintain a dynamic balance between artificial recharge and groundwater abstraction in order to achieve a sustainable long-term MAR operation in the region. [ABSTRACT FROM AUTHOR]

Managed aquifer recharge operations are often conducted in near-bank areas to regulate water resources or reduce seawater intrusion. Yet little is known about the influence of surface water level fluctuations at different temporal scales on MAR performance. A generalized conceptual model was developed based on an investigation site in Western China as a basis to simulate the response surface water level fluctuations on the water table, artificially recharged water lens (formed by the artificially recharged water), groundwater flow paths and average travel times (which is an important control on how quickly contaminants are flushed out of aquifers), and the discharge of the artificially recharged aquifer during the surface water level fluctuation. The results showed a fluctuating groundwater table in the artificially recharged near-bank aquifer under the influence of surface water level fluctuations. The peak values of the increment of the groundwater table induced by artificial recharge decreased with the increase of the period and amplitude of surface water level fluctuation, but the trough values of the increment of water table increases with that. The penetration depth of surface water into the aquifer with a fluctuating surface water level leads to a decreasing increment of the groundwater table which follows a power law. The fluctuating surface water level leads to dynamic changes of artificially recharged water lens morphology and a thinner artificially recharged water lens. A mixing zone of recharged water and ambient water could be found in the artificially recharged near-bank area, which is expected to lead to modifications in the geochemical conditions in the artificially recharged near-bank aquifer. A longer period of surface water level fluctuation leads to a longer average travel time, but the larger penetration depth of surface water and amplitude lead to a shorter average travel time. The peak discharge of the near-bank aquifer was found to decrease with the period of surface water level fluctuation, but it increases with penetration depth and amplitude. This study is important in providing insights into the performance of near-bank managed aquifer recharge with respect to surface water level fluctuation. [ABSTRACT FROM AUTHOR]

Managed aquifer recharge (MAR) is an important approach to address water security, water quality decline, ground subsidence, and aquifer degradation. In this study, the large-scale recharge experiments were conducted in a natural river with multiple water sources. The MAR with multi-source water was investigated by developing an improved matter-element model under a limited recharged quantity and period in Jinan, China. Results showed that the background levels (BL) of groundwater quality before recharge was relatively good. However, the use of different water sources would cause a significant increase in the content of some groundwater quality indexes, which might further induce deterioration of regional groundwater quality. And the water quality in porous and karst aquifer displayed deteriorating trends during different water source recharge. Additionally, the adverse effects of recharge water sources on regional groundwater quality in turn was South-to-North Water Diversion Project (SN) > Yellow River (YR) > Wohushan Reservoir (WR). Meanwhile, the high-risk indexes in groundwater quality were presented during different water source recharge. Accordingly, relevant suggestions and measures were then put forward to optimize the MAR with multi-source water and explore the high-efficiency and low-risk recharge mode.