Upscaling groundwater flow is a fundamental challenge in hydrogeology. This study proposed time‐fractional flow equations (t‐FFEs) for upscaling long‐term, transient groundwater flow and propagation of pressure heads in heterogeneous media. Monte Carlo simulations showed that, with increasing variance and correlation of the hydraulic conductivity (K), flow dynamics gradually deviated from Darcian flow and exhibit sub‐diffusive, time‐dependent evolution which can be separated into three major stages. At the early stage, the interconnected high‐K zones dominated flow, while at intermediate times, the transverse flow due to mixed high‐ and low‐K zones caused delayed rise of the piezometric head. At late times when flow in the relatively high‐K domains reached stability, cells with very low‐K continued to block the entry of water and generate “islands” with low piezometric head, significantly extending the temporal evolution of the piezometric head. The elongated water breakthrough curve cannot be quantified by the flow equation with an effective K, the space‐fractional flow equation, or the multi‐rate mass transfer (MRMT) flow model with a few rates, motivating the development of t‐FFEs assuming temporally non‐Darcian flow. Model applications showed that both the early and intermediate stages of flow dynamics can be captured by a single‐index t‐FFE (whose index is the exponent of the power‐law probability density function of the random operational time for water parcels), but the overall evolution of flow dynamics, especially the enhanced retention of flow at later times, required a distributed‐order t‐FFE with variable indexes for different flow phases that can dominate flow dynamics at different stages. Therefore, transient groundwater flow in aquifers with spatially stationary heterogeneity can be temporally non‐Darcian and non‐stationary, due to the time‐sensitive, combined effects of interconnected high‐K channels and isolated low‐K deposits on flow dynamics (which is the hydrogeological mechanism for the temporally non‐Darcian flow and sub‐diffusive pressure propagation), whose long‐term behavior can be quantified by multi‐index stochastic models.

Management aquifer recharge (MAR) technology is widely applied to solve seawater intrusion caused by groundwater overexploitation in coastal areas. However, MAR creates an important pathway for microplastics (particle size< 5 mm) to enter groundwater. To explore the clogging potential of microplastics in aquifer media, a series of laboratory-scale column experiments were conducted in this study. The hydraulic conductivity of porous media and deposition amount of microplastics were investigated under different experimental conditions. In our study, most of the microplastics were intercepted in the sand column’s surface layer. The difference of particle size in porous media greatly influence the clogging development. The hydraulic conductivity of the aquifer media decreased as the microplastic particle size decreased. When the particle size of microplastic was larger than 300 mm, most of the microplastics deposits on the surface of the porous media, forming a “microplastic accumulation layer”. Microplastics are affected by particle size, flow shear stress and preferential flow during migration. The migration ability of microplastics increased significantly with the increase of hydraulic head difference and decreased with the increase of sand column depth. The bacteria microorganisms are projected to be a new biological control strategy in conjunction with MAR. The study of clogging risk of microplastics particles in porous media during artificial recharge provides novel and unique insights for the management and control of microplastic pollution in groundwater systems.

Managed aquifer recharge (MAR) is widely used globally. However, clogging events remain a major obstacle to long-term operations. This study investigated the effects of natural biofilms on the migration and deposition of suspended particles (SPs) at varying concentrations using column experiments and multiple analytical methods. At 74 h, the K′ in the high-concentration group (HT) with biofilm coating decreased by 77.3%, while, in the high-concentration group (HTCK) without biofilm coating, the K′ decreased by 68.5%. Within the same recharge time, the K′ in the medium-concentration group without biofilm coating decreased by 59.9%. The results show that the biofilm covering the porous medium promotes the clogging of suspended particles. Compared with the high-concentration group, the development of porous medium blockage was slower in the low-concentration suspended particle group. SEM and CT analyses revealed that the biofilms altered the surface roughness of the porous media, thereby promoting SP deposition. The study also confirmed that the interactions between SPs and biofilms in recharge water, including electrostatic interactions, hydrophobic interactions, and extracellular polymer flocculation, collectively exacerbated the clogging process in MAR. XDLVO analysis indicated that the biofilm-coated porous media reduced the electrostatic interaction potential energy and energy barrier between SPs and quartz sand, thereby facilitating kaolin deposition in saturated porous media. Correlation and significance analyses identified hydrophobic interactions as the primary mechanism driving SP–biofilm combined with clogging. Moreover, the reduced SP concentrations in the recharge water increased the SP migration distance in porous media, slowing the clogging progression in low-SP groups. These findings offer valuable insights into the prevention and management of MAR clogging caused by the coexistence of biofilms and SPs.

Karst mining regions frequently encounter ecological and geological challenges during extraction, especially the increased water inflow into mine pits, water contamination, and karst collapse due to dewatering activities. These challenges not only threaten the safety of mineral resource extraction but also escalate operational expenses. To address these concerns, this study offers a detailed examination of the geohydrological conditions in a karst mining area. It integrates multiple data sources, such as the dynamics of groundwater, mine dewatering activities, and precipitation patterns, to identify the primary sources of water ingress into the mines. The result reveals that the primary water inflow of the mine pits is directly recharged by atmospheric precipitation through runoff zones. Additionally, the key factors leading to karst collapses are the decrease in groundwater levels due to dewatering and the stability of surrounding rock. Consequently, this paper presents a set of innovative methods for water hazard prevention and control. Utilizing the GMS (Groundwater Modeling System), the groundwater numerical model is built to estimate water consumption in mining operations, and also to validate the efficacy of these methods. The model reveals that application of these techniques can reduce groundwater inflow of the mine by 34.3%. The set of methods not only substantially lowers the risk of water inrush incidents but also avoids the contamination of groundwater. Consequently, it ensures the safety of mine production, especially in the wet season.