Hydrogeology Journal最新文献

Research on the hydrogeology of andesitic volcanic aquifers in subduction areas is reviewed. Andesitic aquifers are of high interest in volcanic arc islands and subduction zones, where they constitute a strategic water resource. This review gathers a compilation of worldwide results and case studies to propose a generic hydrogeological conceptual model (GHCM). It is based on the geological conceptual model splitting the volcanic edifice, from upstream to downstream, into central, proximal, medial and distal zones. In this geological structure, the GHCM identifies where the main aquifer types (fractured lava, pyroclastic flows, and the volcano-sedimentary basins downstream) and the typical aquitards (lahars, fine pyroclastic falls and surges, indurated pyroclastic flow, and weathered rocks) are structured and organized. To integrate the evolution of volcanoes and some specific volcanic activities, a specific GHCM for old andesitic volcanoes or andesitic shield volcanoes is detailed. The paper also describes how the GHCM results are of use to hydrogeologists in terms of scale (from the lithological units to the regional scale), to effectively site water wells, and to sustainably manage groundwater resources in such aquifers. Among these various scales, the volcanic “flank continuum” is presented as the most adapted to support groundwater resources management. Several ways to improve this GHCM are suggested, notably to better consider the geological complexity of these aquifers.

Karst aquifers are complex systems characterized by high heterogeneity and anisotropy. Karst hydrological duality is evident in processes such as recharge, storage, and flow. The MODFLOW Conduit Flow Process (CFP) simulates this flow duality. In this study, CFP version 2 (CFPv2) was applied to the Yucatan karst in Mexico, known for its well-developed karst features, including subsurface conduits. Given the sparse data regarding the three-dimensional location and connectivity of conduits and underwater coastal springs, the theoretical conduit pathways were inferred from geology or geophysics. CFPv2 was utilized to evaluate these theoretical conduit network arrangements based on indirect data from gravimetry, geophysics, and geological information from the second-largest impact crater on Earth. The Merida Metropolitan Area (a densely populated region in the Mexican state of Yucatan) was selected as the study area. Piezometric data from 43 monitoring wells (collected during the monitoring period 1996–2001) formed the basis for model inversion. Recharge volumes were derived from precipitation data collected from 14 climatic stations. Results were compared with a previous groundwater flow model applied in the same area utilizing the CFP Mode 2, a turbulent flow-enabled single continuum model. Results of this study support the hypothesis of multirings of preferential flow influencing groundwater dynamics, providing important insights regarding the sub-surface in this karst region.

Agent-based models (ABMs) have long been applied in economics and social science research. The combination or coupling of these models with those of natural systems is a more recent application, and their use in conjunction with groundwater flow and transport models can be considered an innovative way to take advantage of their potential. In the Latin American region, sustainable management of groundwater resources can still be considered understudied. Among other characteristics, the existence of large transboundary aquifers in the region adds a further complication for addressing the sustainability of groundwater resource use. In this type of system, the impacts of joint regulations for utilization by different countries, the diversity of socioeconomic drivers and the conservation interests of each group of users might be consistently represented and explored through flow models coupled with ABMs. This review of the scientific literature aims to compile up-to-date information regarding the application of hydrogeological models coupled with agent-based models, focusing on their contributions to the sustainable management of groundwater resources and analyzing their potential for the Latin American region.

The effect of subsurface structures in blocking groundwater seepage has a long-term influence on groundwater level (GWL). A finite difference method (FDM) model considering the actual distribution of subsurface structures in an urban area of Shanghai (China) was established to predict GWL in the phreatic aquifer (Aq0) and the first confined aquifer (AqI). The equivalent hydraulic conductivity (K_eq) of model elements containing subsurface structures, calculated by the effective medium theory, was applied to the model. The predicted GWL fitted the monitored value in Aq0 well. Additional subsurface structures were added to the model to analyze the influence of the distribution type and the proportion (%) of the volume of subsurface structures that occupy the aquifer (V_u). Four scenarios with different distribution types (concentrated, subconcentrated, subscattered, and scattered) and ten scenarios with V_u varying from 5 to 50%, were analyzed. In all scenarios, the regional average GWL in AqI increased compared to the actual conditions because of the decrease in K_eq and the blockage effect on groundwater flow. The influence of scattered distribution on the regional GWL distribution was the smallest, and the subscattered distribution resulted in the most nonuniform GWL redistribution. The blockage effect of the subsurface structures gradually increased with increasing V_u. The increasing rate of ΔL_av (difference in regional average GWL between the predicted and actual scenarios) becomes considerable when V_u is ~29%. Hence, the projected increase in volume of subsurface structures in AqI under the assumed subscattered distribution is suggested to be <29%.

The key factors determining the operational cost and carbon footprint of public water supplies derived from groundwater are identified. Both remain low compared to alternative sources while groundwater levels remain stable and water quality potable, but can increase markedly if derived from overexploited and/or polluted aquifers. Thus, ‘potable source protection zones’ are strongly advocated, and examples from England (UK) and Spain are illustrated. The concept of minimising the carbon footprint of groundwater use for potable water supply is novel, and deserves greater attention.

Saline pans are environments with ephemeral to persistent evaporite crusts, surface and groundwater brine, little to no vegetation, and low topographic gradients. These characteristics make them sensitive to diverse hydrological processes. This research provides guidance on assessing and interpreting fluctuations in saline pan groundwater levels. Observations from the center of the Bonneville Salt Flats, Utah, USA, focused on meteorological and groundwater level fluctuations and were used to quantify evaporation and identify natural environmental controls on saline pan groundwater level variation. Primary water fluxes consist of precipitation and evaporation. Eddy-covariance evaporation measurements, spanning over 1.5 years and capturing diverse surface conditions, were collected. An artificial neural network, trained on meteorological measurements and eddy-covariance-measured evaporation, estimated evaporation over a 6-year period. The saline pan has two states: (1) dry, when water availability rather than evaporative potential limits evaporation, and (2) wet, when evaporative potential limits evaporation. In dry conditions, characterized by evaporation rates of ~0.1 mm/day, groundwater levels with daily average depths ≥5 cm below the surface, demonstrated daily variations >6 cm during summer and seasonal fluctuations >50 cm in response to temperature changes. Groundwater levels did not respond to temperature changes when there was surface water. Groundwater levels rose to the surface under wet conditions. Over multiple years, the system is in balance, with evaporation equaling precipitation.

Fracture conduits serve as the primary channels for groundwater runoff in karst areas, controlling the water level and distribution of flow in the groundwater system. To determine the parameters of fracture-conduit karst systems and to analyze the distribution characteristics of the pressure field and flow field, a pipe network calculation method is presented that discretizes the fracture medium and conduit medium into pipes and nodes. The connection rules for nodes and pipes are established, and different water conductivity coefficients are assigned to discrete pipes. Based on the principles of conservation of mass and energy, nonhomogeneous linear control equations are constructed to represent the discrete pipe network (PN). By solving the equations, groundwater parameters can be calculated for the PN. Meanwhile, a laboratory model test was conducted to validate the PN, and the numerical calculation results aligned well with the laboratory test results. In addition, a simple case is compared and verified, and the calculation results are compared with those obtained using the multiphysics software, COMSOL. The results indicate that the PN method can achieve more accurate calculation results with fewer elements. The method calculates the distribution characteristics of the flow field within the water-conducting medium and elucidates the influence of the properties of the medium on the distribution characteristics of the flow field. The research results provide guidance for the distribution of groundwater flow fields in karst areas and are expected to be applied to calculating groundwater pressures and flows in large-scale fracture-conduit systems.