Ground water最新文献

Preferential flow is common in the vadose zone of bedrock aquifers. Rapid film flow down fracture walls and free-fall flow down open vertical fractures produce velocities that are commonly in the range 10^-4 to 10^-1 m/s.

This benchmark demonstrates that cost-effective consumer ARM desktop clusters can match the parallel modeling throughput of high-end 64-core ×86 workstations. These findings offer groundwater modelers a highly efficient, thermally stable alternative for computationally intensive PEST workflows at a fraction of traditional hardware costs.

Groundwater depletion for agricultural irrigation poses significant environmental and economic challenges. This study introduces a proof-of-concept that combines hydro-economic modeling, scenario-based modeling, and multi-objective optimization to manage pumping curtailment in an over-allocated basin in the western United States. Three optimization scenarios were evaluated, each offering different degrees of management flexibility. Results reveal that scenarios with finer spatial resolution achieved greater environmental benefits per unit profit loss. Additionally, strategies allowing fractional reductions in curtailed wells-rather than complete shutdowns based on water rights seniority-substantially improved efficiency, highlighting the value of increased decision-making flexibility. Although scenario testing can aid stakeholder engagement and strategy exploration, multi-objective optimization provides a systematic framework to quantify tradeoffs between competing objectives. This combined approach demonstrates promise for building consensus and supporting the design of sustainable water management strategies that balance agricultural livelihoods with ecosystem preservation.

Karst aquifers play a crucial role in global water resources. Characterizing their thermal dynamics is essential for improving our understanding of their functioning. However, monitoring karst systems is challenging due to their strong heterogeneity, anisotropy, and limited accessibility. To address these challenges, we deployed an 800-m-long fiber-optic cable within the unsaturated zone of a karst system in the Jura Mountains (eastern France). The objective was to investigate the spatial and temporal variability of cavity air and underground river water temperatures over a 6-month monitoring period. The results highlight a gradual increase in cavity air temperature (CAT) and cavity river temperature (CRT) over the study period, consistent with the diffusion of surface air temperature (SAT). Superimposed on this long-term influence, short-term temperature fluctuations linked to precipitation events reveal the role of advective heat transfer associated with rapid infiltration and mixing in the main conduit. Temperature and electrical conductivity contrasts between the underground river and a lateral tributary indicate that multiple reservoirs contribute to aquifer recharge.

This paper presents exact one-dimensional (1D) analytical solutions for steady-state groundwater flow in a heterogeneous leaky confined aquifer, accounting for spatial variability in both aquifer and aquitard properties. Unlike traditional models that assume uniform conditions, the proposed approach incorporates natural heterogeneity arising from variable depositional and post-depositional processes. The aquifer system is divided into discrete vertical zones, each characterized by distinct hydraulic properties. The solutions describe steady-state flow in a horizontally extensive confined aquifer recharged by leakage from an overlying unconfined aquifer through a thin, heterogeneous aquitard and discharging to a downgradient fixed-head boundary. The upgradient boundary may represent either a no-flow condition or a fixed head. The analytical solutions provide exact 1D, steady-state reference results for assessing the effects of lateral heterogeneity and for evaluating the spatial discretization required in numerical groundwater flow models to resolve sharp hydraulic head transitions and flow redistribution across zones with contrasting conductivities. Validation against MODFLOW 6 simulations demonstrates excellent agreement, confirming the correctness and robustness of the analytical formulation. A Python implementation of the analytical solutions is openly available in a public GitHub repository, ensuring reproducibility and facilitating further exploration of heterogeneous leaky aquifer systems.

Baildown tests are an important and relatively inexpensive way to estimate transmissivity. Huntley (2000) developed baildown test analytical methods to determine LNAPL transmissivity. One of his baildown test methods was based on the Bouwer and Rice (1976) rising head slug test method which for brevity we will call Huntley's Method 1. In Batu's (2012) criticism of Huntley's Method 1, he noted that both Lundy and Zimmerman's Method and Huntley's Method 1 are based on the Bouwer and Rice (1976) rising head slug test method, but he observed that only Huntley's Method 1 included a density correction factor. We took a closer look at the derivation of Huntley's Method 1 and found that a mathematical error led to the density correction factor. The corrected Huntley Method 1 equation is equivalent to the Bouwer and Rice (1976) equation for transmissivity. The density correction factor error in Huntley's Method 1 causes the LNAPL transmissivity value to be approximately 4 to 10 times higher than it should be, potentially resulting in unnecessary remediation costs. In light of the error in Huntley's Method 1, it is recommended that the community use the corrected version of Huntley's Method 1. Because Kirkman's (2013) J-ratio baildown test method is based on the uncorrected Huntley Method 1, its use should also be reconsidered in light of our correction to Huntley's Method 1.

Solute transport simulators aiming to accurately describe the transport of charged chemical species in porous media need to account for electrostatic coupling effects. Each ion in pore water possesses a specific electric charge and molecular diffusion coefficient, properties that determine their mobility and the overall charge balance of aqueous solutions. Depending on the charge, concentration and aqueous diffusion coefficient, the displacement of an ion in solution influences, and is in turn influenced by, other ions in solution by means of electrostatic interactions. This phenomenon has been studied with experiments and numerical simulations in diffusion-dominated regimes, as well as in advection-dominated flow-through systems, showing that electrostatic coupling effects play a relevant role in the spatiotemporal prediction of ion concentrations. However, there is limited availability of solute transport codes incorporating electrostatic coupling, limiting applications of multispecies ionic transport at different scales. This article elaborates on the topic of electrostatic coupling and presents a methodology for incorporating the effect into multispecies solute transport simulations with MODFLOW. The integration is achieved through the Application Programming Interface of the program (MODFLOW-API). This interface enables the access to concentrations and dispersion coefficients of all species during the simulation, which are necessary to calculate a dispersive correction that effectively incorporates electrostatic coupling into the model. Numerical results demonstrate the effectiveness of the coupling strategy, benchmarking the implementation with previously validated numerical simulators and with experimental data.

Groundwater is increasingly needed for water supplies but may have limited utility in some locations because of its salinity. Salinity, often expressed as total dissolved solid (TDS), is frequently estimated using specific conductance (SC) measurements. However, the commonly used proxy (0.65 multiplied by SC to indicate TDS, common in many handheld meters) can result in inaccurate TDS estimates. First, the TDS-SC relationship is not linear over the entire concentration range of groundwater. Furthermore, the TDS (and salinity)-SC relationships vary substantially depending on the major-ion composition. Here we develop a proxy method utilizing SC and major-ion water type to estimate TDS and salinity specifically for groundwaters. Compared to most surface waters, groundwater tends to have a wider range of salinity (fresh to highly saline) and higher concentrations of bedrock-derived solutes such as carbonate ions, silica, and many other ions. The dataset used to develop the proxies includes water chemistry data from 149,059 discrete groundwater samples. The groundwater proxies, which employ nonlinear log-log relations, utilize five water types (HCO₃, Cl, Ca-Mg-SO₄, Na-K-SO₄, and mixed waters), are accurate (median percent difference between TDS and salinity determined using the proxy compared to discrete measurements was <±0.8%) over a wide range of SC (up to 200 mS/cm), rapid, cost-effective, and can be measured on-site.

The N₂/Ar method is valuable for studying legacy nitrate and denitrification progress in groundwater systems. It uses dissolved N₂ and Ar concentrations to calculate the amount of N₂ originating from denitrification (excess-N₂). Successfully applying the method requires accurate values of N₂ and Ar concentrations. Therefore, avoiding degassing and atmospheric contamination during groundwater sampling is crucial for reliable results. In this study, we focus on the effect of sampling devices on N₂, Ar, and the resulting excess-N₂ concentrations. To evaluate this effect over a wide concentration range, we sampled 14 observation wells. One sample was collected using a submersible pump and another using a bladder pump. Furthermore, we collected multiple samples with both pumps at a fifteenth site to assess reproducibility. Additionally, we used a point-source bailer for sampling at this site. The major ion concentrations show that the sampling device does not significantly influence the sample chemistry. In contrast, the measured N₂, Ar, and calculated excess-N₂ concentrations significantly differ between the sampling devices. Overall, the samples collected with the submersible pump show the highest N₂ and Ar concentrations, resulting in the highest excess-N₂ concentrations. N₂ and Ar concentrations of the bladder pump samples are lower, resulting in lower excess-N₂ concentrations. The bailer samples show lower N₂ but similar Ar concentrations to the submersible pump samples, leading to the lowest excess-N₂ concentrations. We conclude that a submersible pump is practical and suitable for collecting groundwater samples to assess denitrification by the N₂/Ar method.