Groundwater最新文献

Reduction potentials of redox couples are fundamental for understanding subsurface geochemistry and guiding water resource exploration and management. Reduction potentials are routinely calculated with the Nernst equation, which requires detailed chemical composition data and complex speciation modeling—factors that limit its application in large-scale or data-limited field settings. To address these limitations, we developed a data-driven simplified Nernst equation that estimates the reduction potentials of individual redox couples using only pH and temperature. By integrating geochemical modeling with a global groundwater chemistry dataset, we demonstrate that pH is the dominant control on redox potential, while temperature and redox species activity play secondary roles. The resulting formulation reduces computational demands while maintaining high-predictive accuracy across diverse groundwater environments. This approach enables rapid and scalable estimation of reduction potentials, supporting applications in geochemical modeling, contaminant transport prediction, and groundwater quality assessments. Furthermore, it offers a thermodynamically grounded yet practical framework for interpreting electron transfer dynamics in natural groundwater systems.

Karst aquifers have evolved secondary porosity features that facilitate heterogeneous recharge and groundwater flow dynamics. These dynamics affect the natural spatial and temporal variability of water quality in the aquifer. However, when recharge occurs near urban and agricultural land use that can introduce contamination, the contamination can conflate natural water quality variability, generating convoluted signals in time and space. Most water quality investigations in karst aquifers rely on groundwater sampling at discrete locations such as wells or springs, which do not always capture the magnitude of water quality heterogeneity. Cave diving in phreatic caves can be used to explore this variability by using water quality sensors and discrete water chemistry samples to explore spatial and temporal water quality changes for improved and targeted water resource management. Our study uses cave diving to document the spatial and temporal variation in water quality within a phreatic cave system in the Floridan Aquifer System (FAS), a karst aquifer in northern Florida. We collect continuous 15-s measurements of dissolved oxygen (DO), temperature, pH, and specific conductance along a 1.1 km transect, which intersects multiple cave passages that drain into the primary cave passage. We also collect discrete water chemistry samples in three separate cave passages within the phreatic cave, as well as at the spring vent, to document spatial and seasonal variability in nutrients, organic matter, and major groundwater ions. Our results show that specific conductance, DO, temperature, and pH vary together spatially in consistent ways, which we use to identify cave passages that receive more direct recharge. Spatial and temporal variability across the cave system was most pronounced for NO_x-N (nitrate + nitrite), DO, and dissolved organic carbon, while major ions showed minimal spatial variability but greater temporal variability. Relationships derived between specific conductance and NO_x-N show a positive correlation, while relationships between ions associated with carbonate mineralogy and specific conductance are negatively correlated, which likely reflects the impact of recharge from agricultural land use surrounding the cave system. Our results highlight water quality complexity in phreatic caves and have implications for local water quality restoration efforts, interpreting water quality data collected at a discrete location, and provide guidance for future water quality studies in phreatic cave systems.

Water interaction between fractures and rock matrix is one of the themes in hydrogeology. Accurate values of Darcy permeability (k_D) of the matrix are desired for better quantification of the water interaction. In contrast to the traditional method using seepage experiments to measure k_D of a rock, this study uses the technique of ultrasonic shear (S-) wave for determining k_D of the rock matrix. From the perspective of waves, Darcy seepage is driven by slow compressional (P-) wave at very low frequencies, and k_D is associated with slow P-wave in the regime of low frequency. Similarly, there is another permeability associated with S-wave, namely, S-wave permeability (k_s). The rock samples are Navajo sandstone and Berea sandstone. Data of the dry sandstones with water are entered into Biot theory for yielding saturated phase velocity (V_s) and the quality factor due to viscous fluid (Q_s). Then, ultrasonically measured V_s and Q_s are fitted with the use of the model output. For Navajo sandstone, low-frequency k_s appears to be 0.107–0.115 darcy, surprisingly close to k_D of 0.1 darcy. For Berea sandstone, low-frequency k_s turns out to be 0.081 darcy, also consistent with k_D of 0.075 darcy. The success robustly shows that Biot theory is applicable to S-wave in isotropic rock free of fractures. More importantly, the comparability between low-frequency k_s and k_D demonstrates that ultrasonic S-wave is an alternative approach to acquiring k_D of the matrix.

Researchers frequently encounter challenges in accessing valuable data encapsulated within university theses, which are predominantly archived in PDF format and remain unpublished in repositories. These documents often encompass original research, including vital environmental and hydrological data, yet they pose difficulties for searching or analysis due to inconsistent formatting and inefficient repository search tools such as keyword searches, which lead to an overwhelming list of documents. Our research team, engaged in developing a groundwater database for the Arequipa region of Peru, encountered this issue directly, with numerous relevant theses dispersed across local university repositories. The manual review process proved excessively time-consuming, necessitating the development of an innovative, automated solution. Our multi-step methodology commenced with optical character recognition (OCR) and Python scripts for keyword scoring, followed by the employment of Large Language Models (LLMs), notably Google's Gemini and the locally hosted Ollama, to semantically analyze content. This facilitated the identification and extraction of pertinent data (e.g., water quality parameters, well locations) and its organization into usable formats such as Excel spreadsheets; subsequent manual checks confirmed a high level of accuracy. The final system enables users to query an extensive number of documents swiftly and contextually, effectively overcoming traditional keyword search limitations. The tool is presently being disseminated among local researchers and institutions, offering a robust solution for accessing and managing regional groundwater data. This methodology possesses the potential for global scaling and adaptation, thereby enhancing access to gray literature and expediting scientific discovery across various disciplines.

The presence of positive wellbore skin, that is, deposits of fine-grained particles from the drilling fluid on the borehole wall, significantly affects the efficiency of water wells. Previous studies of skin samples have shown a significant variability in typology, thickness, and composition but were largely unable to explain the differences. In order to overcome this problem, we therefore (1) significantly expanded the sample data base by investigating skin samples from nine wells with very similar geological and technical conditions and (2) investigated the evolution of the density of drilling fluids during the drilling. The former is done in order to evaluate differences in skin thickness and composition, and the latter to study the differential mobilization of particles. Incohesive and poorly sorted layers form the source of the particles, while the thickest accumulation of particles occurs in highly permeable layers, where the highest exfiltration rates initially occur. For well drillers, we recommend continuous monitoring of drilling fluid density to obtain a measure of the presence of particle-providing layers and the probability of wellbore skin formation.

The Greater Houston region has undergone substantial land subsidence over the past century, with rapid subsidence occurring from the late 1940s to the 1970s and more controlled rates thereafter. The establishment of the Harris-Galveston Subsidence District (HGSD) in 1975 marked a pivotal milestone in subsidence management, primarily by regulating previously uncontrolled groundwater extraction. HGSD's success in reducing subsidence while simultaneously fostering robust economic growth in the Houston area inspired the creation of the Fort Bend Subsidence District (FBSD) in 1989. By 2024, significant subsidence (>0.3 m from 1906 to 2024) had impacted an area of approximately 12,000 km², encompassing nearly all of Harris and Galveston Counties, as well as parts of the surrounding counties. This subsidence led to an irreversible loss of around 12 km³ of groundwater storage capacity—equivalent to 60 times the volume of Lake Houston, or roughly 8 years' worth of water usage for Harris and Galveston Counties as of 2023. About 65% of this loss occurred before HGSD regulations (1906-1978), 20% between 1979 and 2000, and 15% since 2001. Due to groundwater regulations, the extent of subsidence has decreased significantly since the 1990s. By the early 2020s, the areas experiencing subsidence rates exceeding 1 cm/year had decreased to 1500 km², roughly one-twentieth of the greater Houston region, with only 50 km² seeing rates above 2 cm/year. The highest current subsidence rate, approximately 3 cm/year since 2020, occurs in the Katy area, Fort Bend County. This review provides a comprehensive overview of land subsidence and groundwater level monitoring in the greater Houston region, highlighting regulatory developments, technological advancements, key research findings, and the continuing challenges of achieving sustainable groundwater management.

The article deals with computer analysis of flow to pumping well partially penetrating the high conductivity porous water table aquifer. Water level depletion in the pumping well, 3 partially penetrating observation wells, and 6 piezometers of short screen are evaluated in the analysis. The WT software considers the delayed gravity drainage caused by dewatering of the overlying unsaturated zone. This flow is emulated as diffusive crossflow or leakage from an aquitard with an impervious top. The analytical method by Hantush (1962) is applied to confirm the aquifer parameters using the late time drawdown data in all observation wells and piezometers. The software PEST is employed to optimize the aquifer properties and the presumably laminar specific radial loss parameter of the pumping well. The results are compared with two earlier analyses. The k_r and k_z parameters fit the relevant data by Moench et al. (2001), whereas the S_y parameter is close to the value by Tartakovsky and Neuman (2007). An intermediate value is found for the S_s parameter.

This study presents a comprehensive compilation of a hydraulic conductivity (K) database (over 800 measurements) collected over the past seven decades, encompassing test volumes ranging from laboratory to field scales for two principal sedimentary units at the Hanford site in south-central Washington State. Despite both units being gravel-dominated, the geometric mean K of the Hanford formation is orders of magnitude higher than that of the Ringold Formation for the permeameter and pumping test data. In contrast, the lnK variance across test volumes shows only moderate variation between the two units. Analysis of K values across different support scales reveals a clear scale dependence for the Hanford formation, contrasting with Ringold, which exhibits scale-invariant behavior at the field scale. These differences arise from their distinct depositional processes; while the Ringold Formation was deposited gradually over geologic time by fluvial systems, producing consistent K, the Hanford formation was deposited abruptly by catastrophic glacial floods, leading to scale-dependent K variability. The study underscores that scale dependence in unconsolidated sand and gravel aquifers is common but not universal. Calibrated inverse modeling of regional groundwater flow yields high K estimates, with the average for the Hanford formation paleochannel being ~15,000 m/d, ranging from 1002 to 21,514 m/d. Multiple lines of evidence, including pumping tests, support these model-calibrated high K estimates for the Hanford formation paleochannel comprised of open framework gravels. For both sedimentary units, the upscaled K estimates align with the inverse model-calibrated estimates for non-channel portions of the Hanford and Ringold formations. While previous studies examined scale dependence using data from multiple sites, this study focuses on a single site with two sedimentary units analyzed across multiple support scales. To the best of our knowledge, this represents the most extensive compilation of K data for two gravel-dominated formations at the same site, incorporating both laboratory and field test results across varied scales.

Jerusalem, a city held sacred by three of the world's great religions, is located in a semi-arid climate, and its occupation through the millennia has only been made possible by the construction of an extensive and ingenious water supply infrastructure. The settlement of Jerusalem was first made possible by water from the Gihon Spring. Over the centuries, the inhabitants of Jerusalem added several pools and reservoirs to collect and store water. Nearly all buildings, both private and public, also had extensive storage capacity in the form of cisterns. To support a burgeoning population and pilgrim growth during the late Second Temple Period, four aqueducts were constructed to bring additional water into Jerusalem. Much work remains to identify, date, classify, and restore the ancient water works of this great city.