Hydrogeology Journal最新文献

Fractured aquifers are heterogeneous due to the variable frequency, orientation, and intersections of rock discontinuities. A ~100-m-thick Silurian dolostone sequence provides a bedrock aquifer supplying the city of Guelph, Canada. Here, fracture network characteristics and associated influences on hydraulic head were examined using several data types obtained from 24 cored holes in a study that is novel for the quantity and quality of data. High (50–90°) angle joint orientations, heights, and terminations relative to bedding features were determined from acoustic televiewer logs and outcrop scanlines. These data were compared to high-resolution hydraulic head profiles showing head loss over depth-discrete intervals identifying zones with lower vertical hydraulic conductivity. This study reveals that the marl-rich Vinemount Member, traditionally considered the principal aquitard, corresponds to head loss in only 62% of the 24 boreholes. The vertical position of head loss varies across the 90-km² study area and occurs in any of the lithostratigraphic units of the Lockport Group. Within this sedimentary sequence, aquitards are laterally discontinuous or “patchy” at variable depths and relate to: (1) the frequency of the high-angle joints; (2) shorter joint height; and (3) the type of joint terminations. The head loss occurs in thin (2–2.5 m) intervals where the frequency of the high-angle joints is low. Where a large proportion of small joints cross-cut marl bedding planes, head loss is negligible, suggesting that the vertical hydraulic conductivity is not reduced. Overall, these findings are potentially applicable to assessing aquitard and cap rock integrity in carbonate sedimentary sequences worldwide.

Groundwater flow has been investigated in the Sierra Seca, Spain. Maximum recharge to the central core of the mountain occurs at high elevations, which provides recharge to two overlapping karst aquifers constituting a groundwater storage zone at a lower elevation break in slope. Both karst aquifers are associated with three springs arising from the upper part of the permeable formations. The climate is characterized by long and intense periods of drought and short periods of rainfall, which trigger discharges from the springs. Spring flow recession curve analysis, cross-correlation and monitoring of groundwater temperature and electrical conductivity have demonstrated contrasts observed in the hydrodynamic and physicochemical response of the three springs during flood events. One spring records floods with narrow and short peaks of high discharge accompanied by sharp drops in temperature and electrical conductivity. Another spring records floods with somewhat wider peaks and sharp increases in temperature and electrical conductivity (piston effect), whereas the third spring shows great consistency in all monitored characteristics. It is concluded that the absence of a piston effect in the spring with the highest flow rates is due to the contribution of rapidly circulating water that is expelled by semi-active karst networks (overflow) before reaching the saturated zone, which does not occur in the other springs due to the absence of overflow hydrological pathways. The most regular spring owes its functioning to the contribution of infiltrated water in the bed of an upstream riverbed, which explains this regularity.

The Cunene Province (Southern Angola) is facing recurrent and pluriannual droughts. Surface water supply could be reinforced using the groundwater resources of the multilayered aquifer systems (MAS) hosted in the siliciclastic sediments of the Kalahari Group. The MAS were first identified in the early 2000s in Northern Namibia and recently in the Cunene Province, by studies of the PLANAGEO project based on modern processing and reinterpretation of legacy data from the 1960s and 1970s (electrical resistivity data and deep boreholes). This article presents the results of a time domain electromagnetic (TDEM) survey conducted in the Cunene Province to: (i) contribute to the design of the hydrogeological conceptual model of the transboundary MAS, namely their geometry and extension; (ii) validate the reprocessing of the legacy data; and (iii) guide the future location of boreholes. Results depict the geometry of the sedimentary basin and the characterization of the MAS, with particular emphasis on the intermediate and deep aquifers. The borehole siting, based on the interpretation of the new TDEM data and the legacy data (clay markers in borehole logs), was successful, with a good agreement between estimated and observed horizons of the deep aquifers. However, the presence of clayey layers, a clay-rich matrix in the detrital deposits and saline/brackish groundwater led to uncertainties in the interpretation of the electrical transects. As such, recommendations are made to improve future data collection and mapping of the MAS.

Quantifying historical research trends in the field of hydrogeology is not only generally informative for hydrogeologists but is essential for fostering interdisciplinary collaboration and assessing the relationship between academic study and societal interests in hydrogeologic issues. To address this, a topic model was applied to over 37,000 academic abstracts published in over 20 journals between 1963–2022 in the field of hydrogeology to study the evolution of topic trends through time. Model results were fed into the popular large-language model ChatGPT to assign topic names, representing an unsupervised method. The results indicate that, historically, popular topics related to methodological development and analytical and numerical models analytical and numerical methods in groundwater flow modeling and well hydraulics have given way to topics related to more increasingly complex models (groundwater monitoring and uncertainty estimation and groundwater modeling calibration and simulation) as data and computational capability becomes increasingly available. An insight into the period of boom-and-bust in contaminant hydrogeology is reflected by a shift in focus from topics related to assessment and characterization of contaminant sources toward topics related to degradation and remediation methods. Topics of emerging prevalence (sustainable groundwater resource management, catchment hydrology and runoff processes) in the current period reflect an increasing focus on treating the surface-water/groundwater system as a single system. In addition, results suggest that topic distribution within the field of hydrogeology has become more varied as time has progressed.

Regional sandstone aquifers in arid areas provide prolific water resources that can meet human water demands, but their sustainability is at risk where recharge is very low and significant withdrawals occur. The Saq sandstone aquifer in the Al Ula area (Saudi Arabia) has been investigated through a field survey that included groundwater level measurement, groundwater sampling and analysis, crop inventory mapping and irrigation practice enquiries to assess groundwater abstractions. A groundwater model has been built to assimilate the collected data and investigate the aquifer response under various abstractions scenarios to meet future agricultural and domestic water demand. Since the 1960’s, water levels have dropped by 5–20 m within the Al Ula Valley, with maximum water level drawdowns reaching 30–40 m in Al Ula City. Present water level drawdown rates range from 0.5 to 2 m year^–1 in the agricultural areas of the valley. Less than half of the sampled groundwater is in compliance with regulatory guidelines for drinking water purpose, and high groundwater nitrate concentrations are observed in agricultural areas. Predictive scenarios of decreasing abstractions suggest a reduction in the water level decline by 2050 but do not reverse the current decreasing trend. The estimated recharge is much lower than groundwater abstraction rates and current withdrawals are effectively mining the groundwater reserves. Further challenges arise from a water quality standpoint, due to the presence of radionuclide activities (mostly ²²⁸Ra) in the aquifer above the WHO guidelines.

The transition from Darcy to non-Darcy flow regimes was investigated using column experiments. This revealed key relationships between sediment characteristics and critical thresholds for the onset of the non-Darcy flow regime, as well as inertial flow parameters. An exponential dependence of the critical Reynolds number (Re_c) on hydraulic conductivity (K) and a linear dependence on sediment size (d₅₀) was found. The analysis revealed a potentially universal relationship between the critical hydraulic gradient (I_c) and K, with a power-law exponent of –3/2, consistent with previous investigations. Additionally, I_c was found to be inversely proportional to the power law of the square root of d₅₀. Novel relationships are derived for estimating the Izbash equation inertial exponent (n) and the Forchheimer inertial coefficient ((beta)) based on sediment characteristics. The exponent (n) was found to decrease with d₅₀ and increase with K, following power-law relationships. A new equation is proposed, capable of predicting (beta) with slightly improved accuracy, outperforming numerous and previously proposed empirical equations. Additionally, these data validate the works of Ergun and Irmay as an alternative for (beta) estimation using porosity and sediment size. As the attainment of statistical significance in multiparameter curve fitting can be trivial, it has led to the proliferation of empirical equations for estimating β. This study highlights the limitations of existing empirical methods in determining β and emphasizes the necessity for a universal approach to predict this critical parameter, which will facilitate broader adoption of the Forchheimer equation.

Noble gas recharge temperature (NGRT) and excess air (EA) values, derived from the analysis of noble gases in groundwater, were used to improve the understanding of groundwater recharge mechanisms through the vadose zone of a sandstone aquifer in southern California (USA). The wide range of NGRT and EA values suggests that complex recharge mechanisms exist between two end members: matrix and fracture flow. In particular, combining NGRT and EA values, four groups of wells with different recharge mechanisms were identified: high EA combined with low NGRT suggests recharge is dominated by fast flow through an interconnected fracture network (group A), low EA with high NGRT suggests recharge is controlled by slow flow in the rock matrix (group B), low EA and intermediate NGRT suggests percolation through fractures followed by imbibition into the unsaturated matrix and subsequent matrix flow (group C), and high EA combined with high NGRT in group D suggests flow of water that originally resided in the matrix being pushed into the fracture network by a strong infiltration event (group D). These interpretations were corroborated with tritium groundwater dating and consideration of the potential influence of well completion characteristics on flow processes and measured noble gas concentrations due to mixing. This study demonstrates the contribution of noble gas analysis to identify recharge mechanisms in complex aquifers. This is crucial to inform three-dimensional numerical flow and transport models and to predict future hydrological scenarios in response to climate change.

High-frequency dataloggers for groundwater level monitoring were used in combination with other tools to analyze tidal effects on groundwater levels (GWLs) in the Maputo aquifer, Mozambique. Power spectral analysis was used to ascertain the dominant periodic components in the tide and GWLs, and cross-spectral analysis was used to determine the lag time between them. Wavelet analysis was applied to investigate changes in periodic components over the measured period in the time-frequency domain. The estimated amplitudes and lag times were then used to estimate aquifer diffusivity and the water-table fluctuation (WTF) method was used to compute groundwater recharge. The results identified a 12.42 h dominant periodic component both in the tide and GWLs in the coastal area. However, GWLs lag behind the tide by 2–4 h, depending on the distance of the observation wells to the coastline. The wavelet analysis results showed no changes in the dominant periodic components over time. The estimated specific storage values for four piezometers were estimated to be 3.19 × 10^–5, 5.04 × 10^–5 and 1.02 × 10^–4 1/m, respectively. Annual groundwater recharge for the young sand dune aquifer was estimated for one piezometer with a specific yield of 0.15–0.25 was within the range of 123–205, 185–309, 504–840 and 244–407 mm, for four hydrological years from 2018 to 2021. Estimated specific storage values and recharge rates are essential inputs to support the construction of transient groundwater models for the Maputo aquifer.

Sacred wells and springs are important cultural features in many societies. A recent study in Ireland may be the first detailed countrywide investigation of the hydrogeology and water chemistry of sacred wells. Key findings are discussed in relation to case studies elsewhere. A wide range of hydrogeological settings are represented. There is evidence of anthropogenic impacts at many sacred springs and wells. Communication of potential health impacts is necessary but challenging, because of the sensitivities surrounding these sacred water sources.