Hydrogeology Journal最新文献

The Mississippi Embayment aquifer system (MEAS) and the Coastal Lowlands aquifer system (CLAS) are two principal aquifers in the US Gulf Coastal Plain. Despite their importance to the region, a comprehensive characterization of these aquifers has not been achieved yet. In this study, the horizon-assisted lithologic modeling (HALM) method is introduced to integrate horizon structures and well log data for aquifer characterization. By employing horizon restorations, the HALM method proves to be versatile in incorporating various geologic features into lithologic models. The HALM method was applied to characterize both the MEAS and the CLAS in the Louisiana and southwestern Mississippi regions. The resulting large-scale high-resolution hydrostratigraphic model provides a highly accurate representation of aquifer structures in regionally extensive hydrogeologic units, including synclines, angular unconformities, and faulting. Notably, the model highlights the presence of surficial coarse sediments, indicating significant groundwater recharge zones for the Southern Hills aquifer system, the Chicot aquifer, and the Sparta aquifer. Additionally, the Mississippi River alluvial aquifer and the Chicot aquifer are found to be thick and shallow, making them easily accessible for irrigation purposes. Furthermore, the model reveals significant connections between rivers and alluvial aquifers in northern Louisiana, with reduced river–aquifer contact as one approaches the Gulf of Mexico. Comparing the two aquifer systems, the CLAS exhibits relatively thick and extensive aquifers compared to the MEAS. This study not only contributes to advancements in geologic modeling techniques but also enhances the understanding of regional hydrogeology in the US Gulf Coastal Plain.

Investigations focusing on the impacts of mining on groundwater systems typically provide a qualitative analysis of groundwater flow and chemistry, whereas relatively few studies quantitatively analyze groundwater temperature perturbations induced by mining. This study aims to identify the hydrogeological mechanism responsible for changes to groundwater temperature associated with longwall coal mining. Here, the extreme gradient boosting (XGBoost) method was used to construct three models at different phases of mining disturbance to identify the factors governing groundwater temperature dynamics: (1) a pre-disturbance model; (2) an in-disturbance model; and (3) a post-disturbance model. The feature relative importance (FRI) of input variables contributing to groundwater temperature dynamics was quantified for a long-term groundwater monitoring dataset collected from the Ningtiaota Coalfield, Ordos Basin, China. Pre-mining disturbance groundwater temperatures were stable, and the XGBoost model identified the groundwater level of the respective monitoring wells to be the greatest predictor for variation in groundwater temperature. During mining disturbance, proximal monitoring wells exhibited a decline in groundwater temperature, where the FRI of groundwater temperature in an upgradient monitoring well increased by 151–662% relative to the pre-mining disturbance model. The monitoring of aquifer properties and stable isotope composition of groundwaters provided additional evidence to suggest groundwater temperature decreases were associated with increased recharge contributions from surficial Quaternary aquifers. Post-mining disturbance, groundwater temperature and aquifer specific storage demonstrated recovered to pre-mining conditions. This study provides insights into mining-induced groundwater temperature dynamics as a result of changes to hydraulic connection between aquifers.

Groundwater recharge estimation is important for groundwater resource management especially in arid and semiarid areas, such as Loess Plateau, China. Here, loess deposits form regionally important aquifers, typified by a thick unsaturated zone, facilitating the application of environmental tracers to estimate groundwater recharge rates. In this study, the chloride mass balance (CMB) method was used to estimate groundwater recharge from precipitation for two sites in Inner Mongolia, China. Due to the uncertainty in determining the prerequisite chloride input flux for the CMB method, three different techniques (artificial ³H tracer method, the measured chloride concentration in precipitation, and 1963 tritium peak method) were used to determine the chloride input flux to increase the reliability of the calculated groundwater recharge rates. The different chloride input flux results obtained from the different techniques were found to be consistent. The average groundwater recharge rate calculated from the chloride mass balance method is 0.038 m/year. The groundwater recharge rate obtained in this study was found to be consistent with groundwater recharge rates derived from similar studies in the Loess Plateau.

Mine-water geothermal resources have potential to provide low-carbon heating and cooling in many areas; however, this potential has not been fully realised due to technical, economic and policy challenges. The UK Geoenergy Observatory (UKGEOS) in Glasgow was developed to provide an at-scale research facility designed to help de-risk mine-water geothermal usage. The limited knowledge of the hydrogeological systems altered by former mining activities is a key determinant of the long-term sustainability of water and heat abstraction/reinjection. This work presents a hydrogeological conceptual model developed using groundwater monitoring data obtained during the construction of the Observatory between 2020 and 2022, results from initial pumping tests performed in 2020, and results of hydrochemistry analysis from 25 sampling rounds collected between 2019 and 2022. The analysis of the data provides evidence of the dominant role of mine workings in controlling groundwater flow, with high intra-mine connectivity; increased fracturing in sandstones above mine workings; and limited inter-mine connectivity. Groundwater recharge is meteoric, mean residence times are >50 years, and there is a general upwards circulation from the deeper mine levels to the superficial deposits and the River Clyde. Faults play a significant role in limiting the extent of the highly transmissive mine workings, but there remains uncertainty surrounding the role of the faults in connecting different mine workings and their hydraulic behaviour in nonmined units. The conceptual model, that will be refined as new data become available, will be used to help guide monitoring and sampling programs and plan research activities in the Observatory.

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.