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Seaver, G.A. and Kuzirian, A.M., 2024. Estuary nitrate sources and trends in Buzzards Bay. Journal of Coastal Research, 40(6), 1055–1067. Charlotte (North Carolina), ISSN 0749-0208. The determination of estuary nitrate sources originating through groundwater was the principal objective of this work. This required long timeline (35-year) measurements over many seasonal cycles. Typically, in this study, nitrate sources were an upgradient from estuaries at a significant distance, usually greater than 300 m (1000 ft), whereas groundwater flow that transported the nitrate near the coast in Buzzards Bay, Massachusetts, traveled only 0.45 m/d (1.5 ft/d). Thus, it takes years before a potential newly discovered nitrate source could be confirmed in the estuary. Investigation of estuary nitrate trends and the significance of obtaining winter nitrate measurements to investigations was more fully developed in this work. This showed that determining the estuarian nitrate trends also required a timeline much longer than the variability of the nitrate influx into the estuary. The large, summer-to-winter high nitrate (but not low nitrate) differences and the system's inherent physiological ecology were central to regulating nitrate in an estuary, despite greatly increased groundwater nitrate input. The winter measurement data explained this phenomenon. Finally, the data measurement program completed in Buzzards Bay proved to be ideal in answering these necessarily long timeline questions. The research suggested a new parameter be used to indicate an excess nitrate state of an estuary. These long-term data also allowed meaningful calculations of estuarine and groundwater nitrate and temperature trends. [ABSTRACT FROM AUTHOR]

This study aims to investigate the response mechanisms of groundwater microbial‐toxicological indicators, specifically total bacteria count (TBC) and total coliform count (TCC), to water quality indicators and environmental conditions. Using data from a water source in the western plateau of China, a predictive model focusing on TBC and TCC was developed. An orthogonal experimental design was employed to manipulate environmental conditions such as temperature, pH, and porosity, facilitating laboratory experiments. These experiments measured pH, chemical oxygen demand (COD), oxidation–reduction potential (ORP), TBC, and TCC at varying depths and environmental conditions. Principal component analysis elucidated the mechanisms by which water quality indicators and environmental conditions affect groundwater microbial–toxicological indicators. A prediction model for these indicators in plateau regions was established based on a backpropagation neural network (BP‐NN), using TBC and TCC as target variables and the newly extracted principal components as influencing factors. The results demonstrate that environmental conditions and water quality indicators primarily influence the evolution of groundwater microbial–toxicological indicators by altering the ionic charge quantities, redox conditions, and temperature of the groundwater. The predictive model for groundwater microbial–toxicological indicators shows trends consistent with experimental outcomes, with an average relative error of less than 15%, meeting engineering requirements. Practitioner points: The values of total bacteria count (TBC) and total coliform count (TCC) under different conditions were obtained by column experiments.The influence mechanism of environmental conditions and groundwater indicators on TBC and TCC was elaborated by principal component analysis.TBC and TCC prediction models were established through the investigation of water sources in a plateau area and laboratory experiments. [ABSTRACT FROM AUTHOR]

Intertidal groundwater springs provide thermally stable, nutrient‐rich freshwater that causes fine‐scale variability in water temperature and salinity and promotes biodiversity in coastal estuaries and lagoons. In this study, we combined three thermal sensing techniques to elucidate summer water temperature patterns at the mouths of intertidal groundwater springs and the ambient coastal lagoon in Prince Edward Island, Canada. Thermal infrared imagery captured the spatiotemporal variability in relative temperatures of the lagoon channel and cold‐water plumes from the springs. Thermal anomalies due to the springs were detected at the surface throughout a tidal cycle, suggesting that the thermal plumes were buoyant. Fiber‐optic distributed temperature sensing paired with temperature loggers near the spring outlets recorded groundwater temperatures at low tide (~ 7°C) but ambient lagoon temperatures (up to 26°C) at high tide due to the vertical thermal gradient in the stratified water column. Calculated estuarine Richardson numbers throughout the study confirm intertidal spring buoyancy due to salinity differences. The fiber‐optic distributed temperature sensing results revealed pronounced variations in temperature as evidenced by spatial (3.7°C) and temporal (5.5°C) standard deviations over the cable length during the study and lower mean lagoon bed water temperatures at high tide (22.5°C) than low tide (24.3°C) due to heat advection from tidal pumping. Lagoon temperatures fluctuate at diurnal (solar) and semi‐diurnal (tidal) frequencies. The findings emphasize the efficacy of a multi‐technology approach to reveal fine‐scale and dynamic thermal processes that drive temperature patterns and habitat distribution in coastal lagoon ecosystems and highlight the thermal influence of intertidal springs. [ABSTRACT FROM AUTHOR]

Objective: In a changing climate, the effects of air temperature, precipitation, and groundwater on water temperature and thermal habitat suitability for Gulf Sturgeon Acipenser desotoi, listed as threatened under the U.S. Endangered Species Act, are not well understood. Hence, we incorporated these factors into thermal habitat models to forecast how Gulf Sturgeon may be affected by wide‐ranging climate change scenarios in 2024–2074. Methods: Using data from the Choctawhatchee River, Florida, we developed precipitation‐ and groundwater‐corrected air–water temperature models, compared their accuracy with that of conventional air–water temperature models used in fisheries management, and projected future Gulf Sturgeon thermal habitat suitability for normal physiological functioning and fieldwork (i.e., population sampling and telemetry surgeries) in summer (May–August) under 16 climate change scenarios. Result: Precipitation‐ and groundwater‐corrected models were more accurate than conventional air–water temperature models (mean improvement in adjusted R2 = +0.45; range = +0.09 to +0.75). Water temperature was projected to warm at widely variable rates across climate change scenarios encompassing different air temperature, precipitation, and groundwater regimes. Importantly, Gulf Sturgeon summer aggregation areas were cooler and influenced more by precipitation and groundwater and less by air temperature than were non‐aggregation areas. If precipitation and groundwater—as drivers of cooling—become warm in a changing climate, summer aggregation areas were projected to exhibit thermal habitat degradation equivalent to or greater than that of non‐aggregation areas. Conclusion: Our results add hydrological context to the premise that aggregation areas provide cool water and energetic savings for Gulf Sturgeon during summer, underscoring the importance of protecting these habitats through groundwater conservation, water quality monitoring, and riparian/watershed habitat management. Our findings indicate that identifying thermally appropriate times for fieldwork activities will be increasingly important and time‐restricted as climate change intensifies. However, our research provides managers with a portfolio of water temperature models and an accurate, cost‐effective, management‐relevant approach to forecasting thermal habitat conditions for Gulf Sturgeon and other species in a changing climate. Impact StatementWater temperature models with precipitation and groundwater are accurate and useful, allowing managers to locate key thermal habitats, forecast temperatures, and decide when and where to safely target, capture, tag, and monitor Gulf Sturgeon and other species amid climate change. [ABSTRACT FROM AUTHOR]

The circulation depth of geothermal water providing the geothermal system framework significantly dominates the evaluation of renewal capacity and geothermal resources. The traditional evaluation of circulation depth is based on the groundwater temperature variation in the recharge section and the average geothermal heating rate of geothermal system. However, misunderstanding groundwater temperature distribution in geothermal systems will lead to overestimating groundwater circulation depth based on the recharge section. Temperature measurement in a 1000 m geothermal scientific borehole from the Xinzhou geothermal field of south China is discussed as a case study to reassess the circulation depth of geothermal water. For Xinzhou geothermal system, the recharge and discharge temperatures are from 26.2 °C to 32.6 °C and from 67.0 °C to 98.0 °C, respectively. And the heat exchange temperature at the deepest point is from 121 ℃ to 154 ℃. This indicates that the temperature gradient in the recharge section should be greater than that in the discharge section. But the actual observation is opposite that the temperature gradient in the recharge section and in the discharge section is 3.04 ℃/100 m and 4.97 ℃/100 m, respectively. We proposed that the depth of geothermal water circulation evaluated by the temperature change and the geothermal heating rate in the discharge section represents the top depth of convection in the heat exchange zone, and the depth evaluated by the recharge section represents the advection depth of groundwater in the recharge section. The top depth of convection in the heat exchange zone estimated by the discharge Sect. (0.75–1.49 km) is much shallower than the advection depth of groundwater in the recharge Sect. (3.25–4.34 km). In the convective heat exchange zone (between 4.34 km and 1.49 km), the fault zone at a certain depth is the ideal location for geothermal development to extract water and heat. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate the presence of benzene in the ground and drinking water in the eastern Niger Delta, where multiple oil and gas production facilities are present. Samples from drinking water wells were collected for measurements of benzene, toluene, ethylbenzene, and xylenes (BTEX). Additionally, the dissolved organic carbon (DOC) concentration was determined for the first time to establish the groundwater's total hydrocarbon and non-hydrocarbon load. The groundwater BTEX and benzene levels were up to 3904 µg/L and 3500 µg/L, respectively. DOC concentrations were up to 49 mg/L. The highest benzene concentrations were detected in wells near an underground petroleum pipeline. However, the concentrations decreased with distance from the pipeline to levels less than 0.1 µg/L. Despite benzene contamination, the aquifer has shown promising aerobic attenuation potential, having up to a 7.5 (95%) mg/L DO level and 2.11 mg/L BTEX biodegradation capacity for DO. However, the high groundwater temperature of up to 32.5 °C may weaken attenuation. The benzene and BTEX point attenuation rates ranged from 0.128 to 0.693 day−1 and 0.086 to 0.556 day−1, respectively. Hence, by natural attenuation alone, up to 66.5 and 85 years would be required to reach Nigeria's groundwater benzene and BTEX remediation goals, respectively. [ABSTRACT FROM AUTHOR]

Substantial seafloor morphological changes are rapidly occurring along the Canadian Arctic shelf edge. Five multibeam bathymetric mapping surveys, each partially covering a 15 km2 study area between 120‐ and 200‐m water depth, were conducted over a 12‐year time period. These surveys reveal that 65 new craters have developed between 2010 and 2022, averaging 6.5 m and reaching up to 30 m deep. Remotely operated vehicle investigations revealed massive ice outcrops exposed on two newly formed crater flanks. This ice is not relict subaerially formed Pleistocene permafrost because it is hosted in sediments which were deposited in a submarine setting post‐deglaciation. Low salinity porewater and sediment core ice samples with depleted oxygen isotopic compositions indicate waters with a meteoric signature are discharging and freezing in this area. These ascending brackish groundwaters are likely derived in part from thawed relict permafrost hundreds of meters under the continental shelf. They refreeze as they approach the −1.4°C seafloor, leading to the development of widespread, near seafloor, sub‐bottom ice layers. Conditions appropriate for ice melting also exist nearby where ice is exposed to seawater or warmed by ascending groundwater. Small variations in temperature and salinity lead to shifts between freezing of ascending brackish groundwater or melting of near seafloor ice layers. These conditions have produced a dramatic submarine thermokarst morphology riddled with multi‐aged depressions. Thermokarst geohazards may exist, unmapped, on other Arctic margins with groundwater channeled toward the shelf edge by a relict permafrost cap, and sufficiently cold shelf edge bottom water temperatures. Plain Language Summary: Significant seafloor changes are rapidly happening along the Canadian Arctic shelf edge, where numerous craters and mounds occur. Five seafloor mapping surveys collected over 12 years covering the same area reveal 65 new craters, reaching up to 30 m but averaging 6.5 m deep, were formed between 2010 and 2022. Observations from a remotely operated vehicle showed massive ice outcrops along the flanks of two newly formed craters. Chemical analyses of the ice show that the source of the frozen water is ascending brackish groundwaters that refreeze near the −1.4°C seafloor, forming widespread sub‐bottom ice layers that blister the seafloor producing ice‐cored mounds. The source of the groundwaters is likely melted relict permafrost from beneath the continental shelf. Where ice is exposed to seawater salinity or warmer groundwater, ice melting causes seafloor collapses. Minor temperature and salinity variations cause shifts between freezing of ascending brackish groundwater and melting of near‐seafloor ice layers. These ongoing processes create a dramatic submarine landscape composed of numerous depression and ice‐filled mounds of varying ages. This discovery of sub‐seafloor ice with a groundwater origin significantly expands our understanding of submarine permafrost within the Arctic continental shelves. Key Points: Massive outcrops of submarine ice layers were found within recently formed seafloor craters along the edge of the Arctic continental shelfOn‐going ice growth and decomposition is occurring around seafloor seepages to produce a distinctive submarine thermokarst topographyThermokarst geohazards may exist on other Arctic margins where sub‐zero water temperatures and submarine groundwater seepage occur [ABSTRACT FROM AUTHOR]

This investigation aims to study the influence of various environments, such as groundwater, seawater, mineral water and sub‐zero, on reinforced polyester/S‐glass/sisal composites with nano clay (NC). Composites with a configuration of S‐glass/sisal/sisal/S‐glass (GSSG) with different wt% of NC, such as 0, 2, 4, and 6, were manufactured using the hand lay‐up method. For 6 days, the composites were conditioned in different environments like seawater, mineral water, groundwater at room temperature, and sub‐zero environments at −17°C. The influence of these environments on the tensile and flexural properties of manufactured composites was studied. Composites with 4% NC displayed higher tensile strength, while composites with 2% NC exhibited maximum flexural strength for all the environments. It was perceived that the weight gain was maximum in seawater (0.1857 g) and minimum in mineral water (0.06 g) and sub‐zero (0.101 g) conditions for 6% NC condition. Tensile and flexural strengths were reduced by 27% and 24% when samples were submerged in seawater compared to other environments. TEM images for 4 wt% of NC and 6 wt% of NC were studied for dispersions of NC in Polyester, and the effect of NC mixing with polyester was understood for the hybrid polymer composites. Highlights: A novel hybrid composites were fabricated using a double stirring process.The ultra‐sonication led to uniform distribution of nanoparticles.The mechanical properties and the effect of environments on these properties are studied.SEM images revealed the aging due to various environments.The hybrid composites can store mineral water and the sub‐zero environment. [ABSTRACT FROM AUTHOR]

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The Supreme Court's recent ruling on the Chevron Doctrine will impact future groundwater policy in the United States by limiting federal agencies' interpretative authority. This change may lead to increased judicial involvement, regulatory uncertainty, and shifts in state versus federal dynamics in groundwater regulation. Additionally, the ruling could affect the EPA's ability to address emerging groundwater contamination issues effectively. The decision underscores the need for clear legislative guidance on groundwater management and protection as the regulatory landscape evolves. [Extracted from the article]

Rajgir thermal spring field in Bihar, Eastern India, holds international significance due to its historical and multi-religio-cultural importance. Present study attempted to understand the aquifer system to arrest its diminishing discharge in the backdrop of climate change and urbanization. The study identified three aquifer systems, namely fractured quartzite, basement granite, and overlying alluvium, that are working in tandem toward the delicate balance in recharge and discharge in the thermal spring field controlled by the regional fault system. Geological study along with geophysical surveys through gradient resistivity profiling, vertical electrical sounding, and electrical resistivity tomography is carried out to identify local distribution of the fault system. Based on the study, a geological map of the area is prepared followed by preparation of water table contour map. Study of exploratory borehole tapping the fracture zone reveals that the fracture system is under thermo-artesian condition capable of 5 m3/h yield with 40 m drawdown. This translates into transmissivity of about 1 m2/day. Historical rainfall, spring discharge, and groundwater hydrograph of the area are correlated and show that an average time lag of about 20–30 days exists between peak rainfall and peak groundwater level and about 30 days between peak rainfall and peak discharge. It highlights the importance of local recharge for survival of the thermal spring field. Rainfall and potential evapotranspiration data analysis shows that recharge occurs only when annual rainfall exceeds 850 mm, making the variability in rainfall due to climate change a potential threat to adequate recharge. The area is also witnessing growing urbanization which is altering the local groundwater regime. Analysis of historical water level shows that groundwater table declined by about 2 m in the last decade. Comparison with earlier studies is used to identify the changes in groundwater flow pattern in the area. Spatial variation in groundwater temperature is mapped and statistically analyzed. Results show that temperature above 30.8 °C may be considered as samples having signature of thermal water component. It is also observed that thermal water is restricted in some fixed pathways. Discharge measurements are carried out to study diurnal variation and effect of pumping. A set of private borewells, where thermal water is reported, is also studied. Typically, these wells are limited to the weathered part of the rock formation and do not tap fractures. Based on hydrogeological scenario, a local hydrodynamic model is conceived. Further, a management plan is suggested for sustenance of the thermal spring field with potential solution involving establishment of a carefully regulated zone with prohibition of energized pumping. Based on the present study, Government of Bihar has accepted the recommendation and is in the process of implementation. [ABSTRACT FROM AUTHOR]

This study utilized a pilot-scale distribution network to examine the impact of temperature increases (16 °C, 20 °C, 24 °C) and source variations (treated ground- and surface water) on bulk and biofilm communities over 137 days. Microbial characterization employed flow cytometry and 16 S rRNA gene-based amplicon sequencing to elucidate bulk-biofilm interactions. Bacterial bulk cell densities increased with higher temperatures, while water source variations significantly influenced bulk cell densities as well as the community composition. Additionally, growth curves were fitted on the flow cytometry results, and growth rates and carrying capacities were higher with treated groundwater at elevated temperatures. Conversely, biofilm cell densities remained unaffected by temperature. A mature biofilm was observed from day 70 onwards and a core biofilm microbiome, resilient to temperature and water source changes, was identified. These findings emphasize the importance of water source quality for maintaining biological stability in drinking water systems, particularly in the face of changing environmental conditions. [ABSTRACT FROM AUTHOR]

The rise of groundwater level and the acceleration of flow velocity in the discharge section of a geothermal system is difficult to explain by gravity-driven groundwater system theory alone. The temperature of groundwater increases after being heated in the geothermal systems, resulting in a decrease in groundwater density, an increase in salinity, and a decrease in viscosity. These changes create additional pressure heads, which are collectively recorded as geothermal driving forces. Based on the hydrochemistry and isotopes of hot springs in the Heyuan fault zone, South China, the geothermal driving force was evaluated as a case study. The geothermal driving force, which is mainly caused by the increase of groundwater temperature, increases with the increase of groundwater temperature and decreases with the increase of groundwater salinity. At the deepest position of groundwater circulation in the Heyuan geothermal field, the groundwater temperature reaches a maximum of 113.42°C, and the geothermal driving force generated here also reaches a maximum of +255.88 m. The geothermal driving force gradually decreases from deep to shallow in the Heyuan fault zone, but it makes the average vertical flow velocity of groundwater increase from 3.3×10−3 m/d in the recharge section to 16.8×10−3 m/d in the discharge section. Therefore, the geothermal driving force exists in the discharge section of the geothermal system, and its additional effect accelerates the flow of geothermal water in the discharge section. [ABSTRACT FROM AUTHOR]

São Vicente Medical Spa is located in mainland Portugal (Southwest Europe) and has been using thermal waters for therapeutic purposes for a long time. The Romans were known to have used its sulphureous waters around 2000 years ago. The spa has a Roman bathhouse that is still visible today, and its ruins were discovered during recent excavations. In this work are presented some elements of the Roman baths, the current baths, as well as the main aspects of the thermal park, with the location of the sulphureous water abstractions, including the classic thermal spring, which discharges water at a temperature of 18.6 ºC. The geomorphological, geological, and hydrogeological aspects are outlined, giving particular attention to the water chemistry of the various abstractions to develop multiple applications of geothermometers to contribute to the knowledge of the geohydraulic model at depth and the geothermal potential of the aquifer system. The conclusions are drawn from a conceptual model, including the reservoir depth, which, according to various scenarios, will be between 3 km and 8 km, in a favorable situation, respectively, to reach groundwater with temperatures between 112 ºC and 118 ºC. Finally, some remarks are made about the location of the new groundwater abstraction and the depth to be reached to increase the exploitation flows and their temperature. Lastly, it outlined new studies to improve the current geohydraulic model and to investigate its relationship with the deep aquifer systems in its neighborhood, namely the Entre-os-Rios hydromineral system. [ABSTRACT FROM AUTHOR]

In order to gain a deeper understanding of the effects of environmental factors on the formation of Populus euphratica xylem, this study analysed the anatomical characteristics of Populus euphratica xylem and its response to environmental factors using wood anatomy as an example of Populus euphratica in the Yingsu section of the lower Tarim River. The results showed the following: (1) Throughout the growing season, the number of conduits of Populus euphratica in the two sample sites showed a slow increasing trend with the increase in groundwater burial depth, and the total conduit area showed an increasing and then decreasing trend with the increase in groundwater burial depth. The four indices of total, minimum, average, and maximum conduit areas in Populus euphratica xylem increased significantly with increasing temperatures during the growing season. (2) From the principal component analysis, the anatomical parameters of Populus euphratica xylem were found to be positively correlated with the depth of groundwater, average air temperature, maximum air temperature, minimum air temperature, surface temperature, relative humidity, and saturated water and air pressure deficit in the two sampling sites The most significant effects were found in the air temperature and depth of the groundwater. (3) The contribution of groundwater level and air temperature to different growth stages of Populus euphratica xylem was different. During the early part of the growing season of Populus euphratica, the air temperature was the main factor influencing the number of xylem conduits and total conduit area. As the growing season entered the middle stage, the air temperature and groundwater together affected the conduit parameters. In the later part of the growing season, groundwater became the most important factor affecting the number of conduits and the total conduit area. (4) The sensitivity analyses yielded a sensitive groundwater burial depth of 5.2 m for changes in the number of conduits in the xylem of the Populus euphratica and 5.9 m for changes in the total conduit area; the sensitive air temperature for the total conduit area in the xylem of the Populus euphratica was 22.0 °C, and the sensitive air temperature for the average conduit area was 18.5 °C. The results of this study can have important theoretical significance for understanding the Populus euphratica forests, as well as ecological water resource management in the lower Tarim River. They also provide scientific basis for the restoration and protection of Populus euphratica forests in the lower Tarim River. [ABSTRACT FROM AUTHOR]

The thermal conditions of transitional (ranging from warm to cold) coldwater streams impact the ranges and resource availabilities for biota inhabiting these lotic systems. With ongoing climate change and increasing land modifications, thermal boundaries may shift, altering thermal transition zones and their biotic communities. The objective of this study was to investigate the condition of trout across three forks of the Whitewater River catchment, located in southeastern Minnesota, and to investigate factors influencing fish community composition and distribution. Each fork was characterized into three separate sections: headwater (coolwater), middle (warmwater), and lower (coldwater). Springs were identified throughout each fork, with greatest concentrations in the lower sections of each fork. Using single-pass electrofishing, we sampled 61 sites across the three forks in the Whitewater River system (North = 21 sites, Middle = 19, South = 21), and catch statistics were used to calculate diversity, trout abundance, and trout condition. In general, diversity increased, and trout were healthier but less abundant in middle and headwater sections, whereas diversity decreased slightly, trout condition decreased, and trout abundance increased in lower reaches, with changes differing somewhat among forks. Canonical correlation analysis highlighted strong significant correlations showing that Simpson diversity and trout condition increase going upstream, with high non-trout abundance, while trout catch rates decrease and width narrows. The Whitewater River is a catchment exhibiting transitional temperature-pattern characteristics with generally low fish community diversity and trout conditions that range from thin, normal, and robust. Dominated by a changing landscape (agriculture) and intensifying climate change, we may begin to see stream temperatures increase along with species diversity. Understanding how spring temperature influences species composition and distribution can bring potential stressors to light, increasing our understanding of thermal conditions and helping to mitigate the negative impacts from land use and climate change. [ABSTRACT FROM AUTHOR]

Icing in cut slopes is a serious risk to transportation safety in cold regions. Research on the occurrence process and mechanism of icing is a prerequisite for proposing effective management measures. We took the cut slopes of the K162 section of the Beihei Highway as the research object. We used a combination of field investigation, geological exploration, monitoring, and simulation to study and analyze the power source, occurrence process, and triggering mechanism of icing in cut slopes. The results show that the geologic type of this cut slope is a mudstone–sandstone interaction stratum. Abundant shallow groundwater is the source of water for icing. The excavation of cut slopes extends the effect of negative temperatures on groundwater flow during the winter period. The process of ice formation in cut slopes can be described as follows: As the environmental temperature drops, the surface soil begins to freeze, resulting in a gradual narrowing of the water channel; then, the groundwater flow is blocked, so that the internal pressure begins to rise. When the internal pressure of the pressurized groundwater exceeds the strength of the frozen soil, groundwater overflows from the sandstone layer to the surface, forming icing. The high pore water pressure inside the cut slope is the precursor for the occurrence of icing. The dynamic pressure of the pore water pressure is the main driving force for the formation of icing in cut slopes. The obstruction of the water channel due to ground freezing is the triggering condition for ice formation in cut slopes. [ABSTRACT FROM AUTHOR]

Egypt is a country that heavily relies on agricultural activities. River Nile serves as the primary source of irrigation water for agricultural purposes. El Saieda Basin project, located in the southern western desert of Egypt, represents a massive agricultural project where irrigation water is distributed from the River Nile through an extensive network of canals. This study focuses on evaluating the groundwater resources, the groundwater quality, and the hydrochemical processes affecting the groundwater within El Saieda Basin to provide an additional source of irrigation water and to ensure a safe water supply for the residential villages. Various data sets were integrated, including geomorphology, geology, hydrogeology, hydrogeochemistry and stable isotopes. Based on the geomorphology; the study area includes four geomorphological units, Structural Plateau, Bajada Plain, Eroded old Nubian surface, and Nile alluvial Plain. According to the geology; the study area is located in the southern part of the Western Desert. The dominating geological units in this part of Egypt range in age from Lower Cretaceous to Recent. Regarding the hydrogeology of the study area; the Quaternary aquifer is the main aquifer in the study area where 24 groundwater samples plus two surface water samples (irrigation canal + main Drain) were collected and analyzed. Groundwater salinity classification shows that 17% of the total groundwater samples are fresh groundwater samples with values that range between 550 and 996 mg/l with an average of 775 mg/l. 29% of the total groundwater samples are brackish groundwater samples with values that range between 1177 and 2273 mg/l with an average of 1868 mg/l. In addition, 46% of the total groundwater samples are salty groundwater samples with values that range between 3197 and 4886 mg/l with an average of 4037 mg/l. The rest of the groundwater samples (8%) are saline groundwater samples with a maximum value of 9018 mg/l and an average of 7645 mg/l. The groundwater's temperature ranges from 25 to 30.9 C. However, the measured pH values showed relatively neutral water where the values range from 6.6 to 7.6. The relationship between salinity content and the other ions indicates that sodium, calcium, magnesium, sulfate, and chloride are the effective ions that increase the salinity content. Silicate weathering and dissolution of calcite are the main hydrochemical processes affecting the groundwater. From the saturation indices (SI) results it is indicated that Gypsum and Anhydrite dissolve with negative SI values, whereas iron minerals are supersaturated with positive values. Carbonate minerals are insufficiently soluble in groundwater, with values that fluctuate positively and negatively around zero. From the hypothetical salts, it is indicated that the quaternary groundwater aquifer in the study area is highly evolved as it's enriched with terrestrial and marine residuals indicated by the presence of NaCl, MgCl2, MgSO4, CaSO4, Ca(HCO3)2 salts. From the Environmental Stable Isotopes, it is indicated that all the groundwater samples are enriched by 18O and Deuterium which indicates a recharge from the main irrigation canal and return flow irrigation water. Trace elements results indicated that the groundwater is suitable for human drinking according to the World Health Organization and also for irrigation according to the Australian guidelines for irrigation water quality. [ABSTRACT FROM AUTHOR]

The anatomical characteristics of xylem and their relationship with temperature during the year can be studied at the cellular scale by using micro-coring technology and the wood anatomy method. In this study, we used Populus euphratica Oliv. trees with different groundwater burial depths in the lower Tarim River as the research subjects. Micro-core samples of Populus euphratica were collected near two sampling sites, TY1 and TY2, which have different groundwater burial depths. We analyzed the differences in xylem anatomical characteristics and their relationship with extreme temperatures under these varying groundwater conditions using wood anatomy methods. The results showed that the anatomical parameters at TY1, with a higher groundwater table, were greater than those at TY2, which had a lower groundwater table. Specifically, the conduit density, total conduit area, average conduit area and maximum conduit area of Populus euphratica xylem were significantly and positively correlated with both maximum and minimum temperatures. The principal components of xylem parameters at TY1, with the higher water table, were significantly and positively correlated with both maximum and minimum air temperatures. In contrast, the principal components of xylem parameters at TY2, with the lower water table, were not significantly correlated with either maximum or minimum air temperatures. The sensitivity analysis indicated that the sensitive maximum air temperature for the principal component parameter index change of Populus euphratica xylem was 34.1 °C, and the sensitive minimum air temperature was 16.1 °C. Therefore, different moisture conditions affected the sensitivity of xylem parameter growth to temperature, with the temperature threshold for Populus euphratica xylem growth being between 16.1 °C and 34.1 °C. [ABSTRACT FROM AUTHOR]

Braided rivers can provide substantial recharge to regional aquifers, with flow exchange between surface water and groundwater occurring at a range of spatial and temporal scales. However, the difficulty in measuring and modelling these complex and dynamic river systems has hampered process understanding and the upscaling necessary to quantify these fluxes. This is due to an incomplete understanding of the hydrogeological structures that control river–groundwater exchange. In this paper, we present a new conceptualisation of subsurface processes in braided rivers based on observations of the main losing reaches of three braided rivers in Aotearoa / New Zealand. The conceptual model is based on a range of data, including lidar, bathymetry, coring, particle size distribution, groundwater level and temperature monitoring, radon-222, electrical-resistivity tomography and fibre-optic cables. The combined results indicate that sediments within the recently active river braidplain are distinctive, with sediments that are poorly consolidated and better sorted compared with adjacent deposits from the historical braidplain that become successively consolidated and intermixed with flood silt deposits due to overbank flow. A distinct sedimentary unconformity, combined with the presence of geomorphologically distinct lateral boundaries, suggests that a "braidplain aquifer" forms within the active river braidplain through the process of sediment mobilisation during flood events. This braidplain aquifer concept introduces a shallow storage reservoir to the river system, which is distinct from the regional aquifer system, and mediates the exchange of flow between individual river channels and the regional aquifer. The implication of the new concept is that surface water–groundwater exchange occurs at two spatial scales: the first is hyporheic and parafluvial exchange between the river and braidplain aquifer; the second is exchange between the braidplain aquifer and regional aquifer system. Exchange at both scales is influenced by the state of hydraulic connection between the respective water bodies. This conceptualisation acknowledges braided rivers as whole "river systems", consisting of channels and a gravel aquifer reservoir. This work has important implications for understanding how changes in river management (e.g. surface water extraction, bank training and gravel extraction) and morphology may impact groundwater recharge (and potentially flow, temperature attenuation and ecological resilience) under dry conditions. [ABSTRACT FROM AUTHOR]

The main objective of this research was to develop a geological and geophysical modeling to infer the geometry and thickness in the sedimentary sequence of the middle basin of the Bogotá River with emphasis on the Guadalupe Group, reconstructing the stratigraphic sequence, structural setting, hydrogeological modeling, and potential geothermal uses. Various geophysical methods were applied, including vertical electrical soundings (VES), and magneto telluric soundings (MT-VES), whose results were complemented with the interpretation of seismic lines, regional and local gravity anomaly maps, and borehole data, among others, which allowed to model the subsurface from the surface to depths beyond 3000 meters, with emphasis on the interval between 500m to 1000m depth. Integrated models were developed from interpretations of electrical resistivity data, gravity and magnetic data, reflection seismic and borehole data. Based on the results, potential deep aquifers have been proposed to be confirmed by drilling. These deep aquifers can contribute to satisfy the need for water, which historically has been explored and overexploited from shallower aquifers in this sector of the basin. A recommendation was also made to consider the potential of low enthalpy thermal energy for agro-industrial purposes associated with groundwater's temperature at the depth of this research. As a result, the modeled sedimentary sequence is characterized by a thick quaternary overburden overlying an intensively folded and faulted Neogene, Paleogene, and upper Cretaceous formations, mainly composed of siltstone, sandstones, and shale sequences of fluvial and marine environment, including facies of marine regressions and transgressions near the coastline. The penetration obtained allows establishing a high hydrogeological potential in the first 2000m depth, especially associated with the Guadalupe group, where the Labor and Tierna and Arenisca Dura formations have the highest hydrogeological potential. In addition, the preliminary estimation of thermal gradients suggest that low enthalpy geothermal energy potential is feasible to be used for the agro-industrial demand of energy of the study area. [ABSTRACT FROM AUTHOR]

The Dinaric karst in the north differs from the rest of the karst in Croatia in terms of karstification depth. The infiltrating precipitation drains in cascades from deeply karstified mountainous areas to the shallow or fluviokarst, forming the tributaries of the Kupa River. Time series analyses were conducted on a 5-year dataset to elucidate the hydrogeological conceptual model of the area and clarify disparate findings from tracer tests under varying hydrological conditions. The flow duration curve, autocorrelation functions, and recession curves were used to evaluate the spring discharge variability, the karstification degree, and the karst aquifer's size. The crosscorrelation function and temperature dynamics were employed to assess the spring's response to recharge and the hydrogeological system behavior. Comparative analysis with previous studies was conducted to contextualize the obtained results. The research outcomes delineated several key findings: (i) the deep karst zone is less developed than the shallow karst zone; (ii) groundwater exchange is significantly faster in shallow karst; (iii) groundwater divides in the Kapela Mountain are zonal; (iv) the homogenization of groundwater occurs during periods of high water levels; (v) fast water exchange transpires without concurrent groundwater temperature homogenization; and (vi) a definition of the boundary between deep and fluviokarst in Croatia. [ABSTRACT FROM AUTHOR]

The application of green energy resources is gaining increasing attention in the field of engineering. In cold areas, the groundwater circulation temperature control system (GCTCS) can serve as an auxiliary structure to the bridge deck on highways, effectively preventing the pavement surface from freezing. In this study, a finite element simulation is conducted to establish a bridge structure model of the GCTCS, incorporating both steady-state and transient conditions to investigate its anti-icing performance. Additionally, the influences of various factors, such as wind speed, asphalt concrete layer thickness, groundwater temperature, pipe water flow rate, and pipe spacing, on the temperature of the water film on the pavement surface are investigated and validated through laboratory testing. The results demonstrate that wind speed has a significant influence, with the convective heat loss reaching 90% when the wind speed reaches 10 m/s. Groundwater temperature is the second most influential factor, showing a linear relationship with the water film temperature. Excessive pipe spacing can lead to an uneven temperature distribution on the pavement surface. The thickness of the asphalt concrete layer and the flow rate have minimal effects. However, a low flow rate can result in a significant decrease in the water film temperature. Furthermore, changes in the thermal conductivity of the surface layers also contribute to the anti-icing effect. The simulation analysis of the GCTCS provides valuable guidance for practical engineering in cooler regions where groundwater resources are abundant. [ABSTRACT FROM AUTHOR]

Thermal energy is utilized as an environmentally friendly energy source for seasonal heat and cold storage on a global scale. Specifically, the aquifer thermal energy storage system is highlighted for being cost-effective in cooling and heating applications. The study assesses the sustainability of the aquifer thermal energy storage in the Halabja-Khurmal sub-basin by evaluating six critical criteria: groundwater transmissivity, groundwater temperature, groundwater discharge, groundwater chemistry, population density, and per capita GDP. A multi-criteria decision analysis judgment is applied to analyze all criteria, resulting in a consistency ratio of 0.3% in the analytical hierarchy process. Consequently, the sustainability map for Aquifer Thermal Energy Storage in the Halabja-Khurmal sub-basin for heating reveals that 26.45% of the area is strongly sustainable located in the north and southwestern part of the sub-basin, 73.53% is moderate in the east, central, southeast, and southern regions, 0.02% is weakly sustainable as a tiny area in the southwestern. On the other hand, the sustainability map for Aquifer Thermal Energy Storage in the Halabja-Khurmal sub-basin for cooling reveals that 19% of the area is strongly sustainable located in the north, and southwestern parts of the sub-basin, 78% is moderate in the northeast, east, southeast, west, central, and southern regions, 3% is weakly sustainable as spots in the west and southwestern areas. [ABSTRACT FROM AUTHOR]

Investigating the repercussions of climate change and irrigation timing on groundwater contamination necessitates thorough examination of the fluctuations in seawater and groundwater recharge temperature. This study introduces an innovative numerical approach to analyze groundwater salinity and temperature dynamics across three distinct scenarios using the SEAWAT code based on Henry's problem. The first scenario delves into the impact of seawater temperature, the second focuses on the consequences of aquifer freshwater recharge temperature, and the third amalgamates the effects of both scenarios. Remarkably, the study reveals that saltwater intrusion (SWI) experiences a decline attributable to the aquifer's heightened seawater temperature and the diminished inland freshwater temperature. Furthermore, combining these two scenarios has a more pronounced effect on aquifer pollution; the temperature-induced changes in SWI for this third scanrio reach + 8.10%, + 12.70%, + 16.20%, + 24.90%, + 28.30%, and + 31.80% compared to the case without considering the temperature effect. Notably, our results propose a potential strategy to mitigate SWI by introducing cold freshwater recharge into aquifers, such as irrigation at night time when water temperature is low. This innovative approach underscores the interconnectedness of various environmental factors. It provides a practical avenue for proactive intervention in safeguarding groundwater quality against the adverse impacts of climate change and irrigation practices. [ABSTRACT FROM AUTHOR]

Abstract Thermal energy is utilized as an environmentally friendly energy source for seasonal heat and cold storage on a global scale. Specifically, the aquifer thermal energy storage system is highlighted for being cost-effective in cooling and heating applications. The study assesses the sustainability of the aquifer thermal energy storage in the Halabja-Khurmal sub-basin by evaluating six critical criteria: groundwater transmissivity, groundwater temperature, groundwater discharge, groundwater chemistry, population density, and per capita GDP. A multi-criteria decision analysis judgment is applied to analyze all criteria, resulting in a consistency ratio of 0.3% in the analytical hierarchy process. Consequently, the sustainability map for Aquifer Thermal Energy Storage in the Halabja-Khurmal sub-basin for heating reveals that 26.45% of the area is strongly sustainable located in the north and southwestern part of the sub-basin, 73.53% is moderate in the east, central, southeast, and southern regions, 0.02% is weakly sustainable as a tiny area in the southwestern. On the other hand, the sustainability map for Aquifer Thermal Energy Storage in the Halabja-Khurmal sub-basin for cooling reveals that 19% of the area is strongly sustainable located in the north, and southwestern parts of the sub-basin, 78% is moderate in the northeast, east, southeast, west, central, and southern regions, 3% is weakly sustainable as spots in the west and southwestern areas.

Hydrothermal geothermal energy, as a widely distributed, large reserve and easily exploitable renewable source, can be used for both power generation and building heating. In this study, a numerical simulation of heat extraction performance is conducted based on monitoring well temperature data in a geothermal field in Xiong'an New Area. The effects of the reinjection temperature, injection flow rate, and reinjection rate on the outlet temperature and the reservoir temperature during a long-term operation are analyzed. The results indicate that the lower reinjection temperature can generate a critical disturbance scope for the thermal reservoir during the exploitation process. The impact scope on the thermal reservoir can reach 210.3 m at a reinjection temperature of 25 °C, which is not conducive to maintaining the outlet temperature of production wells in the long-term. The reinjection rate significantly affects both the horizontal and vertical temperature fields of the thermal reservoir. Under reinjection conditions of 30 °C and 40 kg/s, the horizontal and vertical impact scope of the thermal reservoir are 262.3 and 588.5 m, respectively. The reinjection rate is inversely related to the outlet temperature. A decrease from 100% to 70% in the reinjection rate can increase the outlet temperature by 4.21%. However, a decrease in the reinjection rate will lead to a decline in the groundwater level. Therefore, balancing the variation in outlet temperature and groundwater level is crucial in practical engineering. [ABSTRACT FROM AUTHOR]

Alluvial aquifers often exhibit highly conductive embedded formations that can act as preferential pathways for the transport of solutes. In this context, a detailed subsurface characterization becomes crucial for an effective monitoring of groundwater quality and early detection of contaminants. However, small-scale heterogeneities are seldom detected by traditional nondestructive investigations. Heat propagation in porous media can be a relatively inexpensive tracer for groundwater flow, potentially offering valuable information in various applications. In this study, we applied passive Fiber Optics Distributed Temperature Sensing (FO-DTS) to a group of observation wells in a highly heterogeneous phreatic aquifer to uncover structures with different hydraulic conductivity, relying on their response to temperature fluctuations triggered by natural and anthropogenic forcings. A comprehensive data analysis approach, combining statistical methods and physics-based numerical modeling, allowed for a three-dimensional characterization of the subsurface at the experimental site with unprecedentedly high resolution. [ABSTRACT FROM AUTHOR]

Accretionary prisms are composed mainly of ancient marine sediment scraped from the subducting oceanic plate at convergent plate boundaries. Anoxic groundwater is stored in deep aquifers associated with accretionary prisms and can be collected via deep wells. We investigated how such groundwater pumping affects the microbial community in a deep aquifer. Groundwater samples were collected from a deep well drilled down to 1500 m every six months (five times in total) after completion of deep well construction and the start of groundwater pumping. Next-generation sequencing and clone-library analyses of 16S rRNA genes were used to describe the subterranean microbial communities in the samples. The archaea: the prokaryote ratio in groundwater increased significantly from 1 to 7% (0 and 7 months after initiating groundwater pumping) to 59 to 72% (13, 19, and 26 months after initiating groundwater pumping), and dominant prokaryotes changed from fermentative bacteria to sulfate-reducing archaea. The optimal growth temperature of the sulfate-reducing archaea, estimated based on the guanine-plus-cytosine contents of their 16S rRNA genes, was 48–52 °C, which agreed well with the groundwater temperature at the deep-well outflow. Our results indicated that, in deep aquifers, groundwater pumping enhances groundwater flow, and the supply of sulfate-containing seawater activates the metabolism of thermophilic sulfate-reducing archaea. [ABSTRACT FROM AUTHOR]

Dendritic stream networks are an intriguing subject for exploring the spatial and temporal variability of the rare and common bacterial biosphere, yet very few such studies have been conducted. We sampled riverine bacterioplankton at 13 sites in a subarctic riverine network across 3 years, with five sampling times each year. Ordinations showed a consistent pattern of downstream shift for both rare and abundant subcommunities. We also detected a temporal signal, with seasonal community shifts reflecting changes in water temperature and groundwater contribution, and an inter‐annual pattern where the year 2018 differed from other years. Phylogenetic turnover of the rare subcommunity indicated homogeneous selection, whereas the abundant subcommunity was mainly stochastically structured. Transiently rare taxa were the dominant type of rarity with the highest proportion at the headwater regions. The bacterioplankton community was characterized by a small group of core taxa that occurred at most sites with little temporal variation, a very large number of permanently or transiently rare taxa, and taxa shifting through time between the rare and abundant biosphere. While this basic structure could have been detected with less extensive temporal replication, a comprehensive understanding of the rare biosphere in riverine bacterioplankton can only be achieved via inter‐annual, spatially replicated sampling that covers the whole stream network. [ABSTRACT FROM AUTHOR]

As our planet faces the complex challenges of global climate change, understanding and effectively communicating critical environmental indicators have become critical. This study explores the importance of reporting groundwater temperature data as a key component in understanding the broader implications of climate change with the use of new graphical tools. More specifically, the use of the groundwater temperature (GWT) stripes and bi-plots of GWT anomalies vs. time was proposed. For an in-depth examination of this subject, monitoring wells situated in the Piedmont Po plain (NW Italy) were selected, with available daily groundwater temperature data dating back to 2010. All data refer to the groundwater of the shallow unconfined aquifer within alluvial deposits. From the analyses of both GWT stripes and the bi-plot of GWT anomalies vs. time, it was possible to identify a general increase in the positive anomaly, corresponding to an increase in GWT in time in almost all of the monitoring points of the Piedmont plain. Furthermore, the utilisation of GWT stripes demonstrated the capability to effectively portray the trend of the GWT data relative to a specific point in a readily understandable manner, facilitating easy interpretation, especially when communicating to a non-scientific audience. The findings underline the urgent need to improve GWT data search and communication strategies to disseminate valuable information to policy makers, researchers, and society. By illustrating the intricate interplay between groundwater temperature and climate change, this research aims to facilitate informed decision-making and promote a proactive approach towards climate resilience. [ABSTRACT FROM AUTHOR]

The alluvial aquifer of wadi Biskra is located just upstream of Biskra city (city of the Algerian Sahara). This aquifer has an area of 5km² and an average thickness of 20m; the volume of alluvium deduced from geophysics being 100 hm³. The porosity calculations carried out using the curves of the groundwater piezometers yielded an average value of  = 30% for an alluvium volume of 100 hm³ and a stored volume of exploitable water of approximately 30 million m³ Currently 14 boreholes with an average depth of 40m capture water from this aquifer and the exploited flow rates are in total of 1409 m³/h. The flood's surface water of the wadi (four to five floods per year) and the low rainfall average (125 mm/year) cannot explain the non-drying up of the alluvial aquifer. The use of several approaches; hydrogeological (by hour-by-hour monitoring of the variation in the piezometric level), hydrochemical (analysis of groundwater and hour-byhour monitoring of the variation in groundwater and air temperature), hydrological (study of the variation relationship piezometric levels depending on precipitation in the watershed) and structural (analysis of fracturing) highlighted the existence of a third source of supply; this is deep mesothermal water which rises towards the water table and brings to the aquifer a quantity greater than that supplied by flood waters. The presence of this water source explains why the water table does not dry up during the long dry summers and periods of drought. [ABSTRACT FROM AUTHOR]

This article introduces a special issue of the Hydrogeology Journal that focuses on the hydrogeology of arid environments. Arid regions, which cover a significant portion of the Earth's land surface, face challenges in accessing freshwater due to limited surface-water resources. As a result, groundwater resources play a crucial role in providing freshwater in these areas. However, overexploitation of groundwater reserves in many arid countries has become a concern, impacting health, food security, and political stability. The article emphasizes the importance of sustainable groundwater management and the need for accurate data and research to make informed decisions. The special issue includes various articles that explore topics such as groundwater extraction in Jordan, hydraulic properties of volcanic rocks in Ethiopia, groundwater recharge mechanisms in Nigeria, and shared groundwater resources in the Sahel region. The research presented in this special issue contributes to a better understanding of the hydrogeology of arid environments and can inform strategies for managing groundwater resources in these regions. [Extracted from the article]

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The hydrochemical and microelement composition of water and bottom sediments has been determined in the Kuchiger thermal spring (Baikal rift zone). The entry of chemicals with groundwater and high temperatures create favorable and specific conditions for the development of microorganisms. The taxonomic diversity of the microbial community of water and bottom sediments is studied using the analysis of 16S rRNA gene aplicons, and 107 619 nucleotide sequences assigned to 211 operational taxonomic units (OTUs) are analyzed. In the studied samples of water and bottom sediments, bacteria dominate; representatives of archaea account for 0.2–3.1%. The phylum Proteobacteria dominate in microbial communities. The subdominants in the studied samples were the phyla Firmicutes, Chloroflexi, Nitrospirae, Acetothermia, and Actinobacteria, where their ratio vary depending on the biotope. One characteristic feature of the microbial community in the Kuchiger thermal spring is the dominance of chemolithotrophic bacteria. [ABSTRACT FROM AUTHOR]

This study presents a 25 ka reconstruction of the Pleistocene paleoclimate in the South German Molasse Basin. Deep groundwater was sampled at 19 wells in the Upper Jurassic aquifer (UJA). Calculating gas temperatures (NGT) using the UA model with the noble gases Ar, Kr, and Xe led to groundwater recharge temperatures between 0.4 and 4.7°C. Combined with innovative 14CDOC groundwater dating, calculated NGTs revealed up to 8°C cooler soil temperatures during the Pleistocene compared with modern soil temperature. This interpretation agrees well with the observed depleted stable water isotope signature ranging from −83.3 to −86.1 for δ2H and from −10.66 to −11.77 for δ18O, which is characteristic of groundwater of Pleistocene origin in Southern Germany. The temperature differences (∆T) agree remarkably well with calculated NGTs within other European basins (∆T 6–9.5°C) and suggest widespread pronounced terrestrial cooling during the Last Glacial Maximum through the interior of the European continent. Plain Language Summary: To characterize the climate in Southern Germany during the last ice age, we first determined 14CDOC for dating the deep groundwater of the Upper Jurassic aquifer. Subsequently, we looked closer at noble gases and stable water isotopes. The contents in groundwater are mainly controlled by temperature when the groundwater is in contact with the atmosphere during the formation on the earth's surface. Our results show that the calculated noble gas temperatures during this time were up to 8°C colder than modern temperatures. Our findings help to gain a better understanding of Earth's climatic history. Key Points: The noble gas temperatures from deep groundwater in Southern Germany show substantial cooling up to 8°C during the PleistoceneNoble gas temperatures in combination with groundwater dating using the 14CDOC method are helpful for reconstructing the paleoclimateThe deep groundwater in the Upper Jurassic aquifer may be a mixture of meteoric water and Pleistocene glacial meltwater [ABSTRACT FROM AUTHOR]

Rural communities in Mexico and other countries with limited economic resources require a low-cost measurement system for the piezometric level and temperature of groundwater for their sustainable management, since anthropogenic action (pumping extractions), natural recharge and climate change phenomena affect the behavior of piezometric levels in the aquifer and its sustainability is at risk. Decrease in the piezometric level under a balanced level promotes salt intrusion from ocean water to the aquifer, salinizing and deteriorating the water quality for agriculture and other activities; and a decrease in water level under the pumps or well drilling depth could deprive communities of water. Water temperature monitoring is essential to determine electric conductivity and dissolved salt content in groundwater. Using IoT technology, a device was developed that monitors both variables inside the well, and the ambient temperature and atmospheric pressure outside the well. The measurements are made in real time, with sampling every second and sending data to a dedicated server every 15 min so that the visualization can be accessed through a device with Internet access. The time series of the variables measured inside and outside the well were obtained over a period of three months in the rural community of Agua Blanca, Guasave, Sinaloa, Mexico. Through these records, a progressive temporary drawdown of the piezometric level is observed, as well as the frequency of pumping. This low-cost IoT system shows potential use in hydrological processes of interest such as the separation of regional and local flow, drawdown rates and recognition of geohydrological parameters. [ABSTRACT FROM AUTHOR]

Copyright of Grundwasser is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The distribution of groundwater temperature and flow can be used to describe the hydrogeological process in a geothermal system, which is of great significance to the exploitation of geothermal resources. The traditional gravity-driven groundwater system theory takes less consideration of thermal convection, resulting in a deviation in the investigation of geothermal systems. The rise of water table and the acceleration of the flow of geothermal water in the discharge section suggest the existence of geothermal buoyancy. The changes in temperature, salinity and viscosity comprise the physical basis for the formation of geothermal buoyancy. Geothermal buoyancy due to free heat convection in a fault-controlled discharge section is discussed in the Xinzhou geothermal field, South China. The geothermal buoyancy is the additional pressure head created by the increase in temperature, increase in salinity and decrease in viscosity. At the convection point, geothermal buoyancy appears and forms a maximum of + 417.6 m. Geothermal buoyancy gradually decreases in the discharge section due to temperature domination. The salinity effect and viscosity effect on geothermal buoyancy are minor and negligible, respectively. Comparing the vertical velocity of geothermal water in the discharge section (32.47 × 10−3 m/d) and the average vertical circulation velocity (3.15 × 10−3 m/d), the geothermal buoyancy has an obvious acceleration effect on groundwater flow in the discharge section. The geothermal buoyancy at typical points provides the framework and control points for geothermal water flow in the discharge section of a geothermal system. [ABSTRACT FROM AUTHOR]

The groundwater temperature is an important indicator of groundwater dynamic change. Therefore, comprehensively monitoring groundwater temperature, understanding its temporal and spatial distribution characteristics, and studying its change rule can not only reflect the hydrogeological characteristics of groundwater system, but also provide a basis for its identification and division. With an elevation of 3,500 m--2,400 m, the Heilongtan groundwater system of Lijiang, Yunnan Province is a typical mountain and basin landform with wide distribution of soluble rocks, strong development of karst, and combination of faults and folds. Its hydrogeological environment is complex, challenging the delimitation of spring area and groundwater system. Because the study area is located in the plateau mountainous area, and the temperature field of karst groundwater can also reflect the variation of groundwater temperature at different elevations in the mountain and canyon areas on the plateau, this study has a great referential significance for the research of groundwater in other similar areas. Based on previous research results as well as a large number of monitoring data on groundwater temperature obtained in the study area from June to November, 2018, the spatial-temporal variation characteristics of groundwater temperature in the spring area and the variation characteristics of borehole water temperature were compared and analyzed, and the indicative significance of these two types of variation characteristics were discussed. Meanwhile, the feasibility of system division of the Heilongtan spring area was verified. The results show that there is a good spatial correlation between the elevation of groundwater level and temperature, and the groundwater temperature in the recharge area at high altitude is low. From the recharge area to the discharge area, the water temperature experiences a gradual upward trend. The water temperature in the discharge area can also indicate the circulation of groundwater runoff. The lower the water temperature in the discharge area is, the smoother groundwater becomes. In terms of time, as groundwater receives a large amount of rainfall recharge during the flood season, the circulation of groundwater flow increases, which may result in a short storage time of water and the phenomenon that the groundwater temperature in the discharge area is closer to that in the recharge area and that the overall water temperature decreases. At the end of the flood season, as rainfall decreases, the circulation of groundwater flow weakens, and the underground water temperature in the discharge area rises in different degrees. In a certain depth below the surface, the groundwater temperature does not completely conform to the theoretical law that the temperature rises gradually with the increase of depth, On the contrary, the groundwater temperature will remain unchanged or decrease gradually with the increase of depth, the reasons of which can be summarized as follows. (1) The temperature of surface water formed by precipitation is higher than that of groundwater, and the groundwater will be heated during infiltration and recharge. (2) When a deep karst pipeline is developed, the groundwater will "wash" away the heat from the deep, and the groundwater temperature will decrease with the increase of depth. (3) If the vertical movement of groundwater is intense, with large up-and-down disturbances and good temperature exchange conditions, the temperature value will become relatively stable in this active zone. This phenomenon is found in all monitoring points in the discharge area, especially in the period of smooth groundwater flow. (4) Under the influence of solar radiation energy, the surface temperature shows diurnal and seasonal variations. The diurnal variation affects 1--2 m below the surface, and the seasonal variation affects 30 m below the surface. This study shows that there are similarities and differences in the groundwater temperature in the study area, and the groundwater temperature is a good indication for the delimitation of groundwater system. This study also verifies the rationality of the existing delimitation system in the study area. [ABSTRACT FROM AUTHOR]

The impacts of climate change-induced warming on our ecosystems can no longer be neglected, but our understanding of consequences for groundwater ecosystems in general and groundwater quality in particular is alarmingly incomplete. In this review, we therefore provide an overview of the current state of knowledge related to the impact of global warming on our precious groundwater resources. Groundwater warming in shallow aquifers is closely associated with increasing average land surface temperatures and has already reached + 1 K compared to pe-industrial times. Until the end of the twenty-first century, temperature increases in local groundwater of up to + 10 K are possible. Monitoring data, laboratory and field experiments all provide evidence that such temperature increases are sufficient to substantially modify groundwater quality through numerous and interlinked biogeochemical processes, which we have summarized in a conceptual overview. Warming impacts on groundwater are highly site-specific and spatially heterogeneous, which complicates their assessment and prediction. Locally, shallow unconfined and nutrient-rich floodplain aquifers are most susceptible to warming-induced changes. Importantly, processes affecting water quality are not only modified by a long-term rise in groundwater temperatures, but also in the short-term during weather extremes, which is of great relevance for riverbank filtration. At the regional scale, aquifers in cold regions impacted by permafrost thawing are especially vulnerable to warming. As the majority of temperature-sensitive processes affecting groundwater quality are not or only very slowly reversable, we pressingly require comprehensive mechanistic understanding before it is too late to develop suitable countermeasures and management strategies. [ABSTRACT FROM AUTHOR]

Although groundwater discharge is a critical stream temperature control process, it is not explicitly represented in many stream temperature models, an omission that may reduce predictive accuracy, hinder management of aquatic habitat, and decrease user confidence. We assessed the performance of a previously‐described process‐guided deep learning model of stream temperature in the Delaware River Basin (USA). We found lower accuracy (root mean square error [RMSE] of 1.71 versus 1.35°C) and stronger seasonal bias (absolute mean monthly bias of 1.06 vs. 0.68°C) for reaches primarily influenced by deep groundwater as compared to atmospheric conditions. We then tested four approaches for improving groundwater process representation: (a) a custom loss function leveraging the unique patterns of air and water temperature coupling characteristic of different temperature drivers, (b) inclusion of additional groundwater‐relevant catchment attributes, (c) incorporation of additional process model outputs, and (d) a composite model. The custom loss function and the additional attributes significantly improved the predictive accuracy in groundwater‐dominated reaches (RMSE of 1.37 and 1.26°C) and reduced the seasonal bias (absolute mean monthly bias of 0.44 and 0.48°C), but neither approach could identify holdout groundwater reaches. Variable importance analysis indicates the custom loss function nudges the model to use the existing inputs more efficiently, whereas with the added features the model relies on a broader suite of inputs. This analysis is a substantial step toward more accurately representing groundwater discharge processes in stream temperature models and will improve predictive accuracy and inform habitat management. Plain Language Summary: Groundwater flowing into streams and rivers can cool the water during the summer and warm it during the winter. This creates important habitat for animals like trout and dwarf wedgemussels. Resource managers use computer models of stream temperature, but most models do not simulate groundwater flows with much detail. Insufficient accounting for groundwater could lead to predicted temperatures that are less accurate or less trusted. We tested four ways of including groundwater in a stream temperature model. The particular model we used is a type of machine learning model termed "process‐guided deep learning" because it takes advantage of both the computational advances in machine learning and our collective understanding of the science of stream temperature. We found that two approaches, one that focused on patterns between the air temperature and water temperature and one that incorporated additional descriptions of each stream reach, significantly improved the temperature predictions. Our findings have important implications for stream temperature predictions, habitat management, and methods for incorporating scientific expertise into machine learning models. Key Points: Existing process‐guided deep learning stream temperature models perform poorly in reaches with groundwater‐controlled temperaturesA custom loss function or enhanced input data improved predictive performance in monitored but not hold‐out groundwater reachesThe loss function used existing input data more efficiently; the enhanced inputs model spread its reliance to a wider range of inputs [ABSTRACT FROM AUTHOR]

Although deep learning models for stream temperature (Ts) have recently shown exceptional accuracy, they have limited interpretability and cannot output untrained variables. With hybrid differentiable models, neural networks (NNs) can be connected to physically based equations (called structural priors) to output intermediate variables such as water source fractions (specifying what portion of water is groundwater, subsurface, and surface flow). However, it is unclear if such outputs are physically meaningful when only limited physics is imposed, and if structural priors have enough impacts to be identifiable from data. Here, we tested four alternative structural priors describing basin‐scale water temperature memory and instream heat processes in a differentiable stream temperature model where NNs freely estimate the water source fractions. We evaluated models' abilities to predict Ts and baseflow ratio. The four priors exhibited noticeably different behaviors in these two metrics and their tradeoffs, with some dominating others. Therefore, the better structural priors can be identified. Moreover, testing different priors yielded valuable insights: having a separate shallow subsurface flow component better matches observations, and a recency‐weighted averaging of past air temperature for calculating source water temperature resulted in better Ts and baseflow prediction than traditionally employed simple averaging. However, we also highlight the limitations when insufficient physical constraints are implemented: the internal variables (water source fractions) may not be adequately constrained by a single target variable (stream temperature) alone. To ensure the physical significance of the internal fluxes, one can either employ multivariate data for model selection, or include more physical processes in the priors. Plain Language Summary: A new framework called differentiable modeling combines the benefits from neural networks (NNs) and process‐based models. This framework can learn from big data while the process‐based model components (called prior knowledge, or priors) are intended to output intermediate physical variables. However, do such priors matter, can we tell if one set of priors is better than another, and do the intermediate outputs represent the intended physical concepts? We explore these questions with a differentiable stream temperature model where the NN replaces the hydrologic component and estimates parameters pertaining to the stream temperature module. The strong optimizing capability of NNs allows us to avoid some complexities and attribute the differences in model outcomes to the assumed priors. Testing different priors thus yielded many important lessons, for example, the need for having a separate shallow groundwater "bucket," the benefit of placing more importance on recent air temperature when estimating groundwater temperature, and the importance of describing in‐stream temperature. The results show lots of untapped potential with differentiable modeling and the data we have available. Key Points: We can identify better structural priors (process equations) using differentiable models, circumventing intertwined parameter issuesConsidering a separate bucket for shallow subsurface water improves both stream temperature and baseflow simulationThe models selected by the multivariate evaluation produce physically meaningful estimates of water source fractions [ABSTRACT FROM AUTHOR]

Groundwater (GW) is sensitive to climate change (CC), and the effects have become progressively more evident in recent years. Many studies have examined the effects of CC on GW quantity. Still, there is growing interest in assessing the qualitative impacts of CC, especially on GW temperature (GWT), and the consequences of these impacts.This study aimed to systematically review recently published papers on CC and GWT, determine the impacts of CC on GWT, and highlight the possible consequences.The Scopus and Web of Science databases were consulted, from which 144 papers were obtained. After an initial screening for duplicate papers, a second screening based on the titles and abstracts, and following an analysis of topic applicability to this subject after examining the full text, 44 studies were included in this review. The analysed scientific literature, published in 29 different journals, covered all five continents from 1995 to 2023.This review indicated that the subject of GWT variations due to CC is of global interest and has attracted significant attention, especially over the past two decades, with many studies adopting a multidisciplinary approach. A general increase in GWT was noted as a primary effect of CC (especially in urban areas); furthermore, the implications of this temperature increase for contaminants and GW-dependent ecosystems were analysed, and various applications for this increase (e.g. geothermal) were evaluated.This review highlights that GWT is vulnerable to CC and that the consequences can be serious and worthy of further investigation.

The relationship between the soil surface temperature and groundwater level is complex and influenced by various factors. As the soil surface temperature increases, water evaporates quickly from the soil, which can lead to a decrease in the groundwater level. In this study, we analyzed the impact of soil surface temperature on changes in the groundwater level in the Bukhara region of Uzbekistan using data from 1991 to 2020. The Bukhara region experiences regular water shortages, increased soil salinization, and inefficient energy in lift-irrigated areas, which is a typical constellation of challenges to the water–energy–food–environment (WEFE) nexus. The soil surface temperature data were collected from the Hydrometeorological Service Agency, whereas groundwater level data were obtained from the database of the Amelioration Expedition under the Amu-Bukhara Basin Irrigation Systems Authority. We used linear regression analysis and Analysis of Variance (ANOVA) tests to establish the significance of the relationship between the soil surface temperature and groundwater level, as well as the impact of the location of the groundwater level measurements. The results indicate that the model was a good fit to the data, and both the intercept and the soil surface temperature were significant factors that affected groundwater level. The results further suggest that the strength of the relationship between solar radiation and soil surface temperature is very high, with a correlation coefficient of 0.840. This means that when solar radiation increases, soil surface temperature also tends to increase. The analysis also showed that 53.5% of the changes in groundwater level were observed by the regression model, indicating a moderately correlated relationship between the groundwater level and soil surface temperature. Finally, higher solar radiation leads to higher soil surface temperature and higher evapotranspiration rates, which can lead to a decrease in groundwater level. As a result, we observe that the soil surface temperature determines changes in the groundwater level in the study region. [ABSTRACT FROM AUTHOR]

Seasonal variation causes regular fluctuations in river water levels and water temperatures, which affects the distribution of temperature fields and seepage fields in riparian zones. In this paper, the monitoring device was used to continuously monitor Dongting Lake for a period of 1 year, and the temperature distribution characteristics of the riparian hyporheic zone under seasonal variation were analysed. Ten riparian hydrothermal coupling models based on different soil thermal conductivity models were verified, and the optimal model was used to simulate the influence of the flood process on the temperature field and seepage field of the riparian hyporheic zone. The results show that the changes in groundwater level and temperature in the riparian hyporheic zone had obvious lag and attenuation phenomena compared with the changes in river water level and ambient temperature. The temperature field of the riparian hyporheic zone changed obviously in the year. The vertical temperature gradient was large in summer and winter, the stratification phenomenon was obvious, and the temperature field fluctuation was small. The effect of the flood process on the temperature field and seepage velocity in the riparian hyporheic zone was obviously hysteretic. The effect of the flood‐withdrawing process on the temperature change of the shallow layer was greater than that of the flood‐rising process, while the response of the deep layer temperature change to flood‐rising and flood‐withdrawing processes was the opposite. The effect of floods on the variation in groundwater velocity was that the flood‐rising process was greater than the flood‐withdrawing process. [ABSTRACT FROM AUTHOR]

The Gulf of Maine hosts the southernmost remaining population of North American Atlantic salmon. Despite extensive hatchery supplementation since the late 1800s, and more recent riverine habitat restoration efforts and fishing restrictions, US-origin Atlantic salmon populations continue to decline and have remained at low abundance over recent decades. Climate change has been identified as a critical threat to the future of US Atlantic salmon. In this study, we synthesized available information on how habitats used by Atlantic salmon across all their life stages will be affected by climate change as well as the suitability of future conditions for salmon's persistence in the region. Maintaining sufficient cool water refugia during increasing summer temperatures in riverine habitats is required for sustaining salmon in the future. Changes in groundwater quantity and temperature, which will depend on future precipitation and temperature, will be critical factors for river temperatures, as will land use and land cover. While Atlantic salmon's freshwater life stages are heavily documented, the marine phase is relatively less studied. Climate models predict basin-scale changes over the next century, but impacts to salmon are difficult to predict. Furthermore, disparate drivers and differential rates of change between freshwater and marine habitats could present an obstacle to the transition between phases in the future. We have a general understanding of migration patterns and prey preferences but lack a clear picture of how salmon respond to habitat and ecosystem-level changes associated with climate change progression. More research to understand freshwater habitat changes and salmon's marine spatiotemporal distribution responses will enhance capacities to evaluate future risks and predict impacts of climate change to US-origin Atlantic salmon. [ABSTRACT FROM AUTHOR]

Groundwater temperature is one of the main factors that is considered when deciding on installation of a vapor compression refrigeration system with groundwater used for heat transfer. Groundwater temperature measurement is a necessity for the system installation. A total of 75 groundwater wells within the Chiang Mai Basin were selected for temperature monitoring stations. The temperature-depth profile of shallow groundwater showed that temperature had little change below 2 m depth from the water table. The temperature-depth profile of deep groundwater showed the separation of upper and lower temperature zones. Mostly, the temperature of the upper zone of deep groundwater has a positive slope. The temperature of the lower zone of deep groundwater is relatively constant. Both the shallow and deep groundwater temperatures are below the atmospheric temperature. The seasons, hydrogeologic units, and land use types have affected groundwater temperature of the Chiang Mai Basin only little. [ABSTRACT FROM AUTHOR]

A high concentration of fluoride (F−) in drinking water is harmful and is a serious concern worldwide due to its toxicity and accumulation in the human body. There are various sources of fluoride (F−) and divergent pathways to enter into groundwater sources. High F− incidence in groundwater was reported in Raigarh district of Central India in a sedimentary (Gondwana) aquifer system. The present study investigates the hydrogeochemistry of groundwater in the Tamnar area of Raigarh district to understand the plausible cause(s) of high F− concentration, especially the source(s) and underlying geochemical processes. Groundwater samples, representing pre-monsoon (N = 83), monsoon (N = 20), and post-monsoon (N = 81) seasons, and rock samples (N = 4) were collected and analyzed. The study revealed that (i) groundwater with high F− concentration occurs in the Barakar Formation, which has a litho-assemblage of feldspathic sandstones, shales, and coal, (ii) high F− concentration is mainly associated with Na-Ca-HCO3, Na-Ca-Mg-HCO3, and Na-Mg-Ca-HCO3 types of groundwater, (iii) the F− concentration increases as the ratio of Na+ and Ca2+ increases (Na+: Ca2+, concentration in meq/l), (iv) F− has significant positive correlation with Na+ and SiO2, and significant negative correlation with Ca2+, Mg2+, HCO3−, and TH, and (v) high F− concentration in groundwater is found in deeper wells. Micas and clay minerals, occurring in the feldspathic sandstones and intercalated shale/clay/coal beds, possibly form an additional source for releasing F− in groundwater. Feldspar dissolution coupled with anion (OH− or F−) and cation (Ca2+ for Na+) exchange are probably the dominant geochemical processes taking place in the study area. The higher residence time and temperature of groundwater in deeper aquifers also play a role in enhancing the dissolution of fluorine-bearing minerals. Systematic hydrogeochemical investigations are recommended in the surrounding area having a similar geologic setting in view of the potential health risk to a large population. [ABSTRACT FROM AUTHOR]