In cases where the excavation depth reaches the groundwater level as a result of open-pit surface mining operations, open mine pit lakes (MPL) form by the discharge of groundwater to the surface. Processes known to affect the MPL chemistry include groundwater inflow, direct precipitation, pit wall-precipitation contact, groundwater-wall rock interaction, evaporation, and other geochemical and limnological processes taking place within the MPL. While changing the hydrogeological system, mining activities might also affect the groundwater chemistry. Degradation of groundwater quality might occur as a result of the interaction between wall-rock and groundwater within the MPL. For this reason, the chemical characteristics of these mine lakes should be revealed in order to protect the groundwater systems and also before using the water inside MPL’s for different purposes like irrigation. Kesikköprü Dam is a dam located in Bala district of Ankara province, the capital of Türkiye, and has been providing drinking water to Ankara in recent years. Although mining activities have been carried out around this dam since the 1950s, where one of Turkey's richest iron deposits is located, no hydrogeological or hydrogeochemical studies have been carried out prior to this study. Therefore, the aim of this study is to evaluate the hydrogeochemical and stable isotopic characteristics of the mine lakes formed as a result of iron mining activities around Kesikköprü Dam. Within this study, three MPL’s were evaluated whose surface areas range from 0.27 ha to 0.92 ha. The pH and Electrical Conductivity values of these three lakes vary between 8.47-8.58 and 883-2500 µS/cm, respectively. According to the major ion chemistry analyses results, Na, Ca and Mg are the dominant major cations and SO₄ and HCO₃ are the dominant major anions. The major ion chemistry of these lakes have been influenced by reverse ion exchange processes. The MPL waters are oversaturated with respect to certain minerals like dolomite, aragonite, calcite and magnesite. There is dissolved arsenic in concentrations up to 16 µg/l. Dissolved arsenic is found in the form of pentavalent arsenic (As⁵⁺). The stable isotopes of hydrogen and oxygen suggest that there is evaporation from the lake surfaces and the isotopic signatures of MPL water samples prior to evaporation unveiled that there is contribution of groundwater inflow from a shallow groundwater system in the area. The abandoned MPLS’s should be rehabilitated so as to prevent exposure of the groundwater systems which become vulnerable to contaminatation.

Keywords: Open Mine Pit Lakes; Hydrogeochemistry; Stable Isotopes; Dissolved arsenic; Kesikköprü Dam, Ankara; Türkiye

How to cite: Arslan, Ş. and Yurttaş, O.: Hydrogeochemical And Isotopic Assesment of The Open Mine Pit Lakes Near Kesikköprü Dam Area, Türkiye, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-476, https://doi.org/10.5194/egusphere-egu24-476, 2024.

The groundwater contained in the basement formations of sub-Saharan countries is the main source of drinking water for the population in rural and semi-rural areas. Captured by boreholes and wells, it is used for domestic purposes, irrigation, and other socio-economic activities. Given the increased pressure on the resource due to population growth and urbanization, assessing its origin, availability, and quality for sustainable management is imperative. This study was carried out in the Kara River Watershed (KRW) in northern Togo. The study aimed at determining the recharge and mineralization processes of the groundwater in the watershed using conventional graphs, multivariate statistical analyses, and geochemical modelling. Physico-chemical (pH, temperature, and TDS), chemical (Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃^-, SO₄^2-, Cl^-, NO₃^- and SiO₂), and isotopic (δ²H and δ¹⁸O) analyses were carried out on 149 groundwater samples (boreholes and wells). The results showed that the isotopic composition of the groundwater suggests recharge of meteoric origin, often influenced by secondary evaporation and important mixing processes. From a hydrochemical point of view, the groundwater is generally low mineralized with TDS ˂ 1000 mg/L. These waters' main mineralization processes are water/rock interactions and human activities influence. The heterogeneity of the geological formations is responsible for the spatial variability of the water chemistry, with CaMg-HCO₃^-, intermediate, and Na-HCO₃^- water types predominating. Hydrolysis of silicate minerals, ion exchanges, and dissolution of carbonate minerals (calcite and dolomite) are responsible for water mineralization. Nitrates of human and animal origin often strongly degrade water quality. The results of this study will enable decision-makers to implement a relevant strategy for the sustainable management of groundwater resources, particularly in the city of Kara, where human activities massively impact groundwater quality.

Keywords: Recharge processes, hydrochemistry, water/rock interactions, hard-rock aquifer, human activities, Kara River, Togo.

How to cite: Ani, M., Jaunat, J., Marin, B., Huneau, F., and Gnandi, K.: Origin and mineralization processes of groundwater in metamorphic hardrock aquifers in West Africa: Insights from stable isotopes (δ2H and δ18O) and major ions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18288, https://doi.org/10.5194/egusphere-egu24-18288, 2024.

When an open pit mine closes, dewatering to keep the pit dry ceases, causing the water table to start recovering. In arid and semi-arid climates, hydraulic recovery is often predominantly governed by groundwater inflow into the former mine pit and evaporation from the developing pit lake. Low hydraulic conductivities and low hydraulic background gradients as well as high net evaporation rates can cause pit lakes to remain ‘terminal sinks’, i.e., groundwater enters the pit while outflow only occurs via evaporation. With time the ambient hydraulic gradient re-establishes and may cause pit lake water to exit into the adjacent aquifer, transforming the pit into a ‘throughflow system’. Due to prolonged residence times and evapoconcentration, the pit lake water quality may deteriorate as the salinity increases, a specific problem in arid and semi-arid regions, such as the extensive mining regions of Western Australia. Knowing whether a pit lake remains a terminal sink or transitions into throughflow systems is important for mine closure management as the pit lake water quality might decline to a lesser extent under throughflow conditions compared to terminal sinks as residence times of pit lake water decrease with higher outflow rates. Nevertheless, downgradient aquifers might be affected by exiting pit lake water in throughflow systems. Terminal sinks, however, may, over time affect local aquifer systems also: with increasing salinity due to evapoconcentration, the pit lake water becomes denser and may leak along the density gradient into the less dense groundwater.

This work improves the basic understanding of processes that occur during the hydraulic and geochemical evolution of pit lakes after mine closure. The timeframe for transformation from terminal sink to throughflow system, the salinity concentrations in pit lakes and the shape of salinity plumes are investigated through numerical modelling. Furthermore, the impact of density-driven flow under varying environmental factors is explored.

Opposed to what often is intuitively expected to happen in arid climates, it was found that the transformation from terminal sinks to throughflow systems happens frequently and quickly (< 20 years) after the mining operation ceases under a wide range of hydrogeological site conditions. This is while the groundwater heads are still recovering. The evolution of salinity in the evolving pit lake and surrounding aquifers is thereby largely dependent on the initial concentration of surrounding groundwater. When the initial concentrations are low, density-driven flow has no substantial effect over the simulation time of 500 years. However, when the initial groundwater concentration is higher (e.g., TDS > 1500 mg/l) the impact of density-driven flow is significant and higher concentrations in the pit lake see larger impacts on the adjacent aquifer.

Forecasting the hydraulic and geochemical conditions of pit lakes post-mining is essential for mine closure planning and fundamental knowledge to determine any potential use of post-mining landscapes.

How to cite: Moser, B., Cook, P., Miller, T., Dogramaci, S., and Wallis, I.: The hydraulic and chemical evolution of groundwater-fed pit lakes following mine closure, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3267, https://doi.org/10.5194/egusphere-egu24-3267, 2024.

The Kurikka buried valley aquifer system (Western Finland) contains significant groundwater resources in coarse-grained sediments alternating with till layers. Over the past 10 years, this multilayered aquifer system has been the object of growing interest to increase the water supply to the towns of Vaasa, Kurikka and nearby municipalities. In this context, it is important to understand the groundwater flow system to assess its sustainable exploitation rate and implement sustainable management of this resource. The goal of this study was to assess groundwater quality in the Kurikka aquifer system and interpret the geochemical data to better understand groundwater flow patterns. This goal was achieved through the geochemical characterization of groundwater and the use of multivariate statistical analysis to interpret results. 

The study area (600 km²) encompasses 4 buried valleys connected to the main Kyrönjoki valley. Compilation of historical geochemical data (56 samples) from 2011-2021 was completed in June-August 2023 by a large groundwater sampling campaign (42 samples) from observation wells, bedrock boreholes, production wells and springs, covering all parts of the study area. Samples were analyzed for major ions, minor and trace elements and tritium analyses were performed on a subset of 25 samples. Multivariate statistical analysis (Hierarchical Clustering and Principal Components) was carried out based on 18 physicochemical parameters for 98 samples.

Five water groups emerged from the hierarchical classification. The first three clusters (C1-C2-C3) represent water from sediments, cluster 4 corresponds to water from the bedrock in the upgradient areas and cluster 5 represents water from the bedrock deep beneath the buried valleys. The major recharge area is located to the west of the study area, in the topographic highs where less evolved, tritiated waters were found (C3). From the recharge area, groundwater flows to the north, east and south-east. A similar groundwater evolution from Ca-HCO3 to Na-HCO3 water types was observed in both sediments and bedrock in the recharge area (C4). This suggests there is either an evolution within the buried valleys themselves or the buried valleys act as discharge and mixing feature for the evolved bedrock waters. Groundwater from the northernmost buried valley and the northern part of the Kyrönjoki valley (C1) are geochemically distinct from the rest of the study area and contain tritiated waters, reflecting a different context of modern esker with a shallower system. Bedrock groundwater (C4-C5) are characterized by a lower pCO₂ value and higher pH. While one bedrock borehole beneath the central Paloluoma buried valley showed a more evolved water type and was tritium-free, fresh groundwater was still found until 100 m depth, suggesting deep active flow in bedrock.

This study will be complemented by an additional dataset of groundwater residence time tracers (³H, ¹⁴C) and isotope data (⁸⁷Sr, ¹⁸O/²H) that will provide more information on groundwater origin and support the interpretation of the evolution of the water groups found in the Kurikka aquifer system.

How to cite: Pétré, M.-A., Putkinen, N., Ruskeeniemi, T., and Lefebvre, R.: Multivariate statistical analysis of groundwater geochemistry to characterize flow in the Kurikka buried valley aquifer system, Western Finland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3797, https://doi.org/10.5194/egusphere-egu24-3797, 2024.

Nowadays, one of the serious environmental threats is groundwater contamination due to leachate from municipal solid waste landfills. In recent years, the use of stable isotopes as environmental tracers to identify potential groundwater contamination phenomena has found increasing application in environmental engineering. Deuterium (²H) and oxygen (¹⁸O) isotopes have been successfully used to determine contamination phenomena, when groundwater interact with leachate from municipal solid waste landfills with a significant organic amount. In these cases, groundwater present isotopic compositions relating to ²H and ¹⁸O, which highlight an enrichment of δ²H, an enrichment probably caused by methanogenesis phenomena, during which the bacteria preferentially use the "lighter" isotope of hydrogen (¹H) and the remaining part enriched in the "heavier" isotope (²H). A parameter that influences the isotopic content of deuterium and oxygen18 is the deuterium excess (d or d-excess). An index F is then identified as a percentage change in d-excess, which allows the definition of a system of alert levels to evaluate and control the contamination of aquifers by leachate. F index values higher than 1.1 highlight possible phenomena of contamination of the aquifers due to leachate.

In the case study, the results of the isotopic analyses of oxygen18, deuterium and tritium show mixing phenomena of the leachate and groundwater. The influence of the leachate, following mixing phenomena with groundwater, can determine a reduction in the ORP redox potential in groundwater such that it takes on low and sometimes negative values. This condition ensures the establishment of anaerobic environments and reduces the mobilization of metals, such as Mn, in groundwater. Therefore, in the study area, the overlap of these two phenomena seems evident, such as causing the deterioration of groundwater.

How to cite: Franchini, S., De Filippi, F. M., Barbieri, M., and Sappa, G.: The use of water isotopes as environmental tracers in contamination phenomena between groundwater and leachate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18664, https://doi.org/10.5194/egusphere-egu24-18664, 2024.

Human activities, such as agriculture and reclaimed water discharges, are the main sources of pharmaceuticals (PhACs) and emerging contaminants (ECs) in groundwater. Their occurrence is expected to be linked to the hydrogeological dynamics of the aquifer, especially during severe drought periods when recharge from human sources dominates; therefore, it is paramount to relate groundwater flow dynamics and pollutant occurrence to properly control and manage water resources quality.

This study evaluates the presence of ECs, including PhACs and endocrine disrupting compounds (EDCs) along the Onyar River alluvial aquifer (NE Catalonia, Spain; 295 km²) in two sampling campaigns depicting different hydrological scenarios. The first survey took place in June-July 2021 including the analysis of 45 PhACs in 18 groundwater samples, and the second one in March 2023, after almost two years of a severe drought, focused on 12 groundwater and 10 stream water samples for the determination of 45 PhACs, plus 9 transformation products (TPs) and metabolites, and 32 EDCs. Hydraulic head and hydrochemical data were also collected.

Five PhACs were detected in groundwater (acetaminophen, carbamazepine, hydrochlorothiazide, ibuprofen, and venlafaxine) at 0.6 to 57 ng/L in 2021. Sulfamethoxazole was the only antibiotic found. The second campaign (2023) identified eight PhACs in river samples, including trimethoprim, clindamycin, sulfamethoxazole, sulfapyridine, flubendazole, carbamazepine, citalopram, and venlafaxine, ranging from 5.9 to 81.8 ng/L, whereas in groundwater only six PhACs: sulfamethoxazole, sulfamethazine, sulfadiazine, carbamazepine, venlafaxine, and hydrochlorothiazide were identified at 0.5 to 20 ng/L. TPs and metabolites, such as carbamazepine-10,11-epoxy and carbamazepine-2-hydroxy were only found in river samples, while metoprolol acid was present in both river and groundwater samples. Several EDCs were present in both river and groundwater samples, including tolyltriazole, benzotriazole-1H, bisphenol A, caffeine, methylparabens, TCEP, TBEP, TCPP and estrone at concentrations from 0.3 to 142.2 ng/L.

Such distinct results are influenced by hydrological factors. As a general interpretation supported by head and chemical data, stream water induced aquifer recharge due to groundwater withdrawal is more intensive during drought periods when the water table is lower, as in 2023. This enhances the transport of ECs introduced by reclaimed water inputs towards the aquifer. Conversely, in periods with a higher water table: June-July 2021, the hydrological setup reverses and pollutants introduced by stream recharge, yet relevant, do not reach wells located far away from the drainage network because of larger groundwater recharge and reduced withdrawal irrigation rates. Therefore, a temporal variability of ECs concentration in groundwater is not a matter of uncertainty, but a consequence of observable and predictable changing hydrological conditions. Ignoring hydrological variability in the interpretation of PhACs and ECs will result in erroneous actions about preventing pollution migration and understanding their actual hazard to human and environmental health.

Funding: project EC-FATE, call “MINECO-AEI, PID2022-139911OB-C42” and the Ramon y Cajal contract (RYC2020-030324-I).

How to cite: Ros-Berja, N., Gros, M., Santos, L. H., Menció, A., and Mas-Pla, J.: Drought effects on the occurrence of emerging contaminants in an alluvial aquifer: Implications for groundwater resources management., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8712, https://doi.org/10.5194/egusphere-egu24-8712, 2024.

In a first-of-its-kind study from Eastern Himalaya, we analysed the relative controls of vegetation, precipitation, soil properties, and hydrogeology on the diurnal and seasonal variability in three representative groundwater springs typologies using high-resolution discharge data. The three springs, Gaddi- a Fracture spring with forest land-use, Mamley - a Karst spring with forest and agriculture land-use and Kamrang - a Depression spring with agriculture land-use, together provide water security to over 600 households in South District, Sikkim, India, and are managed by local community organisations.

Based on hydrogeological traverse mapping and master recession curve (MRC) analysis, we categorised the Kamrang as a high-discharge depression spring fed by a relatively homogenous aquifer with uniformly high transmissivity (T_s) and storage (S_t) displaying a gradually decreasing smooth recession curve. Conversely, Mamley has a relatively larger springshed area fed by a smaller homogenous aquifer with two components: a low T_s and low S_t component possibly situated in the upper phyllite-quartzite beds and a high T_s and low S_t sitting in the karst environment. Similarly, Gaddi has the largest springshed area covered with dense oak forests overlaying a nearby shallow aquifer with high T_s which empties faster than the main distant aquifer body with low T_s. All three springs were classified as highly variable (Coefficient of variability, C_v > 40 %). Annually, Kamrang (95±22 %) showed the highest variability followed by Gaddi (88±7 %) and Mamley (72±41 %). However, in winter Kamrang and Gaddi showed very stable flows (C_v > ~20 %) whereas Mamley had higher variability (C_v > 30%). In summers, Gaddi showed much higher fluctuations (C_v > 40%) than Kamrang and Mamley.

Strong yet contrasting diel fluctuations in discharge were observed with significantly higher amplitude in the depression spring (Kamrang, 19±16 l min^-1) and the fracture spring (Gaddi, 12±10 l min^-1) than in the karst spring (Mamley, 7±14 l min^-1). The daily troughs in diel discharge occurred early in Mamley (1600 h) followed by Gaddi (1700 h) and Kamrang (2000 h), largely attributed to daily evapotranspiration-related abstraction. Mamley recovered almost instantaneously compared to Kamrang and Gaddi, both of them peaking in the morning (1000 h). Among agriculture-dominated springsheds, relatively high T_s along with moderate saturated soil hydraulic conductivity (K_sat.soil) resulted in lower lag-time in Mamley than Kamrang, which had similarly high T_s but lower K_sat.soil. On the contrary, the lag-time was longest in forest-dominated Gaddi, with the lowest T_s and K_sat.soil. The forest land-use may also have influenced the contrasting observations of Gaddi spring discharge responding faster to high-intensity and low-moderate volume rainfall than agriculture-dominated Kamrang and Mamley. Thus, any land-use change negatively affecting K_sat.soil, such as compaction through grazing and topsoil erosion, is likely to have strong negative effects on the longevity of the spring. On the other hand, fracture springs like Gaddi, fed by a larger catchment, are likely to be immune from the effects of small-scale land-use changes. Our results suggest that any future changes in the precipitation patterns and land-use may significantly impact spring behaviour in the Himalaya.

How to cite: Kumar, M., Sen, S., Badiger, S., Kulkarni, H., and Krishnaswamy, J.: Impact of land-use management and climate variability on hydrological responses of representative groundwater spring typologies in Eastern Himalaya, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-750, https://doi.org/10.5194/egusphere-egu24-750, 2024.

The processes leading to high levels of arsenic, iron, and manganese in a naturally reducing aquifer beneath a landfill are investigated. Between 2016 and 2022, groundwater monitoring (physical-chemical parameters, major and trace inorganic compounds) has been complemented with the analysis of environmental isotopes (tritium, δ²H, and δ¹³C) of groundwater and of the dissolved gases (δ¹³C of CH₄ and CO₂, ¹⁴C of CH₄). Statistics, including Pearson/Spearman correlation and PCA, were used to define the main correlation among variables. The presence of methane and carbon dioxide was attributed to landfill gas migration from the waste as ¹⁴C dating confirmed that methane is modern (F¹⁴C = 1.0684) and likely produced by methyl fermentation within the waste. While methane, enhancing the naturally reducing conditions of the aquifer, appears to be the driver of the high concentration of Fe and As, Mn appears to be governed by carbon dioxide. At the same time, CO₂ may locally lower the pH, thus increasing the dissolution of sedimentary carbonates and ultimately producing high alkalinity and salinity. Furthermore, the reuse of water from leachate treatment to meet circular economy requirements was invoked to explain the elevated levels of tritium and ²H, associated with significantly negative ¹³C, observed in a production well and in a nearby piezometer. The integration of environmental isotopes and geochemical parameters allowed to exclude leachate contamination: tritium, δ²H, and δ¹³C were within the expected range for natural groundwater. No compounds typical of leachate contamination were detected. Environmental isotopes can fruitfully complement traditional monitoring when the comprehension of processes is desired, but this requires an expert judgment and a solid conceptual hydrogeological model.

How to cite: Preziosi, E., Parrone, D., Frollini, E., Ghergo, S., Sciarra, A., Ruggero, L., and Ciotoli, G.: Moderate impact of landfill gas on a naturally reducing aquifer should not be confused with leachate pollution   , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9965, https://doi.org/10.5194/egusphere-egu24-9965, 2024.

Shallow groundwater is an important resource within the framework of potable, continuous, and reliable water supply in the whole of Cameroon, particularly in Bafia, where there is a limited supply of piped-borne water. Increased population and intense agriculture, which involves the use of diverse agrochemicals, make it crucial to assess groundwater quality both for present and future use. The objectives of this study are to (a) identify the major seasonal hydrogeochemical processes, (b) determine groundwater quality with potential health risks and (c) assist local communities and water resource managers to sustainably manage the resource.  57 water samples (31 wells, 20 boreholes, 4 rivers and 2 springs) were collected, filtered, acidified with HNO₃ and analyzed for major ions by Ion chromatography (samples for anions were not acidified) and heavy metals content by ICP-MS (Fe, Co, Ti, Sr, Sb, Al, Cr, Cu, Pb, Ni, As, Zn, Mn, Se, Sn, B, Cd). Results show that groundwater is acidic to neutral, soft to very hard, and generally fresh. Major ion concentrations increased from the rainy to the dry season and were within WHO limits (but for a few). The study shows that albite/anorthite, calcite/dolomite, and ion exchange contribute significantly to the major ion concentration in the study area. The 3 major water facies identified in the rainy season are the Ca-Mg-HCO₃,Ca-Mg-Cl, and Na-Cl types; while two water types are identified in the dry season, including the Ca-Mg-HCO₃ andCa-Mg-Cl types, with mixing types like Ca-Mg-SO₄-Cl and Na-K-HCO₃. Results of heavy metals analyses show that most of the metals are within and some below WHO limits, while high Ti, Mn, Al, Fe, and Sr concentrations were observed in most samples. The heavy metal concentration was evaluated using indices like heavy metal pollution index (HPI), heavy metal evaluation index (HEI), and degree of contamination (Cd). The mean values of HPI and Cd (741 and 5 respectively) exceeded the critical limit, indicating highly contaminated water samples. Based on the HPI and Cd, 93% and 35% of the samples respectively are unacceptable for drinking purposes. Major ions PCA reveals 4 factors; the first is a result of natural processes with silicate weathering and the second reveals anthropogenic influences, mainly fertilizer input. The first factor for heavy metals reveals high pollution from inorganic fertilizers while the second shows water-rock interactions. Agricultural activities have a great impact on the water chemistry around the area; hence, it is recommended that a periodic and systematic study be carried out regularly, especially for the heavy metal concentrations. The study is the first of its kind to provide insight into heavy metals as well as an in-depth evaluation of hydrogeological processes influencing groundwater in the area and thus can offer a valuable reference point for the design of suitable techniques to manage groundwater resources.

How to cite: Tarkang, C. E.-A., Akenji, V. N., Rouwet, D., Ndjama, J., Ako Ako, A., Tassi, F., and Ndam Ngoupayou, J. R.: Evaluation of the Hydrogeochemical Characteristics and Heavy Metals Contamination Levels of Shallow Groundwater in the Bafia Agricultural Area, Centre Region Cameroon., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-580, https://doi.org/10.5194/egusphere-egu24-580, 2024.

Detailed knowledge of the groundwater flow field is one of the fundamental technical prerequisites for designing effective remediation measures for contaminated aquifers.

The environmental issues under discussion concern both the implementation of emergency measures, commonly carried out by means of Pump&Treat (P&T) hydraulic containment systems, and remediation actions, developed through the adoption of in-situ technologies and treatments.

In hydrogeological practice, the analysis of groundwater flow directions is implemented on a piezometric basis, reconstructing the water table trend from point-level measurements. These point measurements are appropriately interpreted using geostatistical contouring algorithms.

However, within a single contaminated site, very specific circumstances may be found, due to both natural and operational reasons or other logistical challenges. The first group includes intrinsic geological factors, which derive e.g. from depositional mechanisms: typically, saturated alluvial systems are characterized by structural heterogeneity and anisotropy that can sometimes influence the design choices for remediation. Similarly, the geometry of the site and the presence of structures in relation to the position of the contamination source and the direction of groundwater flow can influence the location of interventions and installations, such as the position of pumping and monitoring wells, the latter placed behind the hydraulic barrier to verify its effectiveness.

In these environmental contexts, a methodological in-depth study is underway, aimed at combining traditional hydrogeological parameterization techniques with an advanced experimental measurement system with colloidal borescope.

The borescope is an optical device capable of following the movement of colloids in monitoring wells: field observation of the motion of these particles shows that the directional measurements, in addition to being generally consistent with the expected flow field, also provide complementary point-based results compared to those achievable with traditional techniques (Kearl, 1997). The instrument detects the flow of colloids from stagnant conditions up to flow rates close to 3 cm/s, allowing the prevailing azimuthal direction of transport to be established using statistical criteria.

This work describes the preliminary results of unpublished measurements, carried out in contaminated aquifers controlled by hydraulic barriers in operation. The results achieved to date suggest the opportunity for the use of the colloidal borescope to refine the conceptual hydrogeological model in contaminated sites even in dynamic regime situations.

How to cite: Rodighiero, M., Sottani, A., Buggiarin, S., and Vettorello, L.: Using a colloidal borescope to define groundwater flow directions at contaminated sites , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11280, https://doi.org/10.5194/egusphere-egu24-11280, 2024.

Abstract: The depth of groundwater is a critical factor that significantly influences the development and conservation of both surface water and groundwater in lakes located in Northern China, exemplified by Baiyangdian (BYL), the largest lake situated in the North China Plain. It forms a critical foundation for the ecological integrity of BYL by quantifying hydrological fluxes and investigating variations in surface water and groundwater across distinct groundwater depths. To address this inquiry, we established a distributed hydrological model for the basin, enabling the simulation of surface runoff (horizontally) and vertical processes such as evapotranspiration and infiltration. Findings for the period 1966-1980 reveal an overall shallow groundwater condition in the Baiyangdian plain area, with a multi-year average depth of approximately 4 meters. Precipitation recharge, lake evaporation, surface water inflow, surface water outflow, groundwater inflow, and groundwater outflow during this phase were quantified at 187 million m³, 288 million m³, 960 million m³, 683 million m³, 160 million m³, and 40 million m³, respectively. The predominance of horizontal flux (62%) signifies rapid lake water replenishment. Conversely, during the later period of 1981‒2018, groundwater depth in the plain area substantially increased, averaging 23.48 meters. Precipitation recharge, lake evaporation, surface water inflow, surface water outflow, and groundwater outflow were computed at 179 million m³, 227 million m³, 294 million m³, 118 million m³, and 127 million m³, respectively. The horizontal flux contribution diminished to 22%, while the vertical flux surged to 78%, indicating slower lake water renewal and heightened risks of water quality degradation. Climate change and human activities emerged as drivers of rising groundwater depth, subsequently weakening water cycle dynamics over BYL. In the future, the comprehensive recovery of groundwater facilitated by the South-to-North Water Diversion for lake and river replenishment will play a pivotal role in reinstating water cycle dynamics and enhancing ecological integrity. This study establishes a foundation for understanding the intricate interactions between lakes, rivers, and aquifers as groundwater depth evolves over time. It holds significance for water conservation and the preservation of BYL's water quantity and quality in the future.

Key words: Baiyangdian Lake; distributed hydrological model; hydrological flux; Groundwater depth

How to cite: Cui, Y., Long, D., and Cui, Y.: Hydrological Impacts of Groundwater Depth on Lakes in Northern China: Exploring the Mechanisms through Climate Change and Human Activities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8680, https://doi.org/10.5194/egusphere-egu24-8680, 2024.

As our planet faces the complex challenges of global climate change, understanding and effectively communicating critical environmental indicators becomes critical. This study explores the importance of monitoring and reporting variation of groundwater temperature as a key component in understanding the broader implications of climate change.

Groundwater, a key reservoir of the Earth's freshwater, plays a crucial role in moderating surface temperature and sustaining ecosystems. However, its temperature dynamics remain poorly studied despite its fundamental influence on groundwater dependent ecosystems and geothermal processes.

This research synthesises groundwater temperature data from 15 different monitoring wells located in the unconfined shallow aquifer, consisting of gravel and sand, of Piedmont Po plain (NW Italy).
Daily groundwater temperature data, available from 2010 onwards, were analysed and statistical elaboration performed evaluating the trend and the temperature anomalies.
The regional distribution of mean monthly groundwater temperatures varied 7.7 and 14.0 ◦C and showed a general increase of the value up to 2.1 °C/10 years.
Because the findings underline the urgent need for improved data communication strategies to disseminate valuable information to policy makers, researchers and the society, a proposal of dissemination approach is proposed in the paper.

By illustrating and communicating 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. The study not only contributes to the expansion of knowledge on climate science and groundwater impacts, but also underlines the imperative of easy and accessible reporting of data in addressing the multiple challenges posed by a rapidly changing global climate.

How to cite: Egidio, E., De Luca, D. A., and Lasagna, M.: Connecting the dots: groundwater temperature data as a key element in Climate Change conversation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-934, https://doi.org/10.5194/egusphere-egu24-934, 2024.

Deep groundwater extraction alters both the reservoir's hydraulic and hydrochemical state. Although deep groundwater is part of the hydrologic cycle, it is considered a limited resource regarding the original hydrochemical composition and age structure. Mineral water producers share the privilege to use this resource for commercial purposes. Here, geological protection against surface influences and highly constant hydrochemical conditions are legally required.

This study evaluates the development of a deep groundwater aquifer that has been used for bottled water production since the 1900s. Production stopped in late 2019, offering the unique opportunity to study the recovery of the aquifer. Detailed data from the past 40 years show a hydrochemical stratification in the mineral water aquifer with salinity and age increasing with depth. The saltwater horizon seems to have been lowered significantly due to extraction, and the hydraulic potential has also decreased. A connection to shallow groundwater was confirmed through the detection of herbicide metabolites. Isotope activities and metabolite concentrations indicate that the travel times are between 5-10 years.

After the shutdown of the operation, the hydraulic potential increased and some of the wells are now again artesian. In the first analyses of the hydrochemical conditions the deepest wells reveal increasing salinity and CO₂ concentrations. This indicates that the saltwater horizon is now moving upwards. The shallower wells, however, still show slightly decreasing salinity and are far away from the original hydrochemical composition. This indicates that the water extraction at this site has to be considered a mining operation.

The measurements of the hydraulic and hydrochemical development together with an investigation of the flow paths for the recharge will allow an assessment of the sustainability of the groundwater extraction at this and other sites.

How to cite: Hegels, M. and Baumann, T.: Depletion of a Mineral Water Aquifer – Implications on Sustainable Groundwater Management, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1888, https://doi.org/10.5194/egusphere-egu24-1888, 2024.

Climate changes cause droughts and storms in many places, impacting sustainable development. Water scarcity caused by climate change will be a significant obstacle to climate adaptation and sustainability. Therefore, rainfall harvesting is becoming a significant approach in arid regions that suffering from water scarcity. Such an approach allowed for capturing and holding water resources in ponds, lakes, and groundwater aquifers needed to expand agricultural, urban, and industrial activities. In this project, radar and optical remote sensing data have been integrated with climatic, hydrologic, and geological data that successfully enabled the identification of potential water accumulation zones and optimum areas for rainwater harvesting. The processing of the SRTM, Sentinel-1&2, Landsat-8, TRMM, ALOS/PALSAR, and InSAR coherence change detection (CCD) data revealed geomorphic, structural, and hydrologic properties of the catchments and rainfall intensity zones of Wadi Safag which is a significant drainage system that drains into the Red Sea, Egypt. Several factors were combined, after assigning weights to each using a GIS-based knowledge-driven methodology. The results delineated the promising areas for rainfall harvesting and groundwater potential zones (GPZs). Additionally, the results identified the optimum areas for constructing lakes and dams to store rainwater and protect the mining, industrial, and tourism areas in the studied basin. Overall, identifying the probable areas for water accumulation and groundwater abstraction is crucial for planners and decision-makers for the achievement of sustainable development in Wadi Safaga, Egypt.

How to cite: Abdelkareem, M., M. Mansour, A., and Akawy, A.: Revealing the plausible areas for rainwater harvesting and groundwater abstraction for the accomplishment of sustainable development purposes in arid regions , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11780, https://doi.org/10.5194/egusphere-egu24-11780, 2024.

Stagnation points have been found to be useful in characterizing groundwater flow regimes in 2D or 3D domains. However, in 3D basins with complicated water table undulation and/or fluctuation, knowledge on stagnation points is limited. In this study, we first derived transient solution of basinal flow under spatially undulating and periodically changing water table in 3D Tóthian basins and examined the occurrence of stagnation points. Based on the analysis of groundwater flow systems distribution in simple 3D basins, we extend the method of delineating groundwater flow systems in 2D profiles using stagnation points to delineating 3D groundwater flow systems using stagnation or pseudostagnation lines, which consist of a series of stagnation or pseudostagnation points. This novel approach was successfully applied to 3D synthetic basins with more complex water table configuration (with undulations in all directions). Based on the transient hydraulic head solution in 3D Tóthian basins with a periodically fluctuating water table, it was found that the evolution of (pseudo)stagnation lines are controlled by the combination of hydraulic diffusivity and the period of the water table fluctuation, both of which determine the dimensionless response time. The change in shape of (pseudo)stagnation lines, induced by spatial undulations and/or temporal fluctuations of the water table, also reflects the variation of groundwater flow systems in penetration depth and horizontal range. The method proposed here improves the efficiency of partitioning groundwater flow systems in 3D domains, and our analytical study of (pseudo)stagnation lines partially fills the knowledge gap between stagnation points and stagnation zones.

How to cite: Zhang, Z.-Y., Jiang, X.-W., Zhou, P.-Y., Batelaan, O., Wang, X.-S., Han, P.-F., and Wan, L.: Stagnation and pseudostagnation lines for separating 3D groundwater flow systems in Tothian basins, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3297, https://doi.org/10.5194/egusphere-egu24-3297, 2024.

The phosphate mining from the Beni Amir deposit, located in the southern part of Central Morocco, presents many difficulties, due to the presence of groundwater, which can either partially or completely submerge the phosphate layers. This challenge becomes particularly pronounced in the context of climate change conditions and water scarcity.

To address these issues, a hydrogeological study has been conducted aiming to understand the aquifer’s function and ensure sustainable phosphate extraction from the deposit. Initially, geological, and hydrogeological information from 692 boreholes were collected and analyzed to develop a 3D hydro-stratigraphic conceptual model, which indicate that approximately 73% of the deposit is at least partially submerged by the groundwater, while the remaining 27% constitutes the dry zone.

Additionally, a numerical model was developed and calibrated using the MODFLOW code. Calibration was accomplished under both steady-state and transient conditions by adjusting model parameters until the model's solution aligns with known data, utilizing 580 observed groundwater levels measured in 2023 and 7 pumping wells. The model’s performance was evaluated using R², RMSE, and NRMSE coefficients, showing high accuracy and consistent model performance.

The hydrogeological model was executed to evaluate the effects of the dewatering process in the surrounding mining areas, revealing a high impact on groundwater resources and the water table level. These findings will be employed to strategize well-considered plans for optimal groundwater pumping and mine dewatering strategies, ensuring the safety of mining operations throughout different stages of mine development.

How to cite: Heddoun, O., Ait Lemkademe, A., and Benzaazoua, M.: Sustainable Phosphate Mining: Hydrogeological Insights and Numerical Modeling of the Beni Amir Phosphate Deposit, Morocco, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-434, https://doi.org/10.5194/egusphere-egu24-434, 2024.

Water availability in the border region of New Mexico and Texas, US, and Chihuahua, Mexico, is limited. The transboundary aquifers of the Hueco Bolson, Mesilla (US)/Conejos Medanos(Mexico), and Valle de Juarez in Mexico, as well as the surface water of the Rio Grande, are the primary sources of this border area. The transboundary aquifer of Mesilla, known by this name in the US, is called Conejos Medanos on the Mexican side; the southern part of this aquifer is located in the north of Chihuahua, Mexico. In this area, water is scarce and does not exist recharge. Then, the transboundary aquifers in the area are being depleted. These challenges, along with the rapid population growth, have created significant issues for water management in the transboundary region, as they also involve challenges in maintaining water availability. Therefore, it is necessary to understand the groundwater flow to promote the sustainability of the transboundary aquifers and promote groundwater recharge in the area.

A comprehensive understanding of this aquifer's groundwater dynamics and flow patterns is essential to ensure effective transboundary water resource management. This study employed ArcGIS 10.4.1 to conduct a geospatial analysis of binational drawdown data of static groundwater levels from 2019. The Municipal Water and Sanitation Board of Juarez City (JMAS by its acronym in Spanish) provided the data from the Mexican side. At the same time, the United States Geological Service (USGS) supplied information from the US side. Results show groundwater flowing from north to south into Mexico, forming cones of depression around JMAS-administered well infrastructure supplying water to Juarez City. These findings indicate the aquifer's sensitivity, emphasizing the potential influence of intense pumping on groundwater availability and future economic growth. The research offers insights into data-driven approaches for understanding groundwater dynamics in transboundary regions, promoting sustainable water resource management, water security, and cross-border cooperation, which is good for promoting the Transboundary Aquifer Assessment Program (TAAP), Transboundary Groundwater Resilience (TGR) Network of Networks (formerly known as TGRR) funded by the National Science Foundation's Accelerating Research through International Network-to-Network Collaborations (AccelNet) program. This network promotes collaborative efforts, which are essential to address transboundary aquifer management issues and ensure the resiliency and sustainability of groundwater resources for current and future generations on both sides of the border. As we face increasing water-related challenges in a changing world, this study highlights the importance of understanding and managing transboundary aquifers as critical components of sustainable water resources management strategies.

How to cite: Garcia Vasquez, A. C., Samani, Z., Granados, A., and Fernald, S. ".:  "Groundwater Dynamics of the Transboundary Mesilla-Conejos Medanos Aquifer by Geospatial Analysis to Addressing Depletion Challenges and Find Sustainable Solutions along the US-Mexico Border.", EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13342, https://doi.org/10.5194/egusphere-egu24-13342, 2024.

Climate projections from the IPCC for the Mediterranean indicate anticipated increases of up to 3.5ºC in average temperatures and a consequential reduction of approximately 10% in precipitation. Such projections suggest a shift in climatic regimes, predicting an escalation in extreme events, particularly floods. In the face of water scarcity, diverting floodwater to the sea signifies a significant loss of a valuable resource. Enabling the recharge of this water into the aquifer not only increases water resources but also mitigates flood severity and enhances resilience against droughts.

To identify optimal locations for aquifer recharge strategies, the integration of remote sensing and Geographic Information Systems (GIS) proves invaluable. In this study, we coupled both tools to propose a methodology for locating the best places for Managed Aquifer Recharge using floodwater. For that, we have processed a set of river images using Sentinel-2 satellite imagery to evaluate the evolution of river width. Subsequently, this data was integrated into a proposed multicriteria analysis to determine the optimal location for MAR. Upon establishing the methodology, we applied it to the Llobregat River (Spain), a crucial source of groundwater supplying Barcelona. Located in the Mediterranean region, the aquifer is particularly vulnerable to the impending droughts predicted by the IPCC.

How to cite: Ferrer, N., Rodríguez-Escales, P., Fernández, D., and Martínez, J. I.: Utilizing Remote Sensing Data to Locate Managed Aquifer Recharge Facilities Using Floodwater , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12919, https://doi.org/10.5194/egusphere-egu24-12919, 2024.

The Cuitzeo groundwater flow system in central Mexico is facing challenges due to intensive groundwater extraction, nitrate pollution, and a decline in groundwater levels. To understand the processes underlying these environmental impacts, we used compiled data from 2013 and employed cluster analysis to identify distinct groups. Four groups were identified based on flow trajectories, incorporating geological information, structural features, and hydrochemical diagrams such as Piper, Gibbs, and Mifflin.

The determined flow trajectories or components consist of local, intermediate, and two regional components. The spatial distribution of these flow components is associated with recharge areas and structural features, displaying a non-sequential evolution to groundwater flow direction.

This work presents preliminary findings from the analysis of environmental problems such as nitrates and a decrease in groundwater levels, contributing to an enhanced understanding of the origins of these impacts and offering insights for future solutions.

How to cite: Olea Olea, S., Llanos Solis, A. G., Eric, M.-C., Priscila, M.-O., Felipe, A. V., Salgado Albiter, A. C., Sierra García, B. A., and Ramírez González, L.: Groundwater flow components and environmental problems in a groundwater flow system, center-west Mexico, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2954, https://doi.org/10.5194/egusphere-egu24-2954, 2024.