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The role of groundwater flow systems in solving water management and environmental problems

The session aims to bring together scientists studying various aspects related to groundwater flow systems, and their role in solving water management and environmental problems.
Understanding groundwater flow systems requires knowledge of the governing processes and conditions from the local to regional and basin-scales, including porous and fractured porous media. Moreover, problems connected to groundwater management underline the importance of sustainable development and protection of groundwater resources.
In this context of groundwater flow understanding, the session intends to analyze issues connected to groundwater management and its protection from degradation with respect to quantity and quality (e.g. due to overexploitation, conflicts in use, climate change, resource development or contamination). Papers related to methods of defining groundwater flow, and preventing, controlling and mitigating harmful environmental impacts related to groundwater, including those in developing countries, are also welcome.

Co-sponsored by IAH-RGFC
Convener: John Molson | Co-conveners: Daniela Ducci, Jim LaMoreaux, Manuela Lasagna, Judit Mádl-Szőnyi
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Fri, 30 Apr, 09:00–10:30

Chairpersons: John Molson, Manuela Lasagna, Jim LaMoreaux

5-minute convener introduction

Tobias Langmann et al.

Worldwide, climate change as well as socio-economic changes are increasing pressure on water supply in coastal regions and lead to major changes in groundwater recharge as well as the regional water balance as parts of the hydrosystem. These changes are threatening water security and, thereby, impede the fulfillment of the SDG 6 targets, esp. SDG targets 6.2., 6.4. and 6.6 of the UN 2030 Agenda for Sustainable Development. Thus, a modern water management demands innovative and profound methods and tools that comprehensively cover these complex changes. To address this challenge,  in the BMBF project "go-CAM" (Implementing strategic development goals in Coastal Aquifer Management) we took the methodological approach of developing new groundwater status indicators (e.g. chloride concentration in groundwater, position of saltwater/freshwater interface, freshwater volume) and corresponding target functions implemented in a new online-based management and evaluation tool called "CAM" (Coastal Aquifer Management). Both the physically based indicators as well as the target functions tackle economic as well as ecological issues. The groundwater status indicators are directly derived from the results of high-resolution, process-based (hydrological and hydrogeological) modeling of coastal hydrosystems. Due to their physical nature, the indicators are only applicable with appropriately designed climate and socio-economic scenarios for coastal water management if they are generated with models that also capture the system-relevant processes: Groundwater recharge, groundwater abstraction, discharge dynamics through drainage systems, sea level rise and groundwater discharge to the sea and saltwater intrusion.

The CAM platform is a tool that provides a way to make the results of the complex and extensive numerical modeling usable for a wider community and thus allow for a more efficient result exploitation. Building on the indicators and the selection of target functions and weighting factors the CAM tool uses Multi-Criteria Decision Analysis techniques (MCDA) to strengthen transparency and objectivity in decision-making processes and encourage communication between decision-makers in the water sector of coastal regions. In this way, the application of the CAM tool contributes to the establishment of an integrated water resources management and to derive and discuss future water management strategies as well as concrete measures.

Our methodological approach as well as the results are presented applied to a regional coastal groundwater study area in the northwestern part of Germany, the Sandelermöns region, which covers an area of about 1,000 km².

How to cite: Langmann, T., Schöniger, H. M., Schneider, A., and Sander, M.: Managing coastal aquifers in climate and socio-economic change: An indicator-based multi-criteria decision system approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12064, https://doi.org/10.5194/egusphere-egu21-12064, 2021.

Mara Meggiorin et al.

In the coming years, water resource management will become more and more important for satisfying competing water-related needs under the pressure of water scarcity and climate change. The choice of how to allocate water is difficult, uncertain, and context specific. This study aims to bring to the fore a significant example of sustainability of groundwater system management under specific requirements and dependence on irrigation activities. The groundwater system at hand is the Bacchiglione basin, near Vicenza (Veneto, Italy), an essential water asset for local ecosystems, human needs and economic activities. Its recharge mainly happens in the northern unconfined portion by three factors: river seepage, rain and irrigation infiltrations.

Historically, the contribution of irrigation practices has been fundamental for recharging the hydrogeological system. However, local irrigation authorities have begun to replace traditional irrigation techniques, such as the field overflow or draining channels, with more innovative techniques, such as piping grids with sprinkling devices. The shift towards more efficient methodologies, whose main goal is to save water, puts under pressure the local groundwater system because of the reduced artificial recharge.

Currently, the present irrigation network, techniques and activity schedule yields an overall annual irrigation contribution of approximately 5.4 m3/s, about the 25% of the total inflow at the basin scale. This flow is expected to decrease in the future. By modelling the system (via FEFLOW), this study concerns possible scenarios by changing the irrigation technique. As an example, all currently overflowed fields are converted to sprinkling irrigation. This technical change leads to an estimated inflow decrease of 1.6 m3/s during the irrigation period between May and August, without considering the consequent decreased dispersion by distribution channels. This scenario highlighted an area particularly affected by a piezometric drawdown which is of particular interest because in the district many wells for the public supply authorities are located.

Our study confirms irrigation as an important recharging factor within the Bacchiglione basin. The project of ​​making agriculture more efficient with 'good practices' involves in this specific case a lowering groundwater level, comparable to climate change and land use change effects. To counteract such resource depletion, local irrigation authorities have already tested managed aquifer recharge measures, like e.g. forested infiltration areas. To be effective, however, such interventions should be planned at larger spatial scales to grant adequate long-term effects. Moreover, the present work suggests to keep active irrigation channels in winter months to increase seepage and also to sustain local habitats and ecosystems and maintain the rural landscape.

How to cite: Meggiorin, M., Passadore, G., Bertoldo, S., Sottani, A., and Rinaldo, A.: How irrigation good practices can put under pressure the groundwater system of the Bacchiglione Basin (Italy), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1484, https://doi.org/10.5194/egusphere-egu21-1484, 2021.

Luca Zini et al.

After abundant rainfalls, the Mucille area (Ronchi dei Legionari, Northeastern Italy) is subject to frequent flooding. Although this area has always been exposed to such hazard, these inundations become problematic since 2001 as they more frequently affect housing and recreational areas, leading the population to believe that the swallow holes draining the area stopped functioning. The increased frequency of intense rainfall events led the municipal technicians to involve the Department of Mathematics and Geosciences of the University of Trieste to assess the situation. The Mucille karstic depression is fed by a spring area and drained by two swallow holes one of which is permanently active while the other operates only during floods. The Mucille springs represent the westernmost drain of the Classical Karst aquifer. During floods, as in-situ discharge measurements are impossible, only a hydrologic balance model may assess the inflow or outflow discharges. The extension of the flooded areas has been mapped. The obtained flooded surface together with high resolution DEM coverage allows to calculate the volume of surface water. Combined with water table levels recorded in an adjacent piezometer, this volume can be computed over time. Thus, the hydrologic balance (inflow minus outflow) can be estimated. This model has been applied to several flood events among which, two were the most important in terms of flooded areas: one in December 2017 and the other in November 2019. During the event of December 2017, the water level reached 7,5 m a.s.l. and the difference between the inflow and the outflow was 880 l/s. The day following the peak, the discharge difference decreased to 273 l/sand the 5 subsequent days the water balance was close to equilibrium. From the eighth day on, the outflow became predominant resulting in a negative budget between -233 and -78 l/s. The flood event of November 2019 reached the maximum inundated area at a water level of 7,8 m a.s.l. with a difference between the inflow and the outflow of 750 l/s . Two days after the peak a negative balance of -200 l/s was recorded and remained negative for the next 5 days. A period of intermittent precipitations increased again the inflow up to 600 l/s. Following a period of ten days with a negative balance the water level returned to the initial values of 5 m a.s.l. This study provides evidences fundamental for the design of measures to mitigate the risk. It estimates the discharge of the swallow holes, confirming their efficiency. Nonetheless it also emphasises the need to improve their draining capacity, especially considering the unsuspected high outflow of the springs at the onset of the flood.

How to cite: Zini, L., Turpaud, P., and Calligaris, C.:  Water management in the Mucille area (NE Italy) through hydrologic balance estimation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12006, https://doi.org/10.5194/egusphere-egu21-12006, 2021.

Ronan Abhervé et al.

While it is well understood and accepted that climate change and growing water needs affect the availability of water resources, the identification of the main physical processes involved remains challenging. It notably requires to filter interannual to interdecadal fluctuations and extreme events to isolate the underlying trends. Metropolitan areas are specifically subject to growing pressures because of the significant and increasing demand, combined with the strong anthropization of land uses.

The Meu-Chèze-Canut catchment supplies the city of Rennes with drinking water (680 km² - 500 000 users, Brittany, France). In this field laboratory, we explore the dynamics of the water cycle and water resources availability. In this context, water supply is mostly coming from reservoir storage for which levels shows a medium-term vulnerability in response to frequent relatively dry years. Based on retrospective data analysis, we describe the relationship between climatic forcing (precipitation, temperature) and water availability (aquifer storage, river discharge and reservoir storage) in different parts of the catchment that are characterized by distinct lithological and topographical settings. We then evaluate the resilience of both surface and groundwater resources, their past evolution and their resilience to climate change and increasing societal needs.

Water resources availability in these catchments relies on two geological formations with distinct hydrodynamics properties: the Armorican sandstone and Brioverian schist. To assess the resilience of the system, we specifically analyzed the relationships between monthly effective precipitation and stream discharge within nine sub-catchments over the past 30 years. We observe annual hysteresis relationships - that is, a time lag between precipitation and discharge highlighting the capacity of the landscape to temporarily store water - with significant variability in shapes across the catchments. We argue that topographic and lithological factors play key roles in controlling this variability through their impacts on subsurface storage capacity and characteristic drainage timescales. We propose perspectives based on the complementary use of calibrated groundwater models to leverage these results and provide adaptive water management strategies.

How to cite: Abhervé, R., Roques, C., Longuevergne, L., Louaisil, S., de Dreuzy, J.-R., and Aquilina, L.: Spatial variability and changes in storage-discharge relationships of crystalline catchments: implications for resilience and water resources management, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9056, https://doi.org/10.5194/egusphere-egu21-9056, 2021.

Aiga Krauze et al.

European water policy requires to carry out nine tests for characterisation of groundwater bodies status, including the development of joint transboundary groundwater management principles. 

Gauja/Koiva and Salaca/Salatsi Rivers have a joint, Estonian/Latvian transboundary water cycle, including the groundwater recharge and discharge cycling. Despite the fact that groundwater is the only drinking water source in Gauja/Koiva and Salaca/Salatsi River basins and ensures the existence of many groundwater dependent ecosystems, the overall awareness of integrated cross-border management practice is still poorly understood and poorly linked in implementation of concrete groundwater protection actions. 

Taking into account the above-mentioned aspects, Latvian and Estonian groundwater and groundwater dependent ecosystems specialists from research, nature protection and groundwater resources management institutions have joined forces in the project funded by the Interreg Estonia-Latvia program: "Joint actions for more efficient management of common groundwater resources in Estonia and Latvia "(WaterAct).

The ongoing Est-Lat project “WaterAct” (2020–2022) of joint transboundary groundwater management project organised into the three activity blocks: (1) The capacity building of the joint groundwater transboundary management through exchange of knowledge and best management practices between project partners and key experts in other European Union countries; (2) Assessment of groundwater resources in transboundary River basins to improve groundwater management in accordance with valid international directives; (3) Dissemination and outreach activities to increase the overall awareness of ecosystems friendly groundwater management and protection of key actors working with groundwater assessments and locals. 

Firstly, the joint cross-boundary principles of identification and status assessment of shared groundwater bodies will be developed. Adaptation of existing knowledge, cross-boundary harmonization and development of needed methodologies will be used. 

Secondly, the joint cross-boundary assessment principles will be implemented into groundwater resources management. The status assessment of shared groundwater bodies will be carried out in close cooperation between project partners to create materials necessary for the development of last River Basin Management Plans (2022-2027), required by the Water Framework Directive and Groundwater Directive.

Thirdly, the dissemination of project results will be carried out (1) by compilation of Guidelines of Groundwater Dependent Ecosystems for different levels and fields of decision making and experts, (2) by compilation of Spring Water Monitoring Guide for Volunteers and starting volunteer monitoring. For volunteer monitoring, a special web-based map application will be developed (allikad.info). 


The project of “Joint actions for more efficient management of common groundwater resources” (WaterAct, Est-Lat155) funded by ERDF Interreg Estonia-Latvia cooperation programme.

How to cite: Krauze, A., Terasmaa, J., Lode, E., Bikše, J., Türk, K., Tarros, S., Polikarpus, M., Marandi, A., Ojamäe, K., and Priede, A.: Joint actions for more efficient management of common groundwater resources in Estonia and Latvia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1979, https://doi.org/10.5194/egusphere-egu21-1979, 2021.

Oussama Dhaoui et al.

Most future scenarios for water resources are predicting water scarcity, with a decrease in the amount
of precipitation and limitation on groundwater recharge for the next five decades. In arid and semi-
arid areas, the water quality is a great problem and groundwater salinization is one of the principal
causes of degradation of water resources worldwide.
Menzel Habib aquifer is located in the northwest of Gabès region (southeastern Tunisia), included in
the arid Mediterranean bioclimatic area, with dry hot summers and relatively warm winters.
Groundwater geochemistry from the study area shows a Na-Cl and Ca-Mg-Cl-SO 4 dominant facies.
The high groundwater mineralization and its correlation between total dissolved solids and major ions
suggest a contribution of SO 4 , Cl, Na, Ca and Mg in groundwater salinization processes.
The salinization of groundwater is mainly associated with the Triassic evaporites, with the dissolution
of halite, anhydrite and gypsum, occurring in the area, and related to the tectonic context of the
region. Additionally, other geochemical processes occurred, such is the cation exchange mechanisms.
Changes in precipitation patterns and intensity, with water scarcity, low recharge and excessive
pumping have affected groundwater quantity and quality. Nowadays, the occurrence of climate
changes scenarios is a major drawback for water use for irrigation and drinking water supply in arid
and semi-arid regions, such as Menzel Habib aquifer.

How to cite: Dhaoui, O., Horta Ribeiro Antunes, I. M., Agoubi, B., and Kharroubi, A.: Management of groundwater salinization under a climate change scenario in an aridarea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7783, https://doi.org/10.5194/egusphere-egu21-7783, 2021.

Claudia Cherubini et al.

Abu Dhabi is one of the arid regions in the world having less than 100 mm of rainfall per annum. The renewability of freshwater occurs only in the eastern part. The groundwater resources under desirable quality are very concise due to limited dilution/rainfall and higher rate of evaporation. Hence, in recent decades, desalinated water has been introduced for agriculture activities and surplus desalinated water is injected into the aquifer as artificial recharge. This study is conducted to understand the impacts in the aquifer system caused by the introduction of desalinated water for agriculture activities and for aquifer recharge structures. The simulation was carried out from 2000 to 2050 using reported rate of groundwater pumping and of desalinated water with 0.1 g/l, 0.5 g/l, 1 g/l, 1.5 g/l and 2 g/l degrees of salinity. A wide range of decline in the groundwater table is noticed in the western part of the aquifer due to less rainfall recharge. The results confirm that this region demands either reduction in agricultural activities or additional usage of desalinated water by which the pumping of groundwater can be reduced further. The improvement in the groundwater quality is noticed in the aquifer due to the addition of less saline desalinated water into the aquifer. This study confirms the long term suitability of existing aquifer recharge structure. Also, it expresses the need of further management practices in quantifying the desalinated water contribution for agriculture activities.


How to cite: Cherubini, C., Sadhasivam, S., Pastore, N., and Ghirotti, M.: Impacts of Desalinated Irrigation Water in the Abu Dhabi surficial aquifer, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13095, https://doi.org/10.5194/egusphere-egu21-13095, 2021.

Ismail Abd-Elaty et al.

Groundwater is the main source of drinking water in the Nile Delta. Unfortunately, it might be polluted by seepage from polluted streams. This study was carried out to investigate the possible measures  to  protect groundwater  in the Nile delta aquifer using a numerical model (MT3DMS - Mass Transport 3-Dimension Multi-Species). The sources of groundwater contamination were identified and the total dissolved solids (TDS) was taken as an indicator for the contamination. Different strategies were investigated for mitigating the impact of polluted water: i) allocating polluted drains and canals in lower permeability layers; ii)  installing cut-off walls in the polluted drains, and finally, iii) using lining materials in polluted drains and canals. Results indicated these measures effective to mitigate the groundwater pollution. In particular, the cut-off wall was effective for contamination reduction in shallow aquifers, whereas it had no effect in the deep aquifer, while lining materials in polluted drains and canals were able to prevent contamination and to protect the freshwater in the aquifers.  It is worth mentioning that this study was partially supported by a bilateral project between ASRT (Egypt) and CNR (Italy).



How to cite: Abd-Elaty, I., Zelenakova, M., Straface, S., Vranayová, Z., Abu-hashim, M., Negm, A., and Scozzari, A.: Investigating the possible measure to protect groundwater from polluted streams in Arid and Semi-Arid Regions: the Eastern Nile Delta case study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14734, https://doi.org/10.5194/egusphere-egu21-14734, 2021.

Isabel Margarida Horta Antunes and Ameno Bande

Groundwater is vulnerable to contamination from natural and anthropogenic activities. The agricultural and human activities associated with hydrological characteristics influence the quality of groundwater. The City of Tete is in the Nharthanda Valley (Zambezi River, Central Mozambique). The city faces a set of serious structural issues of access to water such as a precarious public water supply system, including a lack of network management, water rationing, and a poor sewerage system. Groundwater is collected from the aquifer for the public water supply system of the old city of Tete and a for a traditional agro-livestock farm, which is irrigated by artesian wells. Groundwater abstraction has increased in the last few decades, and it was identified as a risk for groundwater quality and quantity. Groundwater physic-chemical and microbiological parameters obtained from fifteen boreholes and eleven wells have been determined to assess water quality. The presence of potential contaminant activities throughout the Nhartanda Valley and adjacent areas associated with contamination of the Zambezi River contribute to the degradation of water quality. The high vulnerability index for most chemical and microbiological elements indicates that groundwater is easily reached by bacteria and viruses and other potentially toxic substances. Most of the water parameters, from wells and boreholes, exceed the water referenced values allowed for human consumption and agricultural use. The protection of the Nhartanda Valley aquifer system is necessary and urgent. The identification of the most vulnerable areas provides important information for groundwater management, such as the indication of protection measures in aquifer systems.

How to cite: Antunes, I. M. H. and Bande, A.: Management of groundwater sustainability and contamination - a Mozambique case study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-910, https://doi.org/10.5194/egusphere-egu21-910, 2021.

Miguel Angel Marazuela et al.

Many drinking water systems worldwide are based on river bank filtration. From a quantitative point of view river bank filtration systems are highly reliable because of the high permeability of alluvial aquifers linked to high production rates. However, there might be an increased risk of contamination because of the short residence time between the river and the production well, especially during flood events.

Flood events change the river-aquifer hydraulic interactions and may increase infiltration rates (e.g., due to an increased hydraulic head, larger river infiltration widths, or erosion of a siltation layer). This leads to changes in groundwater flow paths and production wells might abstract water with a shorter residence time and lower quality. Groundwater quality may degrade during flood events due to the presence of undesirable chemicals (e.g., wastes water treatment plant overflow) and the occurrence of faecal indicator bacteria such as E.Coli.

Groundwater modelling can assist in developing strategies to protect river bank filtration from such undesired contamination by predicting optimal operation conditions. The key impediment of this approach is significant uncertainties in subsurface properties and the associated uncertainties of the groundwater flow paths. To reduce uncertainties in model predictions, anthropogenic tracers including the MRI contrast agent gadolinium and artificial sweeteners were used in this study. They revealed sources and flow patterns, and have been used to derive mixing ratios representing different temporal and spatial scales. Including anthropogenic tracers into the objective function of the calibration process also lead to more accurate estimation of groundwater flow paths. This was critical to predict the best water works operation strategy during flood events.

How to cite: Marazuela, M. A., Herrera, P., Erlmeier, K., Brünjes, R., Brunner, P., and Hofmann, T.: Reducing the risk for contamination of river bank filtration systems using inverse modelling and anthopogenic traces, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2388, https://doi.org/10.5194/egusphere-egu21-2388, 2021.

Gabriela Patricia Flores Avilés et al.

In the semi-arid Bolivian Altiplano, the Katari and Lago Menor Basin, ranging between 6000 and 3800 m a.s.l. in altitude, hosts a major aquifer in Quaternary sediments of fluvioglacial and paleolacustrine origin. This basin supports a population of over 1.2 million of inhabitants and the largest city in the Altiplano, El Alto, one of the Latin America’s fastest growing cities in the 1980s. This rapid urban growth was accompanied by minimal land planning, and lack of basic infrastructure and environmental policies. In addition, the region is greatly affected by climate change, causing the glaciers to shrink. A multi-tracer approach was used to understand the main hydrogeochemical processes taking place along the groundwater flow, and to evaluate the impact of anthropogenic activities on groundwater quality and nitrate concentrations. In the upper part of the aquifer (above 4000m), in the Piedmont subsystem, siliciclastic and evaporitic rocks host groundwater of high quality. Here, groundwater chemistry is dominated by silicate weathering leading to a Ca(Mg)-HCO3 facies, low nitrate concentrations (<3.2 mgL-1), and low mineralization. At lower altitude, the anthropogenic impact is revealed by the increase in NO3- concentrations, reaching up to 35.6 mg L-1.  Nitrate stable isotopes allowed discriminating three main nitrate contributions:  leaching from areas influenced by manure piles, use of synthetic N fertilizers, and leakage from sewage collection pipes. Natural attenuation of nitrate occurs when fresh groundwater mixes with brackish groundwater of evaporitic origin. On the other hand, in the lacustrine plain (~3860 to 3810 m a.s.l), the groundwater geochemistry is dominated by evaporite dissolution and calcite precipitation, while nitrate originates from nitrification of synthetic fertilizers. This first hydrogeochemical study of one of the major groundwater systems in the Northern Altiplano is an important step towards a better management of this crucial water resource for the sustainable development of this region.

Fundings :

The present study was undertaken with the financial support of the Plurinational State of Bolivia provided through the Program “100 Scholarships for Postgraduate Education within the Framework of Technological and Scientific Sovereignty”, Supreme Decree 2100 (1 September 2014), and partly funded by LABEX OSUG@2020, ANR grant no.ANR-10-LABX-56 (financed by the Future Investments programme launched by the French government and implemented by the ANR).

How to cite: Flores Avilés, G. P., Duwig, C., Sacchi, E., Spadini, L., Savarino, J., and Ramos Ramos, O. E.: Hydrogeochemical and nitrate isotopic indicators of vulnerability in the Katari-Lago Menor basin-aquifer, Lake Titicaca-Bolivia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12837, https://doi.org/10.5194/egusphere-egu21-12837, 2021.

Mary Etuk et al.

One of the major challenges for the sustainable development of the federal capital territory of Abuja (Nigeria) is related to the access to safe fresh water resources. This area lies within the drought prone parts of the Sahel region. As in many regions of the world there has been growing competing demands for fresh water as a result of population growth and groundwater quality degradation. In this context, the paucity of data and in depth knowledge of aquifer features and groundwater flow makes groundwater management even more complex, with a severe impact on access to safe water resources for the local populations. To address this challenge, the purpose of the presented research is to generate information on aquifer settings and its vulnerability and on the qualitative and quantitative assessment of the available groundwater resources. Remote sensing and GIS were applied to improve the available information on groundwater resources of Abuja. Fundamental information such as recharge rate, availability and vulnerability of groundwater to pollution was determined. Aquifer vulnerability zones were delineated using the DRASTIC model by integrating layers of depth to groundwater, aquifer recharge, aquifer media, soil type, topography, impact of vadose zone and hydraulic conductivity.  The study area covers about 8000km². The elevation ranges from 62 to 843m a.s.l. with the highest elevations at the North Eastern parts and the lowest elevations at the South Western parts of the study area. There are three soil types in the area, the silty clay, silt loam and clay with clay being the predominant soil type. The five major rock types in the area include migmatite gneiss, schist and metasediment, sandstone and river alluvium, granite and quartzite. The aquifer type is phreatic and the depth to groundwater ranges from 2.8 to 21.9 m. The high recharge areas occurred mostly in highly fractured areas covered with metasedimentary rocks, migmatite gneiss and sandstones. The groundwater vulnerability zones in the study area were grouped into four classes: High, moderate, low and very low. The highly vulnerable zones are the North Eastern parts of the study area covering most parts of Bwari and parts of the municipal council areas and also the Southern parts of the study area covering parts of Kuje and Abaji. They constitute the highly fractured areas covered with silt loam soil type. The very low vulnerable zones are the North Western and Central parts covering mostly Gwgwalada and Kwali areas.  This study demonstrates that GIS and remote sensing techniques are efficient and cost effective tool for delineation of groundwater vulnerability zones. The information obtained will be used as a basis for a geochemical characterization of groundwater quality in the region with the overall goal of supporting new groundwater management plans in the region.


How to cite: Etuk, M., Ogbonnaya, I., Viaroli, S., Petrini, R., and Re, V.: Vulnerability Assessment of Shallow Aquifers in Abuja using GIS and Hydrogeological Parameters, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8712, https://doi.org/10.5194/egusphere-egu21-8712, 2021.

Chiara Zanotti et al.

Groundwater is a key resource to fulfil human drinking needs worldwide. Therefore, guaranteeing a safe and constant supply of drinking water to the public has been an important focus at European level. Recently, the EU approach to drinking water monitoring radically changed, moving from the simple water quality monitoring, toward a more comprehensive risk assessment, involving the whole supply chain from collection to distribution. Particularly, EU Directives 2015/1787 and 2020/2184 endorsed the Water Safety Plan (WSP) system which requires a detailed assessment of every possible dangerous event.

Groundwater extraction constitutes the first step of the supply chain, and therefore the most vital. In this work, an approach to assess groundwater wells vulnerability in the scope of WSP is proposed, considering natural and anthropogenic hazards, through a hydrogeological, hydrochemical and hydrodynamical characterization. The study area is the Lake Iseo morainic amphitheatre (ca. 180 km2) in the Brescia province, Northern Italy. Particularly, 17 wells have been analyzed, serving 4 municipalities.

Two main dangerous events have been considered as possible hazard for the collected groundwater: a) anthropogenic impact from the surface, related to the land use, and b) natural contamination by reduced species consequent to the degradation of natural organic matter.

Groundwater extraction vulnerability to these two dangerous events has been assessed, considering several hydrogeological aspects: a) the kind of the exploited aquifer (shallow, confined, semiconfined), b) groundwater depth for the shallow aquifers, c) permeability of the vadose zone for the shallow aquifers and d) red-ox conditions of the collected groundwater.

To assess these parameters, lithostratigraphic, chemical and piezometric data were analyzed, reaching a deep understanding of the system by characterizing the different exploited groundwater bodies from a hydrogeological, hydrochemical and hydrodynamic point of view.

Hydrogeological sections were elaborated, covering the whole amphitheater, 7 in the N-S direction and 7 in the W-E direction. The interpretation of these sections allowed to identify the distribution of the main aquifer bodies and the relationships between the various hydrogeological units. To evaluate the red-ox conditions and perform groundwater quality characterization, chemical data were analyzed, including major ions and red-ox sensitive species, through boxplot and statistical analysis. Furthermore, piezometric levels were analyzed to identify groundwater depth, flow directions and watersheds. Of the 17 wells, one resulted to be confined with reducing conditions. Among the remaining, 7 are semiconfined while 9 are shallow, with oxidizing conditions in both cases. Concerning groundwater depth, 13 present values above 40 m, 2 between 20 m and 40 m, and 1 below 20 m. As regards the vadose zone permeability, 9 present high permeability, 7 medium. Totally, in terms of vulnerability to anthropic impacts, one well has low vulnerability, 9 medium and 6 high, while in terms of vulnerability to natural contamination one well has high vulnerability and the remaining low.

This approach allowed a deep understanding of the system and constitutes a reproducible methodology to assess groundwater wells vulnerability to natural and anthropogenic contaminations.

Funding: this work was supported and carried out in cooperation with Acque Bresciane, water supplier.

How to cite: Zanotti, C., Rotiroti, M., Fumagalli, L., Caschetto, M., Sartirana, D., and Bonomi, T.: Hydrogeological and hydrochemical characterization to assess wells vulnerability in the scope of Water Safety Plans, a case study in Northern Italy., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2106, https://doi.org/10.5194/egusphere-egu21-2106, 2021.

Swagatam Chakraborty et al.

Use of environmental or artificial tracers has been an effective approach to characterize groundwater flow and solute transport, tracking pollutant migration and determine travel time. However, availability of a distinctive number of tracers, variability in interaction with the aquifer matrix, and analytical detection limits are namely few of the significant concerns to be addressed and which led us to focus on employing novel DNA tracers.

Besides the quality of being unique, improbably prevalent in nature and environmentally friendly, DNA tracers can be synthesized virtually in infinite numbers of distinct sequences, rendering them a potential candidate for multi-tracer applications for subsurface and groundwater flow characterization. Studies have already demonstrated the potential of DNA tracing in groundwater studies but a blueprint for methodical application and analysis is required.

In this study, we investigate the applicability of DNA tracers in determining hydraulic parameters of a natural aquifer, such as, hydraulic conductivity, effective porosity, dispersivity, and travel time, the most significant characters of a matrix, influencing solute or pollutant transport. In addition, we aim to leverage the applicability of the tracers in terms of minimizing the uncertainty in estimating the parameters.

In order to capitalize on these advantages of DNA tracers with the aim of addressing the aforementioned objectives, this research focuses on employing multiple dsDNA (ds=double stranded) tracers in a 1.3 m long three-dimensional sand-filled aquifer tank. Under forced-gradient water flow conditions, distinctly sequenced, monodispersed dsDNA tracers are instantaneously injected through injection wells, taking into account different scenarios. The scenarios consider different configurations of injection and sampling strategies. Samples collected periodically were subjected to quantitative polymerase chain reaction (qPCR) for DNA concentration estimation. All the silica-encapsulated DNA particles were comparable in size and surface properties.

Individual breakthrough curves from each of the scenarios are carefully analysed for determining water flow and hydraulic properties. In addition, the experiments producing multiple breakthrough curves are cumulatively analysed for obtaining a minimal uncertainty for the parameter estimations.

How to cite: Chakraborty, S., Arachchilage, C., Elhaj, R. H. M., Foppen, J. W., Bogaard, T., and Schijven, J.: Multiple DNA-tracer transport approach for determining aquifer matrix properties in a laboratory 3D aquifer sand tank: a methodical perspective, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16366, https://doi.org/10.5194/egusphere-egu21-16366, 2021.

Adrien Selles et al.

Crystalline rocks aquifers are usually represented with a low porosity and hydraulic conductivity giving low well yields. Over the world, more than 880 millions people live on crystalline basement rocks. Thus, abilities to spot sufficient groundwater resource in these systems are crucial. Nevertheless, assessment of the sustainable reservoirs in crystalline basement aquifers is challenging. The well-admitted conceptual model presents a stratiform-weathered profile above a fractured zone showing a decreasing fracture density with depth. The interconnection between these two compartments defines the hydraulic parameters: the weathered profile is capacitive while the fractured zone is transmissive.

French Guiana is mostly composed of Paleoproterozoic rocks belonging to the Guiana Shield. It was formed during protracted periods of intense suprasubduction related magmatism, metamorphism and deformation, culminating with the Transamazonian orogeny, bracketed between 2.3 and 1.9 Ga. This peculiar geological history creates a large diversity of geological units from undeformed granitic units to ultramylonitized shears-zone related meta-volcano-sedimentary units and through brittle to ductile deformed units. Furthermore, over almost 200 Ma, the French Guiana recorded a deep weathering phase leading to heterogeneous and complex profiles up to 80-100 m deep. In such a context, hydrogeological exploration is thus puzzling, especially as French Guiana is covered by the Amazonian Forest, reducing direct observations.    

We use a multi-disciplinary method from remote sensing to field observations through geophysical tomography to propose conceptual models of groundwater circulation helping us to localise precisely (meter scale) exploration borewells. After 15 years of hydrogeological surveys, the BRGM has studied plural units: (i) classical isotropic unit (Mahury Massif (MM)) and Granitic unit (Mana), (ii) ductile to brittle deformed units separated by strike-slip fault (Rosebel-Bonidoro unit (RBU) and Armina Unit (AU)), (iii) ultramilonitized unit (Paramaca Unit (PU)). A large heterogeneity of hydrogeological conceptual models for each context arise from our results. Notwithstanding this diversity and thanks to these conceptualizations, we were able to propose successfully useable sustainable resources, confirming the robustness of the method.     

The MM and Mana are classical isotropic units displaying a deep weathered profile. The confined aquifer is located into the fractured layer with yield reaching 15 m3.h-1. Crosscutting dolerite dyke is attested to be an interesting hydrogeological target with yield near 20 m3.h-1. The highest yields in French Guiana for crystalline basement rocks (30 m3.h-1) are found in confined aquifer in PU context. This record could be due to the ultramylonitic deformation giving a high permeable unit. Three different places were studied for the AU (Sparouine, Roura, Beauséjour). As for the PU, aquifers are all confined. Yields are systematically low (around 2-5 m3.h-1). The RBU is an interesting and contrasting unit because it does not show developed weathered profile. It seems that an unconfined aquifer must probably recharge surroundings units (i.e. PU and AU).

This work highlights the high potential of ductile to ultramylonitic shear zones for groundwater resource. Taking together, these conceptual models highlight that, in French Guiana and probably in entire Guiana Shield, Transamazonian tectonometamorphic structures as well as early Jurassic extensive faults correspond to sustainable useable groundwater resources.

How to cite: Selles, A., Aertgeerts, G., Brisset, N., and Lhotelin, M.: Heterogeneity of hydrogeological conceptual models in crystalline basement aquifers under equatorial climate: case study of French Guiana, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2517, https://doi.org/10.5194/egusphere-egu21-2517, 2021.

Irene Kinoti et al.

Distributed integrated hydrological models (IHMs) are the most effective tools for estimating groundwater recharge in arid and semi-arid areas characterized by thick unsaturated zone. It is also important to capture spatio-temporal aquifer dynamics by using real-time or near-real-time data, for sustainable water resources management. However, such data is often unavailable in developing countries where monitoring networks are scarce. In recent years, remote sensing has played an important role in providing spatio-temporal information for evaluation and management of water resources. Nevertheless, application of remote sensing in groundwater studies is still limited and has mainly focused on assessment of groundwater recharge and groundwater storage as well as to provide boundary conditions and driving forces for both standalone groundwater models and IHMs. This study entails application of remote sensing data in developing the distributed integrated hydrological model for Stampriet transboundary multi-layered aquifer system shared between Namibia, Botswana and South Africa. A numerical model has been set – up using MODFLOW 6 coupled with the Unsaturated Zone Flow (UZF) Package where Climate Hazards Infrared Precipitation with stations (CHIRPS) rainfall data and Global Land Evaporation Amsterdam Model (GLEAM) potential evapotranspiration data were implemented as the model driving forces. Other input data used include digital elevation model, and land-use/landcover and also soil datasets to define unsaturated zone parameters. The model has been calibrated with groundwater level measurements as the state variables in transient conditions at daily time step for a period of 16 years. The model-simulated unsaturated zone and groundwater storage was compared to GRACE-derived sub-surface storage anomaly, further also used to constrain the model. The calibrated model provides spatio-temporal water flux dynamics as well as water balances and hence an understanding of the groundwater-resource dynamics and replenishment. This information is shown useful for proper management of the transboundary water resource as well as for policy making.

How to cite: Kinoti, I., Leblanc, M., Olioso, A., Lubczynski, M., and Poulain, A.: Remote sensing for assessment of groundwater resources, A case study of Stampriet Transboundary Aquifer, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7444, https://doi.org/10.5194/egusphere-egu21-7444, 2021.

Cong-Thi Diep

Imaging the extent of salt water intrusion in the Luy river coastal aquifer (Binh Thuan) using electrical resistivity tomography (ERT)

Diep Cong-Thi1,3, Linh Pham Dieu1,3, Robin Thibaut1, Marieke Paepen1, Hieu Huu Ho3,

Frédéric Nguyen2, Thomas Hermans1


1Department of Geology,Ghent University, 9000-Gent, Belgium

2 Department of Urban and Environmental Engineering,Liege University and Department of Civil Engineering, KU Leuven, B- 4000 Liège and 3000 Leuven, Belgium

3 Department of Marine Geology, Vietnam Institute of Geosciences and Mineral Resources (VIGMR), 100000 Hanoi, Vietnam


Seawater intrusion has been one of the most concerning issues of the Vietnam South Central provinces in recent years, especially in the Binh Thuan province which is characterized by a hyper-arid climate. During the dry season extending from November to April, seawater intrudes through estuaries and threatens groundwater resources. The latter are under increasing pressure due to water extraction for agri- and aquaculture. To evaluate the current state of salinity in the shallow coastal aquifer, 21 electrical resistivity tomography (ERT) measurements were collected along the downstream part of the Luy river based on the previous saltwater intrusion boundary which was estimated from water samples collected from shallow boreholes. The data were inverted to get the resistivity distribution of the subsurface and interpreted in terms of salinity. Comparison with well data shows that resistivity values below 6.5 Ohm.m correspond to the presence of saltwater in the aquifers. On the right bank of the river, a higher elevation dune area contains a freshwater aquifer which limits the intrusion of saltwater. On the left bank dominated by lowland areas, saline water fills almost the entire thickness of the aquifer, except locally for small thin freshwater lenses. At larger distances from the sea, the aquifer displays a complex distribution of fresh and saline lenses. Those variations seem to be correlated with the presence of clay lenses, recharge sources and irrigation practices. ERT data also reveals the depth of the rock basement. The geophysical observations show that the extension of saltwater intrusion is much larger and more complex than expected from existing borehole data and is not limited to interaction with the river.

KEYWORDS: saltwater intrusion, groundwater, electrical resistivity tomography, Luy river.  

*Corresponding Authors. Email: Diep.CongThi@UGent.be; Linh.PhamDieu@Ugent.be; robin.thibaut@ugent.be; marieke.paepen@ugent.be; hohuuhieu@yahoo.com; f.nguyen@uliege.be; thomas.hermans@ugent.be

How to cite: Diep, C.-T.: Imaging the extent of saltwater intrusion in the Luy river coastal aquifer (Binh Thuan) using electrical resistivity tomography (ERT), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4960, https://doi.org/10.5194/egusphere-egu21-4960, 2021.

Marco Rotiroti et al.

Discretizing anthropogenic and natural contaminations represents a crucial step in groundwater management and regulation. Natural background levels (NBLs) have a huge impact on groundwater protections and remediation strategies, but it is still an issue on the ground in terms of reliability and accuracy, thus its derivation needs further scientific efforts.

The derivation of local NBLs (LNBLs) is intended to overcome the limitation of considering a groundwater body (GWB) homogeneous, hence accounting hydrogeochemical heterogeneities within the aquifer system.

This work presents a statistical approach assessing LNBLs for sensitive redox species (As, Fe, Mn, NH4) in 30 GWBs within the Lombardy Region. Under the monitoring network of the Regional Agency for Environmental Protection of Lombardy (ARPA), more than 500 wells were investigated, thus each GWBs were identified within 4 aquifer types: shallow, intermediate, deep Po Plain aquifers and Alpine valley aquifers. The initial dataset underwent preselection and multivariate analyses, appointing at each well a geogenic redox zonation. It leaded to discretize geochemically-homogeneous subgroups and characterize them as function of site-specific natural facies: oxidised (293 wells), reduced (199 wells) and saline (11 wells). Interquartile range criteria, validations’ tests (Mann-Kendall and Shapiro-Wilk), probability density histograms and probability plots inferred temporally and spatially the datasets, one for each target species, discretized for aquifer and natural facies appartenances. This resulted in the identification of the statistical distributions from redox-homogeneous sets of data from which the LNBLs were derived.

Considering the Po Plain aquifer (shallow, intermediate and deep), NBLs derivation for As revealed three subgroups within the oxidised facies, for which the NBLs values are of 2, 3 and 7 μg/L, four subgroups ascribe to the reduced facies with NBLs of 13, 49, 71 and 291 μg/L, and two subgroups for the saline facies with NBLs of 3 and 12 μg/L. According Fe, two are the subgroups within the oxidised facies, with NBLs of 40 and 94 μg/L, four subgroups fall in the reduced facies with NBLs of 653, 1430, 3200 and 6000 μg/L; within the saline facies, two subgroups are identified with NBLs of 1647 and 6000 μg/L. Two subgroups characterize the oxidised facies for NBLs of Mn with values of 8 and 27 μg/L, and NBLs of 34, 216, 485, 912 and 1514 μg/L refer to five subgroups in reduced facies, while within the saline facies fall two subgroups with NBLs of 381 and 921 μg/L. With regards to NH4, NBLs reach values of 49, 110 and 190 μg/L for the three subgroups within the oxidised facies, whereas values of 834, 2600, 3090, 4480 μg/L are derived for the four subgroups in the reduced facies; the two subgroups ascribed to the saline facies reveal NBLs of 1860 and 6620 μg/L.

Data demonstrate how an in depth understanding of aquifers’ redox-zonations turned out to be functional for assessing LNBLs. Regional Legislation (D.G.R. 23novembre2020 n.3903) has been amended on the basis of the outcomes of this work, revealing site redox-specific LNBLs of practical significance.


Funding: this work was granted and carried out in collaboration with Lombardy Region.

How to cite: Rotiroti, M., Caschetto, M., Zanotti, C., Parini, M., Cipriano, G., Bonomi, T., and Fumagalli, L.: Local natural background levels assessment through a groundwater redox zonation, the case of Lombardy Region., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3772, https://doi.org/10.5194/egusphere-egu21-3772, 2021.

Susana Rodriguez Padilla et al.

The aim of this research is to establish the groundwater baseline in a sub-basin located in the southwest of Mexico City, an area affected by anthropogenic activities.

The methodology consists of groundwater sampling in 40 sites to measure major ions and physicochemical parameters as temperature, pH, Eh, and total dissolved solids. The end-member mixing analysis was applied using the groundwater flow system approach. The groundwater baseline was established using flow components that were defined.

The main results are: to found four groundwater flow components: 1) local, 2) intermediate, 3) cold regional, and 4) hot regional; to established a groundwater baselines; to relate the anomalous concentrations of nitrate and sulfate due to anthropogenic activities in the area; to associate the fertilizer use, wastewater, and the canal leaching black waters as the principal sources of these concentrations.

The conclusions show the importance to use the groundwater flow system approach to differentiate natural processes as hydrochemical evolution due to water-rock interaction of the anthropogenic influence. In the context where groundwater is extracted without knowing its baseline and the anthropological implications, the groundwater flow system approach to permit generated best management and administration strategies.

How to cite: Rodriguez Padilla, S., Olea Olea, S., and Escolero Fuentes, O.: Establishment of groundwater baseline using end-member mixing analysis in the groundwater flow system approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6642, https://doi.org/10.5194/egusphere-egu21-6642, 2021.

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Fri, 30 Apr, 11:00–12:30

Chairpersons: Daniela Ducci, Judit Mádl-Szőnyi, John Molson

Chiara Avataneo et al.

Weathering and erosion of asbestos-bearing rocks, such as meta-ophiolites (e.g. serpentinite rocks and metabasites), is the principal natural cause of asbestos water dispersion in Naturally Occurring Asbestos (NOA) rich settings. Water pollution by asbestos may occur as a consequence of superficial and groundwater flow through natural rock formations with NOA, depending on several characteristics of either the rocks (e.g. mineralogical composition, fracture grade) and hence the water (e.g. pH, speed).

Given the importance of groundwater resources for both drinking water and agricultural and industrial activities, groundwater asbestos pollution represents an environmental problem and could even constitute a risk for human health. In fact, waterborne asbestos can come into contact with human beings as airborne fibres after water vaporization, or by ingestion, especially if they are present in drinking water. While a lot is known about diseases caused by airborne asbestos respiration, not enough has been yet understood about potential noxiousness of its ingestion. For this reason, the necessity to set a Maximum Contaminant Level (MCL) for asbestos in potentially usable water is still debated.

As the North-Western and Central Alps are rich in NOA and also in naturally occurring asbestiform minerals non-asbestos classified, it’s essential to understand if, how and which type of mineral fibres can eventually be released into water and to correlate them to the geolithological and hydrogeological characteristics of the area.

The results of a surface water and groundwater sampling and analysis campaign, settled in the North-Western Alps, will be presented. The main aim is to investigate the principal aspects related to asbestos and asbestiform fibres presence in water, in particular their natural occurrence in groundwater, linked to hydrological and geolithological characteristics of the reservoir. Furthermore, laboratory test to study the flow of polluted water through a packed column will be designed and observations on the methodology to evaluate waterborne mineral fibres behaviour into porous media will be presented.

These data are fundamental to monitor asbestos (and asbestiform) fibres transportation due to water flowing into NOA and to better understand the relationship among geology, hydrogeology and mineral fibres presence in water.

How to cite: Avataneo, C., Belluso, E., Capella, S., Lasagna, M., and De Luca, D. A.: Groundwater flow in Naturally Occurring Asbestos (NOA) rich settings: new findings on the relation among concentration, types and mobility of mineral fibres, and geological characteristics of aquifer formations., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3414, https://doi.org/10.5194/egusphere-egu21-3414, 2021.

Katalin Csondor et al.

In South Transdanubia (Hungary) there are remarkable geothermal and hydrocarbon resources. The area is also characterized by natural thermal water discharge at the boundary of outcropping carbonate hills and adjacent sedimentary basin. These regional discharge areas are favourable sites of hypogenic caves as well. These geofluid systems and groundwater related phenomena are usually investigated separately and their interactions are just neglected. The aim of this study is to give all these groundwater-related resources and phenomena a common framework applying the concept of regional hydraulic continuity, and to complete the basin-scale hydraulic assessment of the area based on preproduction archival measured data. Pressure-elevation profiles, tomographic fluid-potential maps and hydraulic cross-sections were constructed to determine the vertical and horizontal fluid-flow conditions. As a result, two kinds of fluid flow systems could be identified. Within the gravitational flow systems, horizontal flow conditions are dominant and the regional flow direction tends toward the S–SE. In deeper basin regions, an overpressured flow system is prevalent, where fluids are driven laterally from the deeper sub-basins towards their margins. Based on the regional-scale evaluation of fluid flow systems, conclusions could be drawn regarding the geothermal and hydrocarbon potential of the area. Additionally, local-scale phenomena could be explained, and the study emphasizes that knowledge on regional groundwater flow systems is essential to understand local scale groundwater-related phenomena such as recent cave formation in an area. A comparison with the marginal Buda Thermal Karst area allows for generalized conclusions regarding the connections between marginal karst reservoirs and the Pannonian Basin. Furthermore, the results of the study can be directly applied in the exploration and sustainable utilization of groundwater related resources, such as thermal waters and hydrocarbons.

This topic is part of a project that has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 810980. The National Research, Development and Innovation Fund has provided financial support to the research under the grant agreement no. PD 116227.

How to cite: Csondor, K., Csobaji, L., Zentai-Czauner, B., Győri, O., and Erőss, A.: Karst evolution, hydrocarbon and geothermal resources in flow system context (South Hungary), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14896, https://doi.org/10.5194/egusphere-egu21-14896, 2021.

Dupuy Margaux et al.

Deep groundwater circulation increases multiplicity and complexity of groundwater pathways providing a high diversity of intrinsic water properties. Water-rock interactions at depth associated with transit time disparities generate singular mineralisation with high temperature, notable dissolved ions and significant gaseous content. As shown in literature, deep processes involved in gas release can be deduced from fluid gas composition collected at the surface. Widely used as tracers in volcanic areas, seismically- and tectonically-active regions, the gaseous emission monitoring is underused to understand the regional and local groundwater flow patterns that are not linked to an active zone. In order to refine knowledge on complex flow organisation at the origin of diversified mineral springs, this study aims to experiment the use of dissolved gaseous components as a tracer of water up flows interactions.

The oriental plain of Corsica (France) has been chosen for its wide variety of mineral waters (22 springs) emerging at the interface of magmatic (Hercynian orogenesis), metamorphic (Alpine orogenesis) and sedimentary rocks (from the Alpine orogenesis and from Neogene deposits). Dissolved reactive (N2, CO2, CH4, H2S, H2, O2) and noble gases (Ne, Ar, He) on 9 springs have been quarterly sampled (April, July, September & December 2018), and analysed by gas chromatography (µGC).

The first results highlight 3 very contrasted gas abundances:

  • (1) N2-rich thermal waters (54°C), poorly mineralised, with noble gas occurrence as cortege gases. This highlights the influence of deep flow with a long groundwater residence time.
  • (2) CO2-rich cold waters (<20°C), low to highly mineralised, with N2 as cortege gase. This highlights the occurence of deep flow interacting during his upflow with carbonates of metamophosed rocks.
  • (3) CH4-rich cold waters (<20°C), highly mineralised, with H2S and CO2 as cortege gases. This highlights biotic anaerobic activity involvement in gases composition of the mineral waters.

Then, based on the observed abundance of noble gases, theoretical recharge conditions were computed to defined recharge temperature, air- and He-excess. Computation results have stressed out the common origin of these three gas, depending on flow paths, reservoir conditions, biotic and abiotic interaction involvement. The circulation within magmatic reservoir is responsible for the deep N2-rich flow, which shows during his up flow abiotic interactions with metamorphised carbonates rocks, increasing the CO2 content in water. Then under anoxic geological confinement in deep sedimentary layers, the CO2 is reduced into CH4 and N2 into NH4. In the shallowest sedimentary layers, CH4 formed is degraded, due to the occurrence of rich-organic matter lithology, by biotic activity into H2S.

This monitoring substantially contributes to improving the complex hydrogeological model of Corsican mineral springs, highlighting the link between deep regional and local groundwater flow; whose even of the non-conventional tools doesn’t succeed in clearly testified about the deep escape mechanisms of natural fluids in this non-volcanic regions. In absence of current volcanism, seismic- or tectonic-activity, monitoring the dissolved gases releasing at the surface by thermo-mineral springs provides fundamental information about deep and complex flow paths.

How to cite: Margaux, D., Emilie, G., Thierry, L., Eliot, C., Virginie, V., Luc, A., Sebastien, S., Alexandra, M., and Frédéric, H.: Using natural gas emission monitoring to assess the hydrogeological mineral springs genesis in non-active zone: example from the Corsica Island, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4932, https://doi.org/10.5194/egusphere-egu21-4932, 2021.

Marina Ćuk Đurović et al.

Groundwater originating from great depths provide a valuable geochemical sampling medium for exploring the development of the Earth's crust, geological, and hydrogeological resources. This particularly applies to sites of natural springs, where favorable hydrogeological conditions enabled regional discharge. Despite the numerous occurrences of mineral and thermal waters in Serbia, the current understanding of the regional groundwater flow is associated with many open questions that need to be addressed. From a geological standpoint, Serbia is part of the Alpine-Mediterranean mountain belt. From the middle of the Mesozoic to the present, this area underwent processes of subduction, collision, and extensions with accompanying voluminous magmatism and volcanism. As a result of the mentioned geodynamic events, the Serbian territory was a zone of intensive tectonomagmatic processes which had a significant impact on the formation of the hydrogeological structures for forming groundwater enriched with specific elements and elevated temperatures.

Understanding groundwater origin and characterization of a deep circulation is a big challenge since the groundwater pathways and aqueous chemistry are significantly influenced by various factors. To contribute to the characterization of the hydrogeological systems in which the mineral and thermal waters of Serbia are formed, a general hydrochemical study was conducted. During this research 190 of the most significant sources of mineral and thermal waters were sampled, belonging to different geological (geotectonic) units all over Serbia. The applied hydrochemical approach of recognition of deep circulation patterns is based on an analysis of rare earth elements (REE) and natural radioactivity. REE and long-lived radionuclides 40K, 238U, 232Th, 226,228Ra, gross alpha, and beta radioactivity, have proven to be significant fingerprints of water-rock interaction as well as groundwater flow tracers.

The integrated approach of the hydrogeochemical analysis and multivariate statistical method, including spatial mapping of obtained results, was an important process for meaningful interpretation of the data set. The applied approach summarized the complex hydrochemical properties on a general level defining specific hydrochemical fingerprints of hydrogeological systems with distinct geochemical characteristics and flow patterns. Geochemical behavior of natural tracers (REE) and radioactivity contributed to further characterization of deep hydrogeological systems in basins structures, hard rocks (igneous and metamorphic rocks), as well as carbonate environments.

Rare-earth element data (including abundances and fractionation patterns along with anomalies of Ce and Eu and interelement ratios), relationships of U and Th as elements with different geochemical behavior, and the content of Ra in groundwaters have been singled out as important indicators of deep hydrogeological systems. The results showed that the isolated regional hydrogeological systems are in the function of significant tectonic structures/dislocations, but also hydrogeological characteristics and circulation conditions. Further use of the proposed methodology will provide important data from the assessment of the origin of hydro-geofluids in Serbia and contribute to the wider picture in the understanding of the hydrogeological evolution of regional groundwater flow.

Keywords: natural radioactivity, rare earth elements, hydrogeochemical fingerprints, regional groundwater flow

How to cite: Ćuk Đurović, M., Todorović, M., Jemcov, I., and Papić, P.: Long-lived Radioactive Elements and REE as Fingerprints of Deep Groundwater Flow, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7079, https://doi.org/10.5194/egusphere-egu21-7079, 2021.

Shih-Kai Chen et al.

The Taipei Basin, Taiwan has been densely populated and highly economically developed in recent decades. Global climate change has led to frequently flooding and drought events in recent years, formulating suitable measures to mitigate climatic disaster has become a crucial issue in this city. The sponge city concept is one of the most important options for disaster mitigation in highly urbanization areas. However, the city is also potentially threatened by soil liquefaction due to its sedimentary geology and increasing groundwater level. High groundwater level might be a key limiting factor in the promotion of sponge city. The aim of this study was to understand the relationship between rainfall and groundwater level and the impacts of cumulative rainfall, depth to groundwater table, and impervious pavement ratio on the rainfall/groundwater level response in study area. The cross-correlation function (CCF) was applied to analyze the correlation between rainfall and groundwater level data obtained from 20 observed wells and nearby rainfall gages during dry and wet seasons from 2012 to 2017. The significance groundwater recharge response can be found in 61% and 37% of the observation wells during the wet and dry seasons, respectively. Compared with the factors such as cumulative rainfall, and depth to groundwater table, the ratio of surface impervious pavement is the primary affecting factor behind the correlation between rainfall and groundwater level response. The analysis results also show the areas with shallow groundwater level, high imperious pavement ratio, and the groundwater level with no significant response to rainfall, are almost overlapped with the middle and high level liquefaction potential areas in this city. Measures such as the application of the sponge city concept to increase infiltration should be carefully reevaluated in this city. The research results can provide a reference for the future development of urban water resources management and disaster mitigation strategies under the challenge of globe climate change.

How to cite: Chen, S.-K., Lin, Y.-J., and Lee, Y.-Y.: Characteristics of Rainfall- Groundwater Level Response in Taipei City, Taiwan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1015, https://doi.org/10.5194/egusphere-egu21-1015, 2021.

Xiang Li

Baseflow, referred to as the groundwater discharge, is essential to investigate the groundwater system. A common and classic approach to study baseflow is recession analysis method, but current methods confuse the concept of streamflow recessions and baseflow recessions. This confusion leads to a mixing effect of the fluxes from different storage components and theoretically inconsistent recession analysis results accordingly. Therefore, it motivates an improvement and enhanced scientific understanding of the empirically derived baseflow recession characteristics.  In addition, quantifying baseflow from streamflow is defined as the baseflow separation problem. The state-of-the-art baseflow separation tools are in lack of physical rules and have either structural limitations or are inapplicable in regions with insufficient data, which confines the generalization performance. To overcome these issues, we applied a knowledge guided machine learning (KGML) approach to separate baseflow, which embeds physically derived baseflow recession characteristics in the traditional machine learning framework.

Recession parameter, which is derived from empirical recession analysis, has been observed to exceed its theoretical range on a recession event scale. Besides many potential environmental factors, we hypothesize that this well recognized inconsistency is because the quick flow from surficial water bodies has not been successfully excluded based on the recession selection criterion. We conduct recession analysis using both streamflow and baseflow over 1,000 gages across the continental United States. The baseflow was estimated from Eckhardt two-parameter digital filter and was calibrated against the in-stream field data. It was found that for gages whose calibration performance is satisfactory, the baseflow derived recession parameter agrees more consistently with the recession characteristics, which are indicated by the Boussinesq solutions.

Traditional baseflow separation tools partition streamflow into quick flow and base flow. Those tools have data scarcity issues and structural limitations without involving physical perspectives. To introduce physical rules into baseflow separation and overcome data scarcity issues, we apply a recession-based loss function to train the machine learning model such that the recession characteristics of separated baseflow agree with their theoretical behaviors. Guided by the recession knowledge of baseflow on a catchment scale, progress is being made to finalize this KGML implementation and to improve the baseflow separation approach.

How to cite: Li, X.: Evaluate recession characteristics from baseflow and separate baseflow via the knowledge guided machine learning, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3658, https://doi.org/10.5194/egusphere-egu21-3658, 2021.

Steven Reinaldo Rusli et al.

In this study, we estimate the water balance components of a highly groundwater-dependent and hydrological data-scarce basin of the upper reaches of the Citarum river in West Java, Indonesia. Firstly, we estimate the groundwater abstraction volumes based on population size and a review of literature (0.57mm/day). Estimates of other components like rainfall, actual evaporation, discharge, and total water storage changes are derived from global datasets and are simulated using a distributed hydrological wflow_sbm model which yields additional estimates of discharge, actual evaporation, and total water storage change. We compare each basin water balance estimate as well as quantify the uncertainty of some of the components using the Extended Triple Collocation (ETC) method.

The ETC application on four different rainfall estimates suggests a preference of using the CHIRPS product as the input to the water balance components estimates as it delivers the highest r2  and the lowest RMSE compared to three other sources. From the different data sources and results of the distributed hydrological modeling using CHIRPS as rainfall forcing, we estimate a positive groundwater storage change between 0.12 mm/day - 0.60 mm/day. These results are in agreement with groundwater storage change estimates based upon GRACE gravimetric satellite data, averaged at 0.25 mm/day. The positive groundwater storage change suggests sufficient groundwater recharge occurs compensating for groundwater abstraction. This conclusion seems in agreement with the observation since 2005, although measured in different magnitudes. To validate and narrow the estimated ranges of the basin water storage changes, a devoted groundwater model is necessary to be developed. The result shall also aid in assessing the current and future basin-scale groundwater level changes to support operational water management and policy in the Upper Citarum basin.

How to cite: Rusli, S. R., Weerts, A., and Bense, V.: Estimating the water balance and uncertainty bounds in a highly groundwater-dependent and data-scarce areas: An example for the upper Citarum basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9943, https://doi.org/10.5194/egusphere-egu21-9943, 2021.

Daniela Ducci and Elena Del Gaudio

The monitoring data of spatial-temporal variation of groundwater properties (groundwater levels, hydrodynamic properties, chemical and isotopic characteristics, etc.), collected in different times and with different aims, are often scattered or missing. Moreover, a messy database generates huge amounts of data. Especially the handling of time as a fourth dimension usually requires terabytes of storage space. Therefore, an appropriate data collection, storage and management is required, that is a key concept for the 3D/4D GIS. The objective of this study is to produce a comprehensive data management model that optimizes the handling and storage of spatial-temporal data. The 3D / 4D hydrogeological geo-database with WebGIS implementation for the “Terra dei Fuochi” Campania (Italy), is capable of storing information relating to different parameters (groundwater levels, physical-chemical, isotopic characteristics, etc.) in the space and their variation over time.

Moreover, the model will be capable of handling various kinds of spatial-temporal applications. These include the proper handling of temporal variations (e.g. trends in nitrate pollution, decrease of groundwater levels, climate change effects, etc.) and spatial variation (delimitation of contaminated areas, areas with natural high levels of geogenic compounds, etc.) within a 4D model. The storage requirements will be reduced and spatial as well as spatial-temporal operations are accelerated significantly.

This model could also be used by land managers and restoration practitioners with little knowledge of groundwater, but still have an interest in the critical issues of groundwater, assisting the environmental managers in making decisions in environmental recovery projects.

A further development could be a mobile application providing the same results, enabling real time data in the field to be used in decision-making. That will provide a great opportunity for the knowledge advancement of the field of groundwater.

How to cite: Ducci, D. and Del Gaudio, E.: Design of a 3D/4D hydrogeologic geo-database: an application in the so-called “Terra dei Fuochi” area (Campania, Italy), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-835, https://doi.org/10.5194/egusphere-egu21-835, 2021.

Koichi Yamamoto and Fumiya Ono

We have developed a single-dot paper disk type groundwater flow current meter (single-dot PDV), which is a measuring device that easily measures the groundwater flow velocity from the traces of dots printed on paper using dye ink as a tracer. Correction coefficient based on numerical calculation for the coefficient for converting the sensor-flow velocity to the Darcy flow velocity. The correction coefficient can be expressed by a linear function of the hydraulic conductivity, and the flow velocity can be calibrated by an arbitrary hydraulic conductivity. The measurement principle of PDV was that the ink on the paper disc elutes from the paper and moves in the permeable sponge. After that, it was clarified that tailing occurred by dyeing the ink on the drawing paper. The ink movement speed and the groundwater flow velocity are proportional, and it has been shown that it is appropriate to measure the groundwater flow velocity by the tailing length.

How to cite: Yamamoto, K. and Ono, F.: A simple measurement device for groundwater flow velocity using inkjet-printed drawing paper, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-659, https://doi.org/10.5194/egusphere-egu21-659, 2021.

Carmen Serrano-Hidalgo et al.


The Almonte-Marismas aquifer is a multilayer alluvial groundwater body constituted of silts, sands and gravel of fluvial-deltaic and marine origin. It supports Doñana Natural Space (Southern of Spain). It is in direct hydraulic contact with the Atlantic Ocean to the Southwest. Nowadays, the aquifer is subjected to important losses in terms of regional groundwater resources caused by the excessive groundwater pumping for crop irrigation, as well as for tourism water supply in two coastal resorts. This fact causes a subsequent lowering of the phreatic head, and therefore, the water requirements of the ecosystems in this protected area.

Although up to date there is no evidence of saltwater intrusion in this area, there have been several studies warning that seawater advance through the deep layers would likely happen under the present exploitation pattern (Custodio, 1993). The aim of this study is to analyze the possible destabilization of the dynamic balance between the freshwater and saline water in the aquifer. This goal is assessed through numerical simulations of different seawater intrusion scenarios using a 2D model, where the density flow and solute transport model is considered using the SUTRA 3.0 package (Voss et al., 2002) of Modelmuse (Winston, 2014). This work enables the evaluation of the hydrodynamical conceptual model in the aquifer coast, the potential threat of seawater intrusion caused by coastal resort extractions and the consequences that it entails for the nearby natural environment.

Key issues: saltwater intrusion,2D model, SUTRA, Doñana, overexploitation.



Custodio E. 1993. Preliminary outlook of saltwater intrusion conditions in the Doñana National Park (Southern Spain). Study and Modelling of Saltwater Intrusion into Aquifers. Proceedings 12th Saltwater Intrusion Meeting, Barcelona, Nov. 1992. CIHS.CIMNE. Barcelona, 1993: 295-315.

Voss, C. I., and Provost, A.M., 2002 (Version of September 22, 2010), SUTRA, A model for saturated-unsaturated variable-density ground-water flow with solute or energy transport, U.S. Geological Survey Water-Resources Investigations Report 02-4231, 291 p.

Winston, R.B., 2014, Modifications made to ModelMuse to add support for the Saturated-Unsaturated Transport model (SUTRA): U.S. Geological Survey Techniques and Methods, book 6, chap. A49, 6 p., https://dx.doi.org/10.3133/tm6a49.

How to cite: Serrano-Hidalgo, C., Fernandez-Ayuso, A., Guardiola-Albert, C., Heredia-Diaz, J., and Elorza-Tenreiro, F. J.: Modeling saltwater intrusion with SUTRA 3.0 in Almonte-Marismas aquifer coast (Doñana Natural Space, Southern Spain). , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3015, https://doi.org/10.5194/egusphere-egu21-3015, 2021.

Dhanya Narayanan and Eldho t i

Demand for more sustainable aquifer management solution has exacerbated in view of the seawater intrusion occurring in coastal aquifers, particularly in arid areas, where surface water is not aplenty. Feasibility studies showed saline ground water pumping from within saltwater wedge, aiding in mitigation of seawater intrusion and thus re-freshening the aquifer. Such pumping from nearshore aquifer mostly draws water from the sea. The impact is pronounced for higher pumping rates, where the interface would be lowered and toe position get shifted towards seaward side. This implies that, the change in fluid motion may reduce the outflow through seepage face, which in turn affect the circulation of seawater within the wedge. In the present study, a standard test aquifer was simulated with finite difference model, SEAWAT, to know the effect of change in hydraulic gradient due to pumping, on seawater circulation. Saltwater circulation rates were calculated as the ratio between the total inflow across the seaside boundary to terrestrial freshwater flow.  The result demonstrated the shape of interface to resume a depressed conical form establishing a dispersed interface near the surrounding of saline groundwater well. This localized dispersion observed deduce the presence of weak density gradients between two fluids, hence reducing convective overturn. Performance analysis were carried out to infer the interaction between density dependent seawater circulation and change in hydraulic gradient for different pumping rates. This interaction needs to be known in advance before designing saline water pumping rates, as, significant transport of nutrients and contaminants occur within the saltwater wedge.

How to cite: Narayanan, D. and t i, E.: Impact of Saline Ground water Pumping on density dependent Seawater circulation in Coastal aquifers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6961, https://doi.org/10.5194/egusphere-egu21-6961, 2021.

Susanne Åberg et al.

Central Lapland Greenstone Belt is highly prospective for gold and Ni-Cu-PGE deposits. The study area in Sodankylä, in northern Finland, has been glaciated during last ice ages forming complex sedimentary succession with low conductivity till and highly variable sorted sediments, which hydraulic conductivity can be orders of magnitudes higher. The complex Quaternary sediments usually cover weathered/fractured bedrock, which is preserved due to weak glacial erosion and can host bedrock aquifers, as well. Rivers, lakes, streams and mires are common features in northern boreal and subarctic regions and their hydraulic interactions are usually poorly understood.


Planning of mining operations in such environments needs a detailed understanding of water balance and groundwater discharge and recharge patterns, which are linked to subsurface sediments. In baseline studies, present hydrogeology, hydrology and ecology of the development site has usually been studied intensively. However, main rivers in northern Finland have been regulated since the 1970s and surrounding environments are not in their natural stage. The understanding, how much the environments could have been changed due to the regulation, is needed.


The study area locates in the western part of Natura 2000 protected Viiankiaapa mire, which lies about 300 meters above high-graded Ni-Cu-PGE deposit. The regulated River Kitinen is running close to the western edge of the Viiankiaapa mire. The construction of the hydroelectric power plants and the regulation of the River Kitinen has changed the hydrology of the study area from the 1970s onwards. The Matarakoski power plant built in 1995 affected the study area most directly by ending the regular spring floods and rising the river stage.


The changes in the groundwater flow and recharge/discharge patterns were studied with 3D groundwater flow modelling with MODFLOW-NWT and flood modelling with HEC-RAS. Pre-regulation situation was compared to the present stage with two different groundwater flow models in order to understand how regulation of river has affected the groundwater recharge/discharge patterns and flow patterns of the mire. Flood modelling was used to simulate the pre-regulation flood distribution.


The regulation of the River Kitinen has affected the western part of Viiankiaapa mire by raising the water table and smoothing the hydraulic gradient towards the river leading to partial wetting of the mire. Annual water table variations decreased due to ending of the flooding and the regulation created a more stable hydrological environment in mire area.  The stabilization of the hydrological environment, as well as the rising of the water table, might have affected the distribution of habitats of endangered moss species Hamatocaulis vernicosus. The mire might have become more favourable for Hamatocaulis vernicosus, which is resistant to flooding and high water table. This study emphasizes the importance of understanding the interactions of surface water and groundwater and the present and pre-regulated stage of the river in order to assess the difference between the present and natural stage of the mire.

How to cite: Åberg, S., Korkka-Niemi, K., and Åberg, A.: The effect of river regulation on the hydrological conditions of the aapa mire in a mining development site in Northern Finland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16188, https://doi.org/10.5194/egusphere-egu21-16188, 2021.

Duke Ophori

A 3-D Model of Surface Water and Groundwater Interaction in the Central Passaic River

Basin, New Jersey.


Duke U. Ophori

Department of Earth and Environmental Studies

Montclair State University

Upper Montclair

New Jersey 0743

Ph: (973) 464 6238, Email: Ophorid@montclair.edu




Hydrogeologists have believed, over the years, that the development of a groundwater basin results in increase in the basin’s groundwater recharge and decrease in discharge. This basin’s response to development is intricately tied with the natural recharge-discharge behavior of regional groundwater flow systems. A 3-D regional groundwater flow model is developed for the Central Passaic River Basin, New Jersey to evaluate its surface water-groundwater interactions. The models show that groundwater pumping increases recharge and decreases discharge in the basin. Groundwater-fed wetlands are reduced in size by groundwater pumping. These findings will enhance groundwater management in the basin.

How to cite: Ophori, D.: A 3-D Model of Surface Water and Groundwater Interaction in the Central Passaic River Basin, New Jersey., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13782, https://doi.org/10.5194/egusphere-egu21-13782, 2021.

Pierre L'hermite et al.

Mining companies are responsible for after-mining and environmental monitoring to ensure that mining waters released in the environment meet environmental quality standards. Water treatment plants can be used to mitigate surface waters when impacts related to past mining activities is evidenced. Indeed, meteoric recharge through waste rocks and tailings stored on sites often creates Acid Mining Drainage (AMD) or metallic signature that can be transferred to rivers through groundwater flow.

We studied a former uranium mine in Bertholène, Aveyron (France), where tailings, covered by waste rock, are stored in a valley behind a waste rock dyke. Mining waters, coming from both tailing drainage and mine facilities (galleries and open pit mine), are collected to a water treatment plant before release in the environment, meeting the environmental standards. Groundwater flow modelling is required to understand and quantify the different sources of AMD and their fate. The objective of this study is to give new insights on flows to guide the potential additional remediation of the site by testing different management solutions. For this purpose, we have developed a 3D hydrogeological model (MODFLOW) for the entire watershed.

This work is divided into two parts. We first analysed all available climatic and hydrogeological data (precipitation, water level, surface water flow, electric conductivity) using auto-correlations, cross-correlations and water balance calculations. These data come from long-term monitoring (14 years) on 13 piezometers and 4 discharge points. Recent two-year daily monitoring of groundwater levels completes the data set and provides a better understanding of the dynamic of the hydrosystem after precipitation. There is a 5 to 10-day time lag between rainfall and increases in water level and flow rate. The analysis also concludes that flows in the tailings occur under unsaturated conditions and that the water level in the gneiss aquifer never reaches the tailings.

Steady-state modelling developed at the watershed scale confirms that water level does not reach the tailings and allows simulating the impact of different management scenarios. Particle tracking has also been used to identify hydrogeological sub-watersheds of interest, such as those of the former open pit mine or the tailings to compute their water balance.

How to cite: L'hermite, P., Plagnes, V., Jost, A., Reile, B., Kern, G., Descostes, M., and Chautard, C.: Monitoring data analysis and groundwater flow modelling at a former uranium mine in France, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3035, https://doi.org/10.5194/egusphere-egu21-3035, 2021.

Ronglin Sun et al.

Groundwater plays an active role in certain geologic processes that has been recognized in numerous subdisciplines for a long time. According to Toth (1963, 2009), gravity-driven regional groundwater flow is induced by elevation differences in the water table and its pattern is self-organized into hierarchical sets of local, intermediate and regional flow systems.  Convergence of two flow systems results in a stagnant zone called hydraulic trap which is under the discharge area, and diverge of two flow systems results in a stagnant zone called quasi-stagnant zone which is under the water divide. These stagnant zones have been found to be critical to accumulation of transported mineral matter. Based on analytical and numerical solutions, some researchers reported that the local stagnant point or zone that are located under the local counter directional flow system. There is a question that whether hydraulic trap and quasi-stagnant zone is separate or integrate, and whether they are located under the discharge area or water divide or counter directional flow systems.

In this study, two-dimensional numerical cross-sectional model is used to investigate the effect of climate change on local stagnant zones and whether the hydraulic trap and quasi-stagnant zone is separate or integrate. Considering the climate change of basin and the change of rainfall infiltration intensity, a flux upper boundary is used to simulate the rainfall recharge. Then a synthetic homogeneous sandbox with three potential sinks is used to validate the evolution of the hierarchical nested groundwater flow systems considering different rainfall infiltration intensity. Salt tracer test is used to investigate the effect of stagnant zones on solute transport.

According to numerical results, we concluded that the hydraulic traps and quasi-stagnant are possible to be separate only for simple local systems and the two local stagnant zones are located on two sides of the counter directional flow system. When nested flow systems occur, such as local-intermediate, local-intermediate-local, local-regional, the local hydraulic traps and quasi-stagnant zones are always integrated under the local counter directional flow systems. Laboratory results show that when the rainfall infiltration intensity reduce, the groundwater flow pattern will change and the penetration depth and scope of counter directional local flow system will decrease. The corresponding local stagnant zone will slowly be closing to the discharge area of that counter directional local flow system. Salt tracer tests show that there are obvious non-fickian phenomenon in the local stagnant zones in hierarchically nested flow systems even in the homogeneous aquifer.

How to cite: Sun, R., Jiang, L., Liang, X., and Jin, M.: The evolution and non-fickian flow of local stagnant zones in hierarchically nested groundwater flow system under different rainfall infiltration intensity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3929, https://doi.org/10.5194/egusphere-egu21-3929, 2021.

Menggui Jin et al.

The distribution of groundwater ages under transient conditions are investigated by a numerical model coupled groundwater flow and age, and the nested pattern of groundwater flow are determined by the probability density function of residence time. The variation of local groundwater flow system to the fluctuation of upper boundary head evolves rapidly. During the process from the initial steady to the unsteady state, the groundwater age field evolves with simulation time and gradually reaches a new dynamic equilibrium after about 50 years. The age abrupt interface between the local and intermediate flow systems gradually shifts upward, and the scale of the local flow system gradually decreases. The groundwater ages of the regional and intermediate flow systems are mainly controlled by the long-term dynamic component of the upper boundary head, while the local flow systems are mainly influenced by the transient periodic fluctuation. The location of the stagnation points are mainly controlled by the upper boundary head. The larger head difference between recharge and discharge area is, the greater penetrated depth of the stagnation point is. The location of the stagnation point indicates the penetrated depth of the local flow system. The larger head fluctuates, the deeper stagnation point is, leading to a greater penetration depth of the local flow system. Molecular dispersion causes the scatters of residence time probability density function to aggregate near the inflection point, and the aggregation area mainly locates at the junction of basin-scale flow systems. The transition of groundwater flow field will intensify the mixing of old and new water, leading to the blurring or even disappearance of the residence time abrupt interface. The dispersion of groundwater mixing is poor in steady state, and the convective-dispersive effect gradually increases with time in unsteady state. Traditional hydraulics methods based on flow nets and stagnation points can effectively identify the groundwater flow system, but the differences in groundwater chemical characteristics and ages at long-term scales cannot be clearly described by these methods, as well as the evolution of groundwater flow system at long time scale. The groundwater residence time distribution expressed by the probability density function, which comprehensively involves the spatial and temporal information of groundwater interaction, can help accurately distinguish different groundwater flow systems at long time scales. The methods proposed in this study will act as a meaningful guidance for the delineation of groundwater flow system in the real world.

How to cite: Jin, M., Li, Y., Wang, J., and Liang, X.: Groundwater flow pattern and age distribution under transient conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7083, https://doi.org/10.5194/egusphere-egu21-7083, 2021.

Nariman Mahmoodi et al.

Most Wadi systems of the world are threatened by climate change and unsustainable consumption through different water use systems (WUS) which can result in an alteration of the hydrologic regime, a deterioration of water resources, and their valuable ecosystems. The objective of this study is to assess the impact of climate change and growing water demand on the alteration of the Halilrood River’s flow regime and the associated impacts on the ecosystem of the Jazmorian wetland in central Iran. The Soil and Water Assessment Tool (SWAT) model is used to simulate the flow regime of the near and far future (2030-2059 and 2070-2099). Based on 32 Indicators of Hydrologic Alteration (IHA) in conjunction with the Range of Variability Approach (RVA) alterations in the flow regime are evaluated. Impacts of three scenarios for future water use (No-, Constant-, and Projected-WUS) are assessed. No-WUS assumes pristine conditions in the future when no water use system are included in the model (no demand) and we only account for the impact of climate change; Constant-WUS assumes unaltered groundwater demand in the future; and Projected-WUS corresponds to the increases in the number of water use systems in the future (increasing demand). Flow regime alteration assessment indicates that climate change will severely affect the magnitude of monthly and annual extreme flows, frequency and duration of high and low Pulses in the Halilrood Basin, especially in the far future. The comparison of model simulations under different scenarios shows that the impact of climate change was more intense when growing water demand in the future is taken into account. The result of the RVA test indicates moderate and high level of changes for 18 indicators, thus likely affecting the environmental flows required for the health of the downstream wetland.

How to cite: Mahmoodi, N., Kiesel, J., Wagner, P., and Fohrer, N.: Assessing the hydrologic regime alteration of a Wadi system as a proxy on initial ecological responses to climate change and growing water demand, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-580, https://doi.org/10.5194/egusphere-egu21-580, 2021.

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