The Perrot spring (1305 m a.s.l.), located on the right side of the Chalamy Stream, inside the Monte Avic Natural Park (Aosta Valley, NW Italy), is an important source of drinking water for Champdepraz municipality.

The spring is placed on a large slope characterized by the presence of debris covers of various origin (glacial, fluvial and landslide) above the bedrock (serpentinised peridotites and metabasites of the Zermatt-Saas Zone, Penninic Domain) which crops out only in the upper part of the basin.

The water source is fed by rainwater infiltrating and flowing into the shallow deposits, with a permeability by porosity, and into the most fractured portion of the substrate. The water emerges at the contact between the topographic surface and impermeable or semi-permeable basal lithologies (unfractured crystalline rocks and glacio-lacustrine deposits).

The aim of this study is to delineate the recharge processes of the spring and the definition of the recharge area extension that is very important for its conservation.

In this view, an analysis of groundwater spring parameters (e.g. daily discharge, temperature and electrical conductivity) were conducted for the years 2018-2020.

The flow rate ranges between 22 and 47 L/s with two maxima, one in spring and one in autumn; the electrolytic conductivity varies between 60 and 75 S/cm. The variation of groundwater temperature is very low, between 4.9°C and 5.5°C.  The low discharge and temperature variations suggest a relatively high average share of the supply area and a sufficiently deep flow circuit.

The analysis of these data shows the presence of two contributions to the spring supply: a spring contribution from snowmelt, characterized by a low INCREASE in flow rate, and an autumn contribution from rainwater infiltration.

Moreover, sampling campaigns were also carried out in the entire Chalamy stream basin in August 2021 and January, July, September 2022. In particular, water from lakes, rivers, spring and rainwater was sampled.

During the field campaigns, pH, electrical conductivity and temperature were measured in situ. Chemical analysis of major ions and stable isotopes (δ²H and δ¹⁸O) were then conducted on water samples.

The chemical analyses show a groundwater chemistry coherent with the regional geology: the hydrochemical facies is bicarbonate-sodium, the main cations are Ca²⁺ and Mg²⁺ and the anions HCO₃^-.  Finally, isotopic analyses of precipitation and spring water suggest a recharge elevation of around 2,500 m a.s.l.

How to cite: Santillan Quiroga, L. M., Cocca, D., Marchina, C., Lasagna, M., Destefanis, E., Vescovo, G., Bolognini, D., and De Luca, D. A.: Analysis of the recharge process of Alpine Spring through an integrated approach: the case of Perrot spring (Aosta Valley, Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12255, https://doi.org/10.5194/egusphere-egu23-12255, 2023.

This study represents the first regional-scale investigation in the Piedmont Po plain about the relationship between groundwater temperature in the shallow aquifer (GWT) and climate variability.
The aim of this investigation is to study and compare time trends in air temperature (AT) and GWT over a 10-year time period (between 2010 and 2019), and to evaluate possible relationships between the two parameters. For doing so we had used daily measures taken from 41 monitoring wells located in the shallow aquifer and 20 weather stations throughout the Piedmont Po plain area.

Both AT and GWT showed an increase over the observed period with a more pronounced growth of the AT. With regard to AT all the weather stations had shown an increasing trend with a variation in the annual mean 1.7 and 2.2 ^◦C/10 years; moreover, GWT annual mean generally shows a variation between −0.3 and 2.1 ^◦C/10 years. This result allows to state that GWT is more resilient to climate change than AT. However, some monitoring wells in the study area showed a behaviour that partially deviated from the standard trend observed for the majority of the region: these wells were influenced by particular anthropic factors (for example the paddy fields) or natural elements (as the monitoring wells located downstream of melting glaciers, or the wells located close to Rivers). Further investigations will be conducted in future in Piedmont plain areas with different behaviour, in order to better understand their dynamics and the factors that may influence GWT and how they are affected by climate change.

Moreover, this study wanted to stress the importance of the knowledge of the localization in wells of the instruments for the GWT measurement, to have the most accurate and comparable data. As already state in literature the GWT fluctuation in the bottom part of the aquifer was milder than the fluctuation observed in the most superficial part. Therefore, it has been possible to observe that in the study area when the depth of the instrument increased, the maximum and minimum peaks of the GWT shifted in time respect to the maximum and minimum peaks of the AT.

Lastly, we are conducting a groundwater and heat flow simulation of the shallow aquifer of the Turin Plain area using a numerical model with Smoker Heatflow code. The calibration performed with the available hydrogeological setting information of the area and the GWT and AT data will allow us to model the future spatial distribution of GWT in the study area, according to the IPCC forecast scenarios.

How to cite: Egidio, E., Mancini, S., De Luca, D. A., and Lasagna, M.: How Climate Change influence groundwater temperature? A case study in the Piedmont Po Plain (NW Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6980, https://doi.org/10.5194/egusphere-egu23-6980, 2023.

The Mexico City region is a densely populated region in the world and has problems in guaranteeing the supply of drinking water to its inhabitants. Its groundwater flow system is subject to intensive exploitation. The water in the city is coming from a lot of sources as wells located in the city and springs in the ranges. The geology in the basin is mainly in lacustrine sediments; volcanic rocks shallow and deep and carbonate rocks in the depths.

We collected water table values, major ions, and trace elements compositions from other research: wells (1999) and springs (2015) to investigate hydrogeochemical processes as well as to understand the hydrodynamics of groundwater and their chemical differences between ranges and plains. The groundwater chemical composition is related to the water-rock interaction processes.

We applied two inverse model sections (PHREEQC code) in springs and wells. The inverse model section in the springs showed the dissolution of gypsum, biotite, SiO₂ (aqueous), volcanic glass, labradorite, chloride, and precipitation of amphibole, kaolinite, and H₂O (gaseous). Whereas the inverse section model in wells presents the dissolution of CO₂ (gaseous), gypsum, biotite, volcanic glass, halite, plagioclase, olivine, and precipitation of kaolinite and pyroxene.

Understanding the hydrochemical mechanisms of water-rock interactions eventually leads to the development of appropriate strategies for sustainable groundwater management.

How to cite: Olea Olea, S., Gómez Reyes, E., Escolero, O., and Armas Vargas, F. D. J.: Water-rock interaction processes in springs and wells of the Mexico City groundwater flow system, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11700, https://doi.org/10.5194/egusphere-egu23-11700, 2023.

The precipitation constitutes one of the main sources of the groundwater resources. The chemical composition of precipitation is influenced both by natural and anthropic sources. For this reason, it is essential to monitor rainfall potentially able to influence groundwater quality. The Po Plain sector (NW Italy) is one of the most urbanized, industrialized and air polluted area in Europe but few studies have been conducted in this area, particularly in the Piedmont Region.

The main purpose of this study was: I) to provide a preliminary assessment of quality and isotopic composition of rainwater in the western Po Plain, II) to show the spatial and temporal differences of rain chemical composition between the monitoring points, and III) to define the influence of rain to groundwater chemistry.

A long-term trends on the groundwater concentration of NO₃^– and SO₄^2– in the shallow aquifer on 227 monitoring points of the Regional Monitoring network database were conducted (2000-2020 period).

In the last decades, in Europe a large effort was carried out to reduce sulphur and nitrogen emission in the atmosphere. This resulted in a sharp decrease in the deposition of SO₄^2– and nitrogen compounds.

The rain analysis of long-term trends in near regions, revealed a large proportion of significant decreasing trends in the concentration of both sulphate and nitrogen compounds.

Actually also the analysis of groundwater long-term trends revealed a significant decreasing trends in the concentration of NO₃^– and SO₄^2– in the shallow aquifer.

A sampling campaigns was carried out during one year (September 2021 – September 2022) in 4 monitoring points located in the western Po Plain. Rainfall collection occurred every 2 months, for a total of 20 samples. Physical-chemical analyzes of the main ions and isotopic analyzes (δ¹⁸O, δ²H) were conducted for all samples.

The period  September 2021 – September 2022 was characterized by a rainfall deficit in the winter period in the NW Italy, recording a 62% reduction in rainfall (compared to the climatic average of the thirty year period 1981-2010).

The processing of rainfall chemical data has shown different concentrations between the monitoring points and a temporal variability. High NO₃^– and SO₄^2– concentrations were observed.

Rainfalls sampled after the winter dry period (March-April samples) show higher ions concentrations (NO₃^– 13 mg/L, SO₄^2– 4 mg/L) respect to other periods. Differences in rainfall samples depend on the location of the monitoring point (urban or rural areas).

Isotopic data has shown different spatial and temporal isotopic signals, linked to the location and elevation of the monitoring points. In the δ¹⁸O/δ²H diagram all isotopic signals are not placed on the Local Meteoric World Line, potentially linked to climate change.

The isotopic signals are within the ranges of previous studies (δ¹⁸O: -12,6/-6,2; δ²H: -82,15/-35,1 ‰ (min/max)).

In conclusion, the rain ions concentrations are influenced by anthropic pollution, they are affected by dry periods and they appears to influence the concentration in groundwater.

How to cite: Cocca, D., Lasagna, M., Marchina, C., Santillan Quiroga, L. M., and De Luca, D. A.: Chemical and isotopic composition of precipitation in the Piedmont Po Plain (NW Italy): preliminary evaluation of impacts on the groundwater quality, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2088, https://doi.org/10.5194/egusphere-egu23-2088, 2023.

Lake Velence is a shallow soda lake in Hungary, which has a diverse ecosystem and is a popular tourist destination. Because of that, the lake is the focus of continuous interest and is constantly examined in terms of water quality and quantity. In recent years, it has been observed that the lake's water and nutrient budget is negatively affected by climate change. Since the very existence of the lake is threatened, it has become important to assess the quantity of water flowing into and out of the lake. In our research, the emphasis is on the investigation of the groundwater component, since groundwater can represent a significant buffer in the lake's water balance against climate change, and since in water management practice, neither inflow nor outflow of groundwater is currently considered in the lake’s water budget. Therefore, we wanted to understand the nature of the relationship between the lake and the groundwater and quantify the amount of inflowing and outflowing groundwater.

To achieve our aim, we created a regional-scale transient 3D numerical groundwater flow model for the lake's catchment area using Visual MODFLOW. The time series of weather parameters (i. e. amount of precipitation, evaporation, temperature), the discharge rate of surface water courses, and groundwater extraction data from 1990-2020 have been incorporated into the model. To calibrate the model, we used the time series of monitoring wells of unconfined and confined aquifers. The mentioned time series were also analyzed using statistical methods such as the relationship between rainfall, the groundwater level measured in wells, and the lake level.

Our results complemented the previous studies on the lake's catchment area: there is a not insignificant connection between the lake and groundwater, and the lake is fed by local flow systems with shallow penetration depth and relatively short residence time, which are known to be more sensitive to climate change. Finally, we used the calibrated model to test different scenarios, e. g. we have reduced rainfall or increased water withdrawals to highlight the lake's vulnerability to future changes.

The research was supported by the ÚNKP-22-3 New National Excellence Program of the Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund. Part of the research was funded by the National Multidisciplinary Laboratory for Climate Change, RRF-2.3.1-21-2022-00014 project.

How to cite: Baják, P., Hegedűs-Csondor, K., Csepregi, A., Chappon, M., Bene, K., and Erőss, A.: Numerical modeling and time series analysis to quantify the neglected groundwater component in Lake Velence’s water budget – a case study from Hungary, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12278, https://doi.org/10.5194/egusphere-egu23-12278, 2023.

The alluvial aquifer of the Flumendosa delta plain, in south-eastern Sardinia (Italy), is overexploited for drinking and agriculture purposes and it is subjected to ongoing sea water intrusion phenomena. In a context of progressive quali-quantitative deterioration of groundwater resources, development of a sustainable management plan and, eventually, effective remediation actions require a deep understanding of the investigated system. A systematic review of dataset collected from literature, integrated with new field hydrogeological and geochemical data, is performed to improve the knowledge of the aquifer system. Despite the large amount of processed data, many aspects require further investigations. In this frame, a fast-running steady state groundwater flow numerical model is developed as a tool for testing the preliminary assumptions, to address the main uncertainties, and to optimize the acquisition of new field data. The adopted approach follows the methodology proposed by Lotti et al. (2021) for the development of a Numerically Enhanced Conceptual Model (NECoM).

Geometrical discretization of the numerical model is based on results of the 3D hydrogeological reconstruction of the plain area (Arras et al. 2019); simulation of main inflows and outflows, water exchange between surface water bodies and groundwater, irrigation and drinking water withdrawals is performed through the implementation of general head boundaries (GHB), river (RIV), and well (WEL) packages, respectively. Results from the application of the Soil Water Balance code (Porru et al. 2020) are used as input for simulating the average recharge from precipitation. Lateral recharge from the Paleozoic basement is also simulated. More than 4000 heads observations from about 350 wells and piezometers are used as targets in the calibration process; weights are assigned to deal with the high heterogeneity of the dataset quality. RIV and GHB conductance, irrigation well yields, direct and lateral recharge, and hydraulic conductivity are set as parameters in the calibration process. Due to the high sensitivity of some parameters, different calibration cycles are performed; hydraulic conductivities and lateral recharge are then calibrated in the last cycle.

Model results show that the hydrogeological conceptualization used for implementing the numerical model can reproduce the main general features of the piezometric head field. According to field observations, the Flumendosa river shows losing conditions in the western part of the plain and next to the river mouth, while gaining conditions occur in its central part; gaining conditions are also observed along the abandoned branches of the Flumendosa river, also known as foxi. Moreover, mass balance analysis show that the Flumendosa river represents the main recharge input of the whole groundwater system, providing an average inflow of about 4.3 Mm³/year. Nevertheless, several local incongruencies with the observed data were precious to highlight the effects of unknown variables such as agricultural extraction wells, the hydrogeological role of the bedrock or the water exchange between surface and groundwater bodies. The discrepancies, rather than the agreements, provided useful direction for the detection of new data to be collected to capture the salient information needed for a proper water resource management.

How to cite: Arras, C., Lotti, F., Porru, M. C., Piscedda, F. A., and Da pelo, S.: Numerically Enhanced Conceptual Modelling (NECoM) applied to the Flumendosa Plain groundwater system (SE Sardinia, Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13692, https://doi.org/10.5194/egusphere-egu23-13692, 2023.

 In most regions worldwide, the groundwater usage is increasingly common due to the progressive decreasing
of the effective availability of surface water for both quantity regime and quality issues, as a consequence of
global population increasing, global climate change and growing water pollution. Therefore, groundwater is
the most important and safest source for water supply being less affected by pollution and climate changes.
For example, in European Union countries, groundwater provides nearly 70% of the piped water supply and
80% of the drinking water. However, the overexploitation of groundwater may sometimes exceed recharge
over long periods and over extensive areas and the subsequent decline in water table level may affect natural
groundwater discharge and quality, which in turn may have harmful impacts on groundwater dependent
streams, wetlands and ecosystems. For these reasons a correct management of the groundwater resources
is of paramount importance. In this scenario, groundwater modelling, both conceptual and numerical, is
particularly crucial for the sustainable and efficient management of groundwater resources, even more in
the context of expected climate change.
The middle-high Brenta river plain (NW of Veneto, Italy) is characterized by the existence of an important
unconfined to semi-confined foothill aquifer system, that is made of a very thick single-layer of gravellypebbly alluvial deposits, in the northernmost part, whereas in the southern part the aquifer becomes a
multilayer composed of gravelly deposits and levels of silt and clay. The existence of an important aquifer
system is tied to the high annual rainfall amount, about 1200 - 1500 mm/year, however the main
groundwater recharge component of the aquifer is related to the water dispersion from the Brenta river.
Groundwater hosted in the aquifer represents an important resource for drinkable supply, industrial and
agricultural usages. However, over the last decades, the exploitation of groundwater resource and the
meteo-climate regime caused a decrement of the piezometric level alerting the local authorities. Thanks to
the existence of a consistent and continuous monitoring network made up of several meteoric, hydrometric
and piezometric stations, very long time-series of data are available. The availability of a long time-series
allowed to develop Data-Driven models, specifically Multiple Linear Regression Models, of the Brenta river
hydrometric level (using rainfall, snowfall and atmospheric temperature as independent variables) and of the
piezometric level of groundwater in the middle-high plain (using atmospheric temperature, the local rainfall
and the model of Brenta river as independent variables). The regression models were used to make
predictions on the development of the hydrometric level of Brenta river and consequently of the
groundwater level under extreme weather and climate conditions as those of the last years, thus providing
useful information for steering the best water management practices in a zone where strategic groundwater
exploitation systems are located.

How to cite: Franceschi, L., Menichini, M., Raco, B., and Doveri, M.: Data-Driven models for groundwater level forecasting and improvement of waterresource management: example of the Foot-hill aquifer system in the Brenta riverplain (Veneto, Italy) , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15653, https://doi.org/10.5194/egusphere-egu23-15653, 2023.

Water flow is an essential component of the long-term environmental management of former mine sites. Flow through tailings storage facilities (TSF) often generates chemical reactions and releases acidic water. In the case of static leaching, this acidification can last for multiple decades depending on the acid remaining in the tailings. This mining water is then collected and treated in treatment plants before it is released in the environment in compliance with environmental standards. The understanding of the current hydrogeological functioning of the TSF is essential to properly adapt water management today. Given the potential impact of climate change, simulation of future hydrogeological behaviour is also required to ensure sustainable water management over this century.

We developed a daily time step model with HYDRUS 2D to represent the unsaturated hydrogeological functioning of a tailings pile of the former mine of Le Cellier (France). A granulometric analysis over the pile height provided reliable hydraulic properties and showed that the pile heterogeneity can be distributed into three layers. The historical monthly monitoring and the new daily hydrogeological monitoring implemented in 2021 measured the rainfall and discharges from the various drains that collect the water from the pile. As cross-correlations confirmed the fast reaction of drains discharges to rainfall (1 day), we simulated the water flow with the dual porosity package of HYDRUS. We also implemented the vegetation transpiration due to the presence of bushes and coniferous trees over the pile.

The model performance was evaluated by comparing the observed (monthly and daily) discharges and the simulated one. The calibrated model reproduces correctly the annual discharges for the period 2014-2022 as well as the pile fast reaction to rainfall. To evaluate the climate change impacts on the hydrogeological functioning of the pile, we used as input of our calibrated model the daily precipitations and temperatures of the Coupled Model Intercomparison Project (CMIP5) for three climatic scenarios (RCP2.6, RCP4.5 and RCP8.5). The calculation of the Mann-Kendall trend test on the predicted water balance components leads to the conclusion that the effective rainfall should remain stable over the next 100 years. At the end of the century, the frequency of extreme events could increase by 50% and their intensity could rise by 9%. With the calibrated model, we simulated the discharges at the pile outlet and studied their annual changes as well as the pile response to extreme events under climate change. These simulations are essential to ensure an accurate water management for this century.

How to cite: L'hermite, P., Plagnes, V., Jost, A., Reile, B., Blanc-Potard, I., Regnier, D., and Descostes, M.: Present and future flow simulation in a tailings pile at a former mine in France, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6876, https://doi.org/10.5194/egusphere-egu23-6876, 2023.

The simulation of seawater intrusion (SWI) in coastal aquifers under complex hydrogeological conditions typically requires using "variable-density" models, which simulate the groundwater flow and the transport of salt dissolved in water. When combined with optimization algorithms, variable-density models constitute powerful tools to support the management of groundwater resources in coastal systems vulnerable to SWI, sea-level rise and unstainable groundwater abstraction. However, the application of simulation-optimization (SO) to SWI problems has so far been limited by the prohibitive computational effort required by full-scale variable-density models that simulate the aquifer response to proposed groundwater abstraction strategies. A viable solution is thus to develop “surrogate” models that emulate full-scale model responses at a fraction of their computational cost. In this study, a surrogate model of SEAWAT, a popular variable-density groundwater flow model, will be presented. This surrogate is based on the proper orthogonal decomposition (POD) method, which is a projection-based approach where the coefficient matrices and the right-hand side vectors derived through finite-difference discretization of the coupled flow and transport equations, are mapped onto a space of size significantly smaller than the model grid. Preliminary results show that the POD-based surrogate model is remarkably faster than the full-scale model, and provides results of comparable, and thus acceptable, accuracy. These features make the surrogate ideally suited for substituting the full-scale variable-density model within the SO framework adopted to support the management of coastal aquifers.

How to cite: Geranmehr, M., Baù, D., Mayer, A. S., Mancewicz, L., and Yu, W.: Sustainable Management of Coastal Aquifers subject to Seawater Intrusion using Reduced-Order Groundwater Flow Models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7742, https://doi.org/10.5194/egusphere-egu23-7742, 2023.

Sufficient freshwater is needed for several water dependent sectors. However, e.g. climate change, weather extremes, economic growth, urbanization and increased food production make it more complex to guarantee sufficient freshwater for all sectors, even in temperate climates like the Netherlands. The range of weather extremes from extremely dry to extremely wet is expected to increase and to occur more frequently. However, the current Dutch water management system is not designed to anticipate both weather extremes.

Controlled drainage with subirrigation could be a viable measure to i) discharge water only when needed, ii) retain water and iii) recharge water using an external source. This system thus has the potential to 1) improve growing conditions for crops at field scale, 2) reduce peak discharges at regional scale, and 3) increase groundwater recharge on regional scale. Consequently, this system could anticipate both dry and wet extremes. However, the implementation of controlled drainage with subirrigation could significantly alter different water balance components.

We show data and model output of five experimental sites where controlled drainage with subirrigation is applied. Field data were collected over the years 2017-2022, like external water supply, groundwater table and soil moisture content. Other water balance components, crop yield and configuration of the management of the system were modelled with SWAP (Soil-Water-Atmosphere-Plant model), using observations for calibration purposes.

Results show that by subirrigation, water can be applied to the soil and will lead to increased water storage and higher groundwater tables. Groundwater tables were up to 0.7 m higher during the growing season, leading to both increased crop yields and larger groundwater recharge. Drought vulnerability decreased at the test sites. However, the water supply for subirrigation can be high (500 mm per year, on average). Additionally, effects of subirrigation on the water balance components are strongly site-dependent. For example, a resistant layer below the drainage/infiltration pipes is needed to ensure enough resistance to limit downward seepage and to raise the phreatic groundwater level. Furthermore, ditch levels surrounding agricultural fields need to be adjusted to the raised groundwater levels, as too deep ditch water levels result in (unfavorable) drainage and loss of water. Field experiments also show that proper management is important to prevent clogging of the drainage systems.

Construction, topographical location, external water source and proper management are important for subirrigation to be successful. Responsible implementation of subirrigation in terms of the water balance at the regional scale is needed; freshwater availability to apply subirrigation is an issue. When these boundary conditions are met, controlled drainage with subirrigation could raise the groundwater level and improve the soil moisture availability for crops, while still having the option to discharge water when needed.

How to cite: de Wit, J. A. (., van Huijgevoort, M. H. J. (., van Dam, J. C. (., van den Eertwegh, G. A. P. H. (., van Deijl, D. (., and Bartholomeus, R. P. (.: Hydrological consequences of controlled drainage with subirrigation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1517, https://doi.org/10.5194/egusphere-egu23-1517, 2023.

Groundwater is the most crucial drinking water resource in many areas of the world. In spite of its overall abundance, the resource remains vulnerable to pollution, as groundwater quality may be severely affected by urbanization and growth in industrial activities and agriculture. The most sustainable approach to managing groundwater quality is to ensure its protection, thus avoiding contamination. Therefore, accurate groundwater vulnerability assessment methods are necessary tools for groundwater management and protection.

The DRASTIC method is one of the most widely used groundwater vulnerability assessment methods. However, in areas where the main useful aquifers are covered with an extra layer of diverse Quaternary sediments, the original DRASTIC method overestimates the vulnerability of groundwater in overflow areas and in regions where groundwater is occasionally confined. Therefore, the DRASTIC method needs to be modified to increase the accuracy of vulnerability maps in areas with a highly variable Quaternary layer, which remarkably influences the nature of the infiltration conditions.

For this, in this study, the depth to water, soil properties, and impact of the vadose zone parameters of the DRASTIC methodology were modified to be suitable in areas with glacial sediments. Originally, the depth to water parameter (D) allows assessing the distance from the ground surface to the aquifer: the deeper the water table, the lower the contamination risk. In the modified DRASTIC method, the water table is as an alternative compared to the bedrock surface beneath the Quaternary sediments layer. When the piezometric head is above the bedrock surface, the aquifer acts as confined, and the movement of the pollutant to the aquifer is hindered. Therefore, the groundwater vulnerability considering the D-parameter is lower in areas where the piezometric head is above the bedrock surface and higher in areas where it is below the bedrock surface.

Both the original and the modified DRASTIC methodology were applied in an area with glacial sediments located in Central Estonia. The modified DRASTIC method showed significantly better results than the original DRASTIC method. Furthermore, comparing the maps generated using the modified DRASTIC with a former local groundwater vulnerability assessment method showed considerably more similarities than this by the original DRASTIC method. Thus, the modified DRASTIC method is successfully applicable in areas with an extra layer of diverse Quaternary sediments.

The study has been funded by Iceland, Liechtenstein and Norway through the EEA and Norway Grants Fund for Regional Cooperation project No.2018-1-0137 “EU-WATERRES: EU-integrated management system of cross-border groundwater resources and anthropogenic hazards

How to cite: Männik, M., Karro, E., Marandi, A., and Rosentau, A.: Groundwater vulnerability assessment in areas with diverse Quaternary deposits, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6268, https://doi.org/10.5194/egusphere-egu23-6268, 2023.