Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 1 - 50 of 795 results

Title	Presenter Name	Presenter Surname	Area	Conference year	Keywords
Integrating reductive dehalogenase enzyme production into reactive transport modelling to simulate chloroethene biodegradation in groundwater pollution plumes	Diego	Di Curzio		2023	Biodegradation; Chloroethenes plume; Reactive Transport Modeling; Enzyme-Based Kinetics; Reductive dehalogenase enzymes; Groundwater
Abstract Degradation of chloroethene in groundwater primarily occurs via microbially-mediated reductive dechlorination (RD). Anaerobic organohalide-respiring bacteria (OHRB) use chloroethenes as electron acceptors to gain energy. They produce reductive dehalogenase enzymes (RDases) to perform this function by transcription of functional genes into mRNA and translation to proteins (metabolic regulation). However, how hydrodynamics and hydrogeochemistry control the metabolic efficiency of OHRB in biodegrading chloroethene is essential for effective bioremediation design yet an under-investigated topic. For this reason, we implemented a virtual experiment (1D reactive transport model) to investigate the effects of site conditions on transcription-translation and, hence, biodegradation processes within chloroethene plumes. In the model, RD was simulated using Enzyme-Based Kinetics, explicitly mimicking the production of RDases via metabolic regulation, calibrated on microcosm experimental data gained from literature. Features of an actual contaminated site (Grindsted, Denmark) were then used to set up the virtual experiment. Here, chloroethene leaked from a former pharmaceutical factory migrates through a sandy aquifer and gets discharged into the Grindsted stream. Preliminary results show that substrate (electron donors) limiting conditions caused by competing electron acceptors and dispersion and high flow rates represent the key factors controlling biodegradation via RDase production.
Using passive sampling to identify trends in aquatic pesticide pollution in the Western Cape, South Africa	Emma	Davies	Western Cape, South Africa	2023	Imidacloprid, passive water sampling, pesticide, South Africa, surface water, Sustainable Development Goal
Abstract South Africa is the leading user of pesticides in Sub-Saharan Africa, but data on pesticide occurrence in (ground)water is limited. Consequently, there is a need to improve knowledge on transport pathways that cause pesticides to enter the aquatic environment. This research monitored pesticide concentrations in three agricultural catchments in the Western Cape, South Africa, including Grabouw (pome fruit), Hex River Valley (table grapes), and Piketberg (wheat). Passive samplers were deployed in rivers from March 2022- March 2023, adding to a 2017-2019 dataset of analytical and pesticide application data. Field and laboratory methods were developed at Stellenbosch University to measure pesticides using Liquid Chromatography-Mass Spectrometry. For quality control, duplicate samples were analyzed at Eawag, Switzerland. 30 compounds were detected, yet two/three comprise most of the total mass, including an analyte not considered in earlier investigations (dimethomorph). Rainfall-flow relationships and agricultural application could only partially explain detection levels, suggesting that other factors, including non-agricultural application or groundwater input, might influence detections. Two compounds exceeded European Environmental Quality Standards (chlorpyrifos and imidacloprid). Imidacloprid is particularly concerning because it exceeded consistently despite few recorded applications. 2017-2022 imidacloprid data indicates a decreasing concentration trend in Hex River Valley and increasing trends in Piketberg and Grabouw. Consistently high detections during wet and dry periods suggest groundwater input. However, such pesticide transport pathways are poorly understood due to a lack of local evidence. Local authorities must establish a long-term monitoring program to understand better the risk pesticides pose to the aquatic environment and human health.
A mixing analysis to explore the distribution and behaviour of contaminants of emerging concern and regulated organic pollutants in the hydrogeological media. Case study: the endorheic catchment of the Fuente de Piedra Lagoon (Southern Spain)	M	Llamas	Southern Spain	2023	emerging contaminants, Groundwater, mixing model
Abstract An end-member mixing analysis has been conducted for the hydrogeological system of the endorheic catchment of the Fuente de Piedra lagoon (Malaga, Southern Spain). Three end-members have been considered because of the three main groundwater types related to the different kinds of aquifers found in the catchment. The model’s objective is to help understand the distribution of the organic contaminants (including contaminants of emerging concern [CECs]) detected in groundwater samples from the catchment. Results suggest that some contaminants can be related to long groundwater residence time fluxes, where contaminant attenuation can be limited due to low oxygen levels and microbial activity. The three main aquifer types are: (i) unconfined carbonate aquifers with low mineralized water corresponding to two mountain ranges with no human activities over theirs surface; (ii) an unconfined porous aquifer formed by Quaternary and Miocene deposits, exposed to pollution from anthropogenic activities (agriculture and urban sources); and (iii) a karstic-type aquifer formed by blocks of limestones and dolostones confined by a clayey, marly and evaporite matrix from Upper Triassic. The groundwater monitoring campaign for the analysis of organic contaminants was carried out in March 2018. Target organic contaminants included pharmaceuticals, personal care products, polyaromatic hydrocarbons, pesticides, flame retardants and plasticizers. For the mixing model, a dataset was built with the hydrochemistry and isotopic results (δ2 H, δ18O) from the monitoring campaign conducted in March 2018 and from campaigns carried out in previous years and retrieved from the literature.
Validation of algorithms for estimating changes in groundwater storage from GRACE gravity satellite data for Poland	Tetyana	Solovey	Poland	2023	GRACE, groundwater storage assessment, validation
Abstract The development of satellite technologies creates more and more opportunities to build modern tools for monitoring the state of groundwater. The use of the GRACE satellites to monitor GWS changes has become widespread, but the degree of accuracy with which remote sensing data can estimate these changes is unclear. In this study, we quantified changes in the GWS in Poland from 2009 to 2022 using GRACE observations, in-situ data, and GLDAS. Long-term trends and seasonality were calculated and analysed for each time series. The correlation analysis between GRACE TWS, GWS obtained from GRACE and GLDAS, and GWS in situ was performed using linear regression. Pearson and Spearman’s methods show that GRACE performance is good in the region of shallow (up to 3 m) presence of thick (above 5 m) unconfined porous aquifers; however, performance is worse in a region with multiple aquifer systems, including fissured and karst aquifers. In addition, an unrepresentative groundwater GRACE signal is obtained in regions with surface water storage, such as the Baltic Sea area. It was also found that there is very high consistency between the GRACE observations and wells water level changes, while the GWS series obtained from GRACE and GLDAS do not provide adequate compatibility. According to the GRACE data, the results suggest that evapotranspiration and the hydrodynamic system have the greatest impact on the sensitivity of the GWS estimation. The results are important for better processing the GRACE data to obtain a representative signal for the GWS assessment.
Showcasing a global-scale, 3D coastal groundwater salinity model	J	King	The Netherlands	2023	coastal aquifers, global modelling, groundwater salinity, paleo-reconstruction, parallel. SEAWAT, sea level rise
Abstract Being extensively available and of high quality, groundwater is the primary source of freshwater in coastal regions globally. However, due to anthropogenic and natural drivers, groundwater salinisation is a growing threat to this resource’s long- and short-term viability. The causes and timescales of aquifer salinisation are complex and difficult to quantify, information essential for suitably timed mitigation strategies. One way to inform these strategies and develop storylines of future freshwater (un)availability is through 3D groundwater salinity modelling. These models can predict current groundwater distributions and quantitatively assess the impacts of a projected increase in groundwater extraction rates and sea-level rise. Until recently, detailed 3D models on this scale have been largely unattainable due to computational burdens and a shortage of in-situ data. Fortunately, recent developments in code parallelization, reproducible modelling techniques, and access to high-performance computing (e.g., via parallel SEAWAT) have made this feasible. Machine learning and data mining developments have also allowed an unprecedented opportunity to constrain and calibrate those models. With this in mind, we present our progress towards global 3D salinity modelling by showcasing a regional-scale model in the Mediterranean Sea area. This test case uses newly developed, automated geological and salinity interpolation methods to create initial conditions while implemented in a parallelized version of SEAWAT. The modelling outcomes highlight the potential of supra-regional scale modelling in the context of global (planetary) processes and localised anthropogenic effects.
Assessment of hydrochemistry and heavy metal contamination in the groundwater around an abandoned Copper Mine area in Klein Aub, Namibia	Shoopala	Uugulu	Namibia	2023	contamination, Copper, Heavy metal, Klein Aub
Abstract The long mining history in Namibia has resulted in numerous abandoned mines scattered throughout the country. Past research around the Klein Aub abandoned Copper mine highlighted environmental concerns related to past mining. Considering that residents of Klein Aub depend solely on groundwater, there is a need to thoroughly investigate groundwater quality in the area to ascertain the extent of the contamination. This study made considerable effort to characterise groundwater quality using a comprehensive approach of quality assessment and geostatistical analysis. Onsite parameters reveal that pH ranges between 6.82-7.8, electrical conductivity ranges between 678 - 2270 μS/cm, and dissolved oxygen ranges between 1.4 -5.77 mg/L. With an exemption of two samples, the onsite parameters indicate that water is of excellent quality according to the Namibian guidelines. The stable isotopic composition ranges from −7.26 to -5.82‰ and −45.1 to -35.9‰ for δ18O and δ2H, respectively—the groundwater plots on and above the Global Meteoric Water Line, implying no evaporation effect. Hydrochemical analyses show bicarbonate and chloride as dominant anions, while calcium and sodium are dominant cations, indicating groundwater dissolving halite and mixing with water from a recharge zone. The heavy metal pollution index of the groundwater is far below the threshold value of 100, which signals pollution; it contrasts the heavy metal evaluation index, which clustered around 3, implying that the heavy metals moderately affected groundwater. Copper, lead and Arsenic were the main contributors to the values of the indices.
Robust Hydrogeological Conceptual Models Through Interdisciplinary Characterisation – A Case Study	Zandri	Rademan	South Africa	2023	conceptual model, Geophysics, geotechnical, hydraulic testing, interdisciplinary
Abstract The basis of a hydrogeological conceptual model is the comprehensive characterisation of the groundwater system. This ranges from discrete hydraulic feature analysis to local-scale testing to integrated regional-scale aquifer system conceptualisation. Interdisciplinary data integration is critical to each level of characterisation to gain a realistic, yet simplified representation of the hydrogeological system based on various data sources. Incorporation of geological datasets, including (but not limited to) structural and lithological mapping, geotechnical core logs and geophysical surveys, in conjunction with a tailored selection of hydraulic testing techniques, are often underutilised by hydrogeologists. Yet, the contribution of these alternative hydraulic datasets cannot be overstated. A recent hydrogeological assessment and feasibility study forming part of the planned expansion project for a base-metal mine in the Northern Cape, South Africa, offers an ideal, practical example. The localised nature of the project area and the inherently complex geological setting required a more detailed conceptual model and hydrostratigraphic domaining approach. Highly heterogeneous stratigraphy and strong structural aquifer controls necessitated characterisation by reviewing, testing and analysing various datasets. Exploratory core datasets, hydraulic aquifer tests, geological and downhole geophysical datasets, and statistical Rock Quality Designation—hydraulic conductivity relationships were interpreted to produce meaningful, refined hydraulic process identifications. A comprehensive local groundwater framework, discretised into various hydrostratigraphic units and structural domains with specified hydraulic parameters, was incorporated to provide a novel, more robust conceptual understanding of the unique hydrogeological system.
Aquifer storage and recovery (ASR) applications to enhance drinking water supply security in the Sultanate of Oman	Harmen	van den Berg	Oman	2023	Aquifer Storage and Recovery, Oman, desalinated seawater, drinking water supply, groundwater flow modelling, Hydrogeology, recovery efficiency
Abstract Water scarcity has driven many countries in arid regions, such as Oman, to desalinate seawater for freshwater supply. Episodic problems with seawater quality (e.g., harmful algae), extreme weather events that affect energy supply and hence the desalination process have nurtured the urgent need to store desalinated seawater (DSW) in the aquifers for use during emergency and peak demand time. Aquifer Storage and Recovery (ASR) using injection wells is a possible strategic option for Oman Water and Wastewater Services Company (OWWSC) to augment aquifer storage using excess desalinated water during low demand times. ASR strategically serves as a water supply backup to optimize production capacities against seasonal demand patterns. The technical-economic feasibility of implementing ASR schemes was investigated in Jaalan, Oman, using hydrogeological and geophysical field measurements, groundwater flow and hydraulic modelling, and economic analysis. Analysis of modelled scenarios results revealed that the Jaalan aquifer is suitable for storing and recovering about 4,000 m3 /hr in 2045. Various well field designs have been tested and optimized numerically using MODFLOW 6, showing that with 160 dual-purpose wells, 7.9 Mm3 can be injected and abstracted within the constraints defined for a robust and sustainable ASR system. Simulations with the density-dependent flow model (MF6 BUY) show that the injected volume can be fully recovered considering the drinking water quality standard. Other sites were also studied. ASR capacity was found to be site-specific, and the groundwater developments near the ASR site governed its feasibility
Paleo-hydrogeological reconstruction of a complex deep groundwater system in a tectonically active region	H	Levanon	Israel	2023	Dead Sea Rift, Golan Heights, Lagoonary brines, Paleo-hydrology, intrusion/backflow
Abstract The geochemical study of deep aquitard water in the southern Golan-Heights (GH), Israel, reveals the complex paleo-hydrological history affected by the intensive tectonic activity of the Dead Sea Rift (DSR). The sampled water collected from new research boreholes exhibits relatively high salinities (2,000-10,000 mg Cl/L), low Na/Cl ((HCO3 +SO4 )). δ18OV-SMOW and δDV-SMOW values are relatively depleted (~-7‰ and ~-42‰, respectively), while 87Sr/86Sr ratios are enriched compared to the host rocks. Lagoonary brines with similar characteristics (excluding the water isotopic compositions) are known to exist along the DSR. These brines formed 10-5 Ma ago from seawater that transgressed into the DSR and subsequently underwent evaporation, mineral precipitation and water-rock interactions. These hypersaline brines intruded into the rocks surrounding the DSR and based on the current study, also extended as far as the southern GH. Further, following their subsurface intrusion into the GH, the brines have been gradually diluted by isotopically depleted freshwater, leaving only traces of brines nowadays. The depleted isotopic composition suggests that the groundwater system is recharged at high elevations in the north. It is also shown that variable hydraulic conductivities in different formations controlled the dilution rates and subsequently the preservation of the entrapped brines. The paleo-hydrological reconstruction presented here shows that the flow direction has reversed over time. Brines that initially intruded from the rift have since been gradually flushed back to the rift by younger fresh groundwater.
Coupling environmental tracers and modelling and what can they tell us about groundwater sustainability and example from the southwestern Great Artesian Basin (GAB) of Australia	A	Love	Australia	2023	Great Artesian Basin, Environmental tracers, recharge rates
Abstract Recent advances in groundwater dating provide valuable information about groundwater recharge rates and groundwater velocities that inform groundwater sustainability and management. This talk presents a range of groundwater residence time indicators (85Kr, CFCS 14C, 81Kr, 36Cl and 4 He) combined with analytical and numerical models to unravel sustainability parameters. Our study site is the southwestern Great Artesian Basin of Australia where we study an unconfined confined aquifer system that dates groundwater from modern times up to 400 kyr BP. The study area is arid with a rainfall of <200 mm/yr and evaporation in the order of 3 m/yr. Despite these arid conditions we observe modern recharge rates in the order of 400 mm/yr. This occurs via rapid ephemeral recharge beneath isolated riverbeds where the sandstone aquifer directly outcrops. Groundwater dating and stable isotopes of the water molecule indicates that this recharge comes from monsoonal activity in the north of the continent that travel some 1500 kms. Furthermore, this is restricted to recharge in the Holocene.as we move down the hydraulic gradient groundwater “ages” increase and recharge rates dramatically decrease by orders of magnitude. We conclude that there has been a significant decline in monsoonal precipitation and hence recharge in the deserts of central Australia over this time. We present a couple environmental numerical model that describes how to estimate temporal recharge rates and estimates of hydraulic conductivity from groundwater age data that can be used for groundwater management.
Building a Groundwater Educational Pipeline from Elementary to Continuing Education	Todd	Halihan		2023	K-12, PSM, Drilling, online education, professional master’s programs
Abstract Water resources worldwide are stressed, and the number of groundwater professionals required to manage those resources is not being generated in sufficient numbers. Groundwater educational resources must be placed in schools to generate excitement and raise awareness. Additionally, people entering the workforce need training throughout their professional careers. Oklahoma State University partnered with the U.S. National Ground Water Association to develop a framework for providing education and training programs in groundwater that allow for interactive online education at all levels. The Awesome Aquifer 360 program targets grades 5-8, allowing students to conceptually explore aquifers and the people who manage them. The Drilling Basics Online program provides a 40-hour basic safety and drilling training to recruit professionals into the groundwater industry and reinforce safe operations. These programs and future plans for the technique will be discussed.
New challenges for low-enthalpy geothermal resource management at the urban scale	Sara	Barbieri	Milan, Italy	2023	MODFLOW-USG, geothermal energy, heat transport, numerical modelling, resource management
Abstract The study focuses on the overlapping effects of low-enthalpy geothermal plants in urbanized areas, showing the importance of quantifying thermal groundwater exploitation to manage the resource adequately. Geothermal energy connects groundwater use to one of the ever-growing needs nowadays: energy. For low-temperature geothermal, the form of energy we can harness is thermal energy for building heating or cooling, one of the most polluting sectors, representing 34% of CO2 emissions in Europe. As in the main European cities, geothermal energy use is constantly growing, and understanding the status of groundwater exploitation for geothermal purposes is essential for proper resource management. To this end, the study’s first phase focused on quantifying geothermal use in the study area selected in Milan city-Italy. Knowing the characteristics of geothermal plants in the area allows us to understand the extent of the resource exploitation and the consequences of its mismanagement at a large scale. In fact, the plant designers often focus on the local scale, not considering the presence of neighbouring plants, which risks decreasing the plant’s efficiency or amplifying its subsurface thermal effect. To minimize the thermal effects/interferences of geothermal plants in the subsoil, the study of the application of D-ATES systems (Dynamic Aquifer Thermal Energy Storage) with significant groundwater flow is promising. A numerical model of the study area is then implemented with MODFLOW-USG for thermal transport in porous media to evaluate the advantages of installing D-ATES systems instead of typical open-loop systems.
Hydrological processes and evolution in the critical zone of a small island: the case of Pianosa Island in the Tuscan Archipelago	Matia	Menichini	Tuscan Archipelago	2023	unsaturated zone, high-precision lysimeter, effective infiltration, shallow aquifer
Abstract Understanding and quantifying hydrology processes represent a mandatory step in semi-arid/arid regions for defining the vulnerability of these environments to climate change and human pressure and providing useful data to steer mitigation and resilience strategies. This generally valid concept becomes even more stringent for highly sensitive ecosystems, such as small islands like Pianosa. The project intends to deploy a multi-disciplinary approach for better understanding and quantifying the hydrological processes affecting water availability and their evolution, possibly suggesting best practices for water sustainability. First results pointed out as over the last decade the precipitation regime has led to a major rate of evapotranspiration and minor effective infiltration that caused a decreasing of piezometric level over several years. Quantity and chemical-isotopic features of rainfall and effective infiltration water measured/collected by a raingauge and a high precision lysimeter describe the hydrological processes at soil level and characterize the rate and seasonality of groundwater recharge. Hydrogeological and geochemical data of groundwater are highlighting the distribution and relationship among different groundwater components, including the seawater intrusion. Furthermore, the comparative analyses of continuative data monitoring in wells and weather station showed the presence of possible concentrated water infiltration processes during rainfall extreme events that induce a quick response of shallow groundwater system in terms of water level rise and decrease of electrical conductivity. Thus, elements of vulnerability of the aquifer to pollution are pointed out, as well as the possibility to provide technical solutions for enhancing water infiltration and groundwater availability.
Hydrostratigraphy of the Bauru and Guarani Aquifer Systems in the central region of the State of São Paulo (Brazil)	Fernando	Barreto	Brazil	2023	3D Modelling, Bauru Aquifer System, Guarani Aquifer System, hydrostratigraphy
Abstract The Guarani Aquifer System (SAG) is the main public water supply source in Bauru City (Brazil). It mostly consists of sandstones and is a confined unit of fossil waters (~600 thousand years); therefore, it is a non-renewable and finite resource. SAG is overlaid by the Bauru Aquifer System (SAB), predominantly consisting of sandstones, siltstones, and mudstones, and is essential for private water supply in the municipality. In recent decades, constant drops in water levels in SAG and increases in contaminant loads in SAB have been observed in production wells, generating the need to understand the geometry of those aquifer systems. This work presents the preliminary results of the analysis and review of hydrogeological and geophysical data from 59 deep wells and 3D geological modelling using Leapfrog Works® to represent a conceptual model of the study area. SAG has a thickness of up to 356 m in the wells and is represented, from bottom to top, by Teresina, Piramboia, and Botucatu formations. In the north and northeast regions, SAG is covered by a layer of basalts from the Serra Geral Aquifer System (SASG) with a thickness of up to 190 m. The thickness of SASG is variable (or even null) due to the action of important faults with vertical displacements that created structural windows in the region. SAB covers the Araçatuba (basal portion), Adamantina (144 m), and Marília (65 m) formations. The lower contact of SAB is made with SASG or SAG (central region). Project funded by FAPESP (2020/15434-0).
Open access to digital groundwater and geodata supports the green transition and the spatial planning of competing subsurface uses	Klaus	Hinsby	Denmark	2023	FAIR data, UN SDGs, digital geoinformation, digital twins, geohazards, Groundwater, resources management, subsurface, sustainability
Abstract Modern societies rely heavily on subsurface resources and need open access to accurate and standardized scientific digital data that describe the subsurface’s infrastructure and geology, including the distribution of local and regional aquifers up to a depth of five kilometres. These data are essential for assessing and reducing climate change’s impact and enabling the green transition. Digital maps, 3D and 4D models of the subsurface are necessary to investigate and address issues such as groundwater quality and quantity, flood and drought impacts, renewable geo-energy solutions, availability of critical raw materials, resilient city planning, carbon capture and storage, disaster risk assessment and adaptation, and protection of groundwater-dependent terrestrial and associated aquatic ecosystems and biodiversity. For over a decade, EuroGeoSurveys, the Geological Surveys of Europe, has been working on providing harmonized digital European subsurface data through the European Geological Data Infrastructure, EGDI. These data are invaluable for informed decision-making and policy implementation regarding the green transition, Sustainable Development Goals, and future Digital Twins in earth sciences. The database is continuously developed and improved in collaboration with relevant stakeholders to meet societal needs and facilitate sustainable, secure, and integrated management of sometimes competing uses of surface and subsurface resources.
From monitoring networks to near real-time groundwater forecast. A case study in Cape Town Table Mountain Aquifer, South Africa	J	Nicolas	South Africa	2023	Gardénia, MétéEau Nappes, Table Mountain Group, forecast, groundwater monitoring, modelling, near real-time
Abstract Groundwater level monitoring is essential for assessing groundwater’s availability, behaviour and trend. Associated with a modelling tool, groundwater level fluctuations can be predicted in the short to middle term using precipitation probabilities or meteorological forecasts. This is the purpose of the MétéEAU Nappes tool implemented by BRGM for the City of Cape Town (CoCT) in the Table Mountain Group Aquifer (TMGA). This case study shows how near real-time groundwater level monitoring can support the municipality in managing its future groundwater withdrawals. The TMGA is an important source of groundwater in the Western Cape region of South Africa. The upper Nardouw Sub-Aquifer of the TMGA is an unconfined aquifer recharged by rainfall. It had been monitored in the Steenbras area for over 10 years before CoCT started groundwater production from the Steenbras wellfield in 2021. The MétéEAU Nappes forecasting tool is already implemented on many observation wells of the French national piezometric network, where it is used for decision-making by the French administration. It allows, in particular, to anticipate several threshold levels of drought and take appropriate measures. It combines real-time water cycle measurement data with a groundwater level lumped model (e.g. Gardenia model) and extrapolates observations for the next 6 months from statistical meteorological scenarios completed with abstraction scenarios. This tool can help protect the Steenbras wellfield as a critical water source for CoCT in the TMGA. This study was financed by the French Agency for Development (AFD).
Groundwater Flow Modeling for Investigation of Exploitation Induced Land Subsidence	Alper	Elçi	Italy	2023	MODFLOW, Mediterranean, earth observation, land subsidence, over-exploitation
Abstract This paper presents the results of groundwater flow modelling studies that were conducted within the scope of the PRIMA RESERVOIR project. The project’s main goal is to develop an innovative methodology to mitigate land subsidence due to excessive groundwater exploitation in water-stressed Mediterranean watersheds. This objective is achieved by integrating earth-observation-derived land subsidence rates with a coupled implementation of numerical groundwater flow and geomechanical modelling. MODFLOWbased 3-D transient flow models were constructed for the four pilot sites (the coastland of Comacchio in Italy, the Alto Guadalentín aquifer in Spain, the Gediz River basin alluvial aquifer in Turkiye and the Azraq basin in Jordan) that have different hydrogeological properties and pose different challenges concerning water management. Models were calibrated and run for similar simulation periods (2013-2021) to obtain hydraulic head drawdowns and changes in groundwater storage. Land subsidence at these sites was evaluated using Advanced Differential Radar Interferometry (A-DInSAR) on image stacks from the Sentinel-1 satellite. Subsidence rates were then compared to hydraulic head drawdown rates to identify groundwater pumping-induced subsidence areas. The comparison for all study areas suggested that locations of maximum displacements do not necessarily coincide with areas that display the largest head drawdown calculated by the flow models. Other triggering factors, such as the thickness of compressible materials, are also related to high subsidence areas.
Characterization of groundwater dynamics to identify the risks of flooding of the sewerage network of the urban communities of Lens-Liévin (northern France)	G	Picot-Colbeaux	France	2023	aquifer, Groundwater, groundwater inflow, hydrodynamic modelling, piezometry, sewerage network, urban hydrogeology
Abstract The interactions between groundwater and the sewerage networks of the Lens-Liévin urban communities, located in the north of France, locally lead to non-compliance in the operation of the network and the wastewater treatment plants, questioning the city’s economic development policy. Indeed, the infiltration of groundwater inflow in the sewerage network could be the cause. Based on the piezometric measurements carried out in 2022, the surface elevation of the groundwater table is carried out using a kriging approach. The comparison of altitudes between network position and piezometry made it possible to identify the pipes most at risk of the infiltration of groundwater inflow and correspond to those indicated as non-compliant by network managers according to the national decree. Outside this period, the network vulnerability indicators are defined based on simulated piezometry by a 3D hydrodynamic model of the chalky hydrosystem (MARTHE code) established in a transient state. For two past extreme situations, the network would have been flooded at 1.20% in the dry period (1997) and up to 8.30% in the wet period (2001), highlighting the existence of a part of the network systematically flooded. Using the hydrodynamic model according to different prospective scenarios makes it possible to anticipate the actions deployed on the network to guide management and adaptation solutions. However, a modelling methodology that considers the feedback between the dynamics of the groundwater and the flows passing through the networks remains to be developed.
The Roussillon coastal aquifer: using multiple-point statistics and multi-model ensemble to characterize geological uncertainty impact on water resources estimation	Valentin	Dall’ Alba		2023	Coastal aquifer, Groundwater Modelling, Multi-model ensemble, Uncertainty analysis
Abstract Coastal groundwater is a vulnerable resource, estimated to sustain the water needs of about 40% of the world’s population. The Roussillon aquifer is a regional aquifer near Perpignan (southern France). It covers over 800 km2 of land and is used for irrigation, drinking water, and industrial purposes. The aquifer has experienced significant piezometric lowering in the last decades, weakening the regional resource. An important aspect of modelling the hydrodynamic of this aquifer is the need to integrate data from agriculture and drinking water abstraction, natural and anthropogenic recharge, and account for the aquifer’s complex sedimentary arrangement. An ensemble of groundwater models has been constructed to understand the spatial evolution of the saline/freshwater interface and evaluate the impact of groundwater abstraction. Three sets of physical parameter modelling approaches were used. The first is based on the direct interpolation of pumping tests. The second uses sequential indicator simulations to represent the geological uncertainty. The third is based on a detailed conceptual geological model and multiple-point statistics to represent the detailed geological structure. These models provide parameter fields that can be input for the transient state hydrodynamic simulations. Overall, the ensemble approach allowed us to understand the Roussillon plain’s hydrological system better and quantify the uncertainty on the possible evolution of the main groundwater fluxes and water resources over the last 20 years. These models can help to inform management decisions and support sustainable water resource development in the region.
Impact of urbanization on groundwater quantity and quality in Kabul city, Afghanistan	A	Farahmand	Afghanistan	2023	Kabul basin, Urbanization, ground subsidence, Groundwater Quality, land use, land cover
Abstract Groundwater quantity and quality of shallow aquifers have deteriorated in recent years due to rapid development that has created an increased demand for drinking water, which is increasingly being fulfilled by groundwater abstraction. The study evaluates the hydrogeological framework of the Quaternary aquifer of the Kabul basin, Afghanistan, and the impact of urbanization on the groundwater resources around the Kabul city plain. Time series of Landsat satellite LCLU images indicate that the urban area increased by 40% between 2000 and 2020, while the agricultural area decreased by 32% and bare land decreased from about 67% to 52% during this period. The assumed groundwater overdraft 2019 was 301.4×103 m3 /day, while the recharge was 153.4×103 m3 /day, meaning a negative balance of about 54 million cubic meters (MCM) this year. Due to the long-term decline of water levels at 80 90 cm/year, and locally (Khairkhana, Dasht-e-Barchi) 30-50m during 2005-2019, a considerable groundwater drawdown is shown. Groundwater quality, on the other hand, reveals that chloride concentrations and salinity increased throughout the aquifer between 2005 and 2020. The nitrate concentration decreased in most Kabul Plain places over the period. In conclusion, the quantity and quality situation of urban groundwater in Kabul is worrying; urgent scientific and sustainable solutions and measures should be considered to manage this situation.
Real-time iFLUX sensors reveal rapidly changing groundwater flow dynamics in wetland ecosystems	N	Van Putte	Poland, Belgium	2023	Internet of Things, ecohydrology, groundwater flow, sensor development, wetland conservation
Abstract Shallow groundwater dynamics play a crucial role in wetland ecosystems and are key to climate change resilience. Therefore, conserving and restoring wetland areas requires excellent knowledge of groundwater flow dynamics, which are often rapidly changing following extreme weather events and anthropogenic impacts such as groundwater extraction. Traditional methods to estimate groundwater flow require extensive modelling or rely on point measurements, missing the effect of crucial short-term events and impeding quick actions to conserve the wetlands’ ecohydrological status. Here, we present a newly developed sensor that can measure real-time groundwater flow velocity and direction. The sensor probe consists of two bidirectional flow sensors that are superimposed. It is installed in a dedicated pre-pack filter and can measure a broad range of groundwater flow velocities from 0.5 cm/ day to 2000 cm/day. With an IoT (Internet of Things) system, sensor data is wirelessly transmitted and visualized in real-time on an online dashboard. In addition, we show a selection of results from a case study in the Biebrza National Park (Poland) and a nature reserve in Damme (Belgium). In both ecosystems, we could capture changes in groundwater flow velocity and direction resulting from precipitation and evapotranspiration events. As such, we are confident that our sensors provide new insights into rapidly changing groundwater dynamics and will become an invaluable tool in ecohydrological studies worldwide, ultimately leading to more integrated management strategies to protect and conserve remaining wetlands.
Machine learning applied to pumping test analysis	A	Lukas	South Africa	2023	numerical modelling, aquifer test analysis, deep learning, derivative analysis, Machine learning
Abstract Aquifer test analysis is complex, and in many regards, the interpretation resembles an art more than a science. Under the best circumstances, aquifer test analysis is still plagued by ambiguity and uncertainty, compounded by the general lack of information on the subsurface. An approach which has seen widespread adoption in other fields that need to classify time series data is machine learning. A Python script that generates numerical groundwater flow models by interfacing directly with the modelling software produces training data for deep learning. Production yielded 3,220 models of aquifer tests with varying hydrogeological conditions, including fracture, no-flow and recharge boundary geometries. Post-processing exports the model results, and the Bourdet derivative is plotted and labelled for image classification. The image classifier is constructed as a simple three-layer convolutional neural network, with ReLU as the activation function and stochastic gradient descent as the optimizer. The dataset provided sufficient examples for the model to obtain over 99% accuracy in identifying the complexities present inside the numerical model. The classification of groundproofing data illustrates the model’s effectiveness while supporting synthetically prepared data using modern groundwater modelling software.
Management of water-related risks in drinking water supplies	Barbara	Cencur Curk		2023	risk analysis, water-related hazards, water safety plan, water supply system
Abstract With the revision of the European Drinking Water Directive (Directive on the quality of water intended for human consumption 2020/2184) in December 2020, the preparation of Water Safety Plans (WSP) is foreseen according to the guidelines of WHO. Within the EU Interreg Adrion MUHA project, a decision support tool (DST) has been developed to provide a holistic approach to drinking water infrastructure risk analysis. The project mainly addresses four water-related risks: accidental pollution, floods, droughts and earthquakes. The core of the DST is the inventory of hazardous events (causes, their consequences and impacts) for each component of the drinking water supply chain: (1) drinking water source - catchment area, (2) water supply system, and (3) domestic distribution system. For each identified potential hazard, the type of hazard was determined (e.g., biological, chemical, radiological, or physical hazard (including turbidity), inadequate availability of water supplied to customers, safety to personnel, external harm to third parties, including liability). The DST was tested in the partner countries (Italy, Slovenia, Croatia, Serbia, Montenegro and Greece) to verify the resilience of the measures and elaborate the WSP. In the end, the REWAS-ADRION strategy was elaborated, aiming to increase the resilience of drinking water supplies to floods, droughts, accidental pollution, and earthquake-related failures by improving the water safety planning mechanism based on the concept of inter-agency cooperation to support water utilities, civil protection organizations, and water authorities.
onitoring a deep fresh-saline water interface using repeatVertical Electrical Soundings measurements	S	Meekes	The Netherlands	2023	Fresh-saline interface, Geo-electrical, Monitoring, Vertical Electrical Sounding
Abstract Monitoring deep (~100 – 200 m) fresh-saline water interface is a challenge because of the low spatial density of deep boreholes. In this project, Vertical Electrical Soundings measurements were used to evaluate changes in the depth of the interface over various decades. Water quality monitoring is a well-known application of geo-electrical measurements but generally applies to the relatively shallow subsurface. In this case study, the saline groundwater interface is around 120 -200 m deep, and the time interval between the measurements is several tens of years. Several locations showing good-quality existing VES-measurements acquired in the last century were selected to see whether repeat measurements could be performed. The number of locations where a repeat measurement could be performed was limited due to the construction of new neighbourhoods and greenhouse complexes. When interpreting the measurements for the change in the depth of the fresh-salt interface, it is assumed that the transition from fresh to saline groundwater occurs over a small depth range and that the electrical conductivity of the fresh water above this interface has not changed. However, it turned out that the ion concentration of the groundwater in the layers above the fresh-saline interface had increased sharply at almost all locations. This complicated the approach, but still, useful results could be obtained. Based on the measurements, it can be said that the fresh-saline water interface has shifted downwards at 3 locations, and hardly any change has occurred at 5 locations.
An Overview of long-term groundwater development and management – 20 years of Hermanus wellfields	Kornelius	Riemann	South Africa	2023	Monitoring, groundwater management, wellfield development
Abstract Hermanus was originally supplied from springs and groundwater until the De Bos Dam was built in the 1950s. Due to increasing water demand, the municipality commenced wellfield development in 2002. The first wellfield comprised 3 boreholes, of which one borehole was later decommissioned due to reduced yield. Three additional boreholes were drilled recently to ensure abstraction capacity within the licence limits. A second wellfield was developed in the Hemel-en-Aarde Valley north of Hermanus. To ensure the sustainable management of the shared resource and minimise environmental impacts, a monitoring committee was established with all relevant roleplayers, other users, civil society, environmental groups and various commenting and regulatory authorities. A comprehensive monitoring network was established to assist with the scheme’s management and ensure that environmental impacts are minimized. The long-term monitoring (up to 20 years) shows that the groundwater abstraction from the Gateway Wellfield does not impact the environment and other users or increase the risk of saline intrusion. Identified impacts have been mitigated with the assistance of the monitoring committee. The municipality aims to provide at least half of the town’s water demand from groundwater and establish conjunctive use operation between surface water from the De Bos Dam and groundwater from these wellfields. The wellfields ensured sufficient water for the municipality when De Bos Dam’s water levels declined significantly during the Western Cape droughts in 2011 and 2017. The presentation will provide examples of the long-term monitoring records and trends.
Per and Polyfluoroalkyl Substances (PFAS) Groundwater Toolkit	Fern	Beetle-Moorcrof	western United States	2023	PFAS, fate and transport, Groundwater, sampling
Abstract Per and Polyfluoroalkyl substances (PFAS) are ubiquitous on our planet and in aquifers. Understanding PFAS transport in aquifers is critical but can be highly uncertain due to unknown or variable source conditions, hydrophobic sorption to solid organic aquifer matter, ionic sorption on mineral surfaces, changing regulatory requirements, and unprecedentedly low drinking water standards. Thus, a PFAS toolkit has been developed to enable decision makers to collect the hydrogeologic data necessary to understand and better predict PFAS transport in aquifers for the purpose of managing water resources. This toolkit has been tested at a significant alluvial aquifer system in the western United States, which provides water for 50,000 people. Here, the toolkit has provided decision makers with the data necessary to optimize water pumping, treatment and distribution systems. The toolkit describes (1) the design and implementation of a sentinel well network to measure and track PFAS concentrations in the alluvial aquifer over time in response to variable pumping conditions, (2) data collection used to empirically derive input parameters for groundwater fate and transport models, which include the collection of paired aquifer matrix and groundwater samples, to measure PFAS distribution coefficients (Kds) and modified borehole dilution tests to measure groundwater flux (Darcy Velocity) and (3) the use of data collection techniques to reduce cross contamination, including PFAS-free, disposable bailers and a triple-rinse decontamination procedure for reusable equipment. The PRAS transport toolkit has the potential to assist decision makers responsible for managing PFAS contaminated aquifers.
Combined effects of seawater intrusion and nitrate contamination on groundwater quality in the coastal agricultural area of El-Nil River, Algeria	Lamine	Boumaiza	Algeria	2023	Coastal aquifer, Groundwater Quality, nitrate contamination, Seawater Intrusion, stable isotopes
Abstract This study focuses on the coastal agricultural area of El-Nil River (Algeria), where anthropogenic activities heavily impact groundwater resources. A multi-tracer approach, integrating hydrogeochemical and isotopic tracers (δ2HH2O, δ18OH2O, δ15NNO3 and δ18ONO3), is combined with a hydrochemical facies evolution diagram and a Bayesian isotope mixing model (MixSIAR) to assess seawater contamination and distinguish the nitrate sources and their apportionment. A total of 27 groundwater samples and 7 surface water samples distributed over the entire study area were collected. Results show classic inland intrusion combined with an upstream seawater impact through the river mouth connected to the Mediterranean Sea. Results from nitrate isotopic composition, NO3 and Cl concentrations, and the MixSIAR model show that nitrate concentrations chiefly originate from sewage and manure sources. Nitrate derived from sewage is related to wastewater discharge, whereas nitrate derived from manure is attributed to an excessive use of animal manure to fertilise agricultural areas. The outcomes of this study are expected to help decision-makers prepare suitable environmental strategies for effective and sustainable water resources management in the study area.
Groundwater discharge and climate change: The application of RCMs to assess long-term effects of climate change on spring flow along the Apennines	Tommaso	Casati	Italy	2023	Climate change, downscaling, forecasting, GCMs, groundwater discharge
Abstract Global warming affects atmospheric and oceanic energy budgets, modifying the Earth’s water cycle with consequent changes to precipitation patterns. The effects on groundwater discharge are still uncertain at a global and local scale. The most critical step to assess future spring flow scenarios is quantifying the recharge-discharge connection. This research aims to predict the long-term effects of climate change on the discharge of seven main springs with long hydrologic series of discharge values located in different hydrogeological settings along the Apenninic chain (Italy). The investigated springs are strategic for either public water supply or mineral water bottling. The Apennines stretch along the Italian peninsula in a Northwest-Southeast direction, crossing the Mediterranean area that represents a critical zone for climate change due to a decreased recharge and increased frequency and severity of droughts over the last two to three decades. In this communication, the data of one of the chosen springs, called Ermicciolo (42°55’25.8”N, 11°38’29.5”E; 1020 m ASL), discharging out from the volcanic aquifer of Mount Amiata, are presented. Statistical and numerical tools have been applied to analyse the time series of recharge-related parameters in the spring’s contribution area and the spring discharge from 1939 to 2022. To estimate the impact of climate change on the Ermicciolo’s outflow, a regional atmospheric circulation model has been downscaled to the spring catchment area and used to derive the expected discharge at the 2040-2060 time span, according to the build-up data-driven model of the recharge-discharge relationship in the past.
Peculiarities of the chemical composition of the Ordovician aquifer as a source of potable water supply (St. Petersburg, Russia)	E	Kayukova	St. Petersburg, Russia	2023	aquifer properties, ground water contamination, radon, saturation index
Abstract The Ordovician aquifer of the Izhora deposit is widely used for drinking by the population of St. Petersburg and its suburbs. Carbonate Ordovician rocks are intensively karstified. The water is fresh (0,5-0,8 g/l), bicarbonate-calcium on the predominant ions, pH 7.6; calcium content is 50-80 mg/l, magnesium content is 30-60 mg/l and the total hardness is 7,6-8,0 mg-equ./l. Western, northern and northeastern boundaries of the Izhora deposit go along the Baltic Klint, which is evident on the relief. Its southern boundary is along the zone of the dip of Ordovician limestone beneath the Devonian sandstone. The territory of the Izhora plateau belongs to the areas of intensive economic activity. Often, objects of human economic activity are located near drinking water intakes. Almost all sites are marked by excess sanitary norms of chemical elements. Pollution of groundwater in the Ordovician aquifer has been identified in some areas. Priority substances have been identified for assessing the quality of groundwater: total hardness, Fe, Mn, Ba, and B. According to hydrochemical modelling data, Ordovician groundwater is saturated with calcite over most territory. There are many springs of underground water along the Baltic Klint, for example, near the village of Lopukhinka, Duderhof springs and others. The springs waters have natural radioactivity (due to the contact of groundwater with dictyonema shales), which makes their use hazardous to human health.
A Case Study on Capacity Development in Rural Groundwater Supply in Acholiland, Northern Uganda	K	Robey	Northern Uganda	2023	Uganda, capacity development, Geophysics, handpump functionality assessments, rural groundwater supply, Water quality
Abstract Groundwater is the most important source of potable water in rural areas of Acholiland, a sub-region of northern Uganda. Installation of handpumps has been the focus of local government and international aid to provide safe drinking water in Uganda. However, non-functional handpumps are one reason for the abandonment of groundwater resources. For handpumps to be sustainable for years, appropriate siting and construction is required, as well as monitoring. This is common knowledge to specialists working in rural supply, but gaps in knowledge transfer and field skills may exist for the persons installing and maintaining handpump wells. This is a case study of a ten-day field campaign designed to train local participants who actively work in the rural groundwater supply sector. Nine non-functional handpump sites were identified for repair and hydrogeology and geophysical studies. A non-governmental organization, IsraAID, along with Gulu University implemented training by hydrogeology specialists to build local capacity. The training included handpump functionality tests, downhole inspections, electrical resistivity tomography surveys, and water quality sampling, including a novel Escherichia coli test that did not require an incubator. Functionality tests and downhole inspections provided simple but effective ways to assess handpump and well issues. Training in water quality empowered the participants to complete rapid assessments of the quality of the water and start monitoring programs. The success of the project was based on collaboration with multiple organizations focusing on the development of local capacity. The lessons learnt from this campaign should be considered for other rural groundwater supply scenarios.
Groundwater Dependent Ecosystems or wetland dependent groundwater systems: A case study	N	Vermaak	South Africa	2023	Wetlands; groundwater-dependent ecosystems; recharge; groundwater surface water interaction
Abstract The interaction between groundwater and wetlands is poorly understood, even though it has been the topic of many research projects, like the study done at the Langebaan Lagoon. This interaction is complex as it lies at the intersection between groundwater and surface water, but each situation is unique, with different conditions regulating the interaction. Wetlands can be the source of water that recharges groundwater systems on the one hand, while the other is dependent on the groundwater systems. This interaction became part of the project looking at how to implement Managed Aquifer Recharge for Saldanha Bay Local Municipality without having a negative impact on the groundwater-dependent ecosystems, such as the springs and wetlands in the area. Ten wetlands were identified on the Langebaan Road Aquifer Unit, and a monitoring programme was developed. The purpose of the monitoring was to determine the status of the wetlands as a baseline before the implementation of managed aquifer recharge and to determine the level of groundwater dependence. The latter was done by hydrochemical analysis of rainwater, groundwater and water from the wetlands and stable isotope analysis. The ability of the wetlands to act as a recharge point to the groundwater system will be investigated through column experiments and lithostratigraphic analysis of soil columns taken at the wetlands. Groundwater levels will also be plotted as contour lines to determine the intersection of the water table with the wetlands in the area.
From the national hydrogeological map to regional ones. How to identify a suitable level of detail to work with? An application in Kunene and Omusati Regions in Northwestern Namibia	A	Brugeron	Namibia	2023	Kunene, Namibia, Omusati, economic assessment, groundwater potential
Abstract Groundwater is a critical resource in Namibia, particularly in the Kunene and Omusati Regions, which are among the driest in Sub-Saharan Africa. Hydrogeological mapping is essential to ensure this resource’s sustainable use and management. The hydrogeological map of Namibia was updated recently (2021). However, the details of a 1:1M map are too coarse for regional groundwater management. An ongoing study of groundwater potential assessment in the two regions required downscaling the information to 1:250 000. This work made use of geological maps 1:250 000 from the Geological Survey of Namibia, about 430 selected wells including 20 recent boreholes, 117 reinterpreted pumping tests, some existing reports from private companies, academic works including a PhD thesis, interviews with local water resource experts and statistical analysis of 6 500 wells from the National Groundwater Database (GROWAS II) maintained by the Ministry of Agriculture, Water and Land Reform (MAWLR). The regional hydrogeological map obtained was then associated with the recharge evaluated in a separate task of the same project to assess the available groundwater sustainability. By assessing abstraction costs and water demand, the work gives insights into areas where groundwater abstraction can be increased or restricted to ensure sustainable use. As conscientious and serious as this study may be, it does not replace a master plan but allows a global vision of the development potential of groundwater at a regional scale. This study was financed by the French Agency for Development (AFD) under a tripartite agreement (MAWLR-MEFT-AFD).
Characterisation of Groundwater Quality Monitoring Objectives and Background Values: Case Study of the Soutpansberg Region, South Africa	Lindelani	Lalumbe	Soutpansberg Region, South Africa	2023	Background values, Groundwater Quality, groundwater use, land use, monitoring objectives
Abstract atural water-rock interaction processes and anthropogenic inputs from various sources usually influence groundwater chemistry. There is a need to assess and characterise groundwater quality monitoring objectives and background values to improve groundwater resource monitoring, protection and management. This study aims to determine monitoring objectives and characterise monitoring background values for all monitoring points within the Soutpansberg region. This study used long-term groundwater quality monitoring data (1995- 2022) from 12 boreholes and 2 geothermal springs. Monitoring objectives were determined from land-use activities, allocated groundwater use, and water use sectors. Monitoring background values were determined from the physio-chemical parameters from each of the 14 monitoring points. This study determined monitoring objectives and background values of all monitoring points and all physio-chemical parameters in the Soutpansberg region. This study recommends reviewing the determined monitoring objectives and background values every 5 to 10 years to assess any change in land use, groundwater use and sector and monitoring data trends.
he complexity and importance of the intermediate vadose zone - Local-scale, Pore-scale, and Discrete Scale	Matthys A	Dippenaar	South Africa	2023	adhesion, saturated zone, capillarity, cohesion, fracture flow, moisture content
Abstract The intermediate vadose zone underlies the plant root zone and comprises soil and rock. Different soils have different hydraulic and mechanical properties, and the vertical and spatial distributions are variable at a small scale. In South Africa, except for the Cenozoic and Quaternary deserts and coastal deposits, rock forms most of the vadose zone, and the rock fractures exacerbate the complexity. The vadose zone is observed at a small scale and dictates what happens in large scale, as adhesion to mineral surfaces happens first, and cohesion between water molecules is next. The original consideration of the intermediate vadose zone was a black box approach measuring what goes in from the surface and what goes out as groundwater recharge, not accounting for the movement of the vast majority of the freshwater supplied through precipitation. That doesn’t address the preferential flow, velocity, and pore water changes in the medium. Soil science addresses the soil or plant root zone very well. This zone governs the vertical movement of water and controls the ecosystems and biodiversity. However, all evapotranspiration disappears below this zone, and capillarity and gravity both move water into and through the intermediate vadose zone. Movement is no longer solely vertical and will be affected by soil types, intergranular porosity in soil and rock, changing water content, and secondary fractures with different properties in rock. This presentation will cover concepts and advances in this field, emphasising how and why water moves in the intermediate vadose zone.
Distributed recharge in karst-fractured carbonate aquifers: insights from the KARMA EU project for the groundwater resource management of Gran Sasso (Central Italy)	V	Lorenzi	Italy	2023	groundwater management, karst aquifers, recharge assessment
Abstract Water budget assessment and related recharge in karstified and fractured mountainous aquifers suffer a large uncertainty due to variable infiltration rates related to karst features. The KARMA project (karma-project.org), funded by the European Commission, has addressed this knowledge gap. The increase in human withdrawals and the effect of climate change can modify the recharge rate and, consequently, the spring discharge. The regional aquifer of Gran Sasso mountain, Central Italy, has been investigated by monitoring spring discharge isotope composition and calculating the inflow using a GIS approach on 100x100 m cells, considering local conditions, including karst features. The results for the 2000-2022 period highlight the preferential recharge area of the endorheic basin of Campo Imperatore (up to 75% of precipitation) and a mean infiltration of about 50% of rainfall. Different methods applied for recharge evaluation (Turc, Thornthwaite and APLIS) agree with a recharge rate close to 600 mm/year. This amount roughly corresponds to the spring discharge, evidencing: i) a “memory effect” in spring discharge, which is higher than previewed during dry years; ii) a variation in discharge due to rainy and drought year distribution, frequently recorded at springs with delay (1-2 years); iii) no significant trends of spring depletion since last 20 years; iv) the risk of lowering of snow contribution to recharge due to the temperature rise. The results provide updated information to the drinking water companies and the National Park Authority for sustainable management of the available groundwater resources.
Development of Table Mountain Group aquifer wellfields and monitoring networks for the City of Cape Town (Western Cape, South Africa)	Dylan	Blake	Western Cape, South Africa	2023	Critical Zone, Table Mountain Group aquifers, environmental monitoring, wellfield development, “no-regrets” approach
Abstract The City of Cape Town (CCT) initiated its “New Water Programme” in 2017 (during the major 2015-2018 “Day Zero” drought) to diversify its bulk water supply, thereby improving longterm water security and resilience against future droughts. This includes bulk groundwater abstraction from the major fractured Peninsula and Nardouw Aquifers of the Table Mountain Group (TMG) in the mountain catchments east of the CCT. The TMG aquifers are essential in sustaining groundwater-dependent ecosystems associated with the Cape Floral Kingdom – a global biodiversity (but also extinction) hotspot with exceptional endemic diversity. A strong geoethical, “no-regrets” approach is therefore required to develop TMG wellfield schemes for the CCT (and other towns/cities in the Western/Eastern Cape) to reduce the risk of any negative ecological and environmental impacts while still enhancing the drought resilience of the city, providing water for future urban growth, and meeting Sustainable Development Goals 6 and 11. To this extent, the CCT has developed an extensive regional (and local, in terms of Steenbras Wellfield) environmental monitoring network, incorporating a range of in-situ and remote sensing-based measurements across the Earth’s “Critical Zone” – this includes current groundwater, surface water, ecological, soil and meteorological monitoring stations, and future seismo-geodetic monitoring. An ongoing ambition is to include this CCT TMG monitoring network into the “Greater Cape Town Landscape”, which is currently in development as one of six national South African landscapes under the “Expanded Freshwater and Terrestrial Environmental Observation Network” (EFTEON) platform being hosted by the South African Environmental Observation Network.
Alluvial aquifer modelling with MODFLOW in a case of a wellfield in a climate change context (Clermont-Ferrand, France)	Jordan	Labbe	France	2023	Alluvial aquifer, Groundwater Modelling, Climate change, water management
Abstract This work is part of the AUVERWATCH project (AUVERgne WATer CHemistry), which aims to better characterise some Auvergne water bodies, specifically the alluvial hydrosystem of Allier River (France). Alluvial aquifers constitute worldwide a productive water resource, superficial and easily exploitable. In France, 45% of the groundwater use comes from these aquifers. The study site is a wellfield that withdraws 8.5 million m3 of water annually from an alluvial aquifer to produce domestic water for 80% of the local population. At the watershed scale, precipitations have decreased by -11.8 mm/y, air temperatures have increased by 0.06°C/y and the river flow has declined by 20.8 Mm3 /y on 2000 – 2020. In the summer period, at least 50% of the river flow is ensured by the Naussac dam (upstream catchment part), but the recent winter droughts have not allowed the dam to replenish. Thus, water stakeholders are concerned that the productivity of the wellfield could be soon compromised. Based on geological, geophysical, hydrochemical, and hydrodynamic surveys, a numerical model of the wellfield is being developed using MODFLOW. The calibration in natural flow regime is successful using a range of hydraulic conductivities going from 1×10-3 to 1×10-4 m/s (pilot points method), consistent with the pumping tests. Preliminary results show that the river entirely controls the groundwater levels at all observation points. The perspective is now to calibrate this model in a transient regime by integrating domestic water withdrawals to determine how low the river can go without affecting the wellfield productivity.
First Nations Communities as Partners in Hydrogeology	Sarah	Bourke	Australia	2023	Cultural Water Values, First Nations Groundwater Connections, Social Hydrogeology
Abstract Aboriginal and Torres Strait Islander people have inhabited the lands now known as Australia for over 65,000 years. Their communities are intricately connected to the land and waters through culture and tradition. However, there are few examples of integrated water resource management that serve Aboriginal and Torres Strait Islander communities or cultural interests. This is particularly the case for groundwater. In Australia, Indigenous connections to groundwater have historically been overlooked or, in some cases, assumed not to exist. On the contrary, many Aboriginal and Torres Strait Islander cultures have longstanding physical and spiritual connections to a range of artesian and subartesian groundwater resources. These cultures also house accurate records of groundwater systems. Despite this, groundwater management in Australia remains dominated by Western scientific perspectives, and the groundwater sector poorly integrates Indigenous stakeholder concerns or knowledge into groundwater management and planning. IAH Australia has prepared and signed an Indigenous Groundwater Declaration intending to raise awareness among the groundwater community of the value of Indigenous perspectives and knowledge of groundwater systems. This Declaration can be viewed and signed at http://declaration.iah.org.au. This presentation provides examples of effective partnerships between Indigenous Communities and Government or Academic groundwater professionals. While progress has been made, challenges must be overcome to integrate Indigenous knowledge and connections into groundwater resource management.
Micro pore-pressure sensor (MEMs) and analysis technologies – towards a future of multi-scale groundwater monitoring	W	Timms	Australia	2023	multi-scale, pore pressure, sensors, analysis
Abstract Micro-electro-mechanical system (MEMs) technologies coupled with Python data analysis can provide in-situ, multiple-point monitoring of pore pressure at discrete and local scales for engineering projects. MEMs sensors are tiny, robust, inexpensive, and can provide wireless sensing measurements in many electrical and geomechanical engineering applications. We demonstrate the development of MEMs pressure sensors for pore pressure monitoring in open boreholes and grouted in piezometers. MEMs sensors with a 60 m hydraulic head range and centimetre vertical resolution were subject to stability and drawdown tests in open boreholes and in various sand and grouts (permeability 10-8 to 10-2 m/s). The resulting accuracy and precision of the MEMs sensors, with optimal calibration models, were similar to conventional pore pressure sensors. We also demonstrate a framework for estimating in-situ hydrogeological properties for analysis from vented pore pressure sensors. This framework method included Python code analysis of hourly pore pressure data at the millimetre vertical resolution, which was combined with barometric data and modelled earth tides for each borehole. Results for pore pressure analysis in confined boreholes (>50 m depth) included specific storage, horizontal hydraulic conductivity and geomechanical properties. Future improvements in the vertical resolution of MEMs pore pressure sensors and combined these two technologies will enable groundwater monitoring at multiple scales. This could include the deployment of numerous MEMs, at sub-meter discrete scale in boreholes and evaluating local site scale variations in pore pressure responses to recharge, groundwater pumping and excavations in complex sub-surface geological conditions.
The impact of storage and hydrogeological conditions on the design and recovery performance of small-scale urban ASR systems	Niels	Hartog	The Netherlands	2023	Urban Groundwater, Managed aquifer recharge, Aquifer Storage and Recovery, MAR, ASR
Abstract Aquifer storage and recovery (ASR) can play a vital role in sustaining water availability to cope with increasing weather extremes. In urban areas, ASR systems may provide flooding risk mitigation and support urban greenery. However, such systems are often relatively small and therefore, their recovery performance depends more strongly on site-specific storage conditions such as dispersion and displacement by ambient groundwater flow. In this study, we evaluated the impact of these factors by adapting and developing analytical solutions and numerical modelling, with recently established Urban ASR systems as a reference for a wide range of realistic field conditions. We validated the accuracy and usefulness of the analytical solutions for performance anticipation. Results showed that a simple, analytically derived formula describing dispersion losses solely based on the dispersion coefficient (α) and the hydraulic radius of the injected volume (Rh) provided a very good match for all conditions tested where α/Rh<0.2. An expansion of the formula to include the development of recovery efficiency with subsequent cycles (i) was also derived and in keeping with simulation results. Also, displacement losses were found to be significant at groundwater flow velocities that are typically considered negligible, particularly as displacement and dispersion losses disproportionally enforced each other. For specific conditions where the displacement losses are dominant, using a downgradient abstraction well, effectively resulting in an ASTR system, might be beneficial to increase recovery efficiencies despite increased construction costs and design uncertainty.
Units for joint management of cross-border groundwater impacts in Transboundary Aquifers: An overview of concepts and methodologies	C	Morales		2023	cross-border groundwater impacts, hotspots identification, joint management units, time and space scales factor, transboundary aquifers, zoning
Abstract This study aims to contribute to the conceptual and methodological development of units of joint management in transboundary aquifers (TBAs) to prevent and mitigate cross-border groundwater impacts (GWIs) in quantity and/or quality. Joint management units are a relatively new but growing topic in the field of TBAs, and their conceptualisation and appropriate identification are still at an early stage. By reviewing the literature on the subject and elaborating on its terminology, main features, and current methodological progress, a comparison of the existing methodologies for identifying such units is analysed. On this basis, trends and recommendations for further research and application of such methodologies to the joint management of TBAs are presented. The literature on this issue is scarce and has been published mainly in the last five years. These publications lack consistency in the use of concepts and terminology. The above has led to miscommunication and semantic issues in the concept behind such units and in comprehending the particular challenges of identifying them. Still, some directions and methodologies for identifying or directly delineating these management units have been proposed in the literature. However, no analysis from these methodological attempts has been conducted; thus, there are no lessons to be learned about this progress. This research looks forward to closing these gaps and making headway toward dealing with cross-border GWIs in TBAs, thus helping countries meet international law responsibilities and maintaining stable relationships among them.
Water Quality of Cape Town Aquifers – The WWQA African Use Case	K	Riemann	South Africa	2023	WWQA, Water quality, Awareness
Abstract Globally, rivers, lakes and groundwater face complex anthropogenic water quality alterations posing risks to human health, food security and ecosystems. The World Water Quality Alliance (WWQA) forms an open, global consortium, pooling expertise on water quality science and technology innovation and providing a participatory platform for water quality assessments and co-designing tailored and demand-driven services. It addresses priority topics relevant to water governance, scalable water solutions and emerging issues in water management. The African Use Cases provided an initial testbed that puts the quality of surface water and groundwater into the context of the local 2030 Agenda and its multiple linkages across the Sustainable Development Goals. Central to the initial Africa Use Cases was the integration of in-situ, remote sensing-based earth observation and modelling data to derive the best possible current state of water quality (baseline). Of the three African Use Cases, “Cape Town’s Major Aquifer Systems” focused mainly on groundwater quality in an urban environment. One of the success factors for the Cape Town Aquifer Use Case was the ability of the team to integrate the three different data types of the triangle approach on a sub-catchment scale. This required understanding the complex surface and groundwater systems and their interaction (flow paths and fluxes) in the urban environment. A robust stakeholder engagement process and the introduction of transformative art also drove the success of the Cape Town Use Case. The outcomes of this process will be presented and discussed in this presentation.
Modelling the Impact of Groundwater Pumping on Karst Geotechnical Risks in Sete Lagoas (MG), Brazil	Paulo	Galvão	Brazil	2023	Karst hydrogeology; numerical model; water management; subsidence; overexploitation
Abstract Urban karst terrains can experience geotechnical issues such as subsidence or collapse induced/accelerated by groundwater withdrawal and civil works. Sete Lagoas, Brazil, is notable for overexploiting a karst aquifer, resulting in drying lakes and geotechnical issues. This study aims to evaluate the progression of geotechnical risk areas from 1940 to 2020 and to simulate future scenarios until 2100. Historical hydraulic head data from the 1940s (when the first pumping well was installed) to the 2000s, a 3D geological model, and a karst-geotechnical risk matrix for defining risk levels were employed to develop a calibrated Feflow numerical model. The results indicate that, before the first well in 1942, the groundwater flow direction was primarily towards the northeast. In the 1980s, due to the concentration of pumping wells in the central area, a cone of depression emerged, causing the flow directions to converge towards the centre of the cone, forming a zone of influence (ZOI) of approximately 30 km². All 20 geotechnical events recorded between 1940 and 2020 have occurred in high or considerable-risk zones where limestone outcrops or is mantled in association with the ZOI. For future scenarios, if the current global well pumping rate (Q = 144,675 m³/d) from 2020 remains constant until 2100, the high and considerable geotechnical risk zones will continue to expand. A 40% decrease in the global rate (Q = 85,200 m³/d) is necessary to achieve a sustainable state, defined by reduced and stabilized risk zones.
The application of artificial intelligence techniques to support groundwater management in Southern Africa	Z	Gaffoor	South Africa	2023	Big data analytics, Machine learning, transboundary aquifers
Abstract The beneficial groundwater use in the Southern African Development Community (SADC) is well documented. Groundwater plays a vital role in the freshwater supply mix and, in some cases, is the only source of freshwater, especially in the arid region of SADC. However, the management of this resource is hampered by numerous challenges, such as lack of data, limited tools to leverage available data, lack of resources, institutional mismanagement, and climate change, amongst others. Of these challenges, the lack of data and the tools needed to transform this data into information has consequences for the decision-making process. Hence, this research attempts to address this challenge by demonstrating the use of big data and artificial intelligence (AI) to fill data gaps with new unconventional sources and model groundwater processes to transform data into actionable information. The presentation focuses on introducing the landscape of groundwater big data in SADC, followed by a review of regional AI applications. After that, novel approaches to using AI in various aquifers across SADC are demonstrated in their applicability to support groundwater management. Finally, the challenges facing the use of AI in SADC are discussed, followed by opportunities for new research based on the current state-of-the-art AI techniques. The results illustrate that AI can be a helpful tool for supporting groundwater management in SADC. However, the need for enhanced data collection is evident for these techniques to be generally applicable.
Variable-scale conceptual framework for shallow groundwater systems in the low-relief, water-limited Canadian Boreal Plains	K	Hokanson	Canada	2023	Groundwater-surface water interactions, long-term study, recharge, spatiotemporal scales, subsurface connectivity
Abstract Case studies illustrate a conceptual framework for shallow groundwater flow systems’ temporal and spatial variability with groundwater-surface water interactions in the Boreal Plains of Canada. The framework was developed using a twenty-year hydrometric dataset (e.g., climatological and streamflow data, hydraulic heads, vertical hydraulic head gradients, geochemical and isotopic signatures). The region is characterized by low-relief glacial landscapes, with a mosaic of forestlands and peatlands, and a subhumid climate, resulting in spatially heterogeneous storage and transmission properties, variable recharge and evapotranspiration potentials, and highly complex patterns of water movement. Two primary spatiotemporal scales were examined to create a holistic, variable-scale conceptual model of groundwater movement: the large scale (e.g., glacial landforms, regional topography, decadal climate cycles) and the small scale (e.g., individual landcover, local hummocks, annual moisture deficits). Water table behaviour, evapotranspiration rates, and runoff were controlled by a hierarchy of interactions between hydrological processes occurring at different spatiotemporal scales; however, the specific order of controls depends on the hydrogeological setting. The case studies, supported by empirical and numerical modelling, demonstrate that smaller-scale heterogeneities in geology and recharge can dominate over topographic controls, particularly in areas with high conductivity or hummocky terrain, where the climate, geology, and topographic relief are similar. Many hydrogeological studies rely on surface topography as a first‐order control; however, with field observations and modelling, this conceptual framework demonstrates the need to consider the potential dominance of subsurface characteristics and processes, plus climate, especially in landscapes with low recharge and low relief.
Tracing an arenitic aquifer by DNA-labelled nano particles	Alessandro	Gargini	Italy	2023	nanotechnology; DNA-labelled nano particles; arenite; groundwater; tracer test; Northern Apennines
Abstract The results of a full field application of a DNA-based nano tracer in an arenitic aquifer are presented along with the comparison with the breakthrough of a classical tracer injected in parallel. DNA is encapsulated into amorphous silica spheres (nanoparticles), protecting the molecule from chemical and physical stresses. The main advantages of using DNA with classical tracers, like ionic or fluorescent, are the lower detection concentration and the chance to perform multi-tracer tests with many distinct signatures of injection. To the authors’ best knowledge, this is the first tracing adopting nano-particles on full field conditions in a sedimentary fractured aquifer. Preliminary tests in the lab were performed adopting either deionized water or groundwater collected at the experimental site: a set of nanoparticles at a known concentration was dissolved by adding a buffered fluoride solution, and DNA was then quantified by qPCR reaction (SYBR green). The hydrogeological setting is represented by a Miocenic marine arenitic aquifer (Pantano formation) outcropping extensively in Northern Apennines (Italy) and the main groundwater reservoir for public water supply through the uptake of many perennial springs. The main purpose of the tracing was to verify the transmissive capacity of fractures with high aperture (15-20 cm) identified by optical and acoustic televiewers inside an 80 m deep borehole. The injection was performed inside the borehole, and the tracer’s recovery was between 5-15 m, both in the uptake points of two perennial springs and in another borehole drilled nearby.
A methodology for uncertainty quantification of dewatering volumes under the context of open-cast mining	C	Rivera Villarreyes		2023	FEFLOW, Groundwater Modelling, mining, PEST, PESTPP
Abstract Groundwater modelling at the mine sites involves assumptions from the geological model, mining stages, parametrization, and fractures, among others. Modelling work mainly focuses on calibrating against historical measurements before operations (pre-mining) or afterwards (transient calibration). Calibration is carried out mainly with gradient-based algorithms. However, the majorlimitation is the number of model runs, since the number of parameters can easily reach hundreds or more. PEST has become the common tool for parameter estimation. The Jacobin calculation required for the Levenberg Marquardt algorithm requires several model runs. This, a limited factor for the calibration and, subsequently, uncertainty quantification. The next generation of PEST, named PESTPP, is gained popularity in the groundwater community. The great advantage of PESTPP,, compared to the classical PEST, is its new module, Iterative Ensemble Smoother (IES). PESTPP-IES covers both parameter estimation and uncertainty quantification in one goal. Its empirical formulation of the Jacobian matrix reduces the number of runs; thus, the numerical bottleneck can be significantly reduced. PESTPP-IES has been extensively tested in an open-pit mine at the geological complex conditions in the Peruvian Andes. The work involves the task of model simplification, e.g., from a regional model to a detailed local pit model, calibration and uncertainty quantification of pit dewatering volumes. Detailed model was kept calibrated based on hydraulic-head measurements, and dewatering volumes were predicted. All these consider transient changes in the mining plan within the same FEFLOW model. Results validate the methodology and practicability in mining applications.
A conceptual model for methane occurrences in the Western Karoo as part of a geochemical baseline for shale gas development	Danita	Hohne	Western Cape	2023	Western Karoo, shale gas development, shallow and deep groundwater, thermogenic and biogenic methane; isotopes
Abstract Although methane occurrences have been documented in Karoo groundwater in the past, the advent of possible unconventional oil and gas extraction now made it important to determine the type and origin of this methane to assess the possibility of shallow-deep groundwater interaction. During groundwater surveys from 2016-2021, methane was detected at three sites in the Western Karoo: the Soekor sites KL1/65, QU1/65 and an unidentified shallow groundwater borehole (BHA). The Soekor wells were drilled in the 1960-1970s to depths of between 2500-3500 meters in South Africa’s search for oil. On the other hand, Borehole BHA was drilled in 1998 and only up to a depth of 298m. This study aimed to determine methane’s origin through gas and isotope analyses. To do this, groundwater, rock and soil samples were analysed to determine whether the methane is thermogenic or biogenic and its origin. We determined that methane was both thermogenic and biogenic and probably originated from different layers of the Karoo formations and that mixing occurs between deep and shallow aquifer systems at these Soekor sites. This information was used to develop a final conceptual model of what the Karoo underground system might look like and to make recommendations for establishing a groundwater baseline.
The impacts of climate change on groundwater in South Africa	Zaheed	Gaffoor	South Africa	2023	CMIP6, GRACE data, groundwater recharge potentia
Abstract Climate change is expected to have a significant impact on freshwater resources across the globe. Changes in the distribution and quantities of rainfall over the coming decade will impact various earth systems, such as vegetation, contributions to streamflow, sub-surface infiltration and recharge. While groundwater resources are expected to act as a buffer, changes in rainfall will ultimately impact the recharge process and, thus, groundwater reserves. Understanding these changes is a crucial step to adapt better and mitigate climate change’s impacts on water resources. This is valid in South Africa, where much of the population depends on groundwater as a freshwater supply. Hence, this research presents the status quo regarding climate change’s impacts on South Africa’s groundwater resources. Reviewing relevant literature, the impacts on recharge, groundwater quantity (storage changes), discharge and groundwater-surface water interactions, groundwater quality, and groundwater-dependent ecosystems are discussed. In addition, utilizing factors such as rainfall, slope and vegetation cover collected from CMIP6 climate projections, changes in groundwater recharge potential from the past through the present and future are demonstrated. The findings illustrate uncertainty over the long-term impacts of climate change on groundwater for different regions and various aquifers. However, global warming could lead to reduced recharge, which impacts groundwater reserves.
Use of krypton-81 to constrain the reliability of carbon-14 in estimating groundwater ages	S	Lu	China	2023	groundwater dating, krypton-81 isotope, radiocarbon
Abstract Advances in groundwater age dating provide key information for groundwater recharge history and rates, which is of great significance for groundwater sustainable development and management. By far the, radioisotope 14C is the most frequently used in routine investigations. However, groundwater age can be misinterpreted given its dating range of up to 40 ka and its chemically active in nature. In comparison, 81Kr is less frequently used but chemically inert with a dating range of up to 1,300 ka, which overcomes the limit of 14C. Although it is not as precise as 14C when the groundwater age is younger than 40 ka, it may be helpful to determine the reliability of 14C dating results. In this study, we collected eight field samples from coastal aquifers in Nantong, China and analyzed them for 81Kr, 85Kr, and 14C. The 14C results show that all groundwater ages range from 2,400 to 35,300 years, with different correction methods yielding uncertainties of 1,500 to 3,300 years. Four of the 81Kr ages provided upper bounds, while three yielded groundwater ages which are consistent with the 14C dating results within measurement uncertainties. Interestingly, one 81Kr result gave an age of 189+11 - 12ka, whereas the corresponding corrected 14C age was less than 29,200 years. The great difference may indicate modern contamination in the sampling process or mixing between young and old groundwaters. Further investigation is needed to shed more lights in this case. Moreover, it shows the benefits of introducing 81Kr in routine hydrogeological investigations and the groundwater studies.