Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 51 - 100 of 795 results

Title	Presenter Name	Presenter Surname	Area	Conference year Sort ascending	Keywords
Winter irrigation as climate change adaptation strategy in northern Italy	Luca	Alberti	Italy	2023	Adaptation strategies, Climate change, Integrated Water Resources Management, Irrigation, Managed aquifer recharge, flow modelling
Abstract In 2021-23, northern Italy suffered a severe drought due to the absence of rainfall, which strongly affected the pre-alpine lake levels, affecting energy production, agriculture and sustainable river flows. This led to harsh consequences on agriculture, which in the Lombardy region almost completely relied on flooding irrigation methods using water from lakes through Ticino and Adda rivers. As part of the INTERREG Central- Europe project “MAURICE”, which focuses on Integrated Water Resources Management, the winter irrigation practice is proposed as a climate change adaptation strategy. The main project idea is to store surface water in aquifers in periods of exceedance (autumn/winter) using the very dense channels irrigation network as a “natural” infiltration system. The underground storage would increase the groundwater levels, bringing two main advantages during the spring/summer seasons: a good flow rate at plain springs and, in periods of water scarcity, the possibility to extract groundwater for agricultural purposes. Relying on the slow groundwater velocity (about 350 m/y), this practice keeps water stored in the subsoil just below the irrigated areas where the water is needed. In the early project stage, a basin-scale numerical model is presented to test the potentiality of such practice. A specified water volume was distributed on the crop fields during the winter period, and the effects of such managed recharge were evaluated, also considering the possible problems deriving from the groundwater levels increase. The model demonstrates the adaptation measure feasibility, which will be tested at a field scale in a Pilot Area.
Groundwater resource assessment and delineation of resource unit for the Komati catchment within the Inkomati Usuthu Management Catchment area – Mpumalanga Province, South Africa	Collen	Monokofala	South Africa	2023	Catchment scale integrated surface water and groundwater studies
Abstract The recent uncertainties in rainfall patterns have resulted in shortages in the availability of water resources, posing significant risk to the sustainability of all living organisms, livelihoods and economic prosperity. The fact that hidden groundwater resources in semi-arid regions present a challenge to understanding and managing the resources. Various groundwater studies have been undertaken; however, the quantification is generally over-simplified due to a limited understanding of the groundwater flow regime and consideration being mostly given to water supply. Thus, the data is often not comprehensive enough and generally limited in determining how much groundwater is available to supply rural areas. The Komati catchment area is dominated by coal mining in the upper reaches and irrigation and agriculture in the lower reaches, with human settlements competing for these water resources. Five significant dams in the Komati catchment are constructed to deal with the increasing water demand for commercial agriculture in the region. However, given uncertain weather patterns, the water mix approach is imperative. This study focused on understanding the groundwater potential, characterised the aquifer system, delineated the groundwater resource units, quantified baseflow and calculated the groundwater balance that can be used as a guide for the groundwater management protocol for the catchment area. The box model approach (surface-groundwater interaction) was used to characterize the groundwater regime and understand the spatial distribution of the aquifer types, water quality and significant aquifers of interest to protect this important resource.
Numerical groundwater modelling of the Windhoek Aquifer (Namibia) for wellfield management	Jannie	Weitz	South Africa	2023	MODFLOW, Windhoek Aquifer, numerical groundwater modelling
Abstract The City of Windhoek in Namibia has developed wellfields and a managed aquifer recharge scheme within the fractured Windhoek Aquifer to ensure a sustainable potable water supply to the city during drought. A three-dimensional numerical groundwater model of the aquifer was developed using the finite-difference code MODFLOW to determine the potential impacts of varying pump inlet depth elevations and varying production borehole abstraction rates for optimal wellfield and aquifer management. The initial steady-state numerical model was calibrated to September 2011 groundwater levels, representing the best approximation of “aquifer full” conditions (following a good rainfall period and best available data). The subsequent transient numerical model was calibrated against groundwater level fluctuations from September 2011 to August 2019, the period after steady-state calibration for which data was available (and during which monitored groundwater abstraction occurred). The calibrated transient model was used to run various predictive scenarios related to increased emergency groundwater abstraction and estimate potential impacts on the Windhoek Aquifer. These predictive scenarios assessed groundwater level drawdown and recovery, aquifer storage potential, and potential abstraction rates under different pump elevations. Model results indicated a sharp initial groundwater level drop followed by a gradual decrease as groundwater levels approached the 100 m saturated depth mark. Pumping elevations were subsequently updated with recommended abstraction rates and volumes for the entire Windhoek Aquifer. The numerical groundwater model, in association with extensive groundwater monitoring, will be used to assess/manage the long-term sustainable and optimal utilisation of the Windhoek Aquifer.
Data-Driven approach to groundwater level prediction for improving water resource management: the Brenta aquifer system case study (Veneto, Italy)	Linda	Franceschi	Italy	2023	Foothill aquifer system, Climate change, groundwater management, predictive models
Abstract In the context of climate change, this work aims to model the piezometric levels of the foothill aquifer located in the middle-high Brenta river plain (Veneto, Italy) to support managing a groundwater system that provides drinking water for most of the Veneto Region. Using a Data-Driven approach, predictive Multiple Linear Regression Models were developed for the piezometric level at different wells, and scenarios of groundwater level evolution were achieved under dry periods. Results highlighted the high sensitivity of the aquifer to climate extremes, as well as the need to plan actions for mitigating the effects on such a strategic water supply system. Groundwater hosted in the foothill aquifer represents an important resource. However, these systems are highly sensitive to the variation of Meteo-climatic regimes. At the same time, the exploitations can lead to excessive groundwater drawdown and consequent threats of water scarcity. The Data-Driven approach adopted using long time series of meteorological, hydrometric and piezometric data can represent a valid example in these terms. The groundwater level evolution has been well-reproduced by these models. The equations describing models show the close dependence of groundwater from the Brenta River and the high sensitivity of the aquifer to meteo-climate regimes. Given this sensitivity, the forecast of groundwater level evolution under a dry period, similar to 2022, was performed. Results point out a progressive drawdown of groundwater level. These predictive models can be useful for local authorities to maintain these levels over specific critical values.
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.
OFF-SOURCE: A network to address the potential use of offshore freshened groundwater as an unconventional source of potable water in coastal cities.	H	Wazaz		2023	Offshore groundwater, COST Action, scientific networking, unconventional water resources, Transboundary aquifer
Abstract One-third of the world faces water insecurity, and freshwater resources in coastal regions are under enormous stress due to population growth, pollution, climate change and political conflicts. Meanwhile, several aquifers in coastal regions extending offshore remain unexplored. Interdisciplinary researchers from 33 countries joined their effort to understand better if and how offshore freshened groundwater (OFG) can be used as a source of potable water. This scientific network intends to 1) estimate where OFG is present and in which volumes, 2) delineate the most appropriate approaches to characterise it, and 3) investigate the legal implications of sustainable exploitation of the offshore extension of transboundary aquifers. Besides identifying the environmental impact of OFG pumping, the network will review existing policies for onshore aquifers to outline recommendations for policies, action plans, protocols and legislation for OFG exploitation at the local to international levels. Experienced and early-career scientists and stakeholders from diverse disciplines carry out these activities. The Action leads activities to foster cross-disciplinary and intersectoral collaboration and provides high-quality training and funded scientific exchange missions to develop a pool of experts to address future scientific, societal, and legal challenges related to OFG. This interaction will foster new ideas and concepts that will lead to OFG characterisation and utilisation breakthroughs, translate into future market applications, and deliver recommendations to support effective water resource management. The first exchange mission explored the Gela platform carbonate reservoir (Sicily), built a preliminary 3D geometrical model, and identified the location of freshened groundwater
Global potential groundwater recharge in response to climate variability and teleconnection	C	Moeck	Norway	2023	climate variability, global, groundwater recharge, teleconnections, unsaturated zone
Abstract Periodic climate variability, such as that caused by climate teleconnections, can significantly impact groundwater, and the ability to predict groundwater variability in space and time is critical for effective water resource management. However, the relationship between climate variability on a global scale and groundwater recharge and levels remains poorly understood due to incomplete groundwater records and anthropogenic impacts. Moreover, the nonlinear relationship between subsurface properties and surface infiltration makes it difficult to understand climate variability’s influence on groundwater resources systematically. This study presents a global assessment of the impact of climate teleconnections on groundwater recharge and groundwater levels using an analytical solution derived from the Richards equation. The propagation of climate variability through the unsaturated zone by considering global-scale climate variability consistent with climate teleconnections such as the Pacific-North American Oscillation (PNA) and the El Niño/Southern Oscillation (ENSO) is evaluated, and it is shown when and where climate teleconnections are expected to affect groundwater levels. The results demonstrate the dampening effect of surface infiltration variability with depth in the vadose zone. Guidance for predicting long-term groundwater levels and highlighting the importance of climate teleconnections in groundwater management is provided. The obtained insights into the spatial and temporal variability of groundwater recharge and groundwater levels due to climate variability can contribute to sustainable water resource management.
Basin-scale transfer of nitrate pollution from groundwater to surface water in an intensively irrigated system	M	Rotirot	Italy	2023	Cl/Br ratio, Irrigation return flow, Po Plain, boron, dilution, stable isotopes
Abstract Basin-scale studies addressing the transfer of pollutants among groundwater and surface water bodies are essential to support local authorities in the sustainable management of freshwater resources. This work revealed that, in the hydro-system of the Oglio River basin (Northern Italy), nitrate pollution in groundwater, originated by overfertilization, is transferred downstream to surface water bodies via outflow through lowland springs and baseflow to gaining rivers. Downstream groundwater is unaffected due to reducing conditions that facilitate denitrification. It follows that efficient measures to reduce nitrate pollution in surface water bodies should not be applied solely to rivers/streams but, instead, they should include the upstream groundwater body. The work aimed at understanding nitrate pollution dynamics in an intensively irrigated hydro-system, focusing on the role played by the complex interaction among irrigation water, surface water and groundwater. The study relied on nitrate concentration, Cl/Br ratio, stable isotopic composition of water, nitrate and boron in groundwater, river, lake, spring, and rainwater samples. Results highlighted a well-defined spatial distribution of nitrate concentrations in groundwater, mainly driven by irrigation practices: (1) where groundwater-fed irrigation is done, return flow promotes high nitrate concentrations (>50 mg/L) due to groundwater recirculation; (2) where intensive surface-water-irrigation is practised, fed by low-nitrate river water, return flow generates lower nitrate concentrations (<50 mg/L) due to dilution. This work highlighted the importance of a holistic approach jointly investigating surface water, groundwater, and irrigation water when nitrate pollution is examined at a basin scale.
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.
Design and Implementation of Groundwater Protection Schemes in Different Aquifer Settings	Kirsty	Gibson	South Africa	2023	Groundwater Protection Scheme, Groundwater Protection Zone, Aquifer Vulnerability, Aquifer Contamination
Abstract Groundwater is a vital freshwater source, and its role in meeting water demands will become pivotal under future climate change and population growth. However, groundwater supply to meet this demand is at risk as aquifers can be rapidly contaminated, and the cost of aquifer rehabilitation and/or sourcing alternative water supplies can be high. The development of groundwater protection schemes is required to ensure long-term protection of groundwater quality and sustainable groundwater supply. A groundwater protection scheme is a practical and proactive means to maintain groundwater quality and forms an additional methodology for groundwater resource management/protection. There are no legislative guidelines on establishing groundwater protection schemes in water-scarce South Africa, despite groundwater being used extensively. Three groundwater protection schemes were designed and implemented to protect abstraction from a fractured aquifer in an undeveloped natural mountain catchment and two primary aquifers within different urban settings. The approach incorporated protection zone delineation (comprising four zones), aquifer vulnerability mapping/ ranking using the DRASTIC method (with the primary and fractured aquifer systems having varying vulnerabilities), and identification of potentially contaminating activities (which also vary significantly between the urban areas overlying the two primary aquifers, and the generally undeveloped natural mountain catchment fractured aquifer is situated within). Additionally, a protection response was established to determine monitoring frequencies. Practical insights into the design and implementation of these three groundwater protection schemes can serve as a model for implementation in other African aquifer systems.
Hydrological processes in the Arctic catchment of Bayelva River (Western Svalbard-Norway)	Marco	Doveri	Norway	2023	Arctic hydrology, Climate change, groundwater-surface water evolution, melting water
Abstract Streamwater and groundwater are changing in the Arctic region because of significant climate warming. Arctic amplification has intensified the melting of snow cover, glaciers and permafrost, leading to a prominent variation in the annual discharge of rivers, the groundwater occurrence, and their relationships. In high-latitude regions, evaluating groundwater flux/storage and river discharge is challenging due to a lack of hydrogeological data. Changes in river flows and groundwater discharge will alter freshwater and terrigenous material flux, with implications for freshwater and marine ecosystems. Consequently, a more timely and accurate evaluation of surface and groundwater is required. In this framework, through the ICEtoFLUX project (MUR/PRA2021/project-0027), hydrology, geophysics and geochemical-isotopic surveys have been started during 2022 in the Bayelva River catchment (W-Svalbard) from its glaciers and periglacial/proglacial systems up to the Kongsfjorden. The study aims to quantify hydrologic processes and related transport of matter (solid transport, chemical solutes flux) and investigate how subsurface and surface waters interact during active layer development. The first results suggest that electrical conductivity and total suspended solids increase from glaciers to the Bayelva monitoring station, about 1 km from the coast. Seasonal evolution of physical-chemical features was also observed. Results from geophysics data and piezometers indicate that the underground flow is spatially and temporally heterogeneous, both quantitatively and from a physicochemical-isotopic point of view. Springwater characteristics testify to a deep and well-organized groundwater flow path system. This study highlights the high complexity of these systems and their high sensitivity to the meteo-climatic regimes.
Analysis of Heavy Metal Sources in Groundwater and Assessment of Health Risks: An Example from the Southwest Sub-basin of the Shiqi River	Yu	Shi	China	2023	Groundwater; heavy metal elments; source analysis; health risk assessment
Abstract To explore the sources of pollution and health risk profile of heavy metal elements in groundwater,41 sets of representative groundwater samples from the southwest subbasin of the Shiqi River were examined for 10 heavy metal elements, correlation analysis and principal component analysis were used to resolve the possible sources of heavy metal contamination in groundwater. The concentration characteristics and health risk levels of the 10 heavy metals were assessed using the single factor contamination index (Pi), the Nemerow comprehensive contamination index (PN) and the health risk model. The results show that: 1) The average values of heavy metal elements of the groundwater in the study area all met the limit of class III water standard in the quality standard for groundwater; only the maximum value of Al was exceeded, followed by a large variation in the concentrations of Al, Mn and Cr. The heavy metal element with the largest average contribution was Al (65.74%). 2) The results of the single factor contamination index evaluation show that only the heavy metal element Al exceeds the level, and the results of the Nemerow comprehensive contamination index evaluation show that the study area is basically at low pollution levels and the quality of groundwater is good. 3) The results of the multivariate statistical analysis show that Zn, Co and Mn are mixed sources of geological formation and domestic waste, Al, As, and Cu are agricultural sources, Cd, Cr and Ni are industrial sources, and Hg comes from long-range atmospheric transport.
Groundwater resources of the Danakil Depression – hydrogeology in the hottest place on Earth	L	Towers	Umvoto	2023	Danakil Depression, Alluvial aquifer, potash, rift basin, solution mining
Abstract he Danakil Depression of the Afar Rift forms part of the north/south-trending Ethiopia-Eritrean arm of the East African Rift System, whereas the western margin of the depression forms part of an active plate boundary between the western Nubian and eastern Danakil tectonic blocks. Dallol (within the Danakil Depression) currently holds the record for the highest average temperature for an inhabited place on Earth, with annual average temperatures of ~35-36°C. The isolated area was initially explored geologically in the late 1960s, with recent geological and hydrogeological interest in its northeast Ethiopian portion due to easier access, geo-tourism and potash-ore exploration. Potash mining is proposed via solution-extraction techniques, requiring large volumes of water in one of the driest hyper-arid regions. Various hydrogeological investigations were therefore conducted between 2014 and 2016 as part of a feasibility and water resource study towards developing a water resource estimate for the region and proposed mining operations. Alluvial fans on the west side of the rift basin form a major, regional primary aquifer – fan boreholes have yields of 50 litres per second, although groundwater is highly saline (up to 3-5 times the salinity of seawater) and can reach temperatures of 50°C. Groundwater yields of hundreds of millions of cubic metres per annum are potentially available from the saline alluvial fan primary aquifers for potash solution mining. In contrast, groundwater from karstic limestone aquifers could provide a freshwater resource to settlements within the Lelegheddi River basin and the Danakil.
Multiple-tool approach of combining microbial markers with artificial and natural tracers to specify the origin of faecal contamination on karst groundwater catchment scale	M	Sinreich	Switzerland	2023	Karst spring, MST, Catchment, faecal indicators, toolbox, tracers
Abstract Diverse tools exist to study the transfer of contamination from its source to groundwater and related springs. A backward approach, i.e. sampling spring water to determine the origin of contamination, is more complex and requires multiple information. Microbial source tracking (MST) using host-specific markers is one of the tools, which, however, has shown to be insufficient as a stand-alone method, particularly in karst groundwater catchments. A karst spring in the Swiss Jura Mountains was studied concerning the occurrence and correlation of a set of faecal indicators, including classical parameters and bacteroidal markers. Sporadic monitoring proved the impact on spring water quality, mainly during high water stages. Additional event-focused sampling evidenced a more detailed and divergent pattern of individual indicators. A multiple-tool approach, complementing faecal indicator monitoring with artificial tracer experiments and measuring natural tracers, could specify the origin of ruminant and human faecal contaminations. Natural tracers allowed for distinguishing between water components from the saturated zone, the soil/epikarst storage, or freshly infiltrated rainwater. Additionally, the breakthrough of injected dye tracers and their remobilization during subsequent recharge events were correlated with the occurrence of faecal markers. The findings hypothesize that human faecal contamination is related to septic tanks overflowing at moderate rainfall intensities. Linkage with vulnerability assessment and land-use information can finally better locate the potential point sources. Such a toolbox provides useful basics for groundwater protection and catchment management and insight into general processes governing the fate and transport of faecal contaminants in karst environments.
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).
Distribution, Formation Conditions and Genesis of High-Quality Groundwater Containing Metasilicate in Zhaojue County, Southwest China	Shengzhang	Zou	Southwest China	2023	Groundwater; H2 SiO3 ; distribution; formation condition; Zhaojue County; Southwest China
Abstract The drinking water health issues have been considered due to improved living standards in recent years. Finding and developing high-quality groundwater with high-level minerals has become key to improving human health. The hydrochemical test data of 66 springs in Zhaojue County were analyzed using various methods, and the spatial distributions of H2 SiO3 -rich groundwater, hydrogeochemical characteristics, formation conditions and genesis were revealed. The main results including: 1) the groundwater with H2 SiO3 (≥25mg / L) was identified as the low salinity and alkaline water, which distributed in the six areas with the basement rocks of basalt,with a distribution area of about 79 square kilometers. The H2 SiO3 concentration was generally 25.74~46.04 mg/L; the low mineralization characterized the H2 SiO3 -rich groundwater of study area while the main hydrochemical types of groundwater are HCO3 - Ca·Mg, HCO3 -Ca, and HCO3 -Na; the Pearson correlation coefficient between the content of H2 SiO3 in groundwater and the content of pH is relatively high, indicating that the level of H2 SiO3 in groundwater in the study area is significantly affected by the pH value of the solution; the H2 SiO3 -rich groundwater was influenced by the water-rock interactions, the distribution range and solubility of silicate minerals ,the development of surrounding rock fissures, and water conservation and recharge conditions in the county, among which the water-rock interactions play a critical role. The results can provide a basis for the development of mineral water industry and the construction of urban and rural high-quality water sources in Zhaojue County.
Tracing mine water flows in a dolomite quarry, South Africa, using hydrochemistry and stable isotopes	Roger	Diamond	Mooiplaas Dolomite Quarry, Pretoria	2023	dewatering, Hydrochemistry, karst, mining, stable isotopes
Abstract Water resources, including groundwater, are under threat globally from abstraction and pollution, making studies of water flows ever more urgent. South Africa has a growing population, a relatively dry climate and abundant mining activity, all of which increase the importance of water management. Mooiplaas Dolomite Quarry, southeast of Pretoria, has been mining metallurgical grade dolomite since 1969 and is located in the productive karst aquifers of the Malmani Subgroup, Transvaal Supergroup. The site was investigated by sampling precipitation, surface water, groundwater and mine water for hydrochemical and stable isotope analysis from 2011 to 2017, totalling over 400 samples. Nitrate levels in groundwater and mine water were marginally above drinking water limits from explosives residues, and ammonia in the nearby Hennops River was unacceptably high due to municipal sewage outfalls, but otherwise, water quality was very good. Alkalinity from rock weathering, aided by the crushing of dolomite, was the main control on water chemistry. Combined analysis of dissolved matter (TDS, nitrate, Mg, etc.) suggested that the dewatering of the mine and resultant recharge from slime dams caused an aerated zone of groundwater, which mixed with regional groundwater flowing beneath the site. Stable isotopes, with an evaporated signature from mine open water bodies, also showed how mine operations cause recharge to groundwater and subsequent seepage back into the pit lakes. The mine appears not to contaminate the regional groundwater. However, mine designs should avoid situations where process water flows via groundwater back into pits, causing excessive dewatering costs.
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.
Evaluation of the conditions that impact the spreading, impact and groundwater monitoring for the risk of brine leakage from wells into fresh groundwater aquifers	Niels	Hartog	The Netherlands	2023	Groundwater Contamination, brines, density-driven flow, groundwater monitoring, leakage risk
Abstract Contamination of fresh groundwater aquifers by leakage of saline water (brine) from wells may result from various activities, such as salt mining, wastewater or concentrate injection and geothermal heat production. Here, the brine transport and consequences for groundwater monitoring have been explored for a wide range of brine compositions, leakage and hydrogeological conditions using numerical simulations that considered buoyancy impacts from both temperature and density differences. Results show that at close distances to the leak (up to 3-5 meters away), breakthroughs of the salt ( at 1,000 mg/L) occurred within one month of leakage in all modelled scenarios. At a radial distance of 10 meters, with a leak rate of 2 m3 /d, it took three to six months in most cases. For the leakage of relatively warm brines, the heat transport is separated from the salinity due to thermal retardation resulting in monitoring the breakthrough of heat more closely to the depth of the leakage point than the salinity breakthrough. In summary, this study indicates that the mode of dispersion of leaking geothermal brine strongly depends on the brine properties and the leakage and hydrogeological conditions. At the same time, vertical monitoring of temperature and conductivity at a limited distance from brine injection wells (<5m) appears to be a robust method for detecting a possible leak relatively quickly (within a month) and after limited contamination. The monitoring signal in the event of leakage is also sufficiently distinctive to prevent false positives.
Electrical Hydrogeology of Managed Aquifer Recharge from Meter to Kilometer Scales	Todd	Halihan	USA	2023	Byrds Mill Spring, carbonate, electrical resistivity imaging, enhanced aquifer recharge, Karst spring
Abstract While traditional well and spring sampling are limited to the integration of point data and the interpolation of the data across large scales. Electrical measurements of aquifers can be extended across a range of scales and integrated to provide an improved quantitative understanding of groundwater systems. At a site in Oklahoma, USA, a karst-managed aquifer recharge research site is being used to test electrical techniques for aquifer characterization on the kilometer scale and monitoring the aquifer on the meter scale. At the kilometer scale, the data illustrate fault locations, siphons in flow paths, and previously uncharacterized conduits. At the metre scale, the monitoring data illustrate porosity structure, flow paths, and potential biological changes in the subsurface. The results indicate that electrical approaches can significantly change aquifer conceptual models and provide targeted sampling locations in karstic bedrock aquifers.
Assessing groundwater fluxes of transboundary aquifers, using a high-resolution global groundwater model and implications on transboundary cooperation	J	Verkaik	The Netherlands	2023	Global model, transboundary aquifers, transboundary fluxes; comparative assessment
Abstract Worldwide, more than 400 transboundary aquifers (TBAs) have been identified. Only a small number of these aquifers have been assessed in detail. Consequently, little is known about (potential) transboundary impacts. Changes in transboundary groundwater fluxes can indicate potential transboundary impacts as groundwater abstractions can affect such fluxes, indicating potential risks of transboundary contamination. To our knowledge, a quantitative assessment of transboundary aquifer fluxes (TBAFs) is not available because national groundwater models (if existing) often lack a good interaction with surrounding countries. In recent years, a high-resolution global groundwater model (GGM) has been developed as part of the PCR-GLOBWB family of models, having a 5 arcmin (~1010km2 ) resolution. PCR-GLOBWB has previously been used to quantify environmental flows, assess global droughts, and assess climate impacts on global water resources. Recently the 5 arcmin GGM has been updated to 30 arcsec (~11km2 ) using high performance computing (referred to as GLOBGM). We present an application of GLOBGM to assess TBAFs of major TBAs. Results show that even though hydrogeological data are often scarce, a rough order of magnitude of the TBAFs can be assessed. TBA fluxes are compared with groundwater recharge. Although GLOBGM cannot replace assessments of TBAs based on local hydrogeological information and information on groundwater use, the analysis provides valuable information. GLOBGM can be used to quantify the relevance of TBAFs in relation to other fluxes such as from rivers or (future) abstractions. TBAF analyses can also assist in prioritising scarce funds and capacity between TBAs
Groundwater porosities and effective porosities: definitions, physical relevance, and scale issues	Alain	Dassargues	Belgium	2023	REV, drainage effective porosity, effective porosity, porosity, scale issue, transport effective Porosity
Abstract Porosity describes the ratio between the volume of pores, cracks, and fissures and the total volume of a studied geological medium. This notion implies a volume averaging of the medium characteristics using the concept of Representative Elementary Volume (REV). Small volumes can contain only pores, while larger volumes typically contain both pores and fissures. Porosity can be highly scale-dependent, and different porosity values can be measured for the same geological formation. Furthermore, groundwater in the pores and cracks can be partly immobile or mobile. So, the porosity actively involved in groundwater flow can be discussed. A ‘mobile water porosity’ can be defined, but this remains highly dependent on the existing pressure conditions in the geological medium. In unconfined conditions, the term ‘effective porosity’ usually corresponds to the drainage porosity corresponding to the specific yield or storage coefficient. When dealing with solute transport and remediation of contaminated sites, another ‘effective porosity’ is needed to describe the advection velocity of the contaminant. This ‘mobile water porosity’ acting in solute transport processes typically takes lower values than drainage’s ‘effective porosity’. Scale issues must also be expected, as shown by field and lab tracer tests. The term ‘Darcy velocity’ will be banished herein because it induces much confusion. For clarity, we propose to distinguish ‘drainage effective porosity’ and ‘transport effective porosity’. The physical meaning of both terms is discussed, and examples of supporting observations are presented for illustration and discussion.
Can open-source remote sensing data be used to accurately downscale groundwater storage estimates?	C	Viviers	Pretoria, South Africa	2023	GLDAS-2.2, GRACE, Google Earth Engine, Machine learning
Abstract The lack of reliable groundwater level monitoring data hinders the comprehensive understanding and sustainable management of our aquifers. New remotely sensed data products could present novel possibilities to fill in situ data gaps. For example, continuous monthly groundwater storage anomaly estimates at a spatial resolution of 0.25° (28 km) are made available through the Global Data Assimilation System Version 2.2 (GLDAS-2.2) data products that assimilate Gravity Recovery and Climate Experiment (GRACE) data. In this study, it was hypothesised that the open-source, higher resolution Climate Hazards Group InfraRed Precipitation With Station Data (CHIRPS) precipitation data and Moderate Resolution Imaging Spectroradiometer (MODIS) evapotranspiration data could be used to downscale groundwater storage anomalies (GWSA) for local scale investigations. Using an intergranular and fractured aquifer, as well as a karst aquifer as case studies, both enclosed within the Steenkoppies Catchment (A21F), two respective random forest regression (RFR) models were developed to downscale GLDAS-2.2 GWSA. Sampling monthly training data without accounting for temporal lagging resulted in an increased correlation, index of agreement (IA) and improved RMSE for the intergranular and fractured aquifer. Where the correlation between the observed groundwater storage changes and the GLDAS-2.2 groundwater storage estimates were weaker, however, accounting for the temporal lags resulted in an improved RMSE. The final product is a 0.05° (5.5 km) grid of monthly time-series GWSA estimates that can improve groundwater resource assessments, understanding aquifer recharge, modelling accuracies and better overall decision-making regarding Integrated Water Resource Management (IWRM).
Planning for increased water security and preventing salinisation in coastal areas of the Netherlands: A study on the suitability for managed aquifer recharge and extraction of brackish water, including quantification of potential extractable volumes	I	de Groot-Wallast	The Netherlands	2023	Aquifer Storage and Recovery, Managed aquifer recharge, aquifer salinisation, brackish water extraction, suitability maps, Water supply
Abstract Year-round water security is at risk as socio-economic developments lead to increasing water demands, while climate change affects water availability through higher-intensity rainfall and prolonged periods of drought. Coastal zones and deltas with often high population densities experience additional risks of salinisation and land subsidence. These developments ask for creative solutions to secure sustainable and year-round access to fresh water. The subsurface provides storage capacity to actively infiltrate freshwater, bridging the time-gap between demand and supply. Combining infiltration with extraction and desalination of brackish water prevents the salinisation of aquifers whilst providing an additional water source. We call this COASTAR. A Dutch research consortium with partners like water companies and water boards develops COASTAR. Among COASTAR results are suitability maps for Aquifer Storage and Recovery (ASR) and Brackish Water Extraction (BWE) in the coastal zone of the Netherlands. The maps are based on geohydrological factors. A quick-scan analysis was also performed to quantify the nation-wide potential extractable ASR and BWE volumes. COASTAR develops case study models and local scale pilots on ASR and BWE. For two water supply regions, an analysis has been made to geographically match development in water demand with suitability for ASR and BWE as a step in the search for strategic locations to develop ASR and BWE. The suitability maps provide guidance for initiatives’ development and practical experiences from pilot projects; this provides important information for further upscaling of COASTAR approaches.
Keep the flow: Applying a HOPE model	Jacqueline	Goldin	Western Cape, South Africa	2023	community engagement, Governance, social justice, transformative
Abstract Top-down governance systems are not well designed to secure the protection, use and management of groundwater at the local level and, on the contrary, perpetuate ‘wicked’ problems of poor groundwater management and protection. Citizen science promises solutions to these ‘wicked’ problems. We present findings from a project in the Hout Catchment, Limpopo, where citizen scientists monitor water in wells in remote rural settings. We redress the bias towards the natural sciences and pay attention to human systems as it is through engaging with people’s ‘ordinary’ citizens that they will protect their environment for better planetary health. To better understand these human systems that impact groundwater, we emphasise diversity and difference and argue for a HOPE model (heralding optimal participatory equity). HOPE has intrinsic and extrinsic value (equity) (addressing a hydrological void and understanding groundwater features). To achieve this, we open up a toolkit providing very practical methods. Using these tools, we propose that citizen science - taking science away from remote institutions, out of libraries and laboratories - and bringing it close to people is emancipatory and addresses new ways of understanding polycentric governance. Citizen science is transformative; citizens move from a passive state of non-engagement with science to acting as scientists. Disempowered people now have a sense of being part of the betterment of their world and improved water resources management. Narrowing the natural and social sciences divide is crucial for improved polycentric governance.
Understanding the pattern of spatial and temporal variations of groundwater levels using long-term monitoring data	P	Fuku	South Africa	2023	Groundwater decline, Hydrological stresses, long-term monitoring data
Abstract Monitoring regional groundwater levels provides crucial information for quantifying groundwater depletion and assessing environmental impacts. Temporal variation of groundwater levels is the response of the groundwater system to natural and artificial stresses in terms of groundwater recharge and discharge. The complexity and extent of the variation rest on the nature and storage properties of the aquifer system. High groundwater levels are usually found in the recharge zones and low in the discharge zones, resulting in groundwater flow from recharge areas to discharge areas. Continuous decline of groundwater levels has been observed in some of the monitoring boreholes within the National Monitoring Network. Groundwater level decline has been caused either by over-exploitation or reduction of groundwater recharge. Generally, the pattern of spatial and temporal variations of groundwater levels is the consequence of incorporating climatic, hydrological, geological, ecological, topographical, and anthropogenic factors. Therefore, understanding the pattern of spatial and temporal variations in groundwater levels requires a combined approach. A combination approach of National long-term groundwater level monitoring data, Hydrological stresses, Anthropogenic interferences, and characteristics of the groundwater system was used to understand the continuous decline of groundwater levels in selected monitoring stations across the country.
anaged aquifer recharge (MAR) suitability mapping Using GIS-MCDA: The South African perspective	L	Nhleko	South Africa	2023	Managed aquifer recharge, multi-criteria decision analysis, Regional Scale, Suitability mapping
Abstract To increase the security of groundwater resources, managed aquifer recharge (MAR) programs have been developed and implemented globally. MAR is the intentional recharge and storage of water in an aquifer, which will be recovered later. It was previously known and implemented as Artificial Recharge (AR). In South Africa, the documented practice dates back 40 years. There are five main MAR methods: Well-Shaft-Borehole, Spreading-induced bank infiltration, In-channel modifications, and Runoff harvesting. Two regional-scale MAR suitability maps for the Spreading Method (SM) and the Well-Shaft-Borehole (WSB) Method were compiled for South Africa, using the Geographic Information System combined with Multi-Criteria Decision Analysis (GIS-MCDA) methodology. Parameters used to compute the maps included the nature of the different aquifers, groundwater level, water quality (EC), distance to river, terrain slope, mean annual rainfall, land cover, soil moisture availability and clogging (Fe-iron content). To create a suitability map, the parameters were combined using the weighted overlay method and the Analytic Hierarchy Process (AHP – specifically the pairwise comparison). The site suitability maps indicated that most areas in South Africa are suitable for the Spreading and Well-Shaft-Borehole methods. The results were verified with the location of existing MAR schemes and were found to agree. However, these maps are not applicable for siting projects at a local scale but can serve as a guide and screening tool for site-specific studies looking for highly suitable or target areas for MAR implementation
Development of multi-level groundwater governance systems and groundwater capacity development to support local municipalities in the Northern Cape Region	A	Tomlinson	South Africa	2023	groundwater capacity development, groundwater governance, groundwater management, groundwater management plan, standard operating procedures
Abstract The Anglo-American Municipal Capability & Partnership Program (MCPP) has partnered with the Council for Scientific and Industrial Research (CSIR) to implement programs focused on Strategic Water Management and Strategic Planning within the Gamagara and Tsantsabane Local municipalities within the Northern Cape Region. The CSIR appointed GEOSS South Africa (Pty) Ltd to assist with Municipal Groundwater Capacity Development and Support for these two municipalities. This work explores multi-level groundwater governance systems between the local municipality, government, the mining industry, and the private groundwater sector. The scope of the work focused on developing a comprehensive and practical groundwater management plan detailing the standard operating procedures for each municipality. These operating procedures have been drawn up using principles of best practice guidelines for groundwater monitoring and management but have taken site-specific details of the groundwater supply to the respective Municipalities into account. Workshops were conducted where Municipal staff were trained in basic principles pertaining to groundwater and practical skills in monitoring and managing their supply. This has proved very successful in informing Municipalities about their local groundwater system and aquifer. The capacity-building development aspect will ensure that Municipalities have the resources and the knowledge to manage their groundwater resource effectively. GEOSS has undergone several training workshops and offers weekly technical support to the two Municipalities. As the confidence of the municipal staff to manage their resource grows, their independence from the mining companies should lessen.
Mitigating climate change with managed aquifer recharge: 5 Case Studies	D	Hohne	South Africa	2023	Climate change; drought; MAR; nature-based solution; case studies
Abstract In the past decade, Southern Africa has experienced periods of extreme drought. This was especially true in the western Karoo in South Africa. Continuous drought and limited rainfall led to declining aquifer water levels that curtailed sustainable water supply for towns and livestock. The western Karoo is almost completely dependent on groundwater. Managed aquifer recharge (MAR) is being used to reduce the effects of droughts and mitigate climate change impacts. A good understanding of the geology and the behaviour of the aquifers is needed for implementing various MAR designs, including nature-based solutions, which are used to recharge aquifers with limited rainfall. This paper discusses 5 active MAR case studies in the Western Karoo. Here, site-specific MAR methods that use small rainfall events deliver reasonable results, whereas the implemented MAR options keep most aquifers functional. Observations at the MAR sites also showed improved water quality and less bacterial clogging. This improves the environment around the managed aquifer recharge sites. The MAR methods and designs discussed in this paper can be used on a larger scale for a town or a smaller scale for a farm. Maintenance costs are low, which makes these options cost-effective for less wealthy areas.
How to manage the Plitvice Lakes National Park (Croatia) as part of transboundary groundwater resources?	H	Meaški	Croatia	2023	Karstic water resources, Plitvice Lakes, Transboundary aquifer
Abstract The National Park Plitvice Lakes (NPPL) in the Republic of Croatia was declared in 1949 due to its exceptional natural beauty. However, in addition to its attraction, the NPPL also encompasses an area of significant karstic water resources in the Dinaric karst region, on the border between the Black Sea and the Adriatic Sea catchment. In some parts, groundwater connections to the Klokot Spring and Una River in Bosnia and Herzegovina have been assumed by hydrogeological research and proven by tracing tests, which confirm transboundary aquifer. Assessing transboundary aquifer systems already presents challenges in managing this area, considering not only the well-defined physical catchment. Therefore, comprehensive protection is necessary, which must reconcile people’s aspirations for spatial development with the sustainability of natural systems. Protecting karstic water resources can be achieved through separate analyses of the natural vulnerability of surface and groundwater and their integration into a comprehensive protection system. Protection should be layered through three levels: (1) protecting the area from the impact of the upstream catchment, (2) protecting surface water in the catchment that is most affected by anthropogenic influences, and (3) protecting the surrounding area from the impact of the NPPL, which with numerous visitors every year and tourist facilities, also represents significant pressure on downstream catchments. The ultimate goal is a scientifically based proposal for sustainable development of the protected area, in line with the needs of protection and spatial use, and based on an assessment of the overall risk to water resources.
ome Trans-disciplinary Legal Options to Ensure the Protection of South Africa’s Utilisable Groundwater Resources	Carin	Bosman	South Africa	2023	Groundwater governance; water law; protection; land use activities; hydrogeology; aquifer protection zones
Abstract South Africa faces serious water scarcity challenges not only because it is a semi-arid country but also due to climate change. One of the most significant effects of climate change is an increase in temperature, which inevitably increases evaporation. Increased evaporation directly reduces the availability of surface water resources. Groundwater is less susceptible than surface water resources to evaporation and thus offers resilience against the impacts of climate change. Many South African cities, communities, and farmers depend on groundwater for domestic or other socio-economic purposes. This implies that groundwater resources which are currently or potentially utilisable should be identified, and suitable legal measures should be implemented to protect these resources from potential risks of harm or damage posed by anthropogenic activity. First, This article evaluates the effectiveness of the country’s existing regulatory framework to effectively protect South Africa’s groundwater resources and finds that the framework can be improved significantly. Secondly, it explores regulatory opportunities within the existing legal framework to strengthen South Africa’s groundwater governance regime, including using land use planning instruments to facilitate the implementation of groundwater protection zones
Assessment of catchment scale groundwater-surface water interaction in a non-perennial river system, Heuningnes catchment, South Africa	Vincent	Banda	Bellville. Cape Town, South Africa	2023	Aquifer-river interaction, Environmental stable isotope, Geological fault, Hydrochemistry, South Africa
Abstract This study assessed aquifer-river interaction using a combination of geological, hydrological, environmental stable isotope, and hydrochemical data in a non-perennial river system in the Heuningnes catchment. Results showed the depth to groundwater levels ranging from 3 to 10 m below ground level and aquifer transmissivity values of 0.17 to 1.74 m2 /day. The analytical data indicated that Na-Cl-type water dominates most groundwater and river water samples. Environmental stable isotope data of river samples in upstream areas showed depleted δ18O (-4.3 to -5.12 ‰) and δ2H (-22.9 to -19.3 ‰) signatures similar to the groundwater data, indicating a continuous influx of groundwater into the river water. Conversely, high evaporative enrichment of δ18O (1.13 to 7.08 ‰) and δ2H (38.8 to 7.5 ‰) were evident in downstream river samples. It is evident from the local geological structures that the fault in the northeastern part of the study area passing Boskloof most likely acts as a conduit to groundwater flow in the NE-SW direction, thereby supplying water to upstream river flow. In contrast, the Bredasdorpberge fault likely impedes groundwater flow, resulting in hydraulic discontinuity between upstream and downstream areas. Relatively low conductive formation coupled with an average hydraulic gradient of 8.4 × 10−4 suggests a slow flow rate, resulting in less flushing and high groundwater salinisation in downstream areas. The results underscore the significance of using various data sets to understand groundwater-river interaction, providing a relevant water management platform for managing non-perennial river systems in water-stressed regions.
Benefits and costs of managed aquifer recharge: An integrated water governance solution	Andrew	Ross	Australia	2023	Managed aquifer recharge; aquifer storage; water infrastructure; cost-benefit analysis; levelized cost; benefit-cost ratio
Abstract Managed Aquifer Recharge (MAR) provides an integrated water governance solution that improves water security for communities and farmers by storing water in aquifers and managing groundwater extractions to ensure water supplies are available during droughts. Quantitative analysis of levelised costs and benefit-cost ratios (BCRs) of 21 MAR schemes from 15 countries and qualitative assessment of additional social and environmental benefits demonstrates the benefits of MAR compared to water supply alternatives. Cost-benefit analysis provides a systematic method for comparing alternative water infrastructure options. Levelised cost is a widely accepted method of comparing MAR with alternative water infrastructure solutions when market valuations of water are unavailable. The benefits of MAR can be estimated by the cost of the cheapest alternative source of supply or the production value using water recovered from aquifer storage. MAR schemes recharging aquifers with natural water using infiltration basins or riverbank filtration are relatively cheap with high BCRs. Schemes using recycled water and/or requiring wells with substantial drilling infrastructure and or water treatment are more expensive while offering positive BCRs. Most MAR schemes have positive or neutral effects on aquifer conditions, water levels, water quality, and environmental flows. Energy requirements are competitive with alternative sources of supply. This analysis demonstrates strong returns to investment in the reported MAR schemes. MAR provides valuable social and environmental benefits and contributes to sustaining groundwater resources where extraction is managed.
Upscaling Preferential Flow in Heterogeneous Porous Media from the Laboratory to the Field	T	James Oudega	Austria	2023	Heterogeneity, preferential flow, upscaling
Abstract ue to public health or environmental concerns, performing tracer tests in the field by injecting pathogenic microorganisms or contaminants of emerging concern into groundwater is not permitted. Therefore, examining the effects of preferential flow processes on these contaminants under controlled saturated conditions must be done in the laboratory, but the resulting transport parameters cannot be directly applied to field-scale groundwater models. This research considers how an upscaling relationship can be found using a colloidal tracer and three different scales: small laboratory columns (0.1 m scale), a large intact core (1 m scale), and a real-world gravel aquifer (10 m scale). The small columns were filled with gravel from boreholes at the field site, an alluvial gravel aquifer close to Vienna, Austria. The mesoscale consists of an undisturbed gravel column from a gravel pit near Neuhofen an der Ybbs, Austria. Results showed that a certain pattern emerges after an initial scale-dependent threshold, regardless of differences due to the small columns being repacked with aquifer material and the large column and field site being “undisturbed”. In this way, the mesoscale column allows us to gain insight into upscaling processes by incorporating an in-between step when comparing groundwater transport at the column- to the field scale.
Risks related to groundwater resources in the Murray-Darling Basin, Australia	Andrew	Ross	Australia	2023	Groundwater, Murray-Darling Basin Plan, Ecosystems, implementation, policies, research priorities, risks, surface water
Abstract Groundwater governance and risk management in the Murray-Darling Basin in Australia (MDB) are being challenged by the increasing demand for water and the growing scarcity and variability of water supply owing to climate change. Over the past 20 years, consideration of risk related to groundwater in the MDB has evolved from concerns about the impact of groundwater extraction on surface water resources to an integrated assessment of risks to connected water resources and ecosystems. The Basin Plan includes a comprehensive framework for assessing risks to Basin water resources and ecosystems, but further scientific and policy developments are required to implement the plan. Consistent definition and improved assessment of groundwater-surface water connectivity are required, together with longer planning timeframes. Multi-year planning rules and policies must be developed to exploit opportunities for integrated management of groundwater and surface water resources and storage to manage droughts and floods. Risks to groundwater quality and groundwater-dependent ecosystems must be adequately assessed and monitored to avoid adverse impacts on communities and long-term loss of ecosystem services. Further improvements can be made in assessing cumulative risks from coal seam gas and coal mining. Additional research can be targeted towards knowledge gaps and uncertainties that pose the greatest risk to connected groundwater and surface water resources and ecosystem viability. Most importantly, further training and capacity building in water management agencies is critical to enable effective and transparent monitoring and management of Basin water resources.
Geophysics-estimated groundwater levels to assess the accuracy of a numerical flow model	Y	Lévesque	Canada	2023	Eastern Canada, aquifer properties, geophysical methods, groundwater monitoring, numerical modelling, regional piezometry
Abstract Two numerical simulations using Feflow® software were conducted to demonstrate the utility of geophysical data to accurately determine groundwater levels and provide additional data to the groundwater modelling community to improve the model’s accuracy. One simulation is based on regional piezometric data, and the other uses geophysical data acquired through transient electromagnetic (TEM), electrical resistivity (ERT), and ground-penetrating radar (GPR) surveys. After both numerical analyses, the root mean square errors (RMS) obtained from the piezometric data and the multiple geophysical techniques to confirm the correlation between observed and simulated water levels were similar at 3.81 m and 2.76 m, respectively. Through a discrete modelling approach, this study shows that groundwater levels estimated using geophysical tools and methods and those determined by direct observation are comparable. In addition, before the 3D numerical flow model, a 3D geological model was built to fully represent this highly complex, heterogeneous, and anisotropic hydrological environment of the Saint-Narcisse moraine glacial deposits in eastern Mauricie, Québec. This stratigraphic reconstruction with Leapfrog software was necessary to provide a more detailed and realistic representation of this complex aquifer system. This study illustrates how geophysical data can complement direct observations to provide additional hydraulic information to hydrologic modellers. Geophysical surveys provide an extensive set of soft data that can be leveraged to improve groundwater flow models and determine water-table heights, particularly in areas characterized by limited direct piezometric information.
Celebrating hydro-geoheritage – the Table Mountain Dams Trail and Hermanus Water Walk (Western Cape, South Africa)	Dylan	Blake	South Africa	2023	Hydro-geoheritage, Water supply, Table Mountain Group aquifers, Cape Town, Hermanus, Social Hydrogeology
Abstract Hydrogeology and hydrology are commonly overlooked aspects of geoheritage, despite strong geological links. Water in all its forms has played a critical role in the development of Earth, and the shaping of its landforms (in addition to sustaining all life on the planet), and access to water has been the core reason for the establishment of numerous human settlements. The evolution of a settlement’s water supply tracks its development history across the Holocene, providing an excellent tool for teaching the public about human interactions with the Earth and our shared future going forward in a changing climate. To this extent, two self-guided trails (with associated guidebooks and mobile apps) have been developed in areas of the Western Cape province of South Africa with rich water supply histories and hydro-geoheritage – the Table Mountain Dams Trail in Cape Town and the Hermanus Water Walk in the Overberg region. The surface and groundwater supply systems that both trails cover have an inherently unique link with the Ordovician-Devonian Table Mountain Group fractured aquifer systems (including the complex tectonic and geomorphic evolutionary history that has led to the present landscapes), which most residents and international visitors are generally unaware of (despite being major tourist regions in South Africa). It is envisioned that through these guides/trails, the reader/walker will gain a better understanding of/appreciation for the value of water, a greater feeling of ownership for the natural history of the city/region they reside in, and will strive to preserve associated hydro-geoheritage for future generations.
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).
Maximising groundwater value through innovation and technology - the power of membranes	Jean	Loock	South Africa	2023	Membrane Technology, quality, Reticulation, sustainability, Water treatment
Abstract The SADC region has vast potential to alleviate water scarcity and promote growth through the responsible development of groundwater resources. To achieve this, it is crucial to understand the resource’s value, implement sustainable abstraction programs, protect its quality, optimize its usage for regional development, and implement innovative aquifer management programs, including artificial recharge. Greenchain Group is a water treatment company that recognizes the value of water and strategically deploys its expertise to maximize the potential of each drop. As membrane technology specialists and local manufacturers of this advanced technology, we understand how to design integrated solutions to safeguard water quality and accessibility. Our wide range of filtration technologies allows us to select the technology suited to the application and regional groundwater context and to produce high-quality water from various sources, including groundwater. Additionally, by removing contaminants/unwanted constituents from groundwater, we enhance the value of each drop of water for local potable consumption, eliminate the need for overwatering in agriculture, and allow for the creation of new agriculture/industries in regions with poor groundwater quality. This same technology can also treat wastewater and remove contaminants (e.g. chemical of emerging concern, PFAS) and thus is critical to water reuse applications and responsible Managed Aquifer Recharge. Greenchain Group’s treatment systems have been used in various industries, including agriculture, mining, energy, medical, food and beverage, and remote and mobile settings.
Isotope geochemistry disentangles interactions between water and carbon cycle in Mediterranean peatland	Sebastien	Santoni	Mediterranean peatland	2023	Groundwater-Dependent Ecosystem, origin of carbon, peatland-atmosphere interface, peatland-carbon-water system, sources and sinks of carbon
Abstract This research aims to evaluate the carbon storage function of a Mediterranean peatland in changing climate conditions. The scientific strategy relies on a seasonal geochemical survey sourcing the carbon origin by considering the hydrosphere, lithosphere, biosphere, and atmosphere. This unprecedented research on a Mediterranean peatland reveals the seasonality of dissolved carbon inputs from primary production, organic matter oxidation, and time-changing recharge components within the catchment (rainwater, river water, shallow groundwater, deep groundwater). Based on the mixing proportions of all recharge water components, the study applies a reverse end-member mixing analysis to define the theoretical peat water d13CDIC value and compare it to the measured ones. The model explains 65 % of the data, demonstrating the water flow influence on peatland carbon content. In 35% of the cases, peatland processes such as primary production and organic matter oxidation drive the peat water’s carbon content. Peat organic and inorganic properties, d13CTOC, and d13CCO2 data demonstrate the role of groundwater as a CO2 source and the dominance of in situ primary production that argues in favour of carbon storage within such Mediterranean peatland. This research proves the relevance of geochemistry and isotope hydrology tools to disentangle and rank peatland water and carbon processes within peatland hydro-ecosystems. Overall, it reveals the necessity to take into account the interactions between water and carbon cycle processes, with particular consideration for groundwater as a CO2 source at the peatland-atmosphere interface, to build better models for the future evolution of the global climate.
Improved hydrogeological conceptual model through additional ERT profiles in medial-distal facies of andesitic volcanic area: Case study of Pandaan, East Java, Indonesia	Arif	Fadillah	Indonesia	2023	Andesitic stratovolcanoes, Electrical Resistivity Tomography, Groundwater, Hydrogeological, conceptual model, sustainability
Abstract In Java Island, Indonesia, andesitic volcanic aquifers are the main water resource for domestic, agricultural, and industrial use. To guarantee sustainable management, a hydrogeological conceptual model is key. Electrical resistivity tomography (ERT) survey is one tool to characterize aquifer structures and extension, specifically in the medial facies of the Arjuno Welirang volcano. Fadillah et al. (2023) proposed a hydrogeological interpretation of the aquifers in the central to proximal-medial transition zone of the Arjuno Welirang volcano. This interpretation was based on geology, hydrogeology, and ERT and focused on major springs and boreholes. Nine additional ERT profiles and borehole data were collected downstream to enhance the medial facies’ understanding further. Seven ERT lines were conducted throughout the midstream part of the watershed. The results confirm the presence of two superimposed aquifers, a first unconfined aquifer made of volcanic sandstone and breccia with a vertical extension of 25 meters and a confined aquifer from 35 to 120 meters (maximum depth of investigation). This last one consists of tuffaceous breccia and volcanic sandstone and includes lava layers as well. A clayey layer with an average thickness of 10 meters constitutes the aquiclude/aquitard between those two aquifers. Furthermore, two ERT lines were conducted in the vicinity of the major spring located in the distal part of volcanic deposits, highlighting the development of a multi-layer alluvial aquifer system.
A review of slug tests analysis on South African aquifers in potential yield and transmissivity estimations	Rolene	Lubbe	South African	2023	Slug test; Potential yield; Transmissivity; Limitations; Modelling
Abstract Slug tests are preliminary tests applied to determine the hydraulic conductivity and whether it is necessary to perform a pumping test on the borehole under investigation and should never be recommended as a substitute for a pumping test. For this reason, slug tests cannot be related to sustainable yield because slug tests cannot detect boundary conditions. The aim was to develop a methodology to relate slug tests to a potential yield estimation, investigating and reviewing the applicability and accuracy of the slug test methodology in South Africa, applied on fractured rock aquifers as established in 1995. The aim was achieved by reviewing the methodology applied for slug tests that are related to potential yield estimations, identifying the limitations of slug tests, investigating the possibility of updating the potential yield estimation method of 1995, and investigating the possibility of relating slug tests, to potential yield and transmissivity estimations through groundwater modelling. The investigation revealed that using transmissivity values determined through slug test homogenous modelling can be utilised to estimate the potential yield of a borehole under investigation by implementing correlation statistics. Note that this is not an absolute and is subject to limitations.
Understanding informal institutions’ role in groundwater management – Lessons from borderland communities	Kevin	Pietersen	Africa	2023	groundwater governance, informal institutions, transboundary aquifers
Abstract Across Africa, given the pressing challenges of climate change and widespread water, food and livelihood insecurity and poverty, there is an ever-increasing expanding role for groundwater in resilience building, especially in borderland communities. This situation is being investigated in several projects and geographies. This paper’s groundwater management analysis was based on literature reviews, key informant interviews (KIIs), and focus group discussions (FGDs) in selected case study areas throughout sub-Saharan Africa. The KIIs included representatives of water management institutions, community leaders, international development partners, the private sector and non-governmental organisations (NGOs) involved in the use or management of groundwater. The FGDs occurred in borderland communities in Ethiopia, Kenya, and Somalia (with these three countries sharing borders) and Mozambique, South Africa and Zimbabwe (with these three also sharing borders). The findings show that informal institutions such as clan, tribal or ethnic affiliations dictate access to natural resources such as groundwater in borderlands. These same Institutions also play a significant role in conflict resolution in the borderland areas. In addition, informal institutions play an essential role in groundwater management and should also be recognised – in engagements and formal water policies and legislation. Formal organisations, institutions and government structures should strengthen their focus on ensuring that discussions and decisions include informal role players. Further developing and enforcing conventions, land-use plans, and bylaws governing access to and use of groundwater should ensure engagement and co-creation of solutions towards effective water resource management.
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.
Integrated Modeling to Simulate Groundwater and Surface Water Interaction in the Letaba River Catchment, Limpopo Province, South Africa	Masilo	Mohale	South Africa	2023	Catchment., Groundwater, HydroGeoSphere, interaction, surface water
Abstract The current study investigates the spatial patterns and temporal dynamics of the groundwater and surface water interactions for integrated water resource management practices. This follows the results of the groundwater flow conceptual and numerical models developed for the Middle Letaba sub-catchment, indicating that groundwater and surface water interactions play a fundamental role in determining the hydrological water balance. The study area is an example of a fully allocated surface water resource in the northeastern part of South Africa, extensively developed for domestic use and agricultural farming. As a result of the semi-arid nature of the climate, limited surface water resources and increasing water demand, the situation has contributed to groundwater as the only dependable source of water supply for various uses. However, in the last few decades, periodic water level measurements in several boreholes indicated a continuous drop in the piezometric surface over time. This study utilised HydroGeoSphere to simulate water flow processes in a fully integrated and physically based model. The results of the steady-state groundwater flow simulation indicated that recharge from the rainfall and river leakages are the most important components of the inflows that control the availability of groundwater. Water resources management scenarios suggest a continuous decline in water level, which strongly influences the groundwater flow dynamics and future availability of fresh water. Regular monitoring and management of groundwater level and abstraction are required to avoid overexploitation and possible groundwater contamination due to the strong interaction between surface water and groundwater.
Securing Water Supplies – Participatory Groundwater Monitoring and Management in Botswana and Uganda	Piet Kebuang	Kenabatho	Botswana, Uganda	2023	Livelihoods and Pollution, Participatory groundwater monitoring
Abstract Groundwater resources in Africa face increasing threats of over-exploitation and pollution due to urbanization, agricultural and mining activities, yet monitoring remains challenging. Conventional approaches to monitoring groundwater at the exclusion of communities have not been successful. To overcome this, it is important to fully engage and train local communities in monitoring Groundwater Levels (GWLs), Rainfall and Water Quality (RWQ), which are important for understanding groundwater dynamics in wellfields. In this way, villagers can better understand groundwater issues and convey this information to others to cooperatively manage groundwater. A pilot program to monitor GWLs and RWQ by locals was initiated in two villages each in Botswana and Uganda to learn about its effectiveness. Through continuous stakeholder engagement, the local communities in the two case studies have been facilitated, trained and supported in monitoring groundwater and using the information collected to understand groundwater trends and their sustainability. Preliminary results indicate improvement in understanding the importance of groundwater monitoring by the communities and the implications on groundwater sustainability for improved livelihoods. This has become useful to one of the communities engaged in a village-level irrigation project which depends on groundwater resources. This project builds on a successful village-level participatory approach developed in the MARVI project (www.marvi.org.in ). It seeks to contribute to the United Nation’s 2022 call on “Groundwater: making the invisible visible” to highlight the importance of better monitoring and managing this vital resource.
How alluvial storage controls surface water – groundwater interactions in dryland intermittent and ephemeral streams: A case study from semi-arid Australia	M	Zarate	Australia	2023	Groundwater, groundwater recharge, drylands, ephemeral streams, focused recharge, intermittent, semi-arid, streamflow, surface water, water balance
Abstract Water balance partitioning within dryland intermittent and ephemeral streams controls water availability to riparian ecosystems, the magnitude of peak storm discharge and groundwater replenishment. Poorly understood is how superficial geology can play a role in governing the spatiotemporal complexity in flow processes. We combine a new and unusually rich set of integrated surface water and groundwater observations from a catchment in semi-arid Australia with targeted geophysical characterisation of the subsurface to elucidate how configurations of superficial geology surrounding the stream control the variability in streamflow and groundwater responses. We show how periods of stable stream stage consistently follow episodic streamflow peaks before subsequent rapid recession and channel drying. The duration of the stable phases increases in duration downstream to a maximum of 44±3 days before reducing abruptly further downstream. The remarkable consistency in the flow duration of the stable flow periods, regardless of the size of the preceding streamflow peak, suggests a geological control. By integrating the surface water, groundwater and geological investigations, we developed a conceptual model that proposes two primary controls on this behaviour which influence the partitioning of runoff: (1) variations in the permeability contrast between recent channel alluvium and surrounding deposits, (2) the longitudinal variations in the volume of the recent channel alluvial storage. We hypothesise optimal combinations of these controls can create a ‘Goldilocks zone’ that maximises riparian water availability and potential for groundwater recharge in certain landscape settings and that these controls likely exist as a continuum in many dryland catchments globally.
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.