Conference Abstracts

Abstract

Source protection area delineation has evolved over the last decades from fixed radius, analytical and numerical methods which do not consider uncertainty to more complex stochastic numerical approaches where uncertainties are often considered in a Monte Carlo framework. The representation of aquifer heterogeneity in these studies is typically based on a geostatistical representation of hydraulic properties. This presentation compares results from complex stochastic flow and transport simulations, simple homogeneous models, and existing analytical expressions. As a case study, we use the existing drinking supply wells in West Melton located Canterbury’s Selwyn District in New Zealand. Monte Carlo realisations are parameterised in MODFLOW6 so that the prior knowledge of the aquifer’s effective, large scale flow characteristics is honoured. Homogenous simulations are based on the same grid, using the aquifer’s effective properties to parameterise the numerical flow model. In both cases, conservative transport of pathogens is undertaken using Modpath7, using both forward and backward particle tracking. The numerical results are compared with analytical expressions from the international literature. Our results suggest that aquifer heterogeneity needs to be explicitly addressed in all cases. Homogeneous simulations almost certainly underestimate contamination risk and produce unrealistically small source protection areas. Parameterisation of the stochastic heterogeneous realisations also affects the size and extent of the source protection area, suggesting that these need to be carefully considered for practical applications.

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.

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.

Abstract

Since the end of the 1970’s, the Ministry of Agriculture, Water and Land Reform (MAWLR), through the development of the groundwater database (GROWAS II), gathered a great number of data on groundwater quality. In an ongoing study (MAWLR-MEFT-AFD-BRGM, 2023), an opportunity was presented to compile chemical data for groundwater in the two most north-western regions of Namibia, Kunene and Omusati, to elaborate and support decision-making with the available information. A selection of 3256 data presenting a good ionic balance (± 10%) was selected from a large dataset, using metadata from previous BGR projects and the Geological Survey of Namibia at a 1:250,000 scale as supporting information. During the assessment of chemical data, it was depicted that most of the good quality water for human consumption and irrigation is located in the carbonated sedimentary formations at the southeastern part of Kunene and a great part of the northern part of the Kunene region. With more detailed data treatment, it allowed for confirming a natural origin for high fluoride concentration linked to granite, gneiss, old volcanic rocks and high sulphate concentration due to evaporates (gypscrete) in the eastern part of Omusati. In contrast, high nitrate concentrations were found in various lithologies across the two regions confirming local anthropogenic contamination. These results were compared to information obtained through the few published works of local studies to evaluate the accuracy of this large-scale assessment of chemical data.

Abstract

Underground coal gasification (UCG) is a high-temperature mining method that gasifies coal in situ to produce a synthetic gas that can be used as feedstock for industrial purposes. Coal conversion leads to mineral transformation in the gasifier, which ultimately interacts with the rebounding groundwater post-gasification. This poses a groundwater contamination risk, the biggest environmental risk from a UCG geo reactor. There is currently no model for UCG operators and regulators to assess the total risk of groundwater contamination from UCG operations. This study collates literature on groundwater contamination from UCG operations and presents a workable but comprehensive groundwater risk assessment model for a spent UCG chamber. The model follows the source-pathway-receptor arrangement where groundwater contamination sources are identified as ash, char, roof and floor. All possible pathways are assessed for hydraulic connections with the spent geo-reactor via acceptable geochemical tests, including stable isotopes, hydrochemistry and stratification analysis. Finally, the receptor aquifers (e.g. shallow aquifers) are monitored periodically to determine if contamination has occurred.

Abstract

Aquifer Thermal Energy Storage (ATES) is increasingly utilised to optimise the efficiency of Ground Source Heat Pump (GSHP) systems. However, the criteria for selecting ATES over Unidirectional GSHP is not well-defined. Inappropriate selection of AETS can adversely impact the long-term viability and the GSHP system itself, as well as regional hydraulic and thermal sustainability due to adverse groundwater levels and temperature change. This is a concern in urban aquifers, where GSHP systems are increasingly common. There is a perception that ATES is always the most efficient; however, there is no clear definition of efficiency and how it can be readily assessed at the GSHP design stage. It is proposed and demonstrated herein that GSHP efficiency can be assessed by modelling borehole pumping in lieu of complex Coefficient of Performance calculations for the whole GSHP system. Borehole pumping is a more readily definable modelling outcome for comparing options at an individual site but is also a suitable proxy for comparing efficiency at different sites when given as a flow per unit rate of pumping. Operational efficiencies for ATES versus Unidirectional systems are presented using the pumping rate criteria for modelled scenarios. Here, three model inputs are varied: 1) the balance of heating and cooling, 2) the configuration of a single borehole pair across a hydraulic gradient and 3) the hydraulic gradient itself. These were assessed using coupled groundwater flow and heat transport modelling in Feflow to refine the Goldilocks Zone, the perfect balance, for these variables.

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 (~10*10km2 ) 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 (~1*1km2 ) 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

Abstract

Monitoring deep (~100 – 200 m) fresh-saline water interface is a challenge because of the low spatial density of deep boreholes. In this project, Vertical Electrical Soundings measurements were used to evaluate changes in the depth of the interface over various decades. Water quality monitoring is a well-known application of geo-electrical measurements but generally applies to the relatively shallow subsurface. In this case study, the saline groundwater interface is around 120 -200 m deep, and the time interval between the measurements is several tens of years. Several locations showing good-quality existing VES-measurements acquired in the last century were selected to see whether repeat measurements could be performed. The number of locations where a repeat measurement could be performed was limited due to the construction of new neighbourhoods and greenhouse complexes. When interpreting the measurements for the change in the depth of the fresh-salt interface, it is assumed that the transition from fresh to saline groundwater occurs over a small depth range and that the electrical conductivity of the fresh water above this interface has not changed. However, it turned out that the ion concentration of the groundwater in the layers above the fresh-saline interface had increased sharply at almost all locations. This complicated the approach, but still, useful results could be obtained. Based on the measurements, it can be said that the fresh-saline water interface has shifted downwards at 3 locations, and hardly any change has occurred at 5 locations.

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.

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.

Abstract

The Ordovician aquifer of the Izhora deposit is widely used for drinking by the population of St. Petersburg and its suburbs. Carbonate Ordovician rocks are intensively karstified. The water is fresh (0,5-0,8 g/l), bicarbonate-calcium on the predominant ions, pH 7.6; calcium content is 50-80 mg/l, magnesium content is 30-60 mg/l and the total hardness is 7,6-8,0 mg-equ./l. Western, northern and northeastern boundaries of the Izhora deposit go along the Baltic Klint, which is evident on the relief. Its southern boundary is along the zone of the dip of Ordovician limestone beneath the Devonian sandstone. The territory of the Izhora plateau belongs to the areas of intensive economic activity. Often, objects of human economic activity are located near drinking water intakes. Almost all sites are marked by excess sanitary norms of chemical elements. Pollution of groundwater in the Ordovician aquifer has been identified in some areas. Priority substances have been identified for assessing the quality of groundwater: total hardness, Fe, Mn, Ba, and B. According to hydrochemical modelling data, Ordovician groundwater is saturated with calcite over most territory. There are many springs of underground water along the Baltic Klint, for example, near the village of Lopukhinka, Duderhof springs and others. The springs waters have natural radioactivity (due to the contact of groundwater with dictyonema shales), which makes their use hazardous to human health.

Abstract

South Africa is known for droughts and their effect on groundwater. Water levels decrease, and some boreholes run dry during low recharge periods. Groundwater level fluctuations result from various factors, and comparing the levels can be challenging if not well understood. Fourie developed the “Groundwater Level Status” approach in 2020 to simplify the analysis of groundwater level fluctuations. Groundwater levels of two boreholes within different hydrogeological settings can thus be compared. The “Status” can now indicate the severity of the drought and thus be used as a possible groundwater restriction level indicator. The reasons for the groundwater level or the primary stress driver can only be determined if the assessment is done on individual boreholes and the boreholes according to hydrogeological characteristics. The analysis is used to identify areas of risk and inform the authorities’ management to make timely decisions to prevent damage or loss of life or livelihoods. The applicability of this approach from a borehole to an aquifer level is showcased through practical examples of the recent droughts that hit South Africa from 2010-2018.

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.

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.

Abstract

In this study, we assess the potential of large riverbed aquifers in semi-arid Africa, known as sand rivers, to mitigate water scarcity and salinity for multiple-use water supply through a case study of the Limpopo River in Mozambique. Such sand river systems are widespread and still heavily underused at a regional scale, particularly in Mozambique, with the riparian vegetation currently being the primary user, though only consuming a minor fraction of available water. At a local scale, we performed geoelectrical surveys, water level measurements (in river and groundwater), as well as field physicochemical measurements and hydrochemical and isotopic sampling at 38 locations in the river channel, margins and up to 6 km away from the river, over five years. Results show that these shallow systems can be up to a kilometer wide and 15 m thick and, at some locations, can extend laterally beyond the river channel, below thin layers of clay and silt. Large areas of the sand river channel carry runoff yearly, providing optimal conditions for rapid recharge into the coarse sands with a high storage capacity. Connectivity between the river margin and channel is clearly shown at the local scale, even though sand pockets located further away appear isolated (revealed by geophysics), isotopically different and more brackish. Recharge, evapotranspiration and mixing processes are confirmed through hydrogeochemical modelling. The proven connectivity is highly relevant as groundwater is abstracted locally, promoting socio-economic development in water-scarce regions.

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

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.

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.

Abstract

The 16th Lum Nam Jone reservoir is located in Chachoengsao Province, Thailand. Since 2019, water has become highly acidic with a pH of 2.5-3.5 and contaminated by heavy metals. The groundwater plume is associated with high concentrations of Iron (60 – 3,327 mg/L), Manganese (38 – 803 mg/L), Copper (5 –500 mg/L), Zinc (11 –340 mg/L), and high Total Dissolved Solids (2,600 –23,000 mg/L). The hydrogeochemical assessment confirmed that the contamination is related to the molybdenum ore processing plant located upgradient. The industrial wastewater was illegally discharged underground and flowed to the reservoir due to a hydraulic gradient. The main objective of this research is to evaluate the efficiency of different reactive materials for In-situ remediation using a permeable reactive barrier (PRB). The experiment column setup showed that marl has the highest efficiency in elevating pH by 3.6 units. The Fe, Cu, and Zn removal rates by crushed shells were 100, 98, and 60%, respectively. The Fe, Cu, and Zn removal rates by limestone were 100, 73, and 32%, respectively. The Fe, Cu, and Zn removal rates by marl were 100, 100, and 48%, respectively. Regarding the laboratory-scale experiment, the pilot PRB was installed upstream of the reservoir. The PRB was filled with marl at the bottom, overlain by limestone, and then covered with the uppermost rice straw layer. The pH increased by 2.6 units inside PRB (from pH 3.1 to 5.7). A reduction of about 50% in Fe, 85% in Cu, and 50% in Zn had been achieved.

Abstract

Italian urban areas are characterized by centuries-old infrastructure: 35% of the building stock was built before 1970, and about 75% is thermally inefficient. Besides, between 60% and 80% of buildings’ energy consumption is attributed to space heating. Open-loop Groundwater Heat Pumps (GWHPs) represent one of the most suitable solutions for increasing the percentage of energy consumption from Renewable Energy Sources (RES) in cities such as Turin city (NW Italy). However, allowing the diffusion of GWHPs cannot be disregarded by the knowledge about hydrogeological urban settings. As the thermally affected zone (TAZ) development could affect energetically adjacent systems, the TAZ extension must be well-predicted to guarantee the systems’ long-term sustainable use. Different buildings of the Politecnico di Torino are cooled during the summer by 3 different GWHP systems. To investigate possible interactions with other neighbouring plants and to preserve the water resource by capturing its positive and productive aspects from an energy point of view, a complex urban-scale numerical model was set up for comprehensively analysing the impact of the geothermal plants on the shallow aquifer. Different simulation scenarios have been performed to define possible criteria for improving the energy functionality of the groundwater resource. Besides, the extent of the TAZ generated was defined as a function of the specific functioning modes of the different GWHP systems. Numerical simulations, legally required by competent authorities, represent a fundamental tool to be applied for defining hydrogeological constraints derived from the GWHPs diffusion in Italian cities.

Abstract

The Limpopo River Basin (LRB) is highly vulnerable to recurrent floods and droughts, significantly threatening its water and food security. Sustainable groundwater management is necessary to improve resilience. Scientists and stakeholders must collaborate to evaluate management scenarios that can identify sustainable practices. A transboundary basin-scale management instrument was developed using a multisector collaborative modelling approach to identify the role of groundwater in building resilience. The approach used an integrated hydro(geo)logical model, co-created through stakeholder workshops. The model assessed management scenarios identified during a series of local, national and transboundary stakeholders workshops, focusing on improving groundwater storage during wet periods for use during dry periods in a context of population growth and increasing groundwater reliance across the basin. Management scenarios: (1) increasing groundwater abstraction; (2) deforestation; (3) afforestation; and (4) managed aquifer recharge (MAR) using injection wells capturing excess water from major dams, rainwater harvesting through local ponds/ wells, and small water reservoirs. Analysis of scenario outputs suggested that local groundwater storage techniques, especially water harvesting and storage through small-scale water well recharge, were the most effective strategy in reducing the risk and impact of floods and drought at the basin scale. Upscaling this strategy can significantly increase groundwater levels across the basin, supporting increasing groundwater reliance. The study showed that the multisector collaborative modelling approach effectively co-creates management strategies and identifies appropriate and inclusive strategies to improve resilience in data-limiting conditions. The proposed modelling outcomes are useful in making informed decisions regarding water management and transboundary cooperation in the LRB.

Abstract

Groundwater is increasingly being exploited in South African cities as a drought crisis response, yet there is poorly coordinated regulation of increasing urban users and usage and fragmented management of aquifers. Designing interventions and innovations that ensure sustainable management of these resources requires systems thinking, where the city is understood as an integrated, interdependent set of actors and flows of water. This paper presents a study that applied and integrated an urban water metabolism (UWM) analysis with a governance network analysis for two major South African cities facing severe drought risk, Cape Town and Nelson Mandela Bay. ‘Learning Laboratories’ in each city brought together stakeholders from various groundwater-related domains to build a shared understanding of how groundwater fits into the larger system and how various actors shape urban groundwater flows and the health of local aquifers. The UWM quantified all hydrological and anthropogenic flows into and out of each city (or urban system) to conduct an integrated mass balance. How this mass balance changes under varying climate change scenarios and land use was used as a focal point of stakeholder discussions. The governance network analysis highlighted that many state and non-state actors have a stake in shaping the quantity and quality of urban groundwater, such as regulators, service providers, water users, knowledge providers, investors in infrastructure, and emergency responders.

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.

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.

Abstract

The current understanding of groundwater within the larger Bushveld Complex (BC) is evaluated to gauge the potential for deep groundwater, specifically emphasising the lesser investigated eastern limb. From the review of publicly available literature and data, geohydrological databases and statistical analyses are presented as a collation of the current understanding of groundwater in the eastern limb of the BC. Unfortunately, information on deep groundwater (> 300 m) is scarce due to the cost associated with deep drilling, mining exploration holes often neglecting hydrogeological data collection, or lack of public access to this information. Nevertheless, the conceptual model developed from the available information highlights deep groundwater’s variable and structurally controlled nature and the uncertainty associated with groundwater characterisation of the deeper groundwater systems. This uncertainty supports the need for research-based scientific drilling of the deeper fractured lithologies in the eastern limb of the Bushveld Complex. The Bushveld Complex Drilling Project (BVDP) established an opportunity to perform such research-based drilling and was funded by the International Continental Scientific Drilling Program (ICDP). While the main focus of the BVDP is to produce a continuous vertical stratigraphic sequence of the BC, there is a sub-component to collect geohydrological information. The planned borehole, 2 500 m deep, will provide an opportunity to collect information from the deeper systems within the Bushveld Complex and the underlying Transvaal Supergroup, which will inform on the connection between shallow and deeper groundwater.

Abstract

To better understand the role of groundwater contribution to baseflow and EWR in groundwater protection and allocation, groundwater contribution must be quantified. Groundwater contribution to baseflow remains a challenge. Baseflow values have been widely used as groundwater contribution to surface water, which overestimates or underestimates the role of groundwater in the ecological ecosystem sustainability. To achieve the aim of the study, which was to estimate groundwater contribution to baseflow in a perennial river system at a catchment scale of the Upper Berg catchment, three objectives were taken into consideration: 1) To describe the hydrogeology of river morphology for groundwater-surface water interaction, 2) To estimate groundwater contribution to baseflow 3) To demonstrate the use of the background condition in setting resource quality objectives. Baseflow separation method using the Lynne & Hollick and Chapman algorithms, mass balance equation using EC as the tracer, field observation, and hydrochemical analysis methods were used to determine groundwater contribution to baseflow. Based on the hydrogeological cross-section presented, the fractures and faults of the peninsula geological formation dominating the study area predicted groundwater contribution to baseflow, which was confirmed by the calculations. The mass balance equation showed that 2,397 % of the 7.9 % baseflow index calculated at G1H076 and 19,093% of the 7.2% baseflow index calculated at G1H077 was groundwater. The background condition of the Upper Berg catchment was determined to be pristine with clean water.

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.

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.

Abstract

Per and Polyfluoroalkyl substances (PFAS) are ubiquitous on our planet and in aquifers. Understanding PFAS transport in aquifers is critical but can be highly uncertain due to unknown or variable source conditions, hydrophobic sorption to solid organic aquifer matter, ionic sorption on mineral surfaces, changing regulatory requirements, and unprecedentedly low drinking water standards. Thus, a PFAS toolkit has been developed to enable decision makers to collect the hydrogeologic data necessary to understand and better predict PFAS transport in aquifers for the purpose of managing water resources. This toolkit has been tested at a significant alluvial aquifer system in the western United States, which provides water for 50,000 people. Here, the toolkit has provided decision makers with the data necessary to optimize water pumping, treatment and distribution systems. The toolkit describes (1) the design and implementation of a sentinel well network to measure and track PFAS concentrations in the alluvial aquifer over time in response to variable pumping conditions, (2) data collection used to empirically derive input parameters for groundwater fate and transport models, which include the collection of paired aquifer matrix and groundwater samples, to measure PFAS distribution coefficients (Kds) and modified borehole dilution tests to measure groundwater flux (Darcy Velocity) and (3) the use of data collection techniques to reduce cross contamination, including PFAS-free, disposable bailers and a triple-rinse decontamination procedure for reusable equipment. The PRAS transport toolkit has the potential to assist decision makers responsible for managing PFAS contaminated aquifers.

Abstract

This study focuses on the coastal agricultural area of El-Nil River (Algeria), where anthropogenic activities heavily impact groundwater resources. A multi-tracer approach, integrating hydrogeochemical and isotopic tracers (δ2HH2O, δ18OH2O, δ15NNO3 and δ18ONO3), is combined with a hydrochemical facies evolution diagram and a Bayesian isotope mixing model (MixSIAR) to assess seawater contamination and distinguish the nitrate sources and their apportionment. A total of 27 groundwater samples and 7 surface water samples distributed over the entire study area were collected. Results show classic inland intrusion combined with an upstream seawater impact through the river mouth connected to the Mediterranean Sea. Results from nitrate isotopic composition, NO3 and Cl concentrations, and the MixSIAR model show that nitrate concentrations chiefly originate from sewage and manure sources. Nitrate derived from sewage is related to wastewater discharge, whereas nitrate derived from manure is attributed to an excessive use of animal manure to fertilise agricultural areas. The outcomes of this study are expected to help decision-makers prepare suitable environmental strategies for effective and sustainable water resources management in the study area.

Abstract

Global warming affects atmospheric and oceanic energy budgets, modifying the Earth’s water cycle with consequent changes to precipitation patterns. The effects on groundwater discharge are still uncertain at a global and local scale. The most critical step to assess future spring flow scenarios is quantifying the recharge-discharge connection. This research aims to predict the long-term effects of climate change on the discharge of seven main springs with long hydrologic series of discharge values located in different hydrogeological settings along the Apenninic chain (Italy). The investigated springs are strategic for either public water supply or mineral water bottling. The Apennines stretch along the Italian peninsula in a Northwest-Southeast direction, crossing the Mediterranean area that represents a critical zone for climate change due to a decreased recharge and increased frequency and severity of droughts over the last two to three decades. In this communication, the data of one of the chosen springs, called Ermicciolo (42°55’25.8”N, 11°38’29.5”E; 1020 m ASL), discharging out from the volcanic aquifer of Mount Amiata, are presented. Statistical and numerical tools have been applied to analyse the time series of recharge-related parameters in the spring’s contribution area and the spring discharge from 1939 to 2022. To estimate the impact of climate change on the Ermicciolo’s outflow, a regional atmospheric circulation model has been downscaled to the spring catchment area and used to derive the expected discharge at the 2040-2060 time span, according to the build-up data-driven model of the recharge-discharge relationship in the past.

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.

Abstract

Water and contaminant transport processes in the vadose zone through preferential flow paths can be understood using environmental and artificial tracer methods. Further improvement in tracer techniques can be achieved by applying numerical modelling techniques of both water and solute transport, accounting for additional information on water movement and the matric potential of the vadose zone. The vadose zone is often ignored as a key component linking the land surface to the groundwater table, even though it acts as a filter that removes or stores potential contaminants. The water transit time between the surface and the groundwater table is frequently investigated using artificial tracers that normally show conservative behaviour. The main advantage is that the input function can be clearly defined, even though artificial tracers can generally only be applied over a relatively small area. The research is expected to provide insight into the selection and use of environmental and artificial tracers as markers for detecting and understanding the contaminant transport processes and pathways of contaminants in altered vadose zone environments (open-pit quarry). The impact is improved characterisation of the pathways, transport and migration processes of contaminants, and residence times, leading to the development of appropriate conceptual and numerical models of vadose zone flow processes that consider various contaminant sources. The principal aim is, therefore, to systematically examine the transport mechanisms and associated pathways of different environmental and artificial tracers in an open-pit quarry.

Abstract

An approach for evaluating the sustainability of managed aquifer recharge (MAR) has been developed and applied in Botswana. Numerical groundwater modelling, water supply security modelling (SWWM) and multi-criteria decision analysis (MCDA) are combined to thoroughly assess hydrogeological conditions, supply and demand over time and identify the most sustainable options. Botswana is experiencing water stress due to natural conditions, climate change and increasing water demand. MAR has been identified as a potential solution to increase water supply security, and the Palla Road aquifer, located 150 km northeast of the capital, Gaborone, has been identified as a potential site. To evaluate the potential of MAR and if it is suitable for improving water supply security, three full-scale MAR scenarios were evaluated based on their technical, economic, social and environmental performance relative to a scenario without MAR. The numerical groundwater model and the WSSM were used iteratively to provide necessary input data. The WSSM is a probabilistic and dynamic water balance model used to simulate the magnitude and probability of water shortages based on source water availability, dynamic storage in dams and aquifers, reliability of infrastructure components, and water demand. The modelling results were used as input to the MCDA to determine the sustainability of alternative MAR scenarios. The results provide useful decision support and show that MAR can increase water supply security. For the Palla Road aquifer, storage and recovery with a capacity of 40 000 m3 /d is the most sustainable option.

Abstract

The aquifers in the Chao Phraya River basin region were abundant in groundwater. Lately, the groundwater level has been declining due to agricultural activities. While in the wet season, these areas frequently suffered from flooding due to lower elevation than their surroundings. The Managed Aquifer Recharge (MAR) methods were applied to ease problems by constructing artificial recharge wells which can detain stormwater runoff and let it gradually infiltrate into the aquifer directly. For decades, the Department of Groundwater Resources started the MAR project to alleviate groundwater depletion and flooding over specific areas. However, most of the projects in the past lacked follow-up results and evaluation. Thus, later projects attempted to study recharge processes to evaluate the volume of recharged water through structures and calculate the infiltration rate through filter layers within the structures.

Recently, the field experiments of artificial groundwater recharge were conducted as 8-hour and 20-day experiments with shallow recharge wells in the Chao Phraya River basin regions. These two types of experiments provided similar results. The average recharge rates of 8-hour and 20-day experiments are 2.22 m3/hr and 2.57 m3/hr, respectively. Recharge rates of each well were independently distinct depending on sedimentation characteristics, aquifer thickness, and volume of dry voids. During the test, the recharge well continuously encountered the problem of sediment clogging due to using untreated water from neighbouring streams and ponds. This clogging issue needed to be treated regularly to maintain the efficiency of the recharge well.

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.

Abstract

Stable isotopes of the water are widely used in volcanic contexts to identify the recharge area, thanks to a strong orographic effect. Such data help improve the study areas’ conceptual model, especially to identify flow paths through the volcanic edifice. The most common pattern considered is a high to medium-elevation recharge area on a flank of the volcano, feeding both local perched aquifers and a deep basal aquifer. This is quite common for “shield volcanoes”, with the flank comprising a thick accumulation of lava flows. On composite volcanoes, especially in a volcanic arc context, the large diversity of lithologies (effusive/ destructive events dynamics) along the flanks may create a compartmented aquifers system. The Arjuno-Welirang-Ringgit volcanic complex (East Java) has been studied to elaborate a hydrogeological conceptual model. Stable isotopes of the water show significant results in identifying the recharge areas of several aquifers that are outflowing at a similar range of elevation. These results help to propose a water flow pattern from the recharge areas to the main springs with juxtaposed and superposed aquifers. This also leads to constraining the geometry of the aquifers and concluding that one volcanic complex with several recharge areas can feed juxtaposed aquifers. These results also highlight the need to adapt the study scale to each “point of interest” in the volcanic context, as each spring shows a different flowing pattern, preferential recharge elevation, and surface area. These are mandatory data to propose an adapted groundwater management.

Abstract

Groundwater is an essential source of water worldwide. The increased reliance on groundwater has caused the mining of many aquifers, a situation compounded by climate change, rising surface-air temperature, declining precipitation, and reduced groundwater recharge in many regions. The global annual intensity of groundwater use rose from 128 to 155 m3 per capita between 1950 (when the world population was 2.5 billion people) and 2021 (when the population was 7.9 billion people) and is herein projected to rise to 178 m3 per capita by 2050 as the world’s population is projected to increase (to 9.7 billion people by 2050) throughout the rest of the 21st century and beyond. This study projects a global annual groundwater depletion of 1,008 km3 by 2050, representing a 256% rise from the estimated 2010 depletion. This projection is most likely a lower bound of the actual groundwater depletion that would be realized considering environmental flows, historical trends of global economic growth, and climate-change impacts, thus being a harbinger of rising environmental degradation (e.g., land subsidence, seawater intrusion, streamflow reduction, aridification). Measures to achieve groundwater sustainability are herein identified.

Abstract

Water budget assessment and related recharge in karstified and fractured mountainous aquifers suffer a large uncertainty due to variable infiltration rates related to karst features. The KARMA project (karma-project.org), funded by the European Commission, has addressed this knowledge gap. The increase in human withdrawals and the effect of climate change can modify the recharge rate and, consequently, the spring discharge. The regional aquifer of Gran Sasso mountain, Central Italy, has been investigated by monitoring spring discharge isotope composition and calculating the inflow using a GIS approach on 100x100 m cells, considering local conditions, including karst features. The results for the 2000-2022 period highlight the preferential recharge area of the endorheic basin of Campo Imperatore (up to 75% of precipitation) and a mean infiltration of about 50% of rainfall. Different methods applied for recharge evaluation (Turc, Thornthwaite and APLIS) agree with a recharge rate close to 600 mm/year. This amount roughly corresponds to the spring discharge, evidencing: i) a “memory effect” in spring discharge, which is higher than previewed during dry years; ii) a variation in discharge due to rainy and drought year distribution, frequently recorded at springs with delay (1-2 years); iii) no significant trends of spring depletion since last 20 years; iv) the risk of lowering of snow contribution to recharge due to the temperature rise. The results provide updated information to the drinking water companies and the National Park Authority for sustainable management of the available groundwater resources.

Abstract

The City of Cape Town (CCT) initiated its “New Water Programme” in 2017 (during the major 2015-2018 “Day Zero” drought) to diversify its bulk water supply, thereby improving longterm water security and resilience against future droughts. This includes bulk groundwater abstraction from the major fractured Peninsula and Nardouw Aquifers of the Table Mountain Group (TMG) in the mountain catchments east of the CCT. The TMG aquifers are essential in sustaining groundwater-dependent ecosystems associated with the Cape Floral Kingdom – a global biodiversity (but also extinction) hotspot with exceptional endemic diversity. A strong geoethical, “no-regrets” approach is therefore required to develop TMG wellfield schemes for the CCT (and other towns/cities in the Western/Eastern Cape) to reduce the risk of any negative ecological and environmental impacts while still enhancing the drought resilience of the city, providing water for future urban growth, and meeting Sustainable Development Goals 6 and 11.

To this extent, the CCT has developed an extensive regional (and local, in terms of Steenbras Wellfield) environmental monitoring network, incorporating a range of in-situ and remote sensing-based measurements across the Earth’s “Critical Zone” – this includes current groundwater, surface water, ecological, soil and meteorological monitoring stations, and future seismo-geodetic monitoring. An ongoing ambition is to include this CCT TMG monitoring network into the “Greater Cape Town Landscape”, which is currently in development as one of six national South African landscapes under the “Expanded Freshwater and Terrestrial Environmental Observation Network” (EFTEON) platform being hosted by the South African Environmental Observation Network.

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.

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.

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.

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.

Abstract

atural water-rock interaction processes and anthropogenic inputs from various sources usually influence groundwater chemistry. There is a need to assess and characterise groundwater quality monitoring objectives and background values to improve groundwater resource monitoring, protection and management. This study aims to determine monitoring objectives and characterise monitoring background values for all monitoring points within the Soutpansberg region. This study used long-term groundwater quality monitoring data (1995- 2022) from 12 boreholes and 2 geothermal springs. Monitoring objectives were determined from land-use activities, allocated groundwater use, and water use sectors. Monitoring background values were determined from the physio-chemical parameters from each of the 14 monitoring points. This study determined monitoring objectives and background values of all monitoring points and all physio-chemical parameters in the Soutpansberg region. This study recommends reviewing the determined monitoring objectives and background values every 5 to 10 years to assess any change in land use, groundwater use and sector and monitoring data trends.

Abstract

Technological advances in recent years provide a unique opportunity to adopt new instruments for groundwater monitoring to reduce operating costs, obtain higher measuring accuracy and reliability, and accomplish comprehensive real-time monitoring. Microelectromechanical system (MEMS) technology enables small and low-cost energy-saving microsensors and integration with IOT for real-time monitoring. This presentation will discuss the findings of the performance of a newly developed instrument based on a MEMS piezoresistive pressure sensor. We demonstrate a path forward for the expansion of this research. The sensor is designed to be applicable to both open and closed systems for measuring groundwater level and pore water pressure. Tests show that MEMs (0-689 kPa range) can obtain full-scale accuracy between 0.2-0.3% in groundwater level prediction. However, the measurement result mainly depends on the appropriateness of the calibration method. Regarding pore pressure measurement under sealed conditions by gravel sand and cement-bentonite grout, a full-scale accuracy between 0.3% and 0.725% is accessible, depending on the backfill material. However, it was evident that backfill materials have considerable effects on the response time and accuracy of measurement, in which a stiff and less permeable grout can increase inaccuracy and time lag in measurement. Overall, the initial results have shown a promising future for this technology in groundwater monitoring. However, more tests and analyses are still required to improve sensor design, energy consumption for IOT applications, wireless module, installation system and its specifications such as accuracy, conformance, precision, and stability.

Abstract

Unicef is the WASH sector lead globally and is, present at the country level, the main counterpart of government, especially regarding the component of the water balance utilised for potable safe water supplies. This mandate means that Unicef then has a role in looking at water resources nationally and not just as individual projects, and in doing so, contributes to good water governance as an integral part of system strengthening. Ensure this is done in partnership with other ministries and stakeholders that support them through advocacy for humanitarian and developmental access and support in technical areas such as groundwater assessments and monitoring. The focus on groundwater is especially linked with the fact that groundwater plays a major role due to its buffering capacity to climate variations, easier access and global coverage. Since groundwater is the most significant component of accessible freshwater resources, it is in the interest of UNICEF to make this resource more visible to meet both development and humanitarian goals, strengthen national systems and ultimately build resilience in mitigating water scarcity to scale or at the National level. Therefore, examples will be presented where Unicef has engaged on this journey with nations such as Afghanistan, Yemen, Mozambique and Rwanda to understand their water resources better. The overall objective at the National level is to adapt the capacity to withstand and recover as quickly as possible from external stresses and shocks or build resilience.

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.

Abstract

This study aims to investigate the groundwater circulation and hydrogeochemical evolution in the coastal zone of Xiamen, southeast China, which can provide a reference for the development of water resources and the protection of soil and water environment in the coastal areas. A close connection between mountains and the sea characterizes the southeast coast of China. Although rainfall is abundant, the topography limits it, and water resources quickly run into the sea. Coupled with a concentrated population, water is scarce. In addition, this area’s water and sediment environment are influenced by human activities and geological conditions. Its changing trend also needs further study. Therefore, using hydrochemical analysis, isotope technology, numerical simulation and other techniques, this study took Xiamen City on the southeast coast as an example to study the groundwater circulation and the environmental evolution of water and sediment. The results show that although the aquifer is thinner, there is still deep groundwater circulation, and the seawater intrusion range of deep aquifer is much further than that of shallow aquifer. In addition to geological causes, human activities have become the main factors affecting groundwater quality, especially nitrate and lead. The nitrate content even exceeds the content of the major ionic components. Introducing land-based pollutants has also contributed to declining seawater and sediment quality in the Bay area. In general, the main pollutants in coastal areas include nutrients, heavy metals and new pollutants.

Abstract

Groundwater is connected with the earth’s interior, atmosphere, ocean sphere, and human sphere. Fluid, heat, and dissolved materials are crossed over the boundaries of adjacent spheres with different time scales in dynamics. These different time scales include event scales such as earthquakes and Tsunami, seasonal scales such as precipitation seasonality, a decade or longer scales such as climate change, and human scales such as groundwater pumping, land cover/use changes, and social revolutions such as industrialization, green revolution, urbanization, and globalization in Anthropocene. This study shows two examples of groundwater connected with different time scales. The first is thermal signals preserved in groundwater by earthquake, climate change, and anthropogenic impacts with different time scales. Thermal signals in groundwater from the Kumamoto earthquake in 2016 revealed evidence of fluid flow from the earth interior and Aso mountain. The thermal signal in groundwater in Kumamoto also showed the impacts of global warming and urbanization, as well as changes in precipitation and land use. The second example is the connectivity between residence time of groundwater and groundwater consumption in social revolutions such as industrialization and urbanization in the Anthropocene, as well as World War II as an example of groundwater for emergency situations.