Conference Abstracts

Abstract

Machine learning techniques are gaining recognition as tools to underpin water resources management. Applications range widely, from groundwater potential mapping to the calibration of groundwater models. This research applies machine learning techniques to map and predict nitrate contamination across a large multilayer aquifer in central Spain. The overall intent is to use the results to improve the groundwater monitoring network. Twenty supervised classifiers of different families were trained and tested on a dataset of fifteen explanatory variables and approximately two thousand points. Tree-based classifiers, such as random forests, with predictive values above 0.9, rendered the best results. The most important explanatory variables were slope, the unsaturated zone’s estimated thickness, and lithology. The outcomes lead to three major conclusions: (a) the method is accurate enough at the regional scale and is versatile enough to export to other settings; (b) local-scale information is lost in the absence of detailed knowledge of certain variables, such as recharge; (c) incorporating the time scale to the spatial scale remains a challenge for the future.

Abstract

Understanding the sensitivity of groundwater resources to surface pollution and changing climatic conditions is essential to ensure its quality and sustainable use. However, it can be difficult to predict the vulnerability of groundwater where no contamination has taken place or where data are limited. This is particularly true in the western Sahel of Africa, which has a rapidly growing population and increasing water demands. To investigate aquifer vulnerability in the Sahel, we have used over 1200 measurements of tritium (3H) in groundwater with random forest modelling to create an aquifer vulnerability map of the region.

In addition, more detailed vulnerability maps were made separately of the areas around Senegal (low vulnerability), Burkina Faso (high vulnerability) and Lake Chad (mixed vulnerability). Model results indicate that areas with greater aridity, precipitation seasonality, permeability, and a deeper water table are generally less vulnerable to surface pollution or near-term climate change. Although well depth could not be used to create an aquifer vulnerability map due to being point data, its inclusion improves model performance only slightly as the influence of water table depth appears to be captured by the other spatially continuous variables.

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

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.

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

Sand mining in southern Africa is on the rise, fuelled largely by rapid urbanisation. This creates a range of societal and biophysical challenges and supports livelihoods in regions with high unemployment. Relevant scientific studies are scarce. This study explores the impacts of sand mining from ephemeral rivers on Botswana, South Africa and Mozambique communities through field visits, interviews, modelling, remote sensing and legislative analysis. What was expected to be a hydrogeology project focussing on water resources identified a broader range of issues that should be considered. Initial results uncovered a range of negative biophysical impacts, including alteration of hydrological regimes, which in turn affect groundwater recharge and exacerbate drought and flood risks, destruction of riparian vegetation, increased erosion, damage to infrastructure (including bridges and roads), reduced water quality, and the spread of invasive plant species. Equally important are the range of social impacts, such as drowning people and livestock, loss of agricultural land, increased traffic, dust, noise and crime. Complex governance arrangements influence these social and environmental challenges. The findings highlight the need to adopt an inter- and trans-disciplinary approach that considers linkages between human and natural systems. This approach is essential for finding sustainable solutions for the provision of construction materials that limit detrimental impacts on water resources, ecosystems and livelihoods. 

Abstract

Degradation of chloroethene in groundwater primarily occurs via microbially-mediated reductive dechlorination (RD). Anaerobic organohalide-respiring bacteria (OHRB) use chloroethenes as electron acceptors to gain energy. They produce reductive dehalogenase enzymes (RDases) to perform this function by transcription of functional genes into mRNA and translation to proteins (metabolic regulation). However, how hydrodynamics and hydrogeochemistry control the metabolic efficiency of OHRB in biodegrading chloroethene is essential for effective bioremediation design yet an under-investigated topic. For this reason, we implemented a virtual experiment (1D reactive transport model) to investigate the effects of site conditions on transcription-translation and, hence, biodegradation processes within chloroethene plumes. In the model, RD was simulated using Enzyme-Based Kinetics, explicitly mimicking the production of RDases via metabolic regulation, calibrated on microcosm experimental data gained from literature. Features of an actual contaminated site (Grindsted, Denmark) were then used to set up the virtual experiment. Here, chloroethene leaked from a former pharmaceutical factory migrates through a sandy aquifer and gets discharged into the Grindsted stream. Preliminary results show that substrate (electron donors) limiting conditions caused by competing electron acceptors and dispersion and high flow rates represent the key factors controlling biodegradation via RDase production.

Abstract

The Kalahari iron manganese field (KIMF) in the Northern Cape, South Africa, was historically exploited by only three mines, with Hotazel the only town and the rest of the area being largely rural, with agricultural stock/ game farming the major activity. Since 2010, mining activities have increased to more than 10 operational mines with increased water demand and environmental impacts on groundwater. The area is within catchments of the Matlhwaring, Moshaweng, Kuruman and Gamogara rivers that drain to the Molopo River in the Northern Cape. All the rivers are non-perennial, with annual flow occurrence in the upstream areas that reach this downstream area once every 10 years. The area is semi-arid, with annual evaporation nearly five times the annual precipitation. The precipitation is less than 300mm, with summer precipitation in the form of thunderstorms. Vegetation is sparse, consisting mainly of grasslands, shrubs and some thorn trees, notably the majestic camel thorns. The Vaal Gamagara Government Water Supply Scheme imports 11 Ml/d or 4Mm3 /a water for mining and domestic purposes in the KIMF section. The area is covered with Kalahari Group formation of 30 to 150 m thick with primary aquifers developed in the basal Wessels gravels and Eden sandstones for local use. The middle Boudin clay forms an aquitard that isolates and reduces recharge. Water levels range from 25 to 70m, and monitoring indicates local dewatering sinks and pollution. This study will report on the water uses, monitoring and observed groundwater impacts within the current climatic conditions.

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.

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.

Abstract

The geochemical study of deep aquitard water in the southern Golan-Heights (GH), Israel, reveals the complex paleo-hydrological history affected by the intensive tectonic activity of the Dead Sea Rift (DSR). The sampled water collected from new research boreholes exhibits relatively high salinities (2,000-10,000 mg Cl/L), low Na/Cl ((HCO3 +SO4 )). δ18OV-SMOW and δDV-SMOW values are relatively depleted (~-7‰ and ~-42‰, respectively), while 87Sr/86Sr ratios are enriched compared to the host rocks. Lagoonary brines with similar characteristics (excluding the water isotopic compositions) are known to exist along the DSR. These brines formed 10-5 Ma ago from seawater that transgressed into the DSR and subsequently underwent evaporation, mineral precipitation and water-rock interactions. These hypersaline brines intruded into the rocks surrounding the DSR and based on the current study, also extended as far as the southern GH. Further, following their subsurface intrusion into the GH, the brines have been gradually diluted by isotopically depleted freshwater, leaving only traces of brines nowadays. The depleted isotopic composition suggests that the groundwater system is recharged at high elevations in the north. It is also shown that variable hydraulic conductivities in different formations controlled the dilution rates and subsequently the preservation of the entrapped brines. The paleo-hydrological reconstruction presented here shows that the flow direction has reversed over time. Brines that initially intruded from the rift have since been gradually flushed back to the rift by younger fresh groundwater.

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

Water scarcity has driven many countries in arid regions, such as Oman, to desalinate seawater for freshwater supply. Episodic problems with seawater quality (e.g., harmful algae), extreme weather events that affect energy supply and hence the desalination process have nurtured the urgent need to store desalinated seawater (DSW) in the aquifers for use during emergency and peak demand time. Aquifer Storage and Recovery (ASR) using injection wells is a possible strategic option for Oman Water and Wastewater Services Company (OWWSC) to augment aquifer storage using excess desalinated water during low demand times. ASR strategically serves as a water supply backup to optimize production capacities against seasonal demand patterns. The technical-economic feasibility of implementing ASR schemes was investigated in Jaalan, Oman, using hydrogeological and geophysical field measurements, groundwater flow and hydraulic modelling, and economic analysis. Analysis of modelled scenarios results revealed that the Jaalan aquifer is suitable for storing and recovering about 4,000 m3 /hr in 2045. Various well field designs have been tested and optimized numerically using MODFLOW 6, showing that with 160 dual-purpose wells, 7.9 Mm3 can be injected and abstracted within the constraints defined for a robust and sustainable ASR system. Simulations with the density-dependent flow model (MF6 BUY) show that the injected volume can be fully recovered considering the drinking water quality standard. Other sites were also studied. ASR capacity was found to be site-specific, and the groundwater developments near the ASR site governed its feasibility

Abstract

Understanding and quantifying hydrology processes represent a mandatory step in semi-arid/arid regions for defining the vulnerability of these environments to climate change and human pressure and providing useful data to steer mitigation and resilience strategies. This generally valid concept becomes even more stringent for highly sensitive ecosystems, such as small islands like Pianosa. The project intends to deploy a multi-disciplinary approach for better understanding and quantifying the hydrological processes affecting water availability and their evolution, possibly suggesting best practices for water sustainability.

First results pointed out as over the last decade the precipitation regime has led to a major rate of evapotranspiration and minor effective infiltration that caused a decreasing of piezometric level over several years. Quantity and chemical-isotopic features of rainfall and effective infiltration water measured/collected by a raingauge and a high precision lysimeter describe the hydrological processes at soil level and characterize the rate and seasonality of groundwater recharge. Hydrogeological and geochemical data of groundwater are highlighting the distribution and relationship among different groundwater components, including the seawater intrusion. Furthermore, the comparative analyses of continuative data monitoring in wells and weather station showed the presence of possible concentrated water infiltration processes during rainfall extreme events that induce a quick response of shallow groundwater system in terms of water level rise and decrease of electrical conductivity. Thus, elements of vulnerability of the aquifer to pollution are pointed out, as well as the possibility to provide technical solutions for enhancing water infiltration and groundwater availability.

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

Drywells are extremely useful for coping with excess surface water in areas where drainage and diversion of storm flows are limited, facilitating stormwater infiltration and groundwater recharge. Drywells have been used for stormwater management in locations that receive high precipitation volumes, naturally or due to climate change; however, to date, they have not been developed in urban areas overlying karst landscapes. To test the performance of karst drywells, we constructed a pilot system for collecting, filtering, and recharging urban stormwater through drywells in karst rock. The study site is in the Judaean Mountains, an urban residential area in Jerusalem, Israel. The infiltration capacity of the drywells was evaluated using continuous and graduated water injection tests, and its effective hydraulic conductivity (K) was estimated. Drywells’ infiltration capacity was up to 22 m3 /hour (the maximum discharge delivered by a nearby fire hydrant), while monitored water levels in the drywells were relatively stable. Calculated hydraulic conductivities were in the range of K=0.1-100 m/ day, and generally, K was inversely proportional to the rock quality designation (RQD) index (obtained from rock cores during the drilling of the drywells). The pilot system performance was tested in the recent winter: during 9 days with a total rainfall of 295 mm, a cumulative volume of 45 m3 was recharged through the drywell, with a maximum discharge of 13 m3 / hour. High-conductivity karst drywells and adequate pre-treatment filtration can be valuable techniques for urban flood mitigation and stormwater recharge.

Abstract

Groundwater arsenic (As) distribution in alluvial floodplains is complex and spatially heterogeneous. Floodplain evolution plays a crucial role in the fate and mobilization of As in the groundwater. This study presents how groundwater As enrichment is controlled by the spatial disposition of subsurface sand, silt, and clay layers along an N-S transect across the Brahmaputra river basin aquifer. Six boreholes were drilled in the shallow aquifer (up to 60 m) along this transect, and 56 groundwater samples were collected and analysed for their major and trace elements, SO4, PO4, dissolved organic carbon (DOC), and dissolved oxygen (DO). Groundwater As ranges from 0.1 to 218 μg/L on the northern bank while from 0.2 to 440 μg/L on the southern bank of the Brahmaputra. Groundwater in the southern bank is highly reduced (Eh -9.8 mV) with low DO and low SO4 (2 mg/L), while groundwater in the north is less reduced (Eh 142 mV) with low DO and higher SO4 (11 mg/L). Subsurface lithologies show that the aquifer on the southern bank has a very thick clay layer, while the aquifer on the northern bank is heterogeneous and interlayered with intermediate clay layers. Depth comparison of the groundwater arsenic concentrations with subsurface lithological variations reveals that groundwater wells overlain by thick clay layers have higher arsenic, while groundwater wells devoid of clay capping have lesser arsenic. Detailed aquifer mapping could be decisive in exploring potentially safe groundwater from geogenic contamination.

Abstract

On the slopes of Mount Bromo, East Java (Indonesia), the land use of the Rejoso watershed is dominated by rice fields and sugarcane ( lowland area ), agroforestry (midstream) and horticulture and pine plantation in the upstream part. During the last three decades, some land changes driven by socio-economic development, with conversion of agroforests to rice fields, tree monoculture and horticulture, and the development of urban areas nearby, increased pressure on the watershed. Intensive irrigated rice cultivation is using groundwater from free-flowing artesian wells. Due to a lack of management, the hydraulic head and discharge of the major spring are decreasing. Rejoso watershed, like others in urban and rural areas in Indonesia, is facing challenges to guarantee sustainable integrated water resources management. Collective solutions have been implemented between 2016 and 2022 within this watershed. In the downstream, sustainable paddy cultivation and wells management with local stakeholders, aiming at improving water efficiency, have been piloted on 65 ha with 184 farmers. Water governance at the district level was re-activated and strengthened thanks to the project. Various capacity-building tools were used via radio talk shows and workshops. Members of the watershed forum of Pasuruan took some actions to reshape the structure and set up a roadmap. The implementation of collective solutions in the field was a real catalyst and serves all levels of water governance, as it is replicable. This example will be explained and illustrated after the presentation of the socio-hydrogeological context.

Abstract

Northern India and Pakistan face some of the world’s most challenging surface water and groundwater management issues over the coming decades. High groundwater abstraction, widespread canal irrigation, increases in glacier melt and changes to rainfall impact the dynamics of surface water/groundwater interactions in the Indus Basin and Upper Ganges. Studies using newly available data from long-term hydrographs, high-frequency stable isotope sampling and campaign sampling for groundwater residence time indicators are shedding light on the complex interactions between groundwater, surface water and rainfall. Interactions vary spatially: (1) with distance down the catchment, related to the prevailing rainfall gradient, and (2) with position in the canal command, both distance from barrage and distance from feeder canals. Interactions are also observed to vary with time due to (1) the historical evolution of the canal network, (2) patterns in precipitation over the past 120 years, (3) changes in river flow due to glacial melting, and (4) increased pumping, which has also led to increased capture of surface water. Only by understanding and quantifying the different processes affecting groundwater/surface water coupling in the Indus and Upper Ganges is it possible to forecast future groundwater storage changes.

Abstract

Transboundary aquifers in Europe are managed according to the Water Framework Directive (WFD) through international river basin districts (IRBD) management plans. Paragraph 11 in the WFD states that each Member State shall ensure the establishment of a programme of measures, PoM, for each river basin district, RBD, or part of an IRBD within its territory. Easy access to harmonized data from neighbouring countries part of the aquifer is essential to analyse the groundwater status and make proper PoMs. The datasets must be available in machine-readable format via an Application Programming Interface (API) and, where relevant, as a bulk download. The metadata describing the data shall be within the scope of the Infrastructure for Spatial Information in the European Community (INSPIRE) data themes set. The datasets must also be described in a complete and publicly available online documentation describing the data structure. Using a questionnaire survey of nine European countries, groundwater sampling and analysis routines are compared to evaluate if data are comparable and accessible across borders.

Abstract

Faced with climate change and population growth, Dutch drinking water company Dunea is looking for additional water resources to secure the drinking water supply for the coastal city of The Hague. One of the options is to enhance the existing managed aquifer recharge (MAR) system in the coastal dunes by extracting brackish groundwater. Extracting brackish groundwater provides an additional drinking water source, can protect existing production wells from salinization, and can effectively stabilise or even grow the freshwater reserves in the coastal dunes, according to numerical groundwater modelling. To test this concept in the field, a three-year pilot commenced in January 2022 at Dunea’s primary drinking water production site, Scheveningen. Brackish groundwater is extracted at a rate of 50 m3 /h with multiple well screens placed in a single borehole within the brackish transition zone (85-105 meters below sea level). The extracted groundwater is desalinated by reverse osmosis, whilst the flow rate and quality of extracted groundwater are continuously monitored. The hydraulic effects and the dynamic interfaces between fresh, brackish and saline groundwater are monitored with a dense network of piezometers, hydraulic head loggers and geo-electrical measurement techniques. At the IAH conference, the monitoring results of the pilot will be presented. Based on the results of the field pilot and additional numerical modelling, the feasibility of upscaling and replicating the concept of brackish groundwater extraction to optimize MAR and increase the availability of fresh groundwater in coastal areas is reflected.

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 represents a crucial source of drinking water in the Lille metropolitan area. Despite its importance, the resource is vulnerable to the potential evolution of land use: recharge, runoff and evapotranspiration processes in a soil-sealing context and changes in cultural practices. As a result, stakeholders emphasized the importance of exploring the influence of land use on groundwater to ensure sustainable resource management and enhance territorial planning. The 3D hydrodynamic model helped manage groundwater resources, but the (MARTHE code) has a significant limitation in that it does not consider the impact of land use evolution. We propose to investigate the contribution of a hydrological distributed numerical approach incorporating land cover data in groundwater modelling compared to a global approach at the scale of a peri-urban territory. To do so, we use the HELP code by considering the temporal and spatial evolution of land use and their associated characteristics, such as vegetation and soil properties, to detail recharge and runoff over more than 20 years that we incorporate into the initial groundwater model.

The two approaches yielded comparable global water balance results. However, at the local scale, the model accounting for land use showed significantly different hydric components. Choosing the appropriate model depends on the specific research question and spatial scale, and considering land use evolution is crucial for accurate urban planning impact assessments, especially at the district level.

Abstract

For 25 years, the UK’s Environment Agency has commissioned groundwater flow models of the main aquifers in England. These regional-scale models are regularly updated, occasionally recalibrated and used for water resources management, regulatory decisions and impact assessment of groundwater abstractions. This range of uses requires consideration of the appropriate scale of data collection and modelling and adaptation of the groundwater models, with refinement where local impacts on individual springs and seasonal streams are considered and combination and simplification for strategic national water resources planning. The Cretaceous Chalk, a soft white limestone, is the major aquifer of southern and eastern England, supplying up to 80% of the drinking water in this densely populated region. Springs and baseflow of good quality groundwater feed Chalk streams, which are a rare and valuable habitat with a high public profile, but face significant challenges in the 21st century, worsened by climate change and population growth. The modelling informs strategic planning and regulatory decisions, but the model’s scale needs to be appropriate for each issue. The presentation defines these issues and presents examples, ranging from the large-scale, strategic Water Resources East to impact assessment for individual groundwater abstractions and more bespoke local investigations, including simulation of groundwater flood risks. As the scale of investigations reduces, there is increasing importance on the accuracy of information, both temporally and spatially. Model refinement made during local investigations can be incorporated into larger-scale models to ensure that this understanding is captured.

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 Bauru Aquifer System (BAS) is a significant source of water supply in the urban area of Bauru city. Over the last decades, BAS has been widely affected by human activities. This study evaluates the nitrate plume in groundwater from 1999 to 2021 and how it relates to urbanization. The methods used were analysis of the data of 602 wells, survey of the sewer network and urbanization, and reassessment of nitrate concentration data. The seasonal analysis of 267 groundwater samples allowed the identification of concentrations up to 15.1 mg/L N-NO3 - mainly from the area’s central region, where the medium to high-density urban occupation dates back to 1910. Otherwise, the sewage system was installed before 1976. The reactions controlling the nitrogen species are oxidation of dissolved organic carbon, dissolution of carbonates, mineralization, and nitrification. Wells, with a nitrate-increasing trend, occur mainly in the central and northern regions, settled from 1910 to 1980-1990, when no legislation required the installation of the sewage network before urbanization. In turn, wells with stable or decreasing nitrate concentrations occupy the southwestern areas. Over the years, the concentrations of these wells have shown erratic behaviour, possibly caused by the wastewater that leaks from the sewer network. The bivariate statistical analysis confirms a high positive correlation between nitrate, sanitation age, and urban occupation density, which could serve as a basis for the solution of sustainable groundwater use in the region. Project supported by FAPESP (2020/15434-0) and IPA/SEMIL (SIMA.088890/2022-02).

Abstract

Hermanus was originally supplied from springs and groundwater until the De Bos Dam was built in the 1950s. Due to increasing water demand, the municipality commenced wellfield development in 2002. The first wellfield comprised 3 boreholes, of which one borehole was later decommissioned due to reduced yield. Three additional boreholes were drilled recently to ensure abstraction capacity within the licence limits. A second wellfield was developed in the Hemel-en-Aarde Valley north of Hermanus. To ensure the sustainable management of the shared resource and minimise environmental impacts, a monitoring committee was established with all relevant roleplayers, other users, civil society, environmental groups and various commenting and regulatory authorities. A comprehensive monitoring network was established to assist with the scheme’s management and ensure that environmental impacts are minimized. The long-term monitoring (up to 20 years) shows that the groundwater abstraction from the Gateway Wellfield does not impact the environment and other users or increase the risk of saline intrusion. Identified impacts have been mitigated with the assistance of the monitoring committee. The municipality aims to provide at least half of the town’s water demand from groundwater and establish conjunctive use operation between surface water from the De Bos Dam and groundwater from these wellfields. The wellfields ensured sufficient water for the municipality when De Bos Dam’s water levels declined significantly during the Western Cape droughts in 2011 and 2017. The presentation will provide examples of the long-term monitoring records and trends.

Abstract

Groundwater level monitoring is essential for assessing groundwater’s availability, behaviour and trend. Associated with a modelling tool, groundwater level fluctuations can be predicted in the short to middle term using precipitation probabilities or meteorological forecasts. This is the purpose of the MétéEAU Nappes tool implemented by BRGM for the City of Cape Town (CoCT) in the Table Mountain Group Aquifer (TMGA). This case study shows how near real-time groundwater level monitoring can support the municipality in managing its future groundwater withdrawals. The TMGA is an important source of groundwater in the Western Cape region of South Africa. The upper Nardouw Sub-Aquifer of the TMGA is an unconfined aquifer recharged by rainfall. It had been monitored in the Steenbras area for over 10 years before CoCT started groundwater production from the Steenbras wellfield in 2021. The MétéEAU Nappes forecasting tool is already implemented on many observation wells of the French national piezometric network, where it is used for decision-making by the French administration. It allows, in particular, to anticipate several threshold levels of drought and take appropriate measures. It combines real-time water cycle measurement data with a groundwater level lumped model (e.g. Gardenia model) and extrapolates observations for the next 6 months from statistical meteorological scenarios completed with abstraction scenarios. This tool can help protect the Steenbras wellfield as a critical water source for CoCT in the TMGA. This study was financed by the French Agency for Development (AFD).

Abstract

This paper presents the results of groundwater flow modelling studies that were conducted within the scope of the PRIMA RESERVOIR project. The project’s main goal is to develop an innovative methodology to mitigate land subsidence due to excessive groundwater exploitation in water-stressed Mediterranean watersheds. This objective is achieved by integrating earth-observation-derived land subsidence rates with a coupled implementation of numerical groundwater flow and geomechanical modelling. MODFLOWbased 3-D transient flow models were constructed for the four pilot sites (the coastland of Comacchio in Italy, the Alto Guadalentín aquifer in Spain, the Gediz River basin alluvial aquifer in Turkiye and the Azraq basin in Jordan) that have different hydrogeological properties and pose different challenges concerning water management. Models were calibrated and run for similar simulation periods (2013-2021) to obtain hydraulic head drawdowns and changes in groundwater storage. Land subsidence at these sites was evaluated using Advanced Differential Radar Interferometry (A-DInSAR) on image stacks from the Sentinel-1 satellite. Subsidence rates were then compared to hydraulic head drawdown rates to identify groundwater pumping-induced subsidence areas. The comparison for all study areas suggested that locations of maximum displacements do not necessarily coincide with areas that display the largest head drawdown calculated by the flow models. Other triggering factors, such as the thickness of compressible materials, are also related to high subsidence areas.

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

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

Being extensively available and of high quality, groundwater is the primary source of freshwater in coastal regions globally. However, due to anthropogenic and natural drivers, groundwater salinisation is a growing threat to this resource’s long- and short-term viability. The causes and timescales of aquifer salinisation are complex and difficult to quantify, information essential for suitably timed mitigation strategies. One way to inform these strategies and develop storylines of future freshwater (un)availability is through 3D groundwater salinity modelling. These models can predict current groundwater distributions and quantitatively assess the impacts of a projected increase in groundwater extraction rates and sea-level rise. Until recently, detailed 3D models on this scale have been largely unattainable due to computational burdens and a shortage of in-situ data. Fortunately, recent developments in code parallelization, reproducible modelling techniques, and access to high-performance computing (e.g., via parallel SEAWAT) have made this feasible. Machine learning and data mining developments have also allowed an unprecedented opportunity to constrain and calibrate those models. With this in mind, we present our progress towards global 3D salinity modelling by showcasing a regional-scale model in the Mediterranean Sea area. This test case uses newly developed, automated geological and salinity interpolation methods to create initial conditions while implemented in a parallelized version of SEAWAT. The modelling outcomes highlight the potential of supra-regional scale modelling in the context of global (planetary) processes and localised anthropogenic effects.

Abstract

Mt. Fuji is the iconic centrepiece of a large, tectonically active volcanic watershed (100 km2 ), which plays a vital role in supplying safe drinking water to millions of people through groundwater and numerous freshwater springs. Situated at the top of the sole known continental triple-trench junction, the Fuji watershed experiences significant tectonic instability and pictures complex geology. Recently, the conventional understanding of Mt. Fuji catchment being conceptually simple, laminar groundwater flow system with three isolated aquifers was challenged: the combined use of noble gases, vanadium, and microbial eDNA as measured in different waters around Fuji revealed the presence of substantial deep groundwater water upwelling along Japan’s tectonically most active fault system, the Fujikawa Kako Fault Zone [1]. These findings call for even deeper investigations of the hydrogeology and the mixing dynamics within large-scale volcanic watersheds, typically characterized by complex geologies and extensive networks of fractures and faults. In our current study, we approach these questions by integrating existing and emerging methodologies, such as continuous, high-resolution monitoring of dissolved gases (GE-MIMS [2]) and microbes [3], eDNA, trace elements, and integrated 3-D hydrogeological modelling [4]. The collected tracer time series and hydraulic and seismic observations are used to develop an integrated SW-GW flow model of the Mt. Fuji watershed. Climate change projections will further inform predictive modelling and facilitate the design of resilient and sustainable water resource management strategies in tectonically active volcanic regions

Abstract

The alluvial aquifer in the Varaždin region has a long-standing problem with high groundwater nitrate concentrations, mainly from agricultural activities. Since groundwater is used in public water supply networks, it is important to ensure its sustainable use. The aquifer is also used to exploit gravel and sand, and the increased demand for this valuable construction material causes the excavation of gravel pit lakes, making groundwater more vulnerable. Although engineered processes can remove nitrate from groundwater, natural attenuation processes should be investigated to understand the nitrogen behaviour and additional mechanisms for groundwater remediation. Previous research has shown nitrate is a conservative contaminant in the critical zone. Aerobic conditions within an aquifer system prevent significant denitrification. Thus, nitrification is the main process controlling nitrogen dynamics in groundwater. Since groundwater and gravel pit lakes are hydraulically connected, and natural nitrate attenuation exists in these lakes, an additional mechanism for groundwater remediation is possible. This work used isotope hydrochemistry and groundwater modelling to investigate gravel pit lakes as possible sites to reduce nitrate concentration in groundwater. Based on the isotopic composition of groundwater and nitrate concentrations, water balance and solute mass balance were calculated, which made it possible to estimate the nitrate attenuation rate in gravel pit lakes. The gained retardation factor was applied to the groundwater flow and nitrate transport model through several scenarios to evaluate the contribution of gravel pit lakes in reducing the groundwater nitrate concentrations

Abstract

Due to technical, social, and economic limitations, integrated groundwater management presents a significant challenge in developing countries. The significance of this issue becomes even more pronounced in groundwater management, as this resource is often overlooked and undervalued by decision-makers due to its status as a “hidden resource,” despite the fact that it provides multiple ecosystem services. This study aims to establish the technical hydrogeological foundation in rural basins of central Bolivia through alternative, simplified, and cost-effective methods and tools. The study includes applying geophysical techniques, such as Electrical Resistivity Tomography, to determine the conceptual hydrogeological model of a micro-basin. In addition, a soil water balance approach was applied, characterizing 24 biophysical variables to identify groundwater recharge zones, while global circulation models provided a substitute for unreliable meteorological data. Furthermore, a participatory model was developed to identify recharge areas in upper basin areas within the framework of developing a municipal policy for their protection. The participatory model included local knowledge in all stages of methodology development, considering the characteristics of the local plant communities and the spatial distribution of local rainfall. The research findings have already contributed to resolving socio-environmental conflicts in Bolivia and establishing a foundation for effective water governance by empowering local rural communities. This study has demonstrated the feasibility of using alternative, simplified, and low-cost methods and tools to establish the technical hydrogeological basis, which can inform public policies to promote sustainable groundwater management in developing countries.

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.

Abstract

Rising shallow groundwater temperatures are observed in many cities worldwide and are expected to increase further over the next century due to anthropogenic activities and climate change. The impact of groundwater temperature increase on groundwater quality is poorly understood. This study conducted two high-spatial-resolution campaigns in Vienna (Austria, autumn 2021/ spring 2022). At 150 wells, a comprehensive parameter set (e.g. major ions, nutrients, and water stable isotopes) was analyzed in groundwater collected, and at 812 wells, the water temperature was measured. Results are compared to available long-term data on groundwater chemistry (1991-2020). In theory, temperature triggers a cascade of effects, where, finally, the depletion of dissolved oxygen (DO) causes a switch to anaerobic microbial processes and a deterioration of water quality. No direct relation between DO and water temperature was observed between 10 and 20 °C. However, many wells delivered anoxic groundwater, including the one with the highest measured temperature (27 °C). The highest temperatures were consistently observed near potential heat sources (local scale), with a rapid decrease in temperature with increasing distance from these sources. Long-term data from particular high-temperature wells revealed decreased dissolved oxygen after sudden temperature changes of > 5 K. On a regional scale, it is observed that groundwater-surface water interactions and aquifer properties play a pivotal role in oxygen availability and redox conditions. In conclusion, high-spatial-resolution sampling combined with long-term data analysis is needed to determine the impact of temperature on water quality.

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

Globally, rivers, lakes and groundwater face complex anthropogenic water quality alterations posing risks to human health, food security and ecosystems. The World Water Quality Alliance (WWQA) forms an open, global consortium, pooling expertise on water quality science and technology innovation and providing a participatory platform for water quality assessments and co-designing tailored and demand-driven services. It addresses priority topics relevant to water governance, scalable water solutions and emerging issues in water management. The African Use Cases provided an initial testbed that puts the quality of surface water and groundwater into the context of the local 2030 Agenda and its multiple linkages across the Sustainable Development Goals. Central to the initial Africa Use Cases was the integration of in-situ, remote sensing-based earth observation and modelling data to derive the best possible current state of water quality (baseline). Of the three African Use Cases, “Cape Town’s Major Aquifer Systems” focused mainly on groundwater quality in an urban environment. One of the success factors for the Cape Town Aquifer Use Case was the ability of the team to integrate the three different data types of the triangle approach on a sub-catchment scale. This required understanding the complex surface and groundwater systems and their interaction (flow paths and fluxes) in the urban environment. A robust stakeholder engagement process and the introduction of transformative art also drove the success of the Cape Town Use Case. The outcomes of this process will be presented and discussed in this presentation.

Abstract

Urban karst terrains can experience geotechnical issues such as subsidence or collapse induced/accelerated by groundwater withdrawal and civil works. Sete Lagoas, Brazil, is notable for overexploiting a karst aquifer, resulting in drying lakes and geotechnical issues. This study aims to evaluate the progression of geotechnical risk areas from 1940 to 2020 and to simulate future scenarios until 2100. Historical hydraulic head data from the 1940s (when the first pumping well was installed) to the 2000s, a 3D geological model, and a karst-geotechnical risk matrix for defining risk levels were employed to develop a calibrated Feflow numerical model. The results indicate that, before the first well in 1942, the groundwater flow direction was primarily towards the northeast. In the 1980s, due to the concentration of pumping wells in the central area, a cone of depression emerged, causing the flow directions to converge towards the centre of the cone, forming a zone of influence (ZOI) of approximately 30 km². All 20 geotechnical events recorded between 1940 and 2020 have occurred in high or considerable-risk zones where limestone outcrops or is mantled in association with the ZOI. For future scenarios, if the current global well pumping rate (Q = 144,675 m³/d) from 2020 remains constant until 2100, the high and considerable geotechnical risk zones will continue to expand. A 40% decrease in the global rate (Q = 85,200 m³/d) is necessary to achieve a sustainable state, defined by reduced and stabilized risk zones.

Abstract

Huixian Karst National Wetland Park is the most typical karst wetland in the middle and low latitudes of the world and has become an internationally important wetland. The relationship between water quality and aquatic organisms in Huixian Wetland is a hot research topic in wetland ecology. This article focuses on the relationship between the current water quality situation in Guilin Huixian Karst Wetland and the growth of wetland plants. Sixteen sampling points are set up in the wetland to monitor and analyze water quality in wet, normal, and dry seasons. The Kriging index interpolation method is used to obtain a comprehensive water quality interpolation map in the survey area during normal water periods and in combination with the wetland plant survey sample data and the landscape status. A comprehensive analysis of the relationship between wetland plant growth and water quality. The results show that the centre of Huixian Wetland receives recharge from surrounding groundwater, which is greatly affected by the surrounding water quality. The comprehensive water quality is relatively good in the dry season, relatively poor in the normal season, and the worst in the wet season. Agricultural production, non-point source pollution, rural domestic sewage, and human interference affect wetland water quality, which directly affects the structure and function of plant communities and the ecological service function of wetlands.

Abstract

The use of radiogenic isotope tracers, produced through bomb testing (e.g. 3H and 14C), and the application of these isotopes is yet to be fully explored now that atmospheric abundances have returned to background levels. New isotope-enabled institutions and laboratories have recently been established in developing countries to apply isotopes in practical research. This study utilized several laboratories in South Africa and in Europe to compile a robust hydrochemical (major cations and anions) and isotope (d18O, d2H, 3H, 14C, 86Sr/87Sr) dataset of groundwater from 95 sample locations in the Maputo province of Mozambique. Groundwater is hosted in different aquifers and recharged through variable mechanisms ranging from direct infiltration of exposed alluvial soils to inter-aquifer transfer between fractured aquifer systems in the mountainous regions and the weathered bedrock in the lowlands. A combination of hydrochemistry and isotopes provided insight into the heterogeneous nature of recharge, mixing of modern and fossil groundwaters, and aquifer vulnerabilities when combined with other physical parameters in the region. However, it is also clear that grab sampling over a regional spatial extent and two sampling seasons (wet and dry) did not capture all the system variability, and more regular monitoring would uncover details in the system’s behaviour not captured in this study.

Abstract

 Predicting and quantifying the hydrogeological interference of big underground works is a complex effort. This is due to the considerable uncertainty in estimating the key geomechanical and hydrogeological parameters affecting the area of potential interference of the projects. Moreover, the pattern of involved groundwater flow systems is hardly identified, either in natural or disturbed conditions. Base tunnels through mountain ridges are particularly complex in their interactions with groundwater. Several approaches and tools have been published to predict the magnitude and distribution of water inflows inside tunnels and their impact on many receptors (springs, rivers, lakes, wells, groundwater-dependent ecosystems). The research, co-funded by Italferr Spa (Italian railway national company for tunnel design), deals with calibrating and validating these methods based on huge datasets. Main engineering companies provided data from completed base tunnel projects. In particular, in this study, the Drawdown Hazard Index (DHI) method has been calibrated with a dataset of a 15 km long sector of the Gotthard base tunnel drilled through a crystalline geological setting. The calibration involved only the Potential Inflow (PI) parameter to verify the matching between the probability of inflow and the actual output of the excavation, according to the available data in the preliminary stage of the project. An alternative tool based on a machine-learning approach was then applied to the same dataset, and a comparison was presented.

Abstract

Groundwater is the most important source of potable water in rural areas of Acholiland, a sub-region of northern Uganda. Installation of handpumps has been the focus of local government and international aid to provide safe drinking water in Uganda. However, non-functional handpumps are one reason for the abandonment of groundwater resources. For handpumps to be sustainable for years, appropriate siting and construction is required, as well as monitoring. This is common knowledge to specialists working in rural supply, but gaps in knowledge transfer and field skills may exist for the persons installing and maintaining handpump wells. This is a case study of a ten-day field campaign designed to train local participants who actively work in the rural groundwater supply sector. Nine non-functional handpump sites were identified for repair and hydrogeology and geophysical studies. A non-governmental organization, IsraAID, along with Gulu University implemented training by hydrogeology specialists to build local capacity. The training included handpump functionality tests, downhole inspections, electrical resistivity tomography surveys, and water quality sampling, including a novel Escherichia coli test that did not require an incubator. Functionality tests and downhole inspections provided simple but effective ways to assess handpump and well issues. Training in water quality empowered the participants to complete rapid assessments of the quality of the water and start monitoring programs. The success of the project was based on collaboration with multiple organizations focusing on the development of local capacity. The lessons learnt from this campaign should be considered for other rural groundwater supply scenarios.

Abstract

The interaction between groundwater and wetlands is poorly understood, even though it has been the topic of many research projects, like the study done at the Langebaan Lagoon. This interaction is complex as it lies at the intersection between groundwater and surface water, but each situation is unique, with different conditions regulating the interaction. Wetlands can be the source of water that recharges groundwater systems on the one hand, while the other is dependent on the groundwater systems. This interaction became part of the project looking at how to implement Managed Aquifer Recharge for Saldanha Bay Local Municipality without having a negative impact on the groundwater-dependent ecosystems, such as the springs and wetlands in the area. Ten wetlands were identified on the Langebaan Road Aquifer Unit, and a monitoring programme was developed. The purpose of the monitoring was to determine the status of the wetlands as a baseline before the implementation of managed aquifer recharge and to determine the level of groundwater dependence. The latter was done by hydrochemical analysis of rainwater, groundwater and water from the wetlands and stable isotope analysis. The ability of the wetlands to act as a recharge point to the groundwater system will be investigated through column experiments and lithostratigraphic analysis of soil columns taken at the wetlands. Groundwater levels will also be plotted as contour lines to determine the intersection of the water table with the wetlands in the area.

Abstract

Recent advances in groundwater dating provide valuable information about groundwater recharge rates and groundwater velocities that inform groundwater sustainability and management. This talk presents a range of groundwater residence time indicators (85Kr, CFCS 14C, 81Kr, 36Cl and 4 He) combined with analytical and numerical models to unravel sustainability parameters. Our study site is the southwestern Great Artesian Basin of Australia where we study an unconfined confined aquifer system that dates groundwater from modern times up to 400 kyr BP. The study area is arid with a rainfall of <200 mm/yr and evaporation in the order of 3 m/yr. Despite these arid conditions we observe modern recharge rates in the order of 400 mm/yr. This occurs via rapid ephemeral recharge beneath isolated riverbeds where the sandstone aquifer directly outcrops. Groundwater dating and stable isotopes of the water molecule indicates that this recharge comes from monsoonal activity in the north of the continent that travel some 1500 kms. Furthermore, this is restricted to recharge in the Holocene.as we move down the hydraulic gradient groundwater “ages” increase and recharge rates dramatically decrease by orders of magnitude. We conclude that there has been a significant decline in monsoonal precipitation and hence recharge in the deserts of central Australia over this time. We present a couple environmental numerical model that describes how to estimate temporal recharge rates and estimates of hydraulic conductivity from groundwater age data that can be used for groundwater management.

Abstract

Aboriginal and Torres Strait Islander people have inhabited the lands now known as Australia for over 65,000 years. Their communities are intricately connected to the land and waters through culture and tradition. However, there are few examples of integrated water resource management that serve Aboriginal and Torres Strait Islander communities or cultural interests. This is particularly the case for groundwater. In Australia, Indigenous connections to groundwater have historically been overlooked or, in some cases, assumed not to exist. On the contrary, many Aboriginal and Torres Strait Islander cultures have longstanding physical and spiritual connections to a range of artesian and subartesian groundwater resources. These cultures also house accurate records of groundwater systems.

Despite this, groundwater management in Australia remains dominated by Western scientific perspectives, and the groundwater sector poorly integrates Indigenous stakeholder concerns or knowledge into groundwater management and planning. IAH Australia has prepared and signed an Indigenous Groundwater Declaration intending to raise awareness among the groundwater community of the value of Indigenous perspectives and knowledge of groundwater systems. This Declaration can be viewed and signed at http://declaration.iah.org.au. This presentation provides examples of effective partnerships between Indigenous Communities and Government or Academic groundwater professionals. While progress has been made, challenges must be overcome to integrate Indigenous knowledge and connections into groundwater resource management.

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

In response to the Western Cape’s worst drought experienced during 2015-2018, the City of Cape Town implemented various projects to augment its water supply, including desalination, re-use and groundwater. The Cape Flats Aquifer Management Scheme (CFAMS) forms one of the groundwater projects that includes groundwater abstraction and managed aquifer recharge (MAR). The Cape Flats Aquifer (CFA) is a coastal, unconfined, primary aquifer within an urban and peri-urban environment. As such, it is well situated to take advantage of enhanced recharge using high-quality advanced treated effluent but also has challenges related to seawater intrusion (SWI) and risk of contamination. MAR is currently being tested and implemented with a three-fold purpose: (1) to create hydraulic barriers against seawater intrusion and other contamination sources, (2) to protect groundwater-dependent ecosystems harbouring biodiversity, and (3) to increase storage and improve water quality to enhance resilience to effects of drought. As no legislation for MAR exists in South Africa, international guidelines are used to determine water quality requirements related to clogging environmental and health concerns. Further consideration includes aquifer-scale design, the interaction of multiple abstraction and injection wellfields within an area, and the design of individual boreholes to enhance yield and limit clogging. We aim to present progress made to date that includes exploration, wellfield development, monitoring, numerical modelling, aquifer protection, and the lessons learnt.