Millions of people in sub-Saharan Africa rely on hand-pumped boreholes (HPBs) for their water supply, but they are often unreliable, with frequent breakdowns and long repair times. Although there have been previous attempts to understand the difficulty of access to water in rural areas and the functionality of rural water supply systems, they have typically taken ‘siloed’ approaches and focused only on the technical or social factors that influence the supplies’ performance.

A and local researchers in both Africa and the UK, shows that the failure of HPBs is not simply due to a single issue, such as a lack of water or a technical failure: it is the result of a combination of complex social, technical and physical interactions. The study provides crucial information for decision makers across governments, non-governmental organisations (NGOs) and communities aiming to make rural water access more reliable.

The research found that the probability of any failure occurring is dominated by physical and engineering factors: a combination of water levels, the condition of the pump, aquifer yields, and borehole construction and configuration. The length of time the pump was out of action was dominated by social factors including demand, access to spare parts and financing. The project team, led by BGS, tested current HPBs and facilitated interviews and participatory mapping events with water users and managers across Ethiopia, Malawi and Uganda. Combining statistical patterns of HPB failure with lived community experiences led to a new conceptual model that represents the diversity of real-world water-management arrangements.

This paper invites those working in rural water supply in sub-Saharan Africa to consider infrastructure performance through an interdisciplinary lens. These complex interactions can be understood by using frameworks like the one proposed in this study to improve rural water supply performance, which is especially important as rural water systems evolve towards more complex solar and piped technologies.

It’s hoped that understanding these complex interactions around rural water supplies will help governments, NGOs and communities make rural water access more reliable and fairer for all.

Dr Donald John MacAllister, BGS Senior Hydrogeologist the paper’s lead author

This research provides valuable insights into the interconnected drivers of water service downtime. Its findings come at a critical time as groundwater will continue to play a central role in meeting future water demand and strengthening drought resilience. Acting on these insights will be essential to enhance public and private sector support for water service provision through stronger regulation, improved planning, increased financing and enhanced service management.

Vincent Casey, WaterAid

The paper is now available online:

For the first time, a science team has directly documented and extensively sampled a freshened water system beneath the ocean floor off the coast of New England in the USA. This major discovery comes from the initial analyses of sediment cores recovered during the , led by Co-Chief Scientists Professor Brandon Dugan (Colorado School of Mines, Golden, USA) and Professor Rebecca Robinson (Graduate School of Oceanography, University of Rhode Island, USA.

The 872 m of core, retrieved from deep below the sea floor, is now being opened, analysed and sampled by the science team, during almost a month of intensive, collaborative work. The expedition’s scientists are working side by side during January and February 2026 to uncover new insights into the formation, evolution and significance of this newly documented, sub-seabed, freshwater system.

Five BGS staff members are part of the operational team: Jeremy Everest, Margaret Stewart, Raushan Arnhardt (expedition project managers), Mary Mowat (database manager) and Bentje Brauns (hydrogeology). Their role is to coordinate and support the science team to process the core according to IODP³ standards and protocols.

The goal of this expedition went far beyond collecting sediment cores. Scientists also set out to sample the water stored within the sediments, including from sandy layers that act as aquifers and from clay layers known as aquitards that usually keep the water in place beneath the sea floor.

Although roughly 70 per cent of Earth’s surface is covered by water, significant volumes of water also move and are stored below ground. Many coastal communities depend on land-based aquifers for their freshwater supply. What fewer people realise is that, in many parts of the world, the aquifers continue offshore and contain zones of ‘freshened’ water beneath the ocean floor. Scientists have known these offshore systems existed since 1976, but they have remained virtually unexplored until now. During the expedition, the science team successfully documented and sampled freshened water within a zone nearly 200 m thick below the sea floor.

We were excited to see that freshened water exists in multiple kinds of sediments – both marine and terrestrial. Freshened water in such different materials will help us understand the conditions that emplaced the water.

Prof Brandon Dugan, Colorado School of Mines, Golden, USA.

Further analyses, such as age models, conducted by the science team will help to find out where and especially when the water was placed here.

The cores contain sediment with a wide range of composition and ages. It was surprising to see sediment, not rocks, throughout the section. The sediment has not yet transformed into rock – I did not expect to see that and it will be an interesting component of our future work.

Prof Rebecca Robinson, Graduate School of Oceanography, University of Rhode Island, USA.

After a successful coring, sampling and downhole logging campaign last summer, the BGS team is incredibly excited to be supporting the science team to begin the scientific analysis the material collected. The cores have been safely held in their plastic liners since they were drilled out of the seabed and, at the Onshore Operation in Bremen, they are being opened and split, revealing the fresh split-core surfaces for the first time.

The BGS team are contributing to the detailed sampling and analysis of the cores that, when combined with the groundwater samples taken from the borehole, will improve our understanding of the development of the New England shelf and the freshened water reservoirs underlying it. It is such a satisfying moment, after years of effort to acquire the cores, to be rewarded with new data and insights in such an important and societally relevant subject.

David McInroy, marine geoscientist, BGS.

Shedding light on similar water aquifers around the world

The approach used during IODP³-NSF Expedition 501 will not only deepen understanding of offshore freshened groundwater systems off the coast of New England, but will also shed light on similar hidden water aquifers around the world. Because many coastal regions rely on groundwater for their freshwater supply, the expedition’s initial findings are highly relevant to society. The research will also reveal how nutrients such as nitrogen cycle through continental shelf sediments and how these processes influence the abundance and diversity of microbes living in these environments.

These goals align closely with the 2050 Science Framework for Ocean Research Drilling – one of the foundations of the IODP³ scientific programme. Ultimately, the expedition’s research will help to decipher how sediments and fluids cycle through the Earth system and improve our knowledge about sea level changes and freshwater flow beneath the seabed along our coastal shelves. “The researchers will continue to work on and with the samples to decipher more – for example, to date the groundwater more accurately which is critical to advancing our knowledge,” adds Rebecca Robinson.

Background

The expedition is a joint collaboration between the International Ocean Drilling Programme (IODP³) and the US National Science Foundation (NSF). The cores were retrieved during offshore operations between May and August 2025. For onshore operations the science team have met at the Bremen Core Repository, at MARUM – Center for Marine Environmental Sciences of the University of Bremen (Germany). “We greatly appreciate being able to conduct this advanced research at MARUM, supported by its world-class laboratories, exceptional facilities, and dedicated staff,” adds Brandon Dugan

The cores will be archived and made accessible for further scientific research for the scientific community after a one year-moratorium period. All expedition data will be open access in the IODP³ Mission Specific Platform (MSP) data portal in PANGAEA, and resulting outcomes will be published.

International approach

Forty science team members from 13 nations (Australia; China; France; Germany; India; Italy; Japan; the Netherlands; Portugal; Sweden; Switzerland; UK; USA) are taking part in this MSP expedition that consists of two phases: offshore and onshore operations. Offshore operations took place between May and early August 2025.

The expedition is conducted by the European Consortium for Ocean Research Drilling (ECORD) as part of IODP³, funded by IODP³ and the US National Science Foundation (NSF).

More information

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Deep in the heart of the Borneo rainforest lies one of South-east Asia’s most important natural sites: the of Sarawak, Malaysia. Despite being home to one of the most diverse tropical rainforests on the planet, arguably the world heritage area’s most astonishing feature lies underground.

The caves of the Gunung Mulu National Park

Under the limestone ridge of Gunung Api lies the extensive Clearwater cave system. At over 260 km in length and with passages often exceeding 30 m in diameter, it is believed to be the world’s largest cave system by volume, and is a haven for local wildlife.

The nearby Deer Cave is home to an estimated three million wrinkle-lipped bats, which fly out of the cave each evening to feed, creating a stunning visual display. Cave swiftlets also fly many kilometres into the Clearwater cave system to make their nests, which are prized as a local delicacy and used to make bird’s nest soup. Lying in wait to try and catch them as they fly past are cave racer snakes, whilst an astonishing array of cockroaches, millipedes, crabs, crickets and spiders are sustained by the piles of guano (bat poo) that line the cave floor. The ecosystem featured in a series.

History of the caves

Caves are fantastic repositories of geological and archaeological data, preserving information that would otherwise be lost to surface erosion and degradation. They and the deposits they contain hold clues to past landscape change, allowing us to reconstruct how the Earth’s surface has changed over millennia.

The caves were first explored as part of a Royal Geographical Society expedition in 1978. Working in collaboration with the Sarawak Forestry Corporation and the national park, the has been exploring, surveying and undertaking research in the caves ever since. This includes caving expeditions led by Andrew Eavis, a veteran of the 1978 expedition.

Dating of stalagmites and cave sediments indicates the Mulu caves are up to three million years old. Other analysis of cave stalagmites has yielded a climate record spanning hundreds of thousands of years, whilst volcanic ash provides evidence of a massive volcanic eruption in the Philippines 189 000 years ago. More recent archaeological finds also provide evidence of human activity and burials in some of the caves.

Recent research within this incredible cave system led to a surprising discovery about the formation of the caves within it.

Unusual dissolution

One of the unusual aspects of the Mulu caves is the way the cave passages have been sculpted.  Most caves in the region are formed by the dissolution (dissolving or break down) of limestone by acidic water, primarily from rivers flowing through the cave. The action of flowing water on the limestone rock creates small asymmetrical scoops etched into the passage walls, called scallops. These are preserved on the passage walls even after the formative river has abandoned the passage, as the water finds new, lower routes through the rock. The scallops are of interest to scientists as they can be used to deduce past water flow, providing a record of how water flowed through the caves over time.

In the Clearwater cave system, typical scallops are present in the lower levels of the cave system, close to the present river. However, in the older, higher levels of the cave system, which have long since been abandoned by the river, they are strangely noticeable by their absence, having been dissolved away and replaced by unusual corroded and pitted rock architecture.

The passage walls are frequently eroded into small dissolution pots and coated with a weathered crust: analysis has shown these are composed of calcium phosphate minerals, which is highly unusual in caves. Corroded stalagmites are common, dissolved away like rotten teeth to reveal their internal growth rings. These features suggest some form of atmospheric dissolution of the passage walls and stalagmites has taken place in the time since the passage was abandoned by the underground river.

Comparison with other caves suggests these features are generally restricted to tropical cave systems. One of the key aims of recent Mulu expeditions has been to understand how these features form and why. A team of researchers led by BGS geologist Dr Andrew Farrant, cave microbiologist Prof Hazel Barton (University of Alabama), her PhD student J Max Koether and BGS isotope geochemist Dr Andi Smith set out to investigate what may be happening.

Caving and exploration

Undertaking cave research can be hard work. Sampling trips into a cave system over 250 km long takes time and, in some cases, involved making camp underground. It is hard, sweaty, sometimes muddy work, occasionally requiring ropes to climb up pitches or descend vertical drops. But the rewards are enormous: the caves are spectacular, with stunning formations, huge chambers and amazing biota.

The Clearwater streamway is probably one of the finest cave passages in the world. Not only is there the prospect of new scientific discoveries, but also the chance to explore new cave passages where no human has ever trodden. On one trip, the team crawled through a flat-out squeeze to emerge into an undiscovered chamber over 200 m long, 70 m wide and 50 m high (big enough to hold two Airbus A380 jets) and adorned with 20 m-high stalagmites.

Research

Complex ecosystems are a distinctive feature of tropical caves, driven by the daily input of guano from bats and swiftlets. Bats create large piles of pungent excrement beneath their roosts, whilst the swiftlets’ guano is dispersed more widely, sometimes kilometres into the caves. The teams’ initial hypothesis was that the guano was somehow implicated in creating the unusual dissolution forms and smooth walls seen in the caves. Initial analysis of the guano piles in the caves indicated that they are strongly acidic, comparable to stomach acid or lemon juice, with a pH as low as 1.9. This could account for dissolution beneath the guano pile, but not the pervasive dissolution features seen throughout the caves.

Further work on the microbiology of the guano showed that microbial breakdown of urea (from bats) and uric acid (from birds) generates significant quantities of ammonia and carbon dioxide, which are released into the cave air. Measurable plumes of ammonia can be detected in some caves; could this be responsible for the unusual features?

Attention turned to the weathered ‘paste’ seen on many passage walls. This turned out to be teeming with microbial life, in some places containing a higher microbial cell count than cultured yogurt. Analysis of condensation water droplets on the cave walls revealed extraordinarily high levels of nitrate (up to 7000 mg/l; for comparison, the UK drinking water standard is 150 mg/l), whilst drips feeding the stalagmites had little or no nitrate.

These observations suggest that ammonia released into the cave air by the microbial decay of bat and bird guano adsorbs onto water droplets on the passage walls and stalagmites. Here, microbes use the ammonia as a food source, producing nitrates, nitric oxide, nitrogen dioxide and nitric acid as byproducts. This acid dissolves the passage walls and stalagmites, removing the original dissolutional scallops and replacing them with a suite of biogenic dissolution features. It is estimated that, in some places, several metres of dissolution have occurred in just a few tens of thousands of years: geologically speaking, this is a very short time period.

Further work is ongoing to learn more about the microbial processes that occur within the guano and on the cave walls. The discovery of this novel mechanism of cave development has significant implications, such as how we interpret past environments from caves, the preservation of cave art, and the impact of this acidic environment on ropes and other caving equipment.

The great thing about the Mulu Caves Project expeditions is they have enabled us not just to explore new caves, but to do some amazing science too. One thing is clear from our work in the caves; the surface and underground environments are inextricably linked. There is much we still have to discover and one wonders what other secrets are waiting to be discovered beneath Gunung Api…

Publication

Our research has been recently published in the journal Geomorphology.

Farrant, A R, Koether, J M, Barton, H A, Lauritzen, S E, Pennos, C, Smith, A C, White, J, McLeod, A, and Eavis, A J. 2025. . Geomorphology, Vol. 483, 109822. DOI: https://doi.org/10.1016/j.geomorph.2025.109822

Thanks                 

Thanks go to Andrew Eavis and members of the Mulu Caves Project, the Sarawak Forestry Corporation and the Gunung Mulu National Park management and staff, without whom this work would not have been possible. Part of the research was funded by a NEIF steering committee grant to Andi Smith.

About the author

Geologists at BGS have completed a major update to the geological map of the Yorkshire Wolds, where the underlying rocks and sediments play a vital role as natural reservoirs for the region’s underground water resources.

The distinctive white chalk rock of the , which forms the magnificent coastal cliffs, is also present beneath the wolds. The chalk is an ‘aquifer’ and is important as the primary drinking-water source for the area. The new geological mapping will provide detailed and accurate information to inform decision making around the use of groundwater resources.

The geology of some of the area was last mapped in the 1800s, before modern understanding of the impact of tectonics (movement of the ’plates’ that make up the Earth’s crust) on the chalk and before information about differences in the properties of the chalk layers was recorded. At that time, there was no satellite data and underground data was limited, so maps were mostly based on ground observations, with much of it done from horseback! The new mapping provides updated geological data and information for the region and plays a central role in the current BGS national geological mapping programme.

The five-year project involved different remote techniques, including interpretation of 2D seismics (information from small, controlled vibrations that create waves through the rock, which can then be used to map the subsurface), digital elevation models, aerial imagery and borehole records along with field surveys and palaeontological (fossil) analysis. Collectively, these methods and data have significantly improved geological understanding of the chalk aquifer.

The aquifer currently faces a number of pressures, including:

• increased water demand from a growing population as well as industrial uses
• risk of nitrate contamination from agricultural land practices
• risk of salt water from the Humber estuary reaching the aquifer and mixing with drinking water
• improvements to habitats, for example chalk streams

We need to better understand and model how water flows in the Chalk aquifer and the interaction between springs, rivers and abstraction. The new mapping delivers enhanced knowledge that will help to improve regional understanding of both the aquifer and the groundwater resources, as well as localised geological issues that may assist in reducing risks to specific water supply assets, such as water abstraction sites.

Over the past hundred years since the geology of the Yorkshire Wolds was last mapped, our ability to better understand what lies beneath our feet has vastly improved thanks to technological advances and a modern understanding of geology. The updated geological maps will help companies, farmers, local planners and regulators make more informed decisions around the management and protection of the chalk aquifer in the Yorkshire Wolds.

The data also provides a solid geological framework to underpin future work to help mitigate present and future issues faced in the Yorkshire Wolds, including drought, coastal erosion, water quality and saline intrusion into the aquifer.

Laura Burrel Garcia, survey geologist at BGS.

The project was a collaboration between the Environment Agency (EA), Yorkshire Water Services Limited (YWS) and BGS. Recently, EA, YWS and WSP attended BGS’s headquarters in Keyworth, Nottinghamshire, to discuss the conclusion of the project and its outcomes.

The team at the BGS has not just remapped the Yorkshire Wolds; they have also shared their expertise and enthusiasm with all. The outputs of this project will benefit the people of Yorkshire for centuries to come and will greatly assist the Environment Agency in our work to create better places for people and wildlife, while supporting sustainable development.

Ruth Buckley, Environment Agency.

This project has been a wonderful example of collaboration and shared learning. The BGS team members were generous with their time, sharing their expert knowledge of field mapping and interpreting the modern information. It was a pleasure to work with them. The end result is a huge improvement in the collective understanding of the geology, which will feed into improvements in understanding of groundwater flow and a new groundwater model based on the new geology maps. This gives us the ability to better manage East Yorkshire’s water resources and protect the environment now and into the future.  A big thank you to all involved.

Mark Morton, Yorkshire Water Services Limited.

The data produced from this work will form part of the national geological map, which will be freely accessible via the .

Groundwater flooding is the emergence of groundwater at the surface, which can occur in a variety of geological settings, including areas with historical mining. In England and Wales, it’s estimated that groundwater flooding accounts for an estimated £530 million in damages per year.

Project Groundwater Northumbria aims to increase awareness and understanding of groundwater flooding and help prepare for and mitigate flood events through innovative approaches and technologies. The project, in which BGS is a partner, is led by Gateshead Council and is part of the Environment Agency’s Flood and Coastal Resilience Innovation Programme.

Following a major groundwater flood event in Gateshead in 2016, along with several smaller incidents, BGS has constructed a subsurface map and produced a free, 3D geological model of the bedrock in Gateshead. These help better understand the sequences and geometries of the shallower soil layers (superficial deposits) at tens of metres of depth, alongside structures and boundaries in the bedrock to several hundred metres of depth.

The north-east of England was a major centre for coal mining. In areas with historical mining activities like Gateshead, the effect of mine workings on groundwater movement can be significant. The map and model will give a better understanding of how the natural subsurface conditions, combined with the legacy of human activity in the subsurface such as abandoned coal mines, affects the direction of groundwater flow.

The insight provided from the anticipated groundwater flow paths will help identify where groundwater flooding is likely to occur. This will allow Gateshead Council (and other organisations, such as the Environment Agency and Northumbrian Water) to better deploy resources more effectively and monitor the speed and spread of flooding in real time, to help manage and alleviate groundwater flooding in the area.

The 3D geological model of Gateshead, released as part of Project Groundwater Northumbria, will help us to understand the impact of groundwater movement in this area and improve Gateshead Council’s response to future floods.

The model is an innovative step forward in how we capture data. Traditional geological maps don’t allow to us to show the interaction of mine water and groundwater, but we can showcase them with this model. It has really helped us to improve our 3D understanding of coal fields and how water flows through them. In turn, this is part of a wider programme of 3D urban geology across the country.

Project Groundwater Northumbria showcases how multiple organisations can work together on one project with the same aim and highlights the geological and technologies advances that can be achieved.

Ricky Terrington, BGS 3D Geospatial Lead and project leader.

The 3D geology model for Gateshead can now be accessed for free on BGS’s .

The reports produced as part of this project are available to read:

Understanding how heat moves within the subsurface is important for the development of geothermal energy, including ground-source heat pumps. Determining which geological areas are suitable for their installation is vital. For the first time, scientists at BGS have used time-series data at the , which is run by BGS, to look at long-term trends for subsurface heat.

The geo-observatory monitors 62 boreholes, 49 of which were observed every 30 minutes for four years between 2014 to 2018. The analysed data found previously undetected, localised cracks in the geology in the south of the city, where the subsurface is largely clay at that depth. These newly discovered cracks, which can be caused by plant roots, provide pathways that act as recharge routes underneath the south of Cardiff, allowing rain water to enter and be conveyed to the groundwater below.

While a ground-source heat pump can be highly efficient, installing one in one of these newly discovered areas of cracks could lead to performance issues. Specifically, the constant influx of cooler groundwater could hinder the heat pump’s ability to extract heat effectively and the system could potentially affect the groundwater flow and quality.

For geothermal developers looking to install shallow ground-source heat pumps underneath the capital, it’s important that this new data is carefully considered. The research shows that installing a ground-source heat pump in Cardiff deeper than 8 m will help to maximise the technology’s efficiency. 

Using time-system data for the first time in Cardiff has provided vital information to further our understanding of what lies beneath our feet. The discovery of geological recharge pockets in an area where they were previously not thought to occur is an important consideration for future infrastructure projects. It’s essential that geothermal developers take this research into account before installing a shallow ground-source heat pump, to ensure it runs as effectively as possible and is not impacted by recharge.

Ashley Patton, engineering geologist at BGS and research lead.

For more information about the Cardiff Urban Geo-Observatory please email BGS Cardiff (bgswales@bgs.ac.uk).

Chalk: a shared geology

The Upper Cretaceous-aged (commonly known as ‘the Chalk’) is perhaps Europe’s most iconic geological unit. Besides forming the famous white cliffs, the Chalk:

• is a major aquifer, supplying millions of people with drinking water and sustaining rare ecological habitats
• is important for energy as it hosts oil and gas reservoirs in the North Sea, provides the foundation for offshore wind farms and hosts numerous shallow geothermal-energy schemes
• has the potential act as storage for hydrogen and CO2
• is a raw material for cement
• hosts many major civil engineering and infrastructure schemes across northern Europe including, in the UK alone, the recently approved Lower Thames Crossing, HS2, the Channel Tunnel and the new ‘super sewer’, the Thames Tideway Tunnel in London

Yet the Chalk is also one of the most misunderstood geological units. It is a common misconception that it is a uniform rock unit with very little structure or faulting. In reality, it has significant variations in physical properties and is often faulted.

Recent geological mapping in the Chilterns and Yorkshire Wolds, undertaken by BGS in collaboration with the Environment Agency and water companies, has shown how geological discontinuities in the Chalk affect groundwater flow. These discontinuities facilitate the development of dissolutional conduits and rapid flow pathways, creating a very heterogenous aquifer. This heterogeneity generates major challenges for the water industry, civil engineers and planners.

As an aquifer, the Chalk is under pressure, both in terms of water quality and resource. The demand for water, especially in more populated areas of southeast England is increasing, but there is also a need to protect rare chalk stream habitats and maintain river flows. Climate change, drought and contaminants such as nitrate exacerbate the problem. Addressing these issues require a greater geological understanding of the aquifer and how groundwater flows it.

These challenges aren’t just restricted to the UK: France has similar problems in the extensive chalk outcrops across the north of the country, as do the Netherlands, Denmark and Belgium.

Current research

A good understanding of the Chalk Group is needed to better predict groundwater flow and engineering ground conditions. This requires good quality geological maps and 3D models fit for the 21st century, using all the available information including field data, geophysical borehole logs, geophysical surveys and biostratigraphical data. In the UK, geological maps used to show the Chalk Group with just three subdivisions; we now divide the chalk into nine individual mappable formations, reflecting their differing engineering and hydrogeological properties. These more detailed maps are able to show much more geological structure, and are more relavent to engineers and hydrogeologists.

Recent groundwater modelling in BGS work has focused on building the national scale British Groundwater Model, simulating groundwater flooding, and projecting the impact of climate change on chalk streams and public water supplies. Other geological surveys are also modelling groundwater, for example, to investigate the impacts of nitrate and other contaminants on the chalk aquifer.

Likewise, more detailed understanding of the Chalk Group has helped civil engineers better predict ground conditions on major infrastructure projects. For example, BGS maps and models help identify zones of weak faulted ground that might be an issue for tunnelling or road cuttings. Similarly, BGS helped characterise flint content in the Chalk in the Thames Estuary to help design cutting heads for the Lower Thames Crossing tunnel-boring machines. Lessons learned from major projects in the UK can be equally applied in northern France and vice versa.

Common problems: common solutions

A key remit of geological surveys and research institutions is to work to find solutions to geological problems. BGS has teamed up with other northern European geological surveys and research institutes to discuss common interests in the Upper Cretaceous Chalk. Twenty-eight participants from 13 different research institutions and geological surveys, including geologists, hydrogeologists, biostratigraphers and engineering geologists, gathered for the inaugural in the town of Étretat on the French coast. Étretat hosts spectacular chalk cliffs and rock arches made famous by the painter Claude Monet. These amazing outcrops admirably demonstrate how variations in the Chalk influence the local hydrogeology and cliff stability.

Outcomes

Exactly how does the Chalk vary across northern Europe? Many productive discussions were had during the workshop and several common themes were identified. Key to understanding the variability of the chalk is the application of a unified Chalk Group stratigraphy, so variations and changes in rock properties across the Anglo–Paris basin can be better understood and predicted.

Another area of common interest is the development of karst features in the chalk such as sinkholes, dissolution pipes, caves and dissolutional conduits. These are important not only from a hydrogeological perspective, but also as an engineering hazard. The French geological survey, BRGM, has been leading the way here, undertaking numerous tracer tests and identifying sinkholes across Normandy. A similar approach is being taken by BGS, learning from the French.

A third area of interest is incorporating lithological variability and karst into groundwater models. At present, many groundwater models treat the Chalk as a single porous medium, often modelled as just one or two layers. This ignores much of the complexity within the group. Much discussion was had on how to best approach modelling groundwater in the Chalk at a range of scales.

Next steps

This first meeting generated a huge amount of interest and enthusiasm. The next steps are to translate this into concrete actions. Essential to this is identifying potential funding sources for common projects, such as stratigraphical correlations across the Anglo–Paris basin. A special issue on Chalk Group stratigraphy in a relevant journal is another possibility.

Another workshop is being planned for 2026, either in Maastricht or in south-east England.

Thanks

Thanks to Ophélie Faÿ (University of Mons) and Eric Lasseur (BRGM) for organising the event.

About the author

Dr Andrew Farrant is a geologist and karst geomorphologist based at the BGS. He is the Regional Geologist for Southeast England and has extensive experience mapping the Chalk across southern and eastern England.

In rapidly developing urban environments, water-quality protection is particularly challenging due to diverse pollution sources. Protecting water resources by identifying pollutants is essential to safeguarding both human health and the natural environment. A new study on the , led by researchers at BGS in partnership with the Indian Institute of Science (IISc) and the UK Centre for Ecology & Hydrology (UKCEH), presents the first combined assessment of emerging organic contaminants (EOC) and antimicrobial resistance (AMR) indicators from multiple water sources in the Indian city of Bengaluru.

EOCs include chemicals like pharmaceuticals, personal care products and pesticides that can end up in groundwater, often from waste water. AMR happens when bacteria become resistant to antibiotics and spread through contaminated water sources, making infections harder to treat. The new data can help local stakeholders, such as regulators, understand the local groundwater recharge mechanisms and how pollution spreads through water sources, which can affect water quality and safety.

The study

The study assessed the sources of contamination in groundwater in the city and found that contaminants could be linked to rivers, lakes and sewers or piped water, highlighting the widespread vulnerability of groundwater to different pollution sources. This information can be used to improve understanding of the water recharge processes.

Twenty-five samples were collected from groundwater, local surface waters and tap water in the Cauvery Basin in eastern India. The samples were screened for around 1500 pollutants and 125 pollutants were identified. Medical and veterinary-based compounds, including antimicrobials, were the most prevalent, being found in around 60 per cent of samples.

Forever chemicals

High concentrations of polyfluoroalkyl substances (PFAS) were also detected at concentrations higher than in previous studies in Indian cities. PFAS are known as ‘forever chemicals’ due to their durability and widespread presence in the environment, and are linked to a variety of health concerns including certain cancers and reductions in immune function. They are currently unregulated in India but, based on the EU Drinking Water Directive, the threshold for the sum of selected PFAS (0.1 μg/L) was exceeded for all water types except tap water.

Study findings

The water in Bengaluru is consumed by up to 8 million people each day, but our results have highlighted that a variety of chemicals are exceeding international regulatory standards and could pose a potential risk to humans and the natural environment.

Bentje Brauns, BGS Hydrogeologist and study leader

When we compared the levels of the AMR indicator gene to those found in the global literature, some water sources in Bengaluru had concentrations in the same order of magnitude as those found in polluted environments, including waste water and rivers near drug manufacturing facilities.

Holly Tipper, molecular biologist at UKCEH who performed the AMR analyses

The findings suggest the need for developing a comprehensive urban groundwater quality monitoring programme for Bengaluru city.

Sekhar Muddu, IISc

The study addresses a knowledge gap in the occurrence of pollutants and relationships in different water sources in urban India, reinforcing understanding that there is no ‘one size fits all’ data solution to the problem.

Tests need to be undertaken at localised sites across the country to provide a comprehensive overview of India’s water supply in order to ensure that there is minimal risk.

Bentje Brauns

Surface water bodies with recently implemented protection measures, such as prevention of sewage inflow, had fewer EOCs detected than other surface waters and were found to have much lower risk of AMR development. This shows how relatively simply urban protection measures can protect freshwater quality.

Funding

The research underlying this paper was carried out under the UPSCAPE project of the Newton-Bhabha programme, ‘Sustaining water resources for food, energy and ecosystem services’, funded by the UK Natural Environment Research Council (NERC/UKRI) [NE/N016270/1] and the Indian Ministry of Earth Sciences (MoES) [MoES/NERC/IA-SWR/P1/08/2016-PC-II (i), (ii)].

Laboratory analysis, data interpretation and write up were additionally funded by the BGS NC-ODA Grant ‘Geoscience for sustainable futures’ [NE/R000069/1] and the BGS NC International programme ‘Geoscience to tackle global environmental challenges’, NERC reference NE/X006255/1.

D S Read, H J Tipper and A A Singer were supported by the UK Natural Environment Research Council award number NE/R000131/1 as part of the SUNRISE programme delivering National Capability.