Groundwater Source Protection Research Articles

Evaluating hydrogeochemistry and heavy metal contamination of groundwater at Ranipet environs: employing multivariate statistics, agricultural indices, and health risk assessment.

Water plays an essential role in sustaining life on Earth as an indispensable natural resource. In recent decades, dependence on groundwater for domestic and industrial purposes has become inevitable. The Ranipet industrial environs (RIE) has many tanneries and chemical industries, which affects the groundwater quality. This study assessed groundwater quality and its suitability for domestic, agricultural, and human health risk assessments. 40 groundwater samples (28 open wells and 12 bore wells) were collected during pre-monsoon 2022 and analyzed by employing multivariate statistics, standard scatter plots, irrigation indices, and health risk assessment. The results of hydrogeochemical analysis and multivariate statistics affirmed that electrical conductivity (EC), total dissolved solids (TDS), calcium (Ca2+), and magnesium (Mg2+) have controlled the hydrochemistry of RIE. Cadmium (Cd) at 46% and chromium (Cr) at 33% have contaminated the groundwater in the study area, making it unsuitable for human consumption and irrigation. The agricultural indices analysis results show groundwater quality ranging from very poor to unsuitable making it unsuitable and also affects crop productivity. Hazard index (HI) results infer that Cr and Cd severely contaminated the RIE's groundwater, encompassing 14 villages, making the groundwater unfit for drinking, domestic use, and irrigation. Hazard quotient (HQ) and incremental lifetime cancer risk (ILCR) analysis revealed that 2 in 100 infants and 3 in 1000 people over the age of 63 are likely to develop cancer due to Cr and Cd in the REI. This is a need-of-the-hour problem, addressing this issue with preventive measures to ensure the protection of groundwater sources will lead to achieving the Sustainable Development Goal 6 (Clean Water and Sanitation).

A Review on In-Situ Denitrification Technology for Consideration in Jaffna Peninsula Aquifer Remediation

A Review on In-Situ Denitrification Technology for Consideration in Jaffna Peninsula Aquifer Remediation

The antimicrobial resistance profiles of Escherichia coli and Pseudomonas aeruginosa isolated from private groundwater wells in the Republic of Ireland

The role of the natural environment in the dissemination of antimicrobial resistant bacteria has been increasingly recognised in the literature. However, knowledge surrounding the critical factors and mechanisms mediating their occurrence is still limited, particularly in relatively ‘pristine’ groundwater environments. In the Republic of Ireland (RoI), a country characterised by high groundwater reliance, household-based (unregulated) wells provide drinking water to 11% of the population. These private wells are generally located in rural areas, where the risk of microbiological contamination is high due to intensive agricultural practices and high reliance on domestic wastewater treatment systems; both of which are also potential sources of antimicrobials and antimicrobial resistant bacteria. Accordingly, the current research sought to elucidate current rates of antimicrobial resistant bacteria and the principal factors associated with their presence in private wells in the RoI. A total of 250 samples (from 132 wells nationwide) were assessed for the presence of faecal (Escherichia coli) and environmental (Pseudomonas aeruginosa) bacteria, with single isolates from each contaminated sample tested phenotypically against 18 and 9 antimicrobials, respectively. Findings show that while 16.7% of E. coli (n = 8/48) were categorically resistant to ≥1 antimicrobial, with a further 79.2% classified as intermediately resistant, no categorical resistance was found among P. aeruginosa isolates (n = 0/6), with just one intermediately resistant isolate detected. Multivariate regression modelling indicates significantly higher odds of resistant E. coli detection in concurrence with elevated cattle density (OR = 1.028, p = 0.032), aligning with findings of highest resistance rates to veterinary antimicrobials (e.g., streptomycin = 14.6%, tetracycline = 12.5%, and ampicillin = 12.5%). Multivariate model results also suggest overland flow culminating in direct wellhead ingress as a primary ingress mechanism for resistant E. coli. Study findings may inform groundwater source protection initiatives and antimicrobial resistance surveillance moving forward.

Occurrence, Physicochemical Properties and Antibiotic Resistance Patterns of Enteric Bacteria Isolated from Well Water in Ilara-Mokin, Ondo State, Nigeria

Aims: TheoCcurrence and antibiotic resistance patterns of enteric bacteria isolated from well water sources and their physicochemical profile was ascertained in this study. Molecular analysis of the bacterial isolates from well water samples was conducted via polymerase chain reaction (PCR)-based identification.
 Study Design: Experimental design.
 Methodology: A total of 12 wells were collected in triplicates from groundwater sources (wells), and mean values were obtained. The first batch of samples were collected during the dry season in January and February, 2020. The second batch of samples were collected during the rainy season in July 2020. The detection of coliforms and other enteric bacteria were conducted via the most probable number (MPN) method. Polymerase chain reaction (PCR)-based identification and characterization of bacterial isolates were employed. Antibiotic susceptibility test was done using the Kirby Bauer disc diffusion technique. The determination of the physicochemical properties of the well water samples were conducted following customary protocol.
 Results: Well water sample 7 had the highest count at 250 bacterial counts/100ml in the dry season and 200 bacterial counts/100ml in the rainy season, while well water sample 4, 10, and 11 had 14 bacterial counts/100ml in dry season, well water sample 2 had 140 bacterial counts/100ml in the dry season and 250 bacterial counts/100ml in the rainy season, whilst sample 11 had 7 bacterial counts/100ml in the rainy season. Klebsiella pnuemoniae, Escherichia coli, Salmonella typhi and Shigella dysentariae were the Gram-negative organisms enumerated and molecularly-identified as Klebsiella pnuemoniae subsp. Pnuemoniae HS11286, Escherichia coli 0157:H7, Salmonella enterica subsp. Enterica serovar typhimurium and Shigella dysentariae HNCMB 20080 from the well water samples with percentage identity of 97.19%, 87.44%, 80.45% and 96.19% respectively. Klebsiella pnuemoniae showed high resistant rate in augmentin at 67% in dry season and 100% in the rainy season. Shigella dysentariae showed 8.3% resistance to augmentin in the dry season and 75% in the rainy season. E. coli showed 67% and 58% resistance in the dry and rainy season respectively. Water hardness had the highest mean of 98.5 and 99.5 mg/L in dry and rainy season respectively while turbidity, and alkalinity had the least mean value at 1.2 (NTU) and 0.62 mg/L, 1.4 (NTU) and 0.7mg/L in both dry and rainy seasons.
 Conclusion: Findings provided information on the poor quality of the well water, which will be useful in groundwater treatment strategies and policy formulation by appropriate groundwater source protection bodies.

Numerical Modeling and Simulation of the Effectiveness of Groundwater Source Protection Management Plans: Riverbank Filtration Case Study in Serbia

The paper describes the establishment and testing of an algorithm for developing sustainable management plans associated with groundwater source protection against potential pollutants and discusses the effectiveness of individual systems. The applied methodology pertains to groundwater resource management, particularly those cases that involve riverbank filtration. Namely, groundwater (numerical) modeling is employed to examine the groundwater regime and balance, as well as to create protection systems and illustrate their effectiveness. Particle tracking analysis is used to study pollutants’ travel and residence time. On the other hand, PEST with regularization is employed to estimate the numerical model parameters. The proposed method is used in a real case study, which examines the application of the developed algorithm to the protection of a drinking water supply source from an industrial zone, which is a potential source of pollution. The research presented in the paper opens new avenues for future studies involving mathematical multicriteria optimization and decision making about optimal groundwater source protection management plans.

Spatiotemporal dynamics of Escherichia coli presence and magnitude across a national groundwater monitoring network, Republic of Ireland, 2011–2020

Groundwater is a vital drinking water resource and its protection from microbiological contamination is paramount to safeguard public health. The Republic of Ireland (RoI) is characterised by the highest incidence of verocytotoxigenic Escherichia coli (VTEC) enteritis in the European Union (EU), linked to high reliance on unregulated groundwater sources (~16% of the population). Yet, the spatio-temporal factors influencing the frequency and magnitude of microbial contamination remain largely unknown, with past studies typically constrained to spatio-temporally ‘limited’ sampling campaigns. Accordingly, the current investigation sought to analyse an extensive spatially distributed time-series (2011−2020) of groundwater monitoring data in the RoI. The dataset, compiled by the Environmental Protection Agency (EPA), showed ‘high’ contamination rates, with 66.7% (88/132) of supplies testing positive for E. coli, and 29.5% (39/132) exceeding concentrations of 10MPN/100 ml (i.e. gross contamination) at least once during the 10-year monitoring period. Seasonal decomposition analyses indicate that E. coli detection rates peak during late autumn/early winter, coinciding with increases in annual rainfall, while gross contamination peaks in spring (May) and late-summer (August), likely reflecting seasonal shifts in agricultural practices. Mixed effects logistic regression modelling indicates that monitoring sources located in karst limestone are statistically associated with E. coli presence (OR = 2.76, p = 0.03) and gross contamination (OR = 2.54, p = 0.037) when compared to poorly productive aquifers (i.e., transmissivity below 10m2/d). Moreover, 5-day and 30-day antecedent rainfall increased the likelihood of E. coli contamination (OR = 1.027, p < 0.001 and OR = 1.005, p = 0.016, respectively), with the former also being associated with gross contamination (OR = 1.042, p < 0.001). As such, it is inferred that preferential flow and direct ingress of surface runoff are the most likely ingress mechanisms associated with E. coli groundwater supply contamination. The results presented are expected to inform policy change around groundwater source protection and provide insight for the development of groundwater monitoring programmes in geologically heterogeneous regions.

Semiquantitative Risk Assessment Method for Groundwater Source Protection Using a Process-based Interdisciplinary Approach

Potable groundwater resources are at risk as a result of industrial development and an increase in fertilizer use. Protection of the groundwater supply may require the establishment of groundwater source protection zones (GSPZs) to allow the implementation of protective measures. The aim of this study was to develop a new approach to groundwater source risk assessment (GSRA). The risk was defined as the highest of the risks identified for individual potential sources of contamination (PSCs). The risk resulting from a given PSC is the combination of its adverse impact on groundwater, unwanted event probability, and adverse effect and annoyance to the population. A multicriteria assessment method was designed to estimate indices of the potential groundwater impact of industrial facilities and noninert waste landfills with the range and weight method. Application of the proposed approach was tested considering an idealized model and three scenarios involving various industrial PSCs and fertilization practices. The overall nitrogen load was compared to the maximum effective nitrogen load for the crops in question. Sensitivity analysis of this methodology revealed that the main factors influencing the risk to the water supply include the nonreactive contaminant mass load in PSC leachate and the ratio of the groundwater volume abstracted from wells to the amount of water flowing from PSCs into wells, which determines the dilution degree of the contaminant mass. This proposed interdisciplinary approach to GSRA provides a robust basis to reach decisions on GSPZ establishment and the development of a groundwater risk analysis methodology.

The Journey of Establishing Groundwater Source Protection Zones in Kosovo on Example of Lipjan Municipality

The Journey of Establishing Groundwater Source Protection Zones in Kosovo on Example of Lipjan Municipality

Application of Geophysical and Hydrogeochemical Methods to the Protection of Drinking Groundwater in Karst Regions.

To provide theoretical support for the protection of centralized drinking groundwater sources in karst areas, it is necessary to accurately identify the development of karst conduits and analyze the differences in hydrogeochemical characteristics of different karst systems. This provides a scientific basis for the accurate designation of risk zones that may cause drinking groundwater pollution. In this study, a geophysical survey, hydrogeological chemical process analysis and optimized fuzzy cluster analysis were used to gradually improve the understanding of karst water systems. AMT and HDR methods were used to calibrate the resistivity around the water-filling karst conduits, which ranged from 39 to 100 Ω·m. A total of seven karst systems were identified, including four karst systems in the north of the study area, one karst system in the west and two karst systems in the south. Analysis of the hydrochemical data showed that HCO3-Ca and HCO3-Mg-Ca types accounted for 90% of all samples. The δD and δ18O values of their main conduits were −51.70‰ to −38.30‰ and −7.99‰ to −5.96‰, respectively. The optimized fuzzy clustering analysis method based on the weight of variables assigned by AHP more accurately verified karst water systems. Based on these findings, the drinking groundwater source risk zone was designated with an area of 33.90 km2, accounting for 34.5% of the study area. This study effectively improved the rationality and accuracy of the designation of drinking groundwater source risk zones in karst areas, and provided a scientific basis for the identification of karst water systems and decision-making of drinking groundwater source protection in karst areas.

Groundwater Exploitation Zoning Aiming at Management of Sustainable Groundwater Exploitation and Use in Ca Mau Peninsula, Vietnam

The research is financed by KC08.08/16-20: Study of measures for mitigating and adapting to drought and salinity intrusion as natural hazards in Camau peninsula , Ministry of Science and Technology, Vietnam Abstract Groundwater system in Camau Peninsula has 6 main aquifers (not including very poorly productive qh aquifer), of which 4 aquifers are predominantly exploited, namely qp 2-3 , qp 1 , n 2 2 and n 2 1 ; 2 minor aquifers are qp 3 and n 1 3 . Although the aquifers are located over the area, due to complicated fresh/saline interfaces in sections, exploitation and protection of groundwater sources is dealing with many problems. In the paper, information of aquifers is systematized into a map of groundwater exploitation zoning on scale 1:200,000 for the purpose of supplying essential information of water sources management in each socio-economical zone. Keywords : Camau peninsula, potential exploitable groundwater reserve. DOI: 10.7176/JEES/10-4-04 Publication date: April 30 th 2020

Monitoramento da água de poços como estratégia de avaliação sanitária em Comunidade Rural na Cidade de São Luís, MA, Brasil

Como ações de saneamento são escassas ou inexistentes no meio rural, o monitoramento das fontes de água permite o diagnóstico dos riscos e da precariedade das situações de saneamento. Neste estudo foi monitorado sazonalmente a qualidade da água dos poços da comunidade rural “Cinturão Verde” por meio de análises físico-químicas, colimétricas, e parasitológicas para identificação de fontes de contaminação devido à ausência de meios adequados de saneamento. Foram analisadas amostras coletadas em quatro períodos sazonais e detectados coliformes acima dos padrões de potabilidade do Ministério da Saúde nos poços tubulares em três dos quatro períodos sazonais. Foi detectada também a presença de parasita no período seco. Os parâmetros físico-químicos também estavam fora dos padrões da legislação em algumas estações, e foi constatado que esses riscos eram devido à inexistência de serviços de saneamento como: abastecimento com poços sem tratamento, precariedade de esgotamento e proximidade dos mananciais à criação de animais. Conclui-se que o monitoramento permitiu detectar períodos de riscos no uso de águas dos poços, avaliar diferenças regionais, e a necessidade de medidas de desinfecção da água antes de ser utilizada. Estas medidas de saneamento rural podem garantir a proteção dos mananciais de águas subterrâneas.

Karst groundwater source protection based on the time-dependent vulnerability assessment model: Crnica springs case study, Eastern Serbia

The implementation of sanitary protection zones is one of the most widely used approaches for preventive groundwater protection. Current regulations are usually based on the determination of the horizontal groundwater travel time component, while the vertical component is commonly neglected. Karst aquifers are especially sensitive to contamination through the unsaturated zone, and consequently numerous methods for determining intrinsic vulnerability have been developed. Many of these methods take into account the effects in the unsaturated zone, but mostly by indirect means. Vulnerability assessment methods do not fully reflect the component of groundwater residence time, making groundwater delineation zoning more difficult, with possible ambiguous and subjective results. Therefore, a method that incorporates the two equally important components (horizontal and vertical) is needed to facilitate groundwater protection zoning. The time-dependent model represents a redesigned vulnerability assessment method, created for karst aquifers, to incorporate the travel time component. This model incudes horizontal and vertical groundwater flow components and also considers a surface component toward ponor zones. The baseline for groundwater travel time through the unsaturated zone was adopted from the Time–input method. The estimation of the horizontal travel time component was based on the conceptual duality of flow in karst aquifers, which has fast and slow components. For the allogenic part of the karst aquifer catchment area (subcatchments of the ponor zone) travel time components were estimated according to different influencing factors e.g. slope, soil type, vegetation, and rainfall intensity. This methodology was tested on the case example of the Crnica karst source located at the western part of the Kucaj anticline in Eastern Serbia. The methodology was shown to be more accurate and appropriate for the delineation of the groundwater protection zones than existing approaches.

The Importance of Groundwater Vulnerability Maps in the Protection of Groundwater Sources. Key Study: Sarajevsko Polje

In order to ensure effective protection of groundwater sources, it is important to take into account all pollutants and activities that may present a potential risk. In the last period, as a useful tool in the protection of groundwater vulnerability mapping is applied. There are many methods for mapping groundwater vulnerability, some of which are more applicable than others. Although the use of and the choice of methods for assessing vulnerability depending on data availability, scale mapping, spatial distribution of data, hydrogeological and hydrological characteristics and many other parameters that serve as inputs for obtaining valid results.In this regard, this paper will analyze several methods for assessing the vulnerability of groundwater, which can be applied to the source of groundwater in the Sarajevo area. After the analysis, the results of completed vulnerability assessment, and mapping of groundwater vulnerability in the exploration area will be displayed using the COP method. The results will be presented with the help of GIS tools and presented in the form of maps of vulnerability for the catchment area of Sarajevsko Polje.

Evaluation de la vulnérabilité d’un puits pour la protection d’un captage d’eau souterraine basée sur un modèle de transport de soluté: étude de cas au niveau de la ville de Jilin, Nord-Est de la Chine

Well vulnerability assessment is essential for groundwater source protection. A quantitative approach to assess well vulnerability in a well capture zone is presented, based on forward solute transport modeling. This method was applied to three groundwater source areas (Jiuzhan, Hadawan and Songyuanhada) in Jilin City, northeast China. The ratio of the maximum contaminant concentration at the well to the released concentration at the contamination source (c max/c 0) was determined as the well vulnerability indicator. The results indicated that well vulnerability was higher close to the pumping well. The well vulnerability in each groundwater source area was low. Compared with the other two source areas, the cone of depression at Jiuzhan resulted in higher spatial variability of c max/c 0 and lower minimum c max/c 0 by three orders of magnitude. Furthermore, a sensitivity analysis indicated that the denitrification rate in the aquifer was the most sensitive with respect to well vulnerability. A process to derive a NO3−N concentration at the pumping well is presented, based on determining the maximum nitrate loading limit to satisfy China’s drinking-water quality standards. Finally, the advantages, disadvantages and prospects for improving the precision of this well vulnerability assessment approach are discussed.

Start, development and status of the regulator-led national groundwater resources modelling programme in England and Wales

Abstract Over the last 10 years there has been a unique regulator-led programme involving extensive development of regional groundwater models across England and Wales for water resources purposes by the Environment Agency for England and Wales. Eight regionally managed programmes are underpinned by a framework, which has allowed a coordinated national approach. The main uses of the models are for catchment abstraction management and licensing. Models have also assisted in monitoring network design, investigating groundwater quality and implementing groundwater source protection zones. A five-yearly review of the programmes recognized the importance of benefit realization and stakeholder involvement as well as technical good practice. The programme already delivered provides a solid foundation for supporting the management decisions required in areas such as climate change mitigation and integrated catchment management using appropriate tools at a time of rapid organization change and financial uncertainty.

Anomalous behaviour of specific electrical conductivity at a karst spring induced by variable catchment boundaries: the case of the Podstenjšek spring, Slovenia

AbstractAnomalous behaviour of specific electrical conductivity (SEC) was observed at a karst spring in Slovenia during 26 high‐flow events in an 18‐month monitoring period. A conceptual model explaining this anomalous SEC variability is presented and reproduced by numerical modelling, and the practical relevance for source protection zoning is discussed. After storm rainfall, discharge increases rapidly, which is typical for karst springs. SEC displays a first maximum during the rising limb of the spring hydrograph, followed by a minimum indicating the arrival of freshly infiltrated water, often confirmed by increased levels of total organic carbon (TOC). The anomalous behaviour starts after this SEC minimum, when SEC rises again and remains elevated during the entire high‐flow period, typically 20–40 µS/cm above the baseflow value. This is explained by variable catchment boundaries: When the water level in the aquifer rises, the catchment expands, incorporating zones of groundwater with higher SEC, caused by higher unsaturated zone thickness and subtle lithologic changes. This conceptual model has been checked by numerical investigations. A generalized finite‐difference model including high‐conductivity cells representing the conduit network (“discrete‐continuum approach”) was set up to simulate the observed behaviour of the karst system. The model reproduces the shifting groundwater divide and the nearly simultaneous increase of discharge and SEC during high‐flow periods. The observed behaviour is relevant for groundwater source protection zoning, which requires reliable delineation of catchment areas. Anomalous behaviour of SEC can point to variable catchment boundaries that can be checked by tracer tests during different hydrologic conditions. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Contributory area definition for groundwater source protection and hazard mitigation in carbonate aquifers

Abstract Carbonate aquifers provide important sources of potable water but are known to be particularly prone to pollution owing to rapid transfer of pollutants from the surface to springs or boreholes. Source protection zones and groundwater vulnerability maps are commonly used to mitigate against the pollution hazard but cannot be applied simplistically to carbonate aquifers, which are usually highly heterogeneous with overlapping groundwater divides that may vary with water levels. Divergent flow and disjunct contributory areas provide further complexity. Under these conditions, water-tracing experiments, repeated under different flow conditions, are the only tool capable of identifying those areas that contribute recharge to a particular source. Examples of water pollution affecting disjunct and overlapping source contributory areas are presented from the Waitomo area (New Zealand), Cuilcagh Mountain (Ireland) and the Peak District (UK). Source protection zones (SPZ), that have been defined by the Environment Agency in the Buxton area of the Peak District using equivalent porous medium models, are shown to be deficient. Further water-tracing experiments are essential if carbonate aquifers are to be adequately protected from pollution.

Tracer tests, hydrochemical and microbiological investigations as a basis for groundwater protection in a remote tropical mountainous karst area, Vietnam

The Tam Duong karst area in NW Vietnam is among the poorest and remotest regions in the country. The local population largely depends on water from two main karst springs. Due to agricultural activity and untreated domestic wastewaters, the spring water is often microbiologically contaminated. In order to provide a scientific basis for groundwater protection in the area, different field methods have been applied including hydrogeological framework investigations, tracer tests, and hydrochemical and microbiological sampling and analyses. All methods had to be adapted to the conditions of a poor and remote area. These adaptations included, amongst other measures, the use of a portable microbiological water_testing kit and the involvement of the local population in the sampling campaign. The tracer tests showed simple and direct connections between two important swallow holes and the two main springs, and made it possible to determine the linear groundwater flow velocities, which are extremely high (up to 875 m/h). The hydrochemical and microbiological data confirmed the strong impact of the streams sinking into the swallow holes on the spring water quality. Future groundwater source protection strategies should consequently focus on the reduction of polluting activities near the sinking streams and within their catchment areas.

Local Groundwater Source Protection in Ontario and the Provincial Water Protection Fund

Contamination of the water supply of the Town of Walkerton, in May 2000, reinforced the importance of source water protection. The Province of Ontario has since instituted a number of changes in legislation, regulations, policies and practices. Some of these initiatives build on lessons learned through a series of local groundwater management studies that were undertaken through the Provincial Water Protection Fund (PWPF), a program launched by the Ontario Ministry of the Environment in 1998. This paper explores factors that facilitate and constrain groundwater source protection by municipalities and conservation authorities in Ontario. Findings are based on an evaluation of groundwater source protection activities in the communities that participated in the PWPF Groundwater Management Studies (GMS) program. The experiences of the study communities reinforced the importance of leadership (local and provincial); financial resources, skilled staff, and data; horizontal and vertical linkages among the various key organizations and stakeholders; appropriate institutional arrangements; and public support and awareness. Overall, this research found that the PWPF GMS made significant contributions to the state of local groundwater source protection in Ontario and provided a launching pad for subsequent work in many areas.

Implications of flow patterns in the sandstone aquifer beneath the mature conurbation of Nottingham (UK) for source protection

The protection of groundwater sources in urban areas is difficult due to uncertainties in hydrogeology, future changes in pumping, and complexities of land use. This paper presents an improved understanding of the hydrogeology of the Permo–Triassic Sherwood Sandstone aquifer underNottingham, and considers protection policies for this example of a highly developed groundwater system. Groundwater flow models were constructed for the pre-industrial period (before 1850) and for the 1980 s, and confirmed the existing conceptual model of the hydrogeology. In the early period, spring flows were much more significant than they are now, while abstractions through wells account for virtually all the discharge in the recent period. In recent decades, abstraction has fallen, but there has been a significant reduction in recharge from mains leakage so that there has been no overall rise in groundwater levels. Particle tracking revealed that during recent times the regional aquifer has behaved as a series of local flow cells rather than a regional whole due to the numerous abstractions. Wells in the unconfined aquifer capture most of the urban (and potentiallypolluted) recharge with travel-times up to 200 years. Confined wells with travel-times over 10 4 years, will abstract pre-industrial waters for years to come, and are likely to be protected by natural attenuation of pollutants. Deterministic source protection zones will not be fully protective of public and industrial water supplies, due to the likely changes in pumping regimes in future and the resourcing implications of attempting to control polluting activities over the whole city. A risk-based approach to managing urban groundwater may be more practical and useful. It could predict the risks to existing water supplies, and help in the selection of low risk locations for new wells.