Wellhead Protection Areas Research Articles

Delineating well-head protection areas under conditions of hydrogeological uncertainty. A case-study application in northern Greece

The delineation of well-head protection areas, especially for water supply wells, is of most importance in ensuring water quality. The areas delineated under this concept must be large enough to ensure that no pollutants will end-up and be pumped-off by abstraction wells but at the same time, small enough to minimize the social and economic cost of applying restriction measures to nearby land owners. The whole concept of applying well-head protection areas is based on the recognition of the hydrogeological parameters of the aquifer. The fact that these parameters are, by nature, characterized by uncertainty makes the whole application very difficult. In this paper, the delineation of well-head protection areas is simulated through a mathematical model and the methodology is applied on the aquifer of Moudania in Chalkidiki, taking into consideration a number of equally probable realizations of the geological structure of the aquifer. This aquifer is characterized by the spatial variability of its hydrogeological parameters, making the introduction of uncertainty in its simulation, an absolute necessity.

Numerical modeling to well-head protection area delineation, an example in Veneto Region (NE Italy)

The article presents an example of well-head protection area (WHPA) delineation in middle Venetian plain, using geostatistical simulation for the subsoil reconstruction, groundwater flow modeling and automatic calibration.

Influences of heterogeneity on three-dimensional groundwater flow simulation and wellhead protection area delineation in karst groundwater system, Taiyuan City, Northern China

Karstic limestone formation in Lancun spring area is one of the most important drinking water resources for Taiyuan City in Shanxi Province. The mapping of drinking water-protected areas is an effective way to protect drinking water sources. In this study, Lancun spring area in Taiyuan City was considered as a case study. Considering geological deposition and hydrogeological characteristics of this area, the stochastic idea was introduced to structural model establishment to determine the heterogeneity of karst groundwater system and clarify medium parameters. To analyze the influence of heterogeneity on groundwater flow simulation and wellhead-protected area delineation, homogeneous and stochastic hydrogeological parameter models were established and coupled with groundwater flow simulation models. Particle tracer analysis could be performed to determine capture zone. Results showed that stochastic methods could be used to generate a series of possible flow head field distributions and delineate a series of capture zones compared with homogeneous methods; thus, probability distribution was observed instead of a deterministic area. This result could provide a more scientific basis for the design and assessment of protective measures for wellhead areas in karst groundwater systems.

Delineation of Wellhead Protection Areas in the Umbria region. 2. Validation of the Proposed Procedure

In the companion paper [1] a procedure has been presented to delineate the wellhead protection areas in the Umbria region, where a large number of minor groundwater resources are exploited. While the national and the regional regulations do not differentiate in the protection area delineation guidelines between large and small resources, the proposed procedure allows increasing the model complexity with the increase in the resource relevance and hence in the degree of knowledge about the aquifer. In this paper the procedure is tested with reference to actual cases and the results of models with different complexity are compared. The importance of the effects of the mean-regional gradient on the delineation of the protection area for small catchments is pointed out.

Delineation of Wellhead Protection Areas in the Umbria Region. 1. A simplified Procedure

In the Umbria region a large number of small groundwater resources is exploited to supply drinkable water to customers. More than 400 of the wells and springs managed by Umbra Acque S.p.A., one of the three Umbrian managers, draw less than 10 l/s and about 240 of them supply less than 1 l/s. The national and the regional regulations do not differentiate in the protection area delineation guidelines between large and small resources, although different degree of knowledge about the aquifer and economical budget for the operation can be expected. For these reasons, here we propose a procedure for delineating the wellhead protection areas, based on simplified models and techniques, particularly suited for the Umbria region.

Insights from four decades of model development on the Waterloo Moraine: A review

Modelling has played a key role in the evolution of insights on the Waterloo Moraine groundwater system as a water source for Waterloo Region. As models evolved over the last four decades, so did new insights. Starting from a simple layer-cake concept, models eventually became three-dimensional, while the focus changed from well interference to multi-layer analysis, capture zone delineation, wellhead protection areas, groundwater age and the prediction of impact due to various land uses and threats. An important insight gained was that the reliability of predictive methods depends heavily on the travel paths from source to receptor, which in turn depend on the connectivity between the various hydrogeologic units – i.e. the conceptual model. The elusive issue of predictive uncertainty in the delineation of well capture zones is approached at two scales: the local scale representing uncertainty due to heterogeneities within the individual aquifer units, and the global scale representing different conceptualizations and scenarios, where the latter is found to be the dominant uncertainty. In the case of a multi-scenario analysis involving scenarios of equal plausibility, the precautionary approach can be used to arrive at a conservative prediction. Practical applications provide insights on the dynamics of groundwater systems, the impact of changes and threats being imposed and the effectiveness of mitigation measures, as well as the time scale at which threats and mitigation measures act. These insights should help hydrogeologists to use models more effectively, and to better understand and manage predictive uncertainties that inevitably arise in dealing with complex groundwater systems such as the Waterloo Moraine.

A collaborative approach to groundwater protection: The Rural Water Quality Program for Waterloo Region

Source water protection (SWP) efforts in many jurisdictions focus primarily on protecting municipal groundwater wells through a highly technical process known as wellhead protection planning (WHPP). Less attention has been given to implementing a broader approach for protecting groundwater supplies both within and outside municipal wellhead protection areas through stewardship and other approaches that engage diverse stakeholders. Technical approaches to drinking-water safety are necessary, but increasingly it is recognized that they are not sufficient in the context of a complex problem such as groundwater protection. There is growing recognition globally that solutions to complex problems require decision-making processes that involve the integration of expert science, local knowledge and community beliefs and values. In this paper, the example of groundwater protection in the Region of Waterloo, Ontario, is used to illustrate how collaborative approaches can facilitate the integration of scientific and local knowledge with existing community beliefs and values. Factors drawn from the academic and empirical literature are identified and used to evaluate the contribution of stakeholders to program development and implementation.

Wellhead protection area delineation using multiple methods: a case study in Beijing

Determining a wellhead protection area (WHPA) is a basic and important step in protecting groundwater from contamination. Based on availability of data and complexity of hydrogeological conditions, different delineation methods can be adopted. This study’s objective was to examine the relation and difference of the results calculated using six WHPA delineation methods, which ranged from simplified shapes to stochastic models with superior sampling means. All the methods were applied to a well field in Beijing, China. The WHPA probability distribution from a stochastic simulation was used as reference for comparison with other methods. WHPAs calculated using simplified and analytical approaches turned out to be smaller than reference WHPA. Those calculated using the numerical model provided better results but still cannot include a considerable area of reference WHPA. The stochastic approach based on efficient orthogonal Latin hypercube sampling provided an estimation of the probability distribution of WHPA delineation with different degrees of uncertainty, which played an important role in the WHPA delineation of the well field in Beijing. To attain a realistic WHPA delineation in a complex aquifer system, various delineation approaches can be adopted and all results that validate each other must be considered.

An integrated approach for addressing uncertainty in the delineation of groundwater management areas

Uncertainty is a pervasive but often poorly understood factor in the delineation of wellhead protection areas (WHPAs), which can discourage water managers and practitioners from relying on model results. To make uncertainty more understandable and thereby remove a barrier to the acceptance of models in the WHPA context, we present a simple approach for dealing with uncertainty. The approach considers two spatial scales for representing uncertainty: local and global. At the local scale, uncertainties are assumed to be due to heterogeneities, and a capture zone is expressed in terms of a capture probability plume. At the global scale, uncertainties are expressed through scenario analysis, using a limited number of physically realistic scenarios. The two scales are integrated by using the precautionary principle to merge the individual capture probability plumes corresponding to the different scenarios. The approach applies to both wellhead protection and the mitigation of contaminated aquifers, or in general, to groundwater management areas. An example relates to the WHPA for a supply well located in a complex glacial aquifer system in southwestern Ontario, where we focus on uncertainty due to the spatial distributions of recharge. While different recharge scenarios calibrate equally well to the same data, they result in different capture probability plumes. Using the precautionary approach, the different plumes are merged into two types of maps delineating groundwater management areas for either wellhead protection or aquifer mitigation. The study shows that calibrations may be non-unique, and that finding a "best" model on the basis of the calibration fit may not be possible.

Delineating cost‐effective wellhead protection zones in a rural area in Greece

AbstractThe aim of this study is the protection of groundwater resources from nitrate pollution by regulating land use and by establishing guidelines for agricultural activities within specific wellhead protection areas. Wellhead protection zones are specifically designed in four wells in the municipality of Nea Moudania, an area of intensive agricultural activities in northern Greece. Recent water samples from these wells indicate high levels of nitrates concentrations. Wellhead protection areas are delineated through a geographic information systems (GIS) analysis in order to determine the boundaries of protection zones, as well as to identify the land use patterns and the specific crop types around the contaminated wells. Different land use management techniques for groundwater protection zoning are also examined with respect to their implementation cost. The purpose of this analysis is to identify the least expensive management strategy for wellhead protection. The results show that land use changes are always more expensive than implementing agro‐environmental measures.

Avaliação de métodos para a proteção dos poços de abastecimento público do Estado de São Paulo

Os perímetros de proteção de poços têm importante papel na proteção da qualidade da água subterrânea explotada para fins de abastecimento público. Existem vários métodos que permitem definir as dimensões e os formatos das zonas de contribuição, ou seja, a área em superfície onde toda recarga do aquífero é captada pelo poço, além de zonas baseadas em tempos de trânsito, definidas no tempo em que um determinado contaminante pode alcançar o poço. Ambas as zonas permitem o controle do uso do solo com o objetivo de proteger a captação. Este artigo apresentou um estudo comparativo entre três diferentes métodos aplicados nos diferentes aquíferos do Estado de São Paulo. Os métodos estudados foram: raio fixo calculado, baseado na técnica do cilindro, que usa equação de fluxo volumétrico; modelo analítico, com uso da equação de fluxo uniforme; e modelo numérico, por meio de modelos matemáticos de simulação de fluxo. Os resultados mostraram que cada método gerou áreas diferentes, tanto em formato como em dimensões. Os dois primeiros métodos definiram tamanhos de zonas de contribuição semelhantes, porém com formatos diferentes, e aproximadamente 200% maiores do que aqueles definidos com o numérico para as mesmas condições hidrogeológicas. Pelos resultados, depreende-se que a utilização do método analítico é viável numa primeira avaliação, pois os dados para tal já se encontram disponíveis para quase todos os poços de abastecimento público do Estado e sua acurácia é superior ao método raio fixo calculado. Já numa fase posterior, na qual a definição das zonas de contribuição seja mais sensível, o modelo numérico seria a alternativa natural.

Aquifer Vulnerability Assessment and Wellhead Protection Areas to Prevent Groundwater Contamination in Agricultural Areas: An Integrated Approach

To implement successful policies for the protection of groundwater and curtail the possibility of water supply contamination, an early evaluation of aquifer vulnerability is needed. Rather than implementing broad restrictions to land use and effluent discharge, it is more cost-effective and economically favourable to approach protection in a stepwise manner by first assessing the intrinsic vulnerability of the aquifer when defining the level of land use control that is needed to protect groundwater quality. Following aquifer vulnerability evaluation, specific land uses and restrictions should be defined locally for each water supply within the wellhead protection areas (WHPAs), which are identified by means of the groundwater time of travel (TOT). The WHPA should be established for each individual situation, considering the level of vulnerability of the exploited aquifer. We applied our findings to a specific test site in the Piemonte region of NW Italy, following the current local procedure for individuating the WHPAs. Using data gathered from this site-specific exercise, we identified that the procedure allows methods that consider only aquifer parameters to evaluate vulnerability and discourages the use of techniques that already compartmentalize soil parameters in the vulnerability assessment.

Protection of groundwater intended for human consumption: a proposed methodology for defining safeguard zones

Carbonate aquifers constitute a water reserve of essential importance for human supply. For this, it is necessary to establish suitable protection measures in order to achieve the good status of groundwater bodies intended for human supply according to the requirements of the Water Framework Directive. The objective of this paper is to present a methodology to define safeguard zones for the protection of carbonate groundwater bodies intended for human consumption. To do this, firstly the risk of groundwater contamination is evaluated through a combination of characterising pressures and the evaluation of the intrinsic vulnerability to contamination. Secondly, the existing water abstraction points are identified and their zones of contribution are delineated in order to establish priorities when defining protective measures in the region. Finally, the existing wellhead protection areas and those defined according to the proposed methodology must be integrated into the delineated safeguard zones. The results obtained in a carbonate groundwater body in southern Spain are consistent with the existing quality data and they show the percentage of land that must be protected to preserve the quality of water intended for human consumption, thus facilitating their future integration into adequate land use planning tools.

Conceptual Framework for Protecting Groundwater Quality

A conceptual framework is defined to establish safeguard zones in groundwater bodies intended for drinking water according to the requirements of the Water Framework Directive. For this, the foundations of a three-phase methodology within a dynamic process are proposed. The results of the first two phases are presented, which contemplate the distribution of groundwater body abstraction points as well as hydrogeological criteria, evaluation of pressures and aquifer vulnerability, in addition to the defined wellhead protection areas of abstraction points. As a final proposal, it will be necessary for competent authorities to create a recommendations and restrictions guideline, which should be integrated into the rest of the policies related to land-use planning in order to protect groundwater adequately.

Groundwater Protection Using Vulnerability Maps and Wellhead Protection Area (WHPA): A Case Study in Mexico

The need to protect groundwater resources against quality deterioration due to anthropogenic activities is unquestionable. The concept of aquifer pollution vulnerability maps and of wellhead protection areas (WHPA) as protection tools is not new; however, in spite of the elapsed time, their use has been increased as a result of the increase in economic development—and everything that this entails—and the increase in prohibitive costs of treating contaminated water or of the decontamination of aquifers. The study’s objective was to establish an integrated method that defines, first of all, the areas of highest vulnerability in the aquifer, and second, within these areas, the wells that most urgently need protection. To identify these wells, additional criteria were taken, such as well constructive data, pumped volume, and the region’s socioeconomic characteristics (social exclusion index). Once the wells were ranked, several of them were chosen as a pilot study to compare different methods for the delineation of WHPA based on calculated fixed radius and analytical methods and, this way, identify which method or methods best adapt to the characteristics of the study area. The Minkin analytical method proved to offer the best results since it protects well on both sides and achieves a balance in the well’s upgradient distances. It is also worth mentioning that the delimitation of the WHPAs in the study area was limited in respect to hydrogeologic and technical data.

Comparative Identification of Wellhead Protection Areas for Municipal Supply Wells in Gaza

Groundwater is the only source of fresh water in Gaza Strip while its inhabitants and its water consumption increased rapidly. This study aims at preserving and protecting the groundwater from any pollutants caused by 141 industrial installations through the work of delineation of Wellhead Protection Areas (WHPA) for 47 Municipal Supply Wells in Gaza Governorate boundaries. WHPA has been determined in three different methods: Calculated Fixed-Radius Method (CFR), Analytical Method (AM), and Wellhead Analytic Ele-ment Model (WhAEM2000) which is currently used by the United States Environmental Protection Agency (EPA). These methods mainly depend on the time it takes groundwater to travel a specified horizontal dis-tance. Three well zones were delineated for each municipal production well, the first zone is 50 days time of travel (TOT), the second zone is 2 years TOT and the third zone is 5 years TOT. Different values of the ra-dius of WHPA of each well were obtained using the three methods. Consequently, several industrial installa-tions were laid inside the WHPA according to the radius values. The results show that CFR method is the weakest method because it does not take into account regional groundwater flow, causing a hydraulic gradi-ent. WHPAs identified by these methods may be either too large or too small, resulting in wellhead overpro-tection or under protection. Analytical Method incorporates hydrogeologic characteristics of the aquifer, groundwater flow, and hydrogeologic boundaries into the model. Often produces a WHPA that is smaller than the one produced using CRF. WhAEM2000 method is the best method because it uses a hydrogeologi-cal computer model of groundwater flow and it provides a more accurate delineation of the WHPA. It often produces a smaller area to manage than other methods. The study concluded that all industrial installations located in the WHPA should be carefully checked and investigated by governmental authorities. Mitigation measures for pollutants and licenses for the establishment of any new industrial installations could be based on the delineation of WHPAs using the previously mentioned methods.

KT3D_H2O: A Program for Kriging Water Level Data Using Hydrologic Drift Terms

It is often necessary to estimate the zone of contribution to, or the capture zone developed by, pumped wells: for example, when evaluating pump-and-treat remedies and when developing wellhead protection areas for supply wells. Tonkin and Larson (2002) and Brochu and Marcotte (2003) describe a mapping-based method for estimating the capture zone of pumped wells, developed by combining universal kriging (kriging with a trend) with analytical expressions that describe the response of the potentiometric surface to certain applied stresses. This Methods Note describes (a) expansions to the technique described by Tonkin and Larson (2002); (b) the concept of the capture frequency map (CFM), a technique that combines information from multiple capture zone maps into a single depiction of capture; (c) the development of a graphical user interface to facilitate the use of the methods described; and (d) the integration of these programs within the MapWindow geographic information system environment. An example application is presented that illustrates ground water level contours, capture zones, and a CFM prepared using the methods and software described.

RISCO DE POLUIÇÃO DAS ÁGUAS SUBTERRÂNEAS POR VAZAMENTOS EM POSTOS DE ABASTECIMENTO DE COMBUSTÍVEL, NO MUNICÍPIO DE RIBEIRÃO PRETO – SP.

In Ribeirão Preto - SP, the quality of the groundwaters is before a potential threat for leak of the several fuels storage tanks. In the present study, it was aimed at to evaluate the space and temporary distributions of the hydrocarbons concentrations around the wells of activated pumping, and to delineate the areas of protection of wells (APPs), around the wells of public provisioning of water, for calculation of the risk for human health. The models were used APIDSS (American Petroleum Institute Decision Support System) and WHPA (Well Head Protection Area): semi-analytical models, through the software Well Head Protection Área (WHPA) and models of API, like SESOIL (SEasonal SOIL), AT123D and JURY, contained in the package APIDSS. The results demonstrated risk of adverse effect to the human health in a well (50A), and the need of constant monitoring of the located positions inside APPs, seeking to the conservation of the good quality of water distributed for the consumption of the population of Ribeirão Preto - SP.

Reducing Capture Zone Uncertainty with a Systematic Sensitivity Analysis

The U.S. Environmental Protection Agency has established several methods to delineate wellhead protection areas (WHPAs) around community wells in order to protect them from surface contamination sources. Delineating a WHPA often requires defining the capture zone for a well. Generally, analytical models or arbitrary setback zones have been used to define the capture zone in areas where little is known about the distribution of hydraulic head, hydraulic conductivity, or recharge. Numerical modeling, however, even in areas of sparse data, offers distinct advantages over the more simplified analytical models or arbitrary setback zones. The systematic approach discussed here calibrates a numerical flow model to regional topography and then applies a matrix of plausible recharge to hydraulic conductivity ratios (R/K) to investigate the impact on the size and shape of the capture zone. This approach does not attempt to determine the uncertainty of the model but instead yields several possible capture zones, the composite of which is likely to contain the actual capture zone. A WHPA based on this composite capture zone will protect ground water resources better than one based on any individual capture zone. An application of the method to three communities illustrates development of the R/K matrix and demonstrates that the method is particularly well suited for determining capture zones in alluvial aquifers.

An automatic, stagnation point based algorithm for the delineation of Wellhead Protection Areas

Time‐related capture areas are usually delineated using the backward particle tracking method, releasing circles of equally spaced particles around each well. In this way, an accurate delineation often requires both a very high number of particles and a manual capture zone encirclement. The aim of this work was to propose an Automatic Protection Area (APA) delineation algorithm, which can be coupled with any model of flow and particle tracking. The computational time is here reduced, thanks to the use of a limited number of nonequally spaced particles. The particle starting positions are determined coupling forward particle tracking from the stagnation point, and backward particle tracking from the pumping well. The pathlines are postprocessed for a completely automatic delineation of closed perimeters of time‐related capture zones. The APA algorithm was tested for a two‐dimensional geometry, in homogeneous and nonhomogeneous aquifers, steady state flow conditions, single and multiple wells. Results show that the APA algorithm is robust and able to automatically and accurately reconstruct protection areas with a very small number of particles, also in complex scenarios.