Wellhead Protection Area Delineation Research Articles

Optimization-based clustering of random fields for computationally efficient and goal-oriented uncertainty quantification: Concept and demonstration for delineation of wellhead protection areas in transient aquifers

A general approach to deal with parameter uncertainty in natural systems is to use ensembles of many parameter realizations. However, this might result in extremely expensive computational time, especially when additional loops for transient simulation and for optimization are involved. One possibility to mitigate computing time is to use few but well-selected realizations that best represent the involved geological uncertainties, e.g., by clustering techniques.The goal of this paper is to address the search for representative realizations that best approximate the distribution and its tails of a model ensemble. In our test application, this ensemble is used to delineate wellhead protection areas (WHPAs) under transient flow conditions and subject to random heterogeneity of the aquifer. Our approach is based on clustering and proposes that the cluster medoids (representatives) should be optimized not for “statistical representation in the space of some selected proxy metrics”, but for “a minimum of decision-relevant errors”. And, if the underlying decision problem is multi-objective, then the clustering optimization can be made multi-objective, too. In this way, many subsequent analyses can be performed on the condensed set of representative scenarios that would be computationally too expensive otherwise, even if distribution tails and extreme realizations are relevant. We demonstrate the advantage of our clustering optimization methodology on a dynamic probabilistic WHPA delineation, and we compare its performance with a standard clustering analysis.Our results show that: (1) in probabilistic transient WHPA analysis, clustering is a suitable technique to account for geological uncertainty. (2) However, clustering analysis should be based on optimization concepts rather than on simple medoid concepts, and (3) of course, it should use problem-specific and decision-relevant metrics for cluster optimization. In our WHPA application, this leads to a more accurate representation of decision-relevant statistical extremes. (4) The additional extension to multi-objective cluster selection probes to be a valid approach in multi-objective WHPA delineation. (5) Using our framework, we reduce the computational cost of addressing highly expensive simulations.

Delineation of wellhead protection area based on the analytical elements method (AEM) – a case study with comparative research

The delineation of protection zones for groundwater intakes is a difficult task resulting from the significant variability of regional and local environmental conditions. Different methods are used, both simple (analytical or graphic), giving estimated results, and the most reliable, but also the most time-consuming ones, based on numerical groundwater flow models. An alternative method for the delineation of protection zones is the analytical elements method (AEM), which gives solutions like those obtained using FDM/FEM modelling methods with a relatively low degree of complexity. The estimated ranges of protection zones obtained with the use of four methods are presented for the selected test area (groundwater intake around Olesno). Results obtained with the use of the FDM model were taken as reference and CFR and SimpleWHPA were used as simplified methods. Comparative studies indicate that the results obtained by the CFR method differ significantly from the results of other methods, and their reliability is low. The results of the SimpleWHPA method are satisfactory, given the relative simplicity of the method. On the other hand, the results obtained with the AEM are close to the results obtained with the FDM treated as a reference. Considering that AEM is less time-consuming than FDM (which requires the most effort for proper model preparation), the use of AEM in the practice of protection zone delineation seems to be an interesting alternative.

Delineation of Wellhead Protection Areas: Methodology and Application

About 97% of global fresh water is sourced from Groundwater, positioning it as an important, and sometimes the sole, source of drinking-water in many parts of the world. Sustainable Development Goals, Goal No. 6, calls to foster all efforts to ensure access to water and sanitation for all. Nevertheless, with groundwater providing nearly half the world population with drinking water, the responsibly of sustaining this resource is a priority to all. Pumping wells can sometimes, if not carefully protected, be an instant source of pollution to the groundwater. Wellhead protection areas (WHPAs) serve the purpose of protecting the quality of groundwater by means of restrictions imposed on land use activities within the WHPA. Many approaches are being used to delineate WHPAs all over the world. The study used the numerical groundwater flow modeling with particle tracking codes approach, as it allows full interaction of hydrogeological, land-use, PCS, and different extraction rates in delineating the WHPA. The study area is a drinking water plant, located in Menofia Governorate and belongs to the Nile Delta aquifer. The study used 50-day isochron horizontal travel distance for the three pumping wells, located in the drinking water plant. The WHPA radius was determined for wells and the resulted radii range from 37m to 54.5m. Keywords: Wellhead protection area, groundwater protection, contaminant transport, MT3D, groundwater modelling DOI: 10.7176/CER/13-4-04 Publication date: June 30 th 2021

A Dual Delineation Approach to Untangle Interferences in Well Doublets Systems.

Traditional numerical methods for the delineation of wellhead protection areas span deterministic and probabilistic approaches. They provide time-related capture zones. However, none of the existing approaches identifies the groundwater contribution areas related to each source or sink. In this work, the worthiness of the so-called double delineation approach was extended. This task was achieved by simple postprocessing of its dual outputs leading to a highly efficient screening tool. In the particular context of geothermal resources management through the well doublets of the Dogger aquifer in the Paris Basin (France), the approach was extended to forecast the compositional heat breakthrough at production wells. Hence, cold-water breakthrough and temperature decline in production wells are timely assessed in low-enthalpy geothermal reservoirs. The method quantifies how groundwater volumes are moving through space and time between any couple of source and sink. It provides unprecedented tools advancing the enhanced understanding of water resources systems functioning. It is highly recommended to implement the presented concepts in the current and future generations of community groundwater models.

Comparative Study of Methods for Delineating the Wellhead Protection Area in an Unconfined Coastal Aquifer

Various delineation methods, ranging from simple analytical solutions to complex numerical models, have been applied for wellhead protection area (WHPA) delineation. Numerical modeling is usually regarded as the most reliable method, but the uncertainty of input parameters has always been an obstacle. This study aims at examining the results from different WHPA delineation methods and addressing the delineation uncertainty of numerical modeling due to the uncertainty from input parameters. A comparison and uncertainty analysis were performed at two pumping sites—a single well and a wellfield consisting of eight wells in an unconfined coastal aquifer in Israel. By appointing numerical modeling as the reference method, a comparison between different methods showed that a semi-analytical method best fits the reference WHPA, and that analytical solutions produced overestimated WHPAs in unconfined aquifers as regional groundwater flow characteristics were neglected. The results from single well and wellfield indicated that interferences between wells are important for WHPA delineation, and thus, that only semi-analytical and numerical modelling are recommended for WHPA delineation at wellfields. Stochastic modeling was employed to analyze the uncertainty of numerical method, and the probabilistic distribution of WHPAs, rather a deterministic protection area, was generated with considering the uncertain input hydrogeological parameters.

PROBLEMS OF DESIGNING AND SANITARY-EPIDEMIOLOGIC EXPERTIZE OF PROJECTS OF SANITARY PROTECTION ZONES OF UNDERGROUND WATER SUPPLY SOURCES

Introduction. One of the main tasks in the area of public health in Russia is the adequate quality of drinking water supply, i.e. its sound chemical composition and epidemiological safety. The latter is provided among others, by proper wellhead protection activities which aim to ensure sanitary protection of water intakes, water supply and distribution facilities and sites of their location from anthropogenic influence. The aim of the study. The analysis of most common errors revealed during the expertize of wellhead protection (WHP) plans for groundwater intakes. Material and Methods. laws and regulations related to wellhead protection plan development, particular WHP plans, related technical papers. The study is methodologically based on common scientific approaches to investigate social interactions in the field of drinking and domestic water supply such as analytical, comparative, structured system analysis. Results. It is shown that a great deal of uncertainty exists in practical assessment of parameters necessary to estimate wellhead protection area that makes wellhead protection area delineation rather approximate. To enhance the reliability of estimates it is necessary to account for a minimal set of estimation indices and increase the requirements to the quality and scope of project documentation. Conclusion. Authors set forth a complex of additional investigations to refine parameter estimates for wellhead protection plan development, and several new requirements for the project design regarding both the textual part and graphics. Some recommendations to amend current regulations related to wellhead protection are also suggested.

Issues and Options in the Delineation of Well Capture Zones under Uncertainty.

The delineation of wellhead protection areas (WHPAs) under uncertainty is still a challenge for heterogeneous porous media. For granular media, one option is to combine particle tracking (PT) with the Monte Carlo approach (PT-MC) to account for geologic uncertainties. Fractured porous media, however, require certain restrictive assumptions under this approach. An alternative for all types of media is the capture probability (CP) approach, which is based on the solution of the standard advection-dispersion equation in a backward mode, making use of the analogy between forward and backward transport processes. Within this context, we review the current controversy about the correct form of the conceptual model for transport, finding that the advection-diffusion model, which represents the diffusive interchange between streamtubes with differing velocities, is more physically realistic than the conventional advection-dispersion model. For mildly to moderately heterogeneous materials, stochastic theories and simulation experiments show that this process converges at the field scale to an effective advection-dispersion process that can be simulated with conventional transport models using appropriate macrodispersivity values. For highly heterogeneous materials, stochastic theories do not yet exist but there is no reason why the process should not converge naturally as well. Macrodispersivities appear to be formation-specific. The advection-dispersion model can be used for capture zone delineation in heterogeneous granular media. For fractured porous systems, hybrid equivalent porous medium and discrete fracture network or CP-based approaches may have potential. In general, capture zones delineated by PT without MC will always be too small and should not be used as a basis for land-use decisions.

Delineation of Wellhead Protection Areas Containing Seepage Lakes

AbstractThe conventional method of delineating wellhead protection areas using travel times is not well suited for application in wellfields containing seepage lakes. The concentration factor is id...

Delineation of Wellhead Protection Areas in Crete, Greece Using an Analytic Element Model

Groundwater is one of the main sources of drinking water in many regions and therefore investing in its protection is of paramount importance. A very important step in ensuring water of good quality is the delineation of well head protection areas (WHPAs), which is the focus of this research. The area of interest is the basin of the Keritis River, located near the city of Chania, Crete, Greece. The main contamination threats in the area are: i) olive oil industries ii) cemeteries and iii) urban waste from the towns located near or within the basin. The delineation of WHPAs in this work is performed using a more accurate method than a simple fixed radius around the well, which is currently common practice in Greece. A decision support modeling tool called Wellhead Analytical Element Model (WhAEM) was used for this purpose. WhAEM is a groundwater flow model designed to facilitate the delineation of capture zones and mapping well head protection, using the analytic element method. The unique hydrogeology of the modeled area (location of local heterogeneities, discontinuities, rivers, recharge, no-flow boundaries) is taken into account in order to prevent potentially harmful contaminants reaching the water supply. This process can be used as a management tool by water resources managers, stakeholders and public authorities in order to impose rational measures and potential restrictions in urban, agricultural and industrial activities developed in the area.

Some simple procedures for the calculation of the influence radius and well head protection areas (theoretical approach and a field case for a water table aquifer in an alluvial plain)

The paper describes some simple methodologies for the delineation of well-head protection areas, together with an overview of the main regulations published in Italy and Europe. Starting from a general explanation of the main parameters, like the radius of influence and the zone of capture in homogeneous isotropic aquifers, basic methodologies suggested in the literature are then illustrated. Different criteria are involved: from the simple 200 m radius, to more complex analytical and numerical simulations. Five different approaches are applied and compared, to a well field in a water table aquifer along a river. Results have shown that, while simpler methods can be satisfactory at a first stage of the study, they fail to account correctly, for local heterogeneities. On the other hand the more accurate description of the aquifer obtained with a full numerical model requires extensive time, expertise and amount of data, that are not always available in case of small water supply systems. As many Authors have underlined, one of the most effective outcome of the numerical tool, lays in the capability to increase our knowledge on the groundwater dynamics of the system and the amount of the sustainable yield.

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.

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.

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.

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.