Wellhead Protection Research Articles

Numerical modeling on flow of groundwater energies in transient well capture zones

Capture zone delineation is indispensable in all wellhead protection programs for the safeguarding of groundwater supplies. Transients in the flow model tend to influence the capture zone geometry over time. Thus, transient analyses of well capture zones are superior to the steady-state analogs for all practical cases with time-varying flow parameters. Energy gradients drive groundwater flow like any other natural phenomena. Along with the evolving capture zone, energy transformations within the model domain were also, therefore, assessed to portray the state of the system with time. The energy components, in the form of frictional dissipation and change in internal energy, were estimated at all time steps beside delineating the capture zones. This paper numerically models a two-dimensional homogeneous isotropic confined aquifer and thereby delineating the capture zones by subsequent examination of the energies within. The energy approach facilitated the identification of areas having pronounced transient behavior compared to the entire region within the capture zone and model domain. The current study reveals that there was an unusual increase in the internal energy term for two time periods of the entire cycle investigated and highlighted the compressibility effects of the system. This has been correlated to the change in the distribution of capture fraction values within the capture zones of those specific time periods.

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...

Analyzing the flow of energies within the well capture zones under steady state conditions

Capture zone delineation has been in practice for decades as a part of groundwater management and wellhead protection schemes. The energy possessed by a groundwater particle gets continuously dissipated as it traverses along its path and, is the work done by it. The study of energies within any domain probes into the innate nature of the system and its interaction with the surroundings. Hence energy computations in and around the realms of extraction wells can be used to analyze capture zones from the energy concept. There has been very little research reported on the energy of groundwater flow and specifically that associated with the well capture zones. This work intends to model two-dimensional homogeneous isotropic confined aquifers using finite volume method, then delineate the capture zones and examine the energies within. Steady state aquifer conditions will cause all the work done at the boundaries converted into frictional dissipation. This frictional dissipation was found significant over regions of 95% capture surrounding the well within the capture zone.

Wellhead protection zones for sustainable groundwater supply

Wellhead protection zones (WPZs) and groundwater supply protection areas are strategies to minimize contamination hazards and ensure a safe groundwater supply. Their implementation may require land use restrictions, industrial process changes and/or waste and effluent treatment changes, service adaptations, systematic controls of groundwater levels and groundwater quality and detailed well inspections. The aim of this paper is to present a scheme to ensure the protection of drinking water sources comprising the new pumping field supplying Esperanza and Rafaela cities in Santa Fe Province, Argentina. A 5–10-m radius was adopted for delineating the wellhead operational zones. To define the microbiological and surveillance zones, the fixed radius and Wyssling methods were applied, taking into account the groundwater travel time of 50 and 100 days, respectively. The land activities were inventoried and categorized according to their potential for generating a subsurface contaminant load. A sanitary survey and assessment of pumping wells was made using a checklist. The results have shown that appropriate radii might be 70 m for the microbiological protection zone and 100 m for the surveillance zone. These values were obtained taking into account a pumping rate of approximately 60–70 m3/h. This abstraction rate should be regulated and maintained because it not only affects the validity of the defined zones but also, when it is exceeded, induces an influx of water of different quality to the semi-confined aquifer.

Study on the Comprehensive Mechanism of Hangzhou Water Landscape Governance

The article is to analyze the spatial structure, type structure and the existent main problems of water landscape in Hangzhou. Aiming at “clear water, liquidity, green bank, beautiful scenery, livability, prosperity”, the tasks and construction targets of the mechanism of Hangzhou water landscape are studied form the perspectives of wellhead protection zone, transport water landscape and urban water landscape. In order to solve the problems like dirty, black and odorous urban water, the guiding ideology and comprehensive governance measures are proposed.

A GIS policy approach for assessing the effect of fertilizers on the quality of drinking and irrigation water and wellhead protection zones (Crete, Greece)

Fertilizers have undoubtedly contributed to the significant increase in yields worldwide and therefore to the considerable improvement of quality of life of man and animals. Today, attention is focussed on the risks imposed by agricultural fertilizers. These effects include the dissolution and transport of excess quantities of fertilizer major- and trace-elements to the groundwater that deteriorate the quality of drinking and irrigation water. In this study, a map for the Fertilizer Water Pollution Index (FWPI) was generated for assessing the impact of agricultural fertilizers on drinking and irrigation water quality. The proposed methodology was applied to one of the most intensively cultivated with tree crops area in Crete (Greece) where potential pollutant loads are derived exclusively from agricultural activities and groundwater is the main water source. In this region of 215 km2, groundwater sampling data from 235 wells were collected over a 15-year time period and analyzed for the presence of anionic (ΝΟ−3, PO−34) and cationic (K+1, Fe+2, Mn+2, Zn+2, Cu+2, B+3) fertilizer trace elements. These chemicals are the components of the primary fertilizers used in local tree crop production. Eight factors/maps were considered in order to estimate the spatial distribution of groundwater contamination for each fertilizer element. The eight factors combined were used to generate the Fertilizer Water Pollution Index (FWPI) map indicating the areas with drinking/irrigation water pollution due to the high groundwater contamination caused by excessive fertilizer use. Moreover, by taking into consideration the groundwater flow direction and seepage velocity, the pathway through which groundwater supply become polluted can be predicted. The groundwater quality results show that a small part of the study area, about 8 km2 (3.72%), is polluted or moderately polluted by the excessive use of fertilizers. Considering that in this area drinking water sources (wells) are located, this study highlights an analytic method for delineation wellhead protection zones. All these approaches were incorporated in a useful GIS decision support system that aids decision makers in the difficult task of protection groundwater resources.

The Combined Effect of Cu, Zn and Pb on Enzyme Activities in Soil from the Vicinity of a Wellhead Protection Area

ABSTRACTHeavy metals are known to have adverse effects on soil ecosystems, while soil enzyme activities are sensitive to soil pollution. This study investigated the combined effects of Cu, Zn and Pb on the activities of invertase (IN), urease (U) and alkaline phosphatase (ALP) in soil obtained from the vicinity of a wellhead protection area via an orthogonal array (OA) design method. The experimental results showed the following: (1) Cu showed higher inhibition on the activities of all three enzymes than Zn and Pb when three metals were all present in the soil sample. IN activity, U activity and ALP activity decreased as the levels of Cu increased, and ranged from 15.9% to 55.7%, 3.57% to 78.6%, and 3.23% to 75.3%, respectively. Their lowest values were found in samples at 35 days with 400 mg/kg Cu. (2) Zn and Pb had different influences on the activities of the three enzymes. The lowest IN activity (the highest reduction 58.0%) and U activity (76.8%) were observed when Zn was at the concentration of 100 mg/kg after 35 days, whereas the highest inhibitory function of Zn on ALP activity (75.3%) was at 300 mg/kg after 7 days. When the concentration of Pb increased from 35 to 350 mg/kg, the activities of IN (62.5%) and U (69.6%) were most inhibited at 35 days and 14 days, respectively. However, when Pb was at the concentration of 500 mg/kg after 14 days, ALP activity (72.0%) showed the lowest value. (3) With respect to the three hydrolases in this study, ALP was the most sensitive to the two-variable interactive effects of Cu, Zn and Pb, especially Cu × Pb. It is concluded that the soil ALP activity may be a sensitive tool for assessing additive toxic effect on soil biochemical parameters. To provide more information about the potential ecological risk of chemicals on soil ecosystems, much more should be done to clearly determine the mechanisms of the combined effects of heavy metals in soil.

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.

Baseline groundwater quality in unconventional oil and gas fields

In recent years, expansion of unconventional oil and gas production has prompted significant interest in potential impacts on drinking water resources. In many cases, water quality investigations rely on access to landowner water wells to develop baseline data prior to drilling; respond to spills, complaints, or incidents; or evaluate potential impacts due to drilling, completion, hydraulic fracturing, water management, or well operation. However, differences in water well construction, operation, maintenance, and wellhead protection practices can complicate sampling efforts and introduce artifacts that might confound interpretation of results and definition of baseline conditions. The frequency of sampling and the types of analyses also vary from site to site, ranging from basic field parameters such as conductivity, pH, and water level to comprehensive analyses of organics, inorganics, radionuclides, gases, stable isotopes, and microorganisms. Regulatory agencies may also specify required analytical parameters and monitoring frequency. This paper highlights some of the challenges associated with deriving baseline data from different types of wells and provides preliminary data on the use of chemical fingerprinting to differentiate sources of waterborne contaminants.

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.

A Multi-objective Optimization Concept for Risk-based Early-warning Monitoring Networks in Well Catchments

Groundwater wells are often protected by restricted land use within wellhead protection zones. Unfortunately, one cannot restrict land use in the entire catchment (especially in urban areas), and there is uncertainty in wellhead delineation. Thus, nearly all well catchments have an entire inventory of risk sources. Each of these risk sources may fail at any time, release contamination and affect the well earlier or later. In fact, most catchments are equipped with some form of monitoring network. Such networks, however, often grow historically, follow various purposes that changed over time, and thus are often suboptimal (if not even inadequate) for rigorous risk control. In this work, we propose a concept to plan monitoring networks through multi-objective optimization. The different objectives are minimal costs, maximal probability to detect all possible contaminants once they entered the aquifer, and earliest possible detection. Also, risk sources that are classified as severe versus medium or tolerable should be treated with different priorities. Therefore, we propose to treat detection probability and early-warning time as separate objectives for each risk class. The concept will allow catchment managers to obtain optimal monitoring networks for risk control, and to gain insight into the costs of certainty, the costs of early warning, and the costs of covering top risks versus the luxury situation of controlling even minor risks.

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.

Development of a watershed-based geospatial groundwater specific vulnerability assessment tool.

This study assesses and characterizes the vulnerability of unregulated groundwater systems to microbial contamination in 18 counties in the state of Georgia using a contamination risk screening strategy based on watershed characteristics and elements of the Safe Drinking Water Act's Wellhead Protection program. Environmental data sources analyzed include septic systems, elevation, land use and land cover data, soil, vegetation coverage, demographics, and livestock. A geospatial overlay/index modeling approach was developed to identify areas of higher vulnerability for groundwater pollution by taking into consideration watershed land use, hydrology, and topography (LHT). Sensitivity analysis was used to evaluate the effectiveness of model variables. The results of the model were validated by using field data and output from U.S. EPA's DRASTIC model, a widely used intrinsic vulnerability assessment tool. The validation showed a higher risk of microbial contamination for wells located in a high to medium LHT vulnerability zones. LHT provided a clear distribution of satisfactory and unsatisfactory wells in the three vulnerability zones; however, the majority of wells (>75%), with both satisfactory and unsatisfactory test results, are located in medium DRASTIC vulnerability zone. This difference between LHT and DRASTIC can be attributed to the microbial contamination specific factors incorporated into LHT index. It is concluded that although inclusion of potential contamination sources on adjacent land uses in the vulnerability assessment framework adds to the complexity of the processes involved in a vulnerability assessment, such inclusion provides a meaningful perspective to groundwater protection efforts as an effective screening tool.

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.