Water Supply Wells Research Articles

Enhancement of the geological mapping in weathered plutonic and metamorphic rocks areas using village water supply wells data (lithology and hydrochemistry)

In weathered plutonic and metamorphic rocks areas, because rock outcrops are rare due to the extensive regolith cover, geological mapping is largely based on the interpretation of airborne data and imagery (aerial photographs, satellite images, airborne geophysics when available, etc.). In the sub-Saharan Africa, numerous village water supply campaigns were performed during the last 40 years. Most hydrogeological and geological data from these campaigns are stored and safeguard in country scale databases. In this study, we develop a methodology to improve the existing geological maps in a such geological context with lithological data from the existing databases. These data were not used during past geological mapping; yet they provide a complementary access to the lithology, notably in areas where outcrops are very scarce. We propose a coherent methodology to use and validate such geological data, complementary to field observations on the scarce outcrops, to cope with their uncertainties. We also show that groundwater hydrochemistry, namely the silica content, can be of use to complete the geological mapping. Using data from 735 boreholes drilled in the Koudougou and Léo square study area of Burkina Faso, we validate this new methodological approach and locally propose a more accurate 1:200,000 geological map.

Results of departmental control of bacteriological water pollution within the limits of the “One Health” concept

The article is devoted to the analysis of the state of contamination of water from surface reservoirs and drinking water by bacteriological agents at the facilities of operators of the market of char products under the control of the State Production and Consumer Service in the Kharkiv region and the importance of studying this factor of contamination. Using the sources of domestic and foreign literature, the data of our research, the article presents information on the spread of bacteriological contamination of surface water bodies (from fish farms) and drinking water in the production of food products and the results of sanitary and microbiological control of drinking water samples. Sanitary and microbiological control of water quality establishes the degree of its safety under the requirements for a centralized drinking water supply. The main sanitary test for water contamination by intestinal secretions of warm-blooded animals remains bacteria of the group Escherichia coli (E. coli). Unlike the vast majority of countries, stricter requirements for the quality of drinking water concerning this indicator have been preserved in Ukraine, that is, all types of glucose-positive coliform bacteria are taken into account, not only lactose-positive variants. This approach is justified since many lactose-negative intestinal bacteria can not only enter but also multiply under appropriate conditions in drinking water and harm human health. Water as the main or auxiliary raw material is used in the vast majority of technological processes of food production. Practically all food production is connected with the consumption of water from the water supply system, boreholes, or wells. Although the drinking water that «reaches» the «faucet» of the enterprise producing food products undergoes several stages of purification, it still remains a risk factor for contamination, including bacteriological contamination. The increase in the number of operators of the food market, and non-compliance with the requirements during the circulation of objects of sanitary measures leads to an increase in the risks of contamination and infection of people. Only periodic laboratory bacteriological control of the state of drinking water at the facilities of the food market operator can ensure the circulation of food products that do not harm human health and are suitable for consumption. The relevance of the problem of fecal contamination of drinking water is also due to the periodic lack of electricity, as water purification systems work unstable. Also, it should be noted that the summer of 2024 in Ukraine was abnormally warm. The reproduction of pathogens often depends on the temperature of the water, which is manifested as a ratio of favorable temperature and the manifestation of clinical signs of the disease. Pathogens also have optimal temperature ranges for reproduction. An increase in water temperature will increase the introduction of exotic pathogens originating from regions with a higher environmental thermal index. The destruction of the infrastructure leads to the deterioration of the sanitary and hygienic condition of settlements, and life support facilities, and the complication of the epidemic and epizootic situation. An environment favorable for the spread of dangerous infectious diseases is created. One Health and climate change adaptation can significantly contribute to food security, environmental sanitation, and steps towards regional and global integrated surveillance and response systems

A Conceptual Site Model for Per‐ and Polyfluoroalkyl Substance Water Supply Impacts in a Residential Community

ABSTRACTAt a Class 4 State Superfund site located in a densely developed residential/commercial area in a suburb of New York City, emerging contaminant sampling for PFAS was performed as part of a statewide data‐gathering project. Two per‐ and polyfluoroalkyl substances (PFAS), perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), were detected at concentrations in excess of drinking water standards in bedrock and overburden monitoring wells at the State Superfund site. A bedrock private water supply well sampling program and a PFAS source investigation, consisting of overburden investigations near potential sources (i.e., sites with a history of known or suspected use, storage, or discharge of PFAS), were undertaken to assess exposures and identify and potentially eliminate sources of PFAS contaminants in the bedrock drinking water supply.Relative ratios of PFAS (i.e., PFAS signatures) were plotted geospatially to facilitate comparison of the characteristics of overburden groundwater sampling results to that of nearby bedrock private water supply sampling results. In addition, total PFAS concentrations in overburden groundwater and bedrock private water supply samples were compared to identify potential sources of bedrock groundwater impacts. The PFAS signature analysis revealed that (1) PFAS signatures of overburden groundwater samples were generally consistent with nearby bedrock private water supply samples; (2) total PFAS concentrations detected in overburden groundwater samples were marginally higher than concentrations detected in nearby bedrock private water supplies; (3) there was generally low variability in PFAS signatures throughout the study area (Assessment Area); and (4) overburden groundwater and bedrock private water supply PFAS signatures were similar to that of the nearby wastewater treatment plant effluent discharge, which represents a composite average PFAS signature for domestic wastewater from the area. Finally, septic system tracers were also detected in bedrock private water supply and overburden groundwater samples. Based on the results of the investigation, multiple lines of evidence support the Conceptual Site Model, which is likely applicable to many PFAS‐contaminated drinking water supplies with conditions similar to the Assessment Area: consumer product use and discharge to domestic septic systems in a densely developed residential area, lacking area‐wide municipal water and sewer, with shallow groundwater and bedrock, and a vertical downward groundwater gradient, have resulted in the widespread presence of PFAS in private water supply wells.

Integrated assessment of pollution status of MSW sites: a case study of Uyo, Ikot Ekpene and Oron, Akwa Ibom State, southern Nigeria.

One of the main causes of contaminated groundwater in emerging nations is improper trash disposal in urban areas, which affects the level of groundwater contamination caused by contaminants of municipal solid waste (MSW) origin within the three local government headquarters in Akwa Ibom State, southeastern Nigeria. The main thrust of this research survey is to assess the level of groundwater contaminations and their consequences. The research used statistical data generated from the Electrical Resistivity Survey (ERS) in combination with hydrogeochemical investigations. Analysis of variance of resistivity between Uyo, Ikot Ekpene and Oron was carried out. The test result indicated significant difference in contamination among the three cities. This was followed by a t-test between each pair of dump and control sites in the three cities. The test results showed significant difference between each control and dumpsite. The results showed that leachate layer conductivity is always higher than that of the layer above it. All water samples from boreholes close to the dumpsites were identified by hydrogeochemical analysis to exhibit pH (3.70-4.15) lower than the permissible limit of the WHO; few water samples exhibit increased electrical conductivity (EC), cadmium and total dissolved solids (TDS). Similarly, the bacteriological analyses indicated a high level of microbial load due to the waste dump. Formations found in boreholes close to the dumpsite have litho-correlations which depict intercalations of comparatively impermeable and porous materials. The findings reveal that leachate (contaminate) travels slowly downward, allowing for physical, chemical and biological processes to filter out impurities before they get to the aquifer. It is recommended that no new water supply wells should be placed in areas of abnormally low resistivity and physicochemical and bacteriological parameters, until the reasons for these values are properly assessed.

Occurrence and concentrations of traditional and emerging contaminants in onsite wastewater systems and water supply wells in eastern North Carolina, USA.

Onsite wastewater treatment systems (OWTSs) and private wells are commonly used in Eastern North Carolina, USA. Water from private wells is not required to be tested after the initial startup, and thus persons using these wells may experience negative health outcomes if their water is contaminated with waste-related pollutants including bacteria, nitrate or synthetic chemicals such as hexafluoropropylne oxide dimer acid and its ammonium salt (GenX). Water samples from 18 sites with OWTSs and groundwater wells were collected for nitrate, Escherichia coli (E. coli), total coliform, and GenX concentration analyses. Results showed that none of the 18 water supplies were positive for E. coli, nitrate concentrations were all below the maximum contaminant level of 10 mg L-1, and one well had 1 MPN 100 mL-1 of total coliform. However, GenX was detected in wastewater collected from all 18 septic tanks and 22% of the water supplies tested had concentrations that exceeded the health advisory levels for GenX. Water supplies with low concentrations of traditionally tested for pollutants (nitrate, E. coli) may still pose health risks due to elevated concentrations of emerging contaminants like GenX and thus more comprehensive and routine water testing is suggested for this and similar persistent compounds.

Effluent treatment plants for activities with high pollutant-degradation potential: an analysis of compliance with legal requirements

Sewage treatment plants (STPs), despite being fundamental for controlling environmental pollution, are also potential causes of environmental impact, therefore requiring an efficient self-monitoring plan to verify compliance with legal conditions. In this context, this research investigated the situation of Sewage Treatment Stations of enterprises that develop activities with high polluting degrading potential, located in Juazeiro do Norte – CE, in relation to compliance with legal guidelines. To guide this analysis, conditions were considered in resolutions from the Ceará State Environmental Council and municipal laws and decrees that deal with the matter under consideration. At the Municipal Environmental Authority of Juazeiro do Norte (AMAJU), data were collected from licensed enterprises that carried out high PPD activities, from the treatment technologies for effluents generated in each activity, from the STPs self-monitoring programs, and the types and locations of bodies receivers and the operating condition and physical flow of the AMAJU monitoring sector. The processing of data relating to the delivery of self-monitoring reports was carried out using percentages of 50 and 75%. From the analysis of the results, 48 ​​enterprises were identified that carried out high PPD activities, of which 4 were located in areas that had restrictions on this type of use. It was also verified that there was an important battery of public water supply wells surrounded by such projects. It was found that there are 70 high PPD projects that are under the jurisdiction of AMAJU and that the quality of liquid effluents from their STPs is, under specific conditions, in compliance with the release standards established by COEMA Resolution Nº 02/2017. However, it was found that the majority of the enterprises surveyed were non-compliant regarding the quantity and frequency of sending self-monitoring reports to AMAJU. These weaknesses were attributed to the reduced technical staff of the environmental agency and the absence of its minimum infrastructure for the development of the actions necessary for the implementation of an efficient environmental monitoring system. To contribute to the improvement of this system, it was suggested to strengthen AMAJU's technical, financial and institutional support, in addition to establishing a distinction in relation to the requirements regarding the frequency of analyzes and the periodicity of delivery of liquid effluent self-monitoring reports, for enterprises. with different types and classes.

Risk factors for Cryptosporidium contamination in Minnesota public supply wells.

In a recent monitoring study of Minnesota's public supply wells, Cryptosporidium was commonly detected with 40% of the wells having at least one detection. Risk factors for Cryptosporidium occurrence in drinking water supply wells, beyond surface water influence, remain poorly understood. To address this gap, physical and chemical factors were assessed as potential predictors of Cryptosporidium occurrence in 135 public supply wells in Minnesota. Univariable analysis, regression techniques, and classification trees were used to analyze the data. Many variables were identified as significant risk factors in univariable analysis and several remained significant throughout the succeeding analysis techniques. These factors fell into general categories of well use and construction, aquifer characteristics, and connectedness to the land surface, well capture zones, and land use therein, existence of potential contaminant sources within 200-feet of the well, and variability in the chemical and isotopic parameters measured during the study. These risk categories, and the specific variables and threshold values we have identified, can help guide future research on factors influencing Cryptosporidium contamination of wells and can be used by environmental health programs to develop risk-based sampling plans and design interventions that reduce associated health risks.

An Integrated Framework to Assess the Environmental and Economic Impact of Fertilizer Restrictions in a Nitrate-Contaminated Aquifer

Groundwater nitrate contamination caused by the excessive use of nitrogen-based fertilizers has been widely recognized as an issue of significant concern in numerous rural areas worldwide. To mitigate nitrate contamination, corrective management practices, such as regulations on fertilizer usage, should be implemented. However, these measures often entail economic consequences that impact farmers’ income, and thus should be properly assessed. Within this context, an integrated framework combining the environmental and economic assessment of fertilization restrictions through multi-criteria decision analysis is presented in an effort to efficiently manage groundwater nitrate contamination in rural areas. For this task, various scenarios involving reductions (10%, 20%, 30%, 40% and 50%) in fertilizer application were investigated, evaluated and ranked in order to determine the most suitable option. The environmental assessment considered occurrences of nitrates in groundwater, with a specific emphasis on nitrate concentrations in water-supply wells, as obtained by a nitrate fate and transport model, while the economic analysis focused on the losses experienced by farmers due to the reduced fertilizer usage. Our case-study implementation showed that a 30% reduction in fertilization is the most appropriate option for the area being studied, highlighting the importance of adopting such an approach when confronted with conflicting outcomes among alternatives.

Combining Karhunen–Loève expansion and stochastic modeling for probabilistic delineation of well capture zones in heterogeneous aquifers

The delineation of well capture zones (WCZs), particularly for water supply wells, is of utmost importance to ensure water quality. This task requires a comprehensive understanding of the aquifer’s hydrogeological parameters for precise delineation. However, the inherent uncertainty associated with these parameters poses a significant challenge. Traditional deterministic methods bear inherent risks, emphasizing the demand for more resilient and probabilistic techniques. This study introduces a novel approach that combines the Karhunen–Loève expansion (KLE) technique with stochastic modeling to probabilistically delineate well capture zones in heterogeneous aquifers. Through numerical examples involving moderate and strong heterogeneity, the effectiveness of KLE dimension reduction and the reliability of stochastic simulations are explored. The results show that increasing the number of KL-terms significantly improves the statistical attributes of the samples. When employing more KL-terms, the statistical properties of the hydraulic conductivity field outperform those of cases with fewer KL-terms. Notably, particularly in scenarios of strong heterogeneity, achieving a convergent probabilistic WCZs map requires a greater number of KL-terms and stochastic simulations compared to cases with moderate heterogeneity.

Evaluation of the Water Quality of Three Water Supply Wells in the Urban Area of Chilpancingo, Guerrero, México

Evaluation of the Water Quality of Three Water Supply Wells in the Urban Area of Chilpancingo, Guerrero, México

Application of borehole cameras in the field of Engineering Geology and Hydrogeology

The use of borehole cameras in Bulgaria is increasingly used in hydrogeology and engineering geology. The resulting photographs and movies contribute to solving problems related to the study and assessment of the condition of water supply wells, as well as to obtain a clear picture on the assessment of rock massifs for their suitability for various types of construction. Borehole cameras on the territory of our country are more widely used in the field of hydrogeology compared to engineering geology. The purpose of this article is to present the possible applications of this technology, which has been improved over the years, for the study of rock massifs in their study for various infrastructure objects. Also. to shed light on the benefits of using boreholes in surveying the various water sources.

Wireline log stratigraphy of the lower Cambrian Læså Formation, Bornholm, Denmark.

A detailed correlation of the lower Cambrian Læså Formation on southern Bornholm, Denmark, is based on gamma ray and formation resistivity wireline logs from 25 water supply wells and 5 scientific boreholes. The interpretation hinges on comparison with the wireline log suite obtained in the fully cored Borggård-1 borehole that penetrated the formation in its entirety. The Norretorp Member, 102.9 m thick in Borggård-1, consists predominantly of intensively bioturbated siltstone. Several levels are strongly glauconitic and usually also contain phosphorite nodules. Fine-grained sandstone beds, 0.5–20 cm thick and interpreted as tempestites, occur throughout the unit; a few thicker sandstone layers consist of stacked tempestites. However, many sandstone beds, primarily in the upper 2/3 of the member, have been partly or totally obliterated by the pervasive bioturbation. The overlying Rispebjerg Member, 3.5 m thick in Borggård-1, is dominated by well-cemented medium to coarse-grained quartz sandstone. The variable lithology of the Læså Formation is illustrated by photos of core samples from Borggård-1. The studied wells are located on different fault blocks with 18 km between the easternmost and westernmost well sites. The Norretorp Member is of almost similar thickness throughout the study area whereas the Rispebjerg Member is 2.2–5.6 m thick. The essentially unchanging thickness of the Læså Formation and the sheet like distribution of tempestites demonstrate that the intense faulting of southern Bornholm post-dates deposition. The Norretorp Member is divided into a lower log-unit (57 m thick in Borggård-1) characterized by a moderately variable gamma ray log pattern and an upper log-unit (46 m thick in Borggård-1) exhibiting a more uniform gamma radiation of overall lower intensity. The log-units reflect a more common occurrence of glauconite and phosphorite in the lower part of the member and a higher sand content in the upper part. These lithological differences are also reflected by a generally higher resistivity and P-wave velocity in the upper log-unit. Seven thicker sandstone horizons (15–80 cm thick), labelled S1 to S7, are laterally persistent within the Norretorp Member. Four additional horizons, referred to as MGL [multiple gamma low], MGH [multiple gamma high], MM [middle marker] and GH [gamma high], are also laterally widespread. A readily identifiable red-brown horizon is located at 4.4–5.9 m above the base of the Læså Formation in Borggård-1: it appears to be developed throughout the study area.

Frequency and seasonality of viable Helicobacter pylori in drinking water in Dhamar Governorate, Yemen.

Helicobacter pylori is an important and common bacterial pathogen in humans. The accumulated evidence of the existence of H. pylori in water from different environmental sources suggests a water-borne transmission route. This study aimed to investigate the occurrence of H. pylori in different water sources used by human populations in Dhamar Governorate, Yemen. 250 samples were randomly collected from the municipal water supply network, wells, and springs. The samples were processed, plated onto modified campy-blood agar, and incubated under microaerobic conditions for 4-10 days. Bacterial identification was based on morphological properties and biochemical tests. Bacteriological analysis showed that 9.6% and 13.2% of tap and surface water samples were contaminated with H. pylori, respectively. Despite a higher frequency in samples from rural areas, these were not significantly (p=0.068) more contaminated than the samples from urban areas. Regarding the seasonal variations of H. pylori detection, 85.71% of positive samples were detected in the late winter and spring seasons (February to May). To conclude, H. pylori transmission through water is likely to occur in Dhamar Governorate. Further prospective studies are highly recommended to provide further evidence and a clearer picture of H. pylori transmission.

Efficacy of urban road salt reduction strategies on public supply well quality

Long-term road salt application has increased chloride (Cl−) concentrations in public drinking water wells in many cold climate communities. A range of Best Management Practices (BMPs) have been adopted to mitigate the impact of road deicing compounds on groundwater quality. Chronic increases in chloride levels have been observed in several municipal well fields within the southern Ontario Regional Municipality of Waterloo (RMOW). In response, the RMOW and City of Kitchener implemented a plan to reduce salt application on roads by 25% within the local capture zones of one of the impacted well fields, the Greenbrook Well Field. Here the influence of salt reduction BMPs on subsurface water quality are examined by documenting changes in pore water Cl− concentrations and stored salt mass in vadose zone core samples collected at sites near the well field both before and after the implementation of the BMPs. The data indicate that ~6 years after salt reduction measures were initiated, average pore water Cl− concentration and average cumulative stored chloride mass in the vadose zone had decreased by approximately 60% and 40%, respectively. Groundwater samples collected from shallow monitoring wells installed at each field site showed similar post-BMP reductions in shallow groundwater Cl− concentration (~35%). Long-term (1973–2022) trends in raw water Cl− concentration data from the deeper public drinking water supply wells clearly demonstrate a slow, time-lagged response of the municipal supply wells to the salt reduction BMPs. The combined results suggest that controlled reductions in road salt applications within vulnerable, capture zone regions of public supply wells can reduce the impact of road salt deicing practices on municipal groundwater supplies over time.

Community intervention trial for estimating risk of acute gastrointestinal illness from groundwater-supplied non-disinfected drinking water.

By community intervention in 14 non-disinfecting municipal water systems, we quantified sporadic acute gastrointestinal illness (AGI) attributable to groundwater. Ultraviolet (UV) disinfection was installed on all supply wells of intervention communities. In control communities, residents continued to drink non-disinfected groundwater. Intervention and control communities switched treatments by moving UV disinfection units at the study midpoint (crossover design). Study participants (n = 1,659) completed weekly health diaries during four 12-week surveillance periods. Water supply wells were analyzed monthly for enteric pathogenic viruses. Using the crossover design, groundwater-borne AGI was not observed. However, virus types and quantity in supply wells changed through the study, suggesting that exposure was not constant. Alternatively, we compared AGI incidence between intervention and control communities within the same surveillance period. During Period 1, norovirus contaminated wells and AGI attributable risk from well water was 19% (95% CI, -4%, 36%) for children <5 years and 15% (95% CI, -9%, 33%) for adults. During Period 3, echovirus 11 contaminated wells and UV disinfection slightly reduced AGI in adults. Estimates of AGI attributable risks from drinking non-disinfected groundwater were highly variable, but appeared greatest during times when supply wells were contaminated with specific AGI-etiologic viruses.

Analysis of a Municipal Solid Waste Disposal Site: Use of Geographic Information Technology Tools for Decision Making

In this study, the operation of a final disposal site for municipal solid waste in the state of Chiapas, in Mexico, was evaluated. Several spatial analyses and Geographic Information Technology (GIT) tools were used. It was found that the site’s current operation and location are deficient, partially complying with regulations. The gaseous dispersion is not far-reaching (from 100 to 8725 µg/m3 for landfill gas, and from 0.01 to 0.35 µg/m3 for H2S) but requires attention to avoid olfactory unpleasantness. Liquid emissions (conservative pollutants) move in the east direction of the final disposal site, which can damage the environmental infrastructure (water supply wells) in the long term. The highest and lowest concentrations were found in years 1 (12,270 mg/m3) and 20 (1080 mg/m3), respectively. Thermal emissions around the dumping site are important due to the formation of microclimatic zones. Temperature differences were found during the analysis period, ranging from 8.37 °C in summer to 2.49 °C in winter, which are due to waste decomposition processes and anthropogenic activities. Finally, the change in land use around the dumping site increased at a rate of 5.82% per year, mainly due to the growth of homes, communication routes, and shopping centers.

AWWA Library

This is an abridged excerpt from Chapter 1 of Water Supply Wells: Siting, Drilling, and Construction, second edition (catalog No. 20649‐2E). The book is available from the AWWA Store (www.awwa.org/store).

Modeling of drilling water supply wells with airlift reverse flush agent circulation

Purpose. Determination of the influence of mining and geological conditions of drilling hydrogeological wells with backwash on the technological parameters of the airlift method of cleaning it from drilled rock and the properties of the ascending flow of aerated washing liquids. Methodology. The tasks were solved by a complex research method, including analysis and generalization of literary and patent sources, analytical, experimental studies, using computer and mathematical modeling methods. Findings. An algorithm for the functioning of the airlift circulation method during rotary drilling with backwash has been developed. The algorithm takes into account: hydrostatic and hydrodynamic pressures, and the effect on them of the rate of drilling of the well; the effect of the sludge content in the upstream. The effective values of the airflow rate, the density of the water-air mixture and the velocity of its upward flow are established. A method for estimating the effective values of technological parameters and their changes in the upward flow of the mixture is proposed. A model has been developed that allows analyzing the dependences of the air flow rate, the density of the mixture and the rate of its ascent on the parameters of the well being drilled. The model is applied to typical drilling conditions of a large-diameter water intake well at the Samskoye groundwater deposit on the Mangystau peninsula. Originality. A mathematical algorithm has been developed for the functioning of the airlift backwash method when drilling large-diameter water intake wells. The method is based on the analysis of the pressure balance in the descending and ascending flows of the washing agent. For the case of backwash, a formula for estimating the content of sludge in it was obtained. A method has been developed for determining the average effective density of the mixture in terms of the height of the well, as well as the air content in it. Based on the average effective values, a method is proposed for estimating changes in the density of the mixture, its flow rate and velocity along the upward flow. Practical value. The proposed algorithm is the basis of a computer model that allows you to determine the dependences of the values of the density of the mixture, the content of air and sludge in it and the rate of ascent, from the depth of the well, the depth of the mixer descent, the speed of deepening, the specified velocity of the upward fluid flow, as well as the diameters of the well and drill pipes. Specific modeling results have been obtained in relation to the Samskoye groundwater deposit of the Mangystau peninsula.

Stable Water Isotopes as an Indicator of Surface Water Intrusion in Shallow Aquifer Wells: A Cold Climate Perspective

AbstractGroundwater in shallow aquifers is commonly used for community water supply in cold climates. Shallow groundwaters are inherently susceptible to contamination from land‐use and surface water intrusion threatening drinking water usage. We used a large‐scale snapshot data set of stable water isotopes from shallow glaciofluvial aquifers used for drinking water supply in Northern Finland to assess surface water intrusion risks and recharge conditions. This data set was supplemented by long‐term stable water isotope precipitation data, Geographic Information System proximity analysis and multivariate statistics. The isotope analysis suggest that a warm season contributes about 60% to the total annual precipitation in the region. This is reflected in the aquifers isotopic composition as it represents an approximately equal mixture of warm and cold season precipitation. Groundwater isotope data normalized to precipitation inputs by line‐conditioned excess (lc‐excess) was used to flag the water supply wells impacted by surface water intrusions. The proximity analysis showed some of the wells may be affected by intrusions from gravel pit ponds, lakes and peatland drainage. On the larger scale, the wells in coastal areas were more likely to have evaporated water (intrusion) compared to inland regions of Northern Finland due to lower water availability and the presence of man‐made structures. This application of stable water isotopes with lc‐excess is a useful approach not only for recharge studies but also within water management for supply well surface water contamination risk assessment.

QUANTITY AND QUALITY OF GROUNDWATER OF INTERMOUNTAIN BASIN OF KORÇA IN ALBANIA AND IMPLICATION FOR SUSTAINABLE MANAGEMENT

Korça intermountain basin is the largest of its kind in Albania and from the hydrogeological point of view represents a semiclosed intermountain basin developed in Pliocene-Holocene granular unconsolidated deposits, which maximal thickness is about 300 m. The aquifer consists of intergranular gravelly to sandy layers containing artesian groundwater and the drilling wells are free flowing on most of the basin surface. The main recharge of the intergranular aquifer comes mainly from the rivers and torrents flowing from mountain gorges around the Korça Plain. The natural groundwater drainage of Korça basin is realized through the vertical leakage in the area of the former Maliq marsh. Hydrochemistry of the aquifers show the presence of four main hydrochemical facies which are related mainly to the hydrochemistry of the recharge sources and to the solution processes and ion exchange. In the central part of the basin the water supply wells of the cities Korça and Maliq are located. The natural renewable groundwater resources of the basin are relatively restricted, but the volume resources (or static water resources) are abundant (about 1.1 × 10–9 m3). The perspective of their exploitation is very important, but respecting the “basin yield” concept that is defined as the maximum rate of withdrawal that can be sustained by the hydrogeological system of groundwater basin without causing unacceptable changes to any other environmental component of the basin. To face the problems related to the intensification of the groundwater pumping systematic observations of the hydraulic reaction of the basin and of the possible groundwater quality deterioration and other negative environmental impacts must be organized. The purpose of the present study is for the first time to analyze the abundant basin wide hydrogeological data and to evaluate: (1) geometry and hydraulic parameters of the aquifers: (2) groundwater hydrodynamic conditions; (3) their chemical composition and (4) the natural groundwater resources and the possibility to intensify the groundwater pumping in close relation to the environmental impact.