Drinking Water Purposes Research Articles

Preliminary results of a 3-D groundwater flow model in an arid region of NE Algeria using PMWin: the Inféro-flux phreatic aquifer (Biskra)

Infero-flux phreatic aquifer (Biskra, NE Algeria) is overexploited for irrigation and drinking water purposes since the fifties. The effect is a quali-quantitative deterioration of the groundwater resources mostly due to an insufficient natural recharge. WADIS-MAR Project aims to the realization of a Managed Aquifer Recharge (MAR) in the Biskra area in order to contribute to re-pressuring the piezometric level of the Infero-flux.Groundwater flow models can contribute to the understanding of the groundwater behaviour related to the impact of existing and future activities on groundwater resources including the realization of an MAR system. In this work, the preliminary results for a groundwater flow model developed for the Infero-flux aquifer are presented. They include the model construction and the results of the steady state calibration based on the piezometric head measured in 1966.

INVESTIGATION ON THE EXPERT COMMUNITIES AWARENESS OF THE URBAN RIVER WATER QUALITY, CASE STUDY OF SUGUTAMU RIVER, INDONESIA

Many rivers in urban areas in Indonesia are commonly used as raw water sources for drinking water purposes. Therefore, the water quality of the rivers needs to be maintained. River restoration program becomes a major priority in improving the water sector and environmental, particularly in big cities in Indonesia. Sugutamu River is one of the main rivers passing through the Depok City, West Province of Indonesia. High population . Stakeholder participations should be considered when implementing a participatory program in river restoration project. This program can be developed by increasing the awareness of the community. One of the most important communities is the ‘expert’ communities. In this research, economists, environmental specialists, river engineers, urban planners are selected as the ‘expert’ community. Questionnaires were distributed to the expert communities to investigate how the respondents concern about the importance of river water quality. The result shows that the awareness of the expert community on river water quality and its improvement is higher than on other aspects.

Integrity breaches in a hollow fiber nanofilter – Effects on natural organic matter and virus-like particle removal

Ultrafiltration and nanofiltration have become common methods to treat surface water for drinking water purposes. Common aims of a membrane step are removal of natural organic matter (NOM), softening or adding an extra microbiological or chemical barrier. In most cases, the membrane is considered a good disinfection step; commonly the viral removal is at least 4–log. To ensure a working disinfection, reliable integrity tests are required. In the present pilot study with a hollow fiber nanofilter, the membrane achieved a high NOM reduction, and the difference in parameters related to NOM quality before and after treatment proved to be useful indicators of integrity breaches. Changes in total organic carbon (TOC) concentration, UV-absorbance at 254 nm (UVA254) and fluorescence derived parameters in the permeate flow were related to leaking fibers. On average, UVA254 in the permeate was 3 times higher for a membrane with compromised fibers (0.041 cm−1) compared to an intact membrane (0.013 cm−1), while TOC was less than 2 times as high on average. Thus, this membrane had a higher reduction of UVA254 than TOC and the sensitivity for changes from leakage was higher. Therefore, it is suggested that UVA254 could be used as an indicator for membrane integrity. Additionally, there is a significant (P < 0.01) difference in fluorescence derived parameters between a leaking and an intact fiber, showing that fluorescence also has potential to be applied for online monitoring of membrane processes. During fiber failure, around 2% of the permeate flow passes through one single leaking fiber. The transport depends on the distance between the inflow and the leak, which in most cases are similar and most likely close to the middle of the fiber.

A diagnosis of groundwater quality from a semiarid region in Rajasthan, India

A diagnosis of the groundwater quality of 70 wells sampled during two climatic regimes (dry and raining seasons) from a semiarid area in Rajasthan, India, had been carried out using standard methods. Analysis of the results for various hydrochemical parameters wherein the geological units are alluvium, quartzite and granite gneisses showed that all the parameters did not fall within the World Health Organisation’s acceptable limits for irrigation and drinking water purposes. The order of major cations and anions obtained during the dry and raining seasons are Na+ ˃ Mg2+ ˃ Ca2+ ˃ K+ and Cl−˃ HCO3 − ˃ SO4 2−˃ CO3 −> F− ˃ NO3 −, respectively. A maximum value of nitrate of 491.6 mg/l has been examined and its contamination is due to discriminated highly impacted groundwater samples by agricultural activity and small-scale urbanization. Fluoride (F−) concentration is 6.50 mg/l as a maximum value, whereas values in about 26 % of the samples are more than the permissible limit (1.5 mg/l) for drinking water. The cumulative probability distributions of the selected ions show two individual intersection points with three diverse segments, considered as regional threshold values and highly impacted threshold values for differentiating the samples with the effects of geogenic, anthropogenic and saline water mixing. The first threshold values indicate the background hydrochemical constituents in the study area. The second threshold value of 732 mg/l for bicarbonate indicates that sandy aquifer is being dissolved during wet period, whereas NO3 − concentration of more than the initial threshold value (=75 mg/l) indicates discriminated highly impacted groundwater samples by agricultural activity and urbanization in dry season. Various parameters such as soluble sodium percentage (SSP), salinity (electrical conductivity (EC)), sodium adsorption ratio (SAR), residual sodium carbonate (RSC), Kelley’s ratio (KR), permeability index (PI), residual sodium bicarbonate (RSB) and magnesium absorption ratio (MAR) for the well samples show that, overall, 46 % of groundwater samples are not suitable for irrigation. Further, chloro-alkaline indices (CAIs) were used for distinguishing regional recharge and discharge zones whereas corrosivity ratio (CR) utilized for demarcating areas to use metallic pipes for groundwater supply. In general, groundwater quality is mainly controlled by the chemical weathering of rock-forming minerals. The information obtained represents a base for future work that will help to assess the groundwater condition for periodical monitoring and managing the groundwater from further degradation.

Low cost and sustainable surface water purification methods using Moringa seeds and scallop powder followed by bio-sand filtration

A simple and inexpensive water purification method was developed using natural coagulant (Moringa seed powder) and antibacterial agents (scallop powder) followed by bio-sand filtration. In this study, surface water from different sources (e.g. pond, canal, lake and river) treated with combined Moringa seed powder, and scallop powder (MOSP) at a ratio of 2:1 for 10 minutes showed a clear water layer at the top and a sediment layer at the bottom. The clear water was then passed through an eight-fold sari cloth and/or natural bio-sand filtration and the resulting water was found drinkable. The microbiological and physico-chemical quality of this water showed non-significant differences compared to the US EPA drinking water quality parameters. Moreover, no cytotoxic effect of MOSP with BHK-21 and HeLa cells, nor any bacterial endotoxins were observed, indicating use of MOSP does not pose any adverse health effect. Furthermore, the quality of 6 months stored water at room temperature was found acceptable, indicating the usefulness of this technology for drinking water purposes. On the other hand, the sediment or sludge produced in this process could be used in agricultural fields after proper composting. Therefore, this simple, inexpensive and ecofriendly method could be used in drinking water scarcity areas of the world.

Hydrogeochemical Assessment of Groundwater in the Precambrian Rocks, South Eastern Desert, Egypt

This work refers to the characterization of the hydrochemistry of the southern part of the Eastern Desert in Egypt, on the basis of physico-chemical properties of groundwater occurring in the fractured Precambrian rocks inland and in sedimentary formations on the coastline of the Red Sea. Thirty-five groundwater samples have been collected from the study area for hydrochemical investigations to understand the sources of dissolved ions and assess the chemical quality of the groundwater. Several methods were used to interpret the hydrochemical data, i.e. graphical methods, principal components analysis, ions exchanges indices and saturation indices of various minerals. The results show that the major ionic relationships are Na+ > Ca2+ > Mg2+ and Cl&#45 > > HCO3&#45 and that groundwater chemical characteristics are controlled by natural geochemical processes but also, to a lesser extent, by anthropogenic activities. Natural minerals dissolution, ion exchanges and evaporation play a prominent role in the ion enrichment of groundwater. A comparison of groundwater quality in relation to WHO water quality standards proved that most of the water samples are not totally suitable for drinking water purpose.

Assessment of climate change impact on water diversion strategies of Melamchi Water Supply Project in Nepal

This paper analyzes the climate change impact on water diversion plan of Melamchi Water Supply Project (MWSP) in Nepal. The MWSP is an interbasin water transfer project aimed at diverting water from the Melamchi River of the Indrawati River basin to Kathmandu Valley for drinking water purpose. Future temperature and precipitation of the basin were predicted using the outputs of two regional climate models (RCMs) and two general circulation models (GCMs) under two representative concentration pathway (RCP) scenarios which were then used as inputs to Soil and Water Assessment Tool (SWAT) to predict the water availability and evaluate the water diversion strategies in the future. The average temperature of the basin is projected to increase by 2.35 to 4.25 °C under RCP 4.5 and RCP 8.5, respectively, by 2085s. The average precipitation in the basin is projected to increase by 6–18 % in the future. The annual water availability is projected to increase in the future; however, the variability is observed in monthly water availability in the basin. The water supply and demand scenarios of Kathmandu Valley was also examined by considering the population increase, unaccounted for water and water diversion from MWSP in the future. It is observed that even with the additional supply of water from MWSP and reduction of unaccounted for water, the Kathmandu Valley will be still under water scarcity in the future. The findings of this study can be helpful to formulate water supply and demand management strategies in Kathmandu Valley in the context of climate change in the future.

Triclosan removal by NF from a real drinking water source – Effect of natural organic matter

Nanofiltration (NF) is known as a very effective technology in the removal of micropollutants from surface water for drinking water purposes. In this study, NF of triclosan (TCS) which is a commonly used biocide in many different domestic and industrial applications was investigated in relation to its interaction with natural organic matter (NOM). A laboratory scale cross-flow device was operated in total recycle mode using a thin-film composite membrane with a real surface water. The effect of NOM content on TCS removal was elucidated through addition of humic acid (HA) into raw water. The performance of the membrane was evaluated by TCS retention, as well as flux behavior. The results showed that NOM had a positive effect on TCS removal due to TCS–HA complex formation that limits TCS permeation through the membrane. On the other hand, NOM was found to increase Molecular weight cut off (MWCO), but not resulting in a decrease in TCS rejection due to HA–TCS complex formation. NOM lead to an increase in TCS removal mainly by sorption into the membrane.

Microbial community composition of a household sand filter used for arsenic, iron, and manganese removal from groundwater in Vietnam

Household sand filters are used in rural areas of Vietnam to remove As, Fe, and Mn from groundwater for drinking water purposes. Currently, it is unknown what role microbial processes play in mineral oxide formation and As removal during water filtration. We performed most probable number counts to quantify the abundance of physiological groups of microorganisms capable of catalyzing Fe- and Mn-redox transformation processes in a household sand filter. We found up to 104cellsg−1 dry sand of nitrate-reducing Fe(II)-oxidizing bacteria and Fe(III)-reducing bacteria, and no microaerophilic Fe(II)-oxidizing bacteria, but up to 106cellsg−1 dry sand Mn-oxidizing bacteria. 16S rRNA gene amplicon sequencing confirmed MPN counts insofar as only low abundances of known taxa capable of performing Fe- and Mn-redox transformations were detected. Instead the microbial community on the sand filter was dominated by nitrifying microorganisms, e.g. Nitrospira, Nitrosomonadales, and an archaeal OTU affiliated to Candidatus Nitrososphaera. Quantitative PCR for Nitrospira and ammonia monooxygenase genes agreed with DNA sequencing results underlining the numerical importance of nitrifiers in the sand filter. Based on our analysis of the microbial community composition and previous studies on the solid phase chemistry of sand filters we conclude that abiotic Fe(II) oxidation processes prevail over biotic Fe(II) oxidation on the filter. Yet, Mn-oxidizing bacteria play an important role for Mn(II) oxidation and Mn(III/IV) oxide precipitation in a distinct layer of the sand filter. The formation of Mn(III/IV) oxides contributes to abiotic As(III) oxidation and immobilization of As(V) by sorption to Fe(III) (oxyhydr)oxides.

Filtration of natural organic matter using ultrafiltration membranes for drinking water purposes: Circular cross-flow compared with stirred dead end flow

Application of ultrafiltration membranes for removal of humic acids is investigated below. Membrane filtration processes were compared using two different set-ups: circular flow and stirred dead end flow. The transmembrane pressure, temperature, feed concentration, pH, ionic strength and shear stresses applied on the membrane surfaces were kept constant whilst the permeate flux and solute rejection were measured during the experiments with both set-ups. It was shown that the rejection (both the observed and the true rejection) in the case of circular flow was higher than in the case of dead end flow. The mass transfer coefficients were determined for both set-ups. In the case of stirred dead end, it ranged in from 2.14 to 4.72×10−6m/s; however, for circular cross flow system, the mass transfer coefficients were found in the range 2.24–3.22×10−5m/s. Comparison of the mass transfer coefficients obtained for both systems showed that it was significantly higher for circular flow systems as compared with stirred dead end system at similar operating conditions. Energy consumed per volume of purified water by circular flow system (0.345kW) was found to be much lower when by stirred dead end system (0.955kW). This proved that the performance of circular flow system was more efficient in terms of rejection, mass transfer coefficient and energy consumption.

Exposure to Selected Geogenic Trace Elements (I, Li, and Sr) from Drinking Water in Denmark

The naturally occurring geogenic elements iodine (I), lithium (Li), and strontium (Sr) have a beneficial effect on human health. Iodine has an essential role in human metabolism while Li and Sr are used, respectively, as a treatment for various mental disorders and for post-menopausal osteoporosis. The aim here is to evaluate the potential for future epidemiological investigations in Denmark of lifelong and chronic exposure to low doses of these compounds. The drinking water data represents approximately 45% of the annual Danish groundwater abstraction for drinking water purposes, which supplies approximately 2.5 million persons. The spatial patterns were studied using inverse distance weighted interpolation and cluster analysis. The exposed population was estimated based on two datasets: (1) population density in the smallest census unit, the parishes, and (2) geocoded addresses where at least one person is residing. We found significant spatial variation in the exposure for all three elements, related mainly to geochemical processes. This suggests a prospective opportunity for future epidemiological investigation of long-term effects of I, Li, and Sr, either alone or in combinations with other geogenic elements such as Ca, Mg or F.

Oxyhalide Disinfection By-Products in Packaged Drinking Water and their Associated Risk

Disinfection by-products (DBPs) are formed during treatment of water for drinking purposes. Among these oxyhalide DBPs, viz. bromate, chlorate and chlorite are potentially harmful to humans. In the present study packaged drinking water samples of various commercial brands, available in Mumbai, were analysed for bromide, bromate, chlorite and chlorate ions using ion chromatography. The average concentration levels of bromide, bromate, chlorite and chlorate in packaged drinking water were 28.4, 10.7, 7.1 and 20.8 μg/l respectively. Bromate in 27% samples was found to be higher than the World Health Organization (WHO) guideline value of 10 μg/l, whereas chlorite and chlorate levels were well within the guideline value recommended by WHO. A good correlation between bromide and bromate (r=0.85) indicated formation of bromate from bromide present in drinking water. Health risks (carcinogenic risk and hazard quotient) associated with ingestion of bromate, chlorite and chlorate present in packaged drinking water are presented and discussed.

Preliminary Investigations of Ground Waters in and Around Musheerabad Area, Hyderabad, Telangana

To assess the suitability in relation to drinking water purpose fifteen ground water samples have been collected in and around Musheerabad area. The physico chemical parameters like pH, Conductivity, total dissolved solids (TDS), calcium (Ca2+),magnesium (Mg2+), sodium (Na+), potassium (K+), bicarbonate (HCO32- ) chloride (Cl-), fluoride(F-) sulphate (SO42-) and nitrate (NO3-) were analyzed using standard methods to know the groundwater quality. Except for fluoride and nitrates, values of most of these parameters fall within prescribed limits for drinking purpose (BIS:2012)

A study of physico-chemical properties of ground water of Kheralutaluka, Gujarat, India

The Mehsana district located in North Gujarat has experienced a growing concern because of itsrecent association with Fluoride toxicity in the form of endemic dental and skeletal fluorosis. The extensive agricultural consumption of groundwater in the area has led to the depletion of its quality. Therefore the present study was aimed to evaluate the groundwater quality, by checking its suitability for drinking water purpose and finding out major contaminants in the area. To fulfill the pupose of study water samples from 60 villages were collected and analysed for various physico-chemical parameters including major cations and anions and were statistically analysed. Geochemical evaluation was also performed using Pipers diagram. 53% samples were moderately hard, 30% samples were exceeding permissible limit of alkalinity while 45% samples have high fluoride content. The hydro-geochemical faces shows that water of kheralutaluka is dominated by alkaline earth metals (Ca2­+ and Mg2+) and the major types of water are of Ca-Cl-HCO3, Ca-HCO3-Cl and Na-HCO3-Cl rest all other samples have mix faces.

N-nitrosamines, emerging disinfection by-products of health concern: an overview of occurrence, mechanisms of formation, control and analysis in water

The presence of N-nitrosamines in water bodies used for drinking water purposes may present a more serious risk for humans than regulated disinfection by-products (DBPs) species. Hence, understanding and controlling the incidence of N-nitrosamines represents a contemporary challenge to the water industry. Although many of these molecules potentially formed as DBPs are detected in chlorinated natural waters, few studies have focused on the formation, occurrence, and analysis of N-nitrosamines. Until now, nine N-nitrosamines have been detected in water samples; N-nitrosodimethylamine is the most frequently reported nitrosamine in drinking water. Although there are currently no federal regulations for these molecules in drinking water, this family of N-DBPs is one of three potential groups of contaminants highlighted for possible regulatory action in the near future. This paper gives an overview of the current knowledge concerning the occurrence, precursors, and formation mechanisms of N-nitrosamines in water. In addition, the existing regulations are described and relevant analytical methods used for their quantification in water samples are also discussed.

Geochemistry and fluoride levels of geothermal springs in Namibia

A survey of groundwater from six geothermal springs in Namibia showed high concentrations of dissolved fluoride, with values up to 18.9mg/l. All values are higher than both the WHO limit and the Namibian guideline. High concentrations of fluoride are linked to Na-HCO3 or Na-SO4-HCO3 groundwater types, with increasing sulfate and chloride concentrations towards the south of Namibia. Values of δ2H and δ18O are more negative for the north of the country, and with increasing altitude of springs and distance from precipitation sources towards the southeast from the Indian Ocean. A shift of about 1‰ from the LMWL for Windhoek was observed for δ18O samples, which was probably caused by the exchange with reservoir rocks. Values of δ34S(SO4) reflect mixing of two principal sulfate sources, i.e., dissolution of gypsum originating from playas and interaction with sulfidic mineralization in tectonic bedrock zones. Values of δ13C(DIC) seem to be affected by a variable vegetation cover and mainly by the input of endogenous CO2. Estimated reservoir temperatures vary from 60°C to 126°C, with a maximum value at the Ganigobes site. The geothermal springs of Namibia in this study do not meet drinking water standards and thus their water can be used only for other purposes e.g. for thermal spas. Treatment would be necessary to decrease dissolved fluorine concentrations for drinking water purposes.

Surface Water Quality Assessment of Wular Lake, A Ramsar Site in Kashmir Himalaya, Using Discriminant Analysis and WQI

Multivariate techniques, discriminant analysis, and WQI were applied to analyze a water quality data set including 27 parameters at 5 sites of the Lake Wular in Kashmir Himalaya from 2011 to 2013 to investigate spatiotemporal variations and identify potential pollution sources. Spatial and temporal variations in water quality parameters were evaluated through stepwise discriminant analysis (DA). The first spatial discriminant function (DF) accounted for 76.5% of the total spatial variance, and the second DF accounted for 19.1%. The mean values of water temperature, EC, total-N, K, and silicate showed a strong contribution to discriminate the five sampling sites. The mean concentration of NO2-N, total-N, and sulphate showed a strong contribution to discriminate the four sampling seasons and accounted for most of the expected seasonal variations. The order of major cations and anions was Ca2+&gt;Mg2+&gt; Na+&gt;K+ and Cl-&gt;SO42-&gt;SiO22- respectively. The results of water quality index, employing thirteen core parameters vital for drinking water purposes, showed values of 49.2, 46.5, 47.3, 40.6, and 37.1 for sites I, II, III, IV, and V, respectively. These index values reflect that the water of lake is in good condition for different purposes but increased values alarm us about future repercussions.

Groundwater Quality Assessment in a Coastal Sand Aquifer: Implications for Drinking Water and Agricultural Use

In many countries, specifically those located in semi-arid zones, groundwater is the major source of drinking water, domestic and agriculture use. The present hydro geochemical study was carried out in the coastal sand aquifer of Thiaroye Dakar, Senegal. A total of 36 groundwater samples were collected from different dug wells, piezometers and boreholes in the study area to decipher hydro geochemistry and groundwater quality for determining its suitability for drinking and agricultural purposes. The analytical results of hydro geochemical parameters such as Na + , Ca 2+ , Mg 2+ , Cl - , SO4 2- of groundwater samples in the study area reveals that over 66% were found to be well within the safe range with respect to the world Health Organization for drinking water indicating that most of groundwater sampling sites are fit for drinking with respect of these parameters. The K + concentrations show that 56% of groundwater is suitable for drinking water. On the other hand, NO 3 - concentration show high levels exceeding the maximum permissible limits for drinking standard at almost 61% of groundwater samples indicating groundwater which is unfit for drinking water thus suggesting the need for treatment or precautionary measures to use for drinking water purpose. The TDS and EC values of groundwater indicate respectively that 69.5 and 61% are suitable for drinking water. According to the irrigation quality parameters such %N, SAR, RSC, KR and Ca 2+ /Mg 2+ ratio it was demonstrated that over 80% of groundwater samples in the study area are suitable for irrigation purpose. Furthermore, the interpretation of graphical plots such as Wilcox and US Salinity Laboratory for the classification of groundwater shows that most of the groundwater samples in the study area are suitable for irrigation purpose except for few groundwater samples.

Hydrogeochemistry of Urban Floodplain Aquifer Under the Influence of Contaminated River Seepage in Delhi (India)

Hydrogeochemical and hydrodynamic surface/groundwater interactions were investigated at the urban floodplain aquifer in Delhi, India. The heavily polluted Yamuna River is in hydraulic contact to the groundwater and river seepage results in a contamination plume. A conceptual redox zonation was developed based on the occurrence or absence of terminal electron acceptors. The redox zonation shows an inverted zonation from sulphate-reducing conditions close to the river over manganese- and iron-reducing conditions to a mixed oxic/suboxic zone. This study shows that the occurrence of problematic substances such as ammonium and arsenic in the groundwater is a consequence of the high load of untreated sewage in the river in combination with losing river conditions. Sequential extraction of aquifer material was performed to obtain information on geochemical availability of arsenic associated with different mineral phases and binding forms. Geogenic and anthropogenic arsenic sources contribute to overall arsenic concentration, and arsenic is found to be attributed mainly to amorphous iron oxide and sulphidic phases in the sediment. The contamination plume at the urban floodplain aquifer makes the groundwater unfit for drinking water purposes.

Hydrogeological investigation for assessment of the sustainability of low-arsenic aquifers as a safe drinking water source in regions with high-arsenic groundwater in Matlab, southeastern Bangladesh

• The risk of cross-contamination of deep aquifers by As in Bangladesh was assessed. • Groundwater flow simulations identified regional and local flow-systems. • Cross-contamination is likely to be limited to areas with many irrigation wells. • When groundwater at depth has low As, it can be used for drinking water purposes. • However, installation of deep irrigation wells is strongly discouraged. Exploitation of groundwater from shallow, high prolific Holocene sedimentary aquifers has been a main element for achieving safe drinking water and food security in Bangladesh. However, the presence of elevated levels of geogenic arsenic (As) in these aquifers has undermined this success. Except for targeting safe aquifers through installations of tubewells to greater depth, no mitigation option has been successfully implemented on a larger scale. The objective of this study has been to characterise the hydrostratigraphy, groundwater flow patterns, the hydraulic properties to assess the vulnerability of low-arsenic aquifers at Matlab, in south-eastern Bangladesh, one of the worst arsenic-affected areas of the country. Groundwater modelling, conventional pumping test using multilevel piezometers, hydraulic head monitoring in piezometer nests, 14 C dating of groundwater and assessment of groundwater abstraction were used. A model comprising of three aquifers covering the top 250 m of the model domain showed the best fit for the calibration evaluation criteria. Irrigation wells in the Matlab area are mostly installed in clusters and account for most of the groundwater abstraction. Even though the hydraulic heads are affected locally by seasonal pumping, the aquifer system is fully recharged from the monsoonal replenishment. Groundwater simulations demonstrated the presence of deep regional flow systems with recharge areas in the eastern, hilly part of Bangladesh and shallow small local flow systems driven by local topography. Based on modelling results and 14 C groundwater data, it can be concluded that the natural local flow systems reach a depth of 30 m b.g.l. in the study area. A downward vertical gradient of roughly 0.01 down to 200 m b.g.l. was observed and reproduced by calibrated models. The vertical gradient is mainly the result of the aquifer system and properties rather than abstraction rate, which is too limited at depth to make an imprint. Although irrigation wells substantially change local flow pattern, targeting low-As aquifers seems to be a suitable mitigation option for providing people with safe drinking water. However, installing additional irrigation- or high capacity production wells at the same depth is strongly discouraged as these could substantially change the groundwater flow pattern. The results from the present study and other similar studies can further contribute to develop a rational management and mitigation policy for the future use of the groundwater resources for drinking water supplies.