Quality Of Groundwater Samples Research Articles

A new approach to pollution vulnerability assessment in aquifers using K-means analysis

The most used methods to evaluate the vulnerability to contamination of aquifers are based on overlay index maps, such us DRASTIC, GOD and AVI. These methods assign weighting and rating values to hydrogeological characteristics, introducing subjectivity in the evaluation. In this research, a new methodology is proposed to eliminate some of that subjectivity. The methodology evaluates the vulnerability to contamination of a detrital aquifer using K-means cluster analysis with a new set of parameters. The set is composed of some parameters extracted from these methods, as well as other new ones that have a significant influence on the movement of contaminants. Application of the Principal Components Analysis (PCA) technique before using K-means cluster allowed the selection of the most relevant parameters. To validate the methodology, this was applied to a detrital aquifer located at central Spain (the so-called “Aluviales Jarama-Tajuña” aquifer) with a significant agricultural development. To compare the traditional methods of vulnerability assessment with the K-means cluster, nitrate concentration was used as a pollution indicator. Thus, 23 groundwater quality samples were used to correlate (Spearman´s correlation coefficient) the vulnerability values with nitrate concentration to validate the most suitable method. The results showed that GOD and AVI were not appropriate methods to evaluate the vulnerability of the aquifer, because they have negative or very low correlation with nitrate concentration (− 0.5 and 0.01, respectively). This is due to the use of very few variables that do not represent relevant features for the vulnerability assessment. Alternatively, DRASTIC and K-means cluster analysis obtained higher Spearman´s correlation coefficients (0.34 and 0.48, respectively). The relevant features selected by PCA analysis to use in the K-means low-dimensional analysis were depth of groundwater (D), net recharge (R), and land use (L). The new proposed method grouped data in three clusters that represent low vulnerability (35.9% of the study area), moderate (41.4%) and high vulnerability (22.7%). K-means increases the Spearman’s correlation by 14% with respect to the most approximate conventional method (DRASTIC). Therefore, the results obtained confirm the advantage of joint application of PCA and K-Means analysis, which represents a novel approach for the assessment of groundwater vulnerability in detrital aquifers.

Assessment of Concentration Levels of Contaminants in Groundwater of the Soutpansberg Region, Limpopo Province, South Africa

Groundwater contributions towards improved food security and human health depend on the level of contaminants in groundwater resources. Many people in rural areas use groundwater for drinking purposes without treatment and knowledge of contaminant levels in such waters, owing to parachute research in which research outputs are not shared with communities. This study argues that parachute research exposes groundwater users to health hazards and threatens the food security of communities. Concentration levels of contaminants were measured to ascertain suitability of groundwater for drinking and irrigation purposes. A total of 124 groundwater quality samples from 12 boreholes and 2 springs with physiochemical data from 1995 to 2017 were assessed. This study found high concentration levels of contaminants, such as F−, NO3−, Cl−, and total dissolved solids, in certain parts of the studied area. In general, groundwater was deemed suitable for drinking purposes in most parts of the studied area. Combined calculated values of sodium adsorption ratios, Na%, magnesium hazards, the permeability index, residual sodium carbonate, and total dissolved solids determined that groundwater was suitable for irrigation purposes. The discussion in this paper shows that scientific knowledge generated on groundwater quality is not aimed at developing skills and outputs for improved human health and food security but rather for scientific publication and record keeping, leaving communities where such data has been gathered devoid of knowledge about groundwater quality. In this study, it is recommended that research outputs on groundwater quality should be shared with groundwater users through various initiatives.

Groundwater quality evaluation: a case study of Igando waste dumpsite, southwestern Nigeria

The quality of groundwater samples around Igando area, Lagos State, Nigeria was investigated with the aim of detecting possible influence of dumpsites on nearby aquifers. Thirty-seven (37) groundwater samples were evaluated for their suitability in drinking and agricultural purposes. Physical parameters were determined in situ using portable multi-meter. Flame absorption was used to determine the concentrations of major cations while ion chromatography and titrimetry was used for anions’ concentration. Bacteriological test was conducted using multiple tube technique. Results of in-situ physical parameters revealed pH range of 7.01–7.79, EC range of 20–880 μS/cm while TDS range from 13–590 mg/L. Laboratory analyses showed Ca2+ concentration ranging 1.60–72.80 mg/L and HCO3− ranging 19.52–204.96 mg/L as the dominant ions. None of the ions’ concentrations exceed the WHO drinking limit. Water Quality Index (WQI) classification showed that all samples fall within good to excellent water categories. The majority of the samples are suitable for irrigation using indices such as Sodium Adsorption Ratio (SAR), Kelly’s ratio (KR), and Magnesium Hazard (MH). Bacteriological analyses revealed low total bacterial count and E-coli absence making the samples safe for drinking. Piper diagram indicated two main water-facies (Ca–HCO3 and the Mixed Ca–Mg–Cl). Gibbs’s plots showed that the samples are primarily influenced by rock weathering, while precipitation also contributed. Chloro-Alkaline Index confirmed direct ion-exchange process. Cluster analyses revealed four groups: the first revealed influence of groundwater by anthropogenic activities in the study area, the second and third revealed lithological origin of ions in the water while group 4 indicated pH low influence on the dissolved ions in the waters. The groundwater quality can be said to be fair-good, thus suggestive of minimal interactions between the dumpsites and the groundwater in the area at the time of testing.

Multicriteria-analysis of deep groundwater quality using WQI and fuzzy logic tool in GIS: A case study of Kebilli region, SW Tunisia

The suitability of groundwater for drinking and irrigation purposes is potentially disturbed by a variety of factors, including climate change, salinization and risky agricultural practices. The region of Kebilli (Southwestern Tunisia) is marked by an arid climatic condition with a Saharan tendency. However, the spatial partition of the stress factors was not addressed so far in spite of the increasing demand for groundwater to the agricultural and domestic activities which supports the social and economic pressure. Therefore, Water Quality Index (WQI) and Fuzzy Logic models were applied to evaluate the groundwater quality in the Kebilli region for both drinking and irrigation purposes using the geographic information system (GIS) environment to analyze the spatial partition of various factors. According to the analytical results, the calculated values of WQI are between 83.421 and 436.858 for drinking and range from 50 to 77 for irrigation purposes. The prepared Fuzzy spatial maps show that the “desirable” and “acceptable” classes of groundwater quality samples are situated in the center of the studied region, while the “undesirable” quality of groundwater is observed mainly at the Southeastern sectors due to the domestic and agricultural activities besides the over-exploitation of the aquifer. In addition, the Fuzzy membership levels generated into a GIS-based maps give a high correlation of 0.88 and 0.79 with assessed values of WQI for both drinking and irrigation purposes respectively. Grouping analyses also confirm the resulted maps, in turn, the anthropogenic effects coincides globally with the unsuitable areas for both drinking and irrigation purposes. Consequently the perturbations in the fragile environment of the oasis ecosystem are closely related to the deterioration of the groundwater quality and the intensive use of fertilizers and pesticides for agricultural needs in the Kebilli region. The research results may improve the understanding of the groundwater sustainability and as support decision makers for planning the water management and its protection.

Potential Human Health Risks Due to Groundwater Fluoride Contamination: A Case Study Using Multi-techniques Approaches (GWQI, FPI, GIS, HHRA) in Bilate River Basin of Southern Main Ethiopian Rift, Ethiopia.

The main focus of the present research was to examine the appropriateness of groundwater resources for drinking purposes in the Bilate River Basin of Southern Main Ethiopian Rift, Ethiopia. The groundwater quality index (GWQI), fluoride pollution index (FPI), and human health risk were usedto examine the human health risk factors associated with the intake of high fluoride groundwater. For this purpose, 29 groundwater samples were collected from the existing wells and were analyzed forvarious physicochemical parameters. The dominant cation was Na+, followed by Ca2+, Mg2+, and K+. The dominant anion was HCO3-, followed by Cl-, SO42-, and F-. The Gibbs plotshows thatrock-water interactions are the dominant factor controlling the groundwater chemistry. By using the GWQI, the quality of groundwater samples was 31% excellent, 21% good, 31% poor, and 17% very poor. The fluoride concentration in groundwater ranges from 0.2 to 5.60mg/L (mean, 2.10mg/L). 59% (i.e., 17 wells) of the groundwater samples were not suitable for drinking, because they surpassed the drinking water quality limit of 1.5mg/L. The remaining 41% (i.e., 12 wells) of the samples were suitable for drinking. The FPI indicates that 51.72% of the wells were highly polluted by fluoride. The noncarcinogenic health risk varies from 0.75 to 8.44 for children (83%), 0.34-3.84 for women (62%), and 0.27-3.01 for men (52%), which indicates that children are at higher health risk than women and men due to the physiological condition and the rates of ingestion.

Mapping Freshwater Chlorophyll-a Concentrations at a Regional Scale Integrating Multi-Sensor Satellite Observations with Google Earth Engine

Monitoring harmful algal blooms (HABs) in freshwater over regional scales has been implemented through mapping chlorophyll-a (Chl-a) concentrations using multi-sensor satellite remote sensing data. Cloud-free satellite measurements and a sufficient number of matched-up ground samples are critical for constructing a predictive model for Chl-a concentration. This paper presents a methodological framework for automatically pairing surface reflectance values from multi-sensor satellite observations with ground water quality samples in time and space to form match-up points, using the Google Earth Engine cloud computing platform. A support vector machine model was then trained using the match-up points, and the prediction accuracy of the model was evaluated and compared with traditional image processing results. This research demonstrates that the integration of multi-sensor satellite observations through Google Earth Engine enables accurate and fast Chl-a prediction at a large regional scale over multiple years. The challenges and limitations of using and calibrating multi-sensor satellite image data and current and potential solutions are discussed.

Hydrochemical characteristics and water quality evaluation of shallow groundwater in Suxian mining area, Huaibei coalfield, China

The aim of this study is to evaluate the hydrogeochemical characteristics and water environmental quality of shallow groundwater in the Suxian mining area of Huaibei coalfield, China. The natural formation process of shallow groundwater in Suxian is explored using Piper trilinear charts and Gibbs diagrams, and by examining the ratios between the major ions. United States Salinity Laboratory (USSL) charts, Wilcox diagrams, and the water quality index (WQI) are further employed to quantify the differences in water quality. The results reveal that the main hydrochemical facies of groundwater are HCO3–Ca, and that silicate dissolution is the main factor controlling the ion content in shallow groundwater. The USSL charts and Wilcox diagrams show that most of the water samples would be acceptable for use in irrigation systems. The WQI results for each water sample are compared and analyzed, and the quality of groundwater samples around collapse ponds is found to be relatively poor.

Spatial investigation of groundwater quality and its suitability for irrigation in Yalgaon dam command area in Buldhana district of Maharashtra

The study of groundwater quality parameters is most essential for irrigation water, and its quality is a serious problem around the study area. The spatial analysis of groundwater quality mapping is required and stimulated us to undertake a systematic work of groundwater quality parameters for suitable water exploration of crops from open wells in Yalgaon Dam command area. A detailed study of physico-chemical parameters composition of groundwater was performed from groundwater quality data of three seasons like pre-monsoon, monsoon (rainy) post-monsoon in the year of 2017 and 2018. The groundwater quality data were collected from nine villages in 20 wells samples randomly distributed in viz: Antri-teli, Sakhali, Yalgaon, Ruhikhed-Tekale, Sao, Sagwan, Kolwad, Nandra-koli, Ajispur in Yalgaon dam command area. GIS is a powerful tool for representation and analysis of spatial information related to groundwater resources management. To achieve this aim, the groundwater quality samples were analyzed for the preparation of groundwater quality indices such as pH, electrical conductivity, TDS, cation such as Ca, Mg, Na, K, and anions Cl, Sulphate, Bicarbonate. The results shows that the groundwater was having high salinity and low sodium hazard (C3S1) during pre monsoon (summer) monsoon (rainy) season, and post monsoon (winter) season, the water can be use for irrigation with adoption of proper leaching management. Among all the cations Ca2+, Mg2+ and K+ was below the permissible limit in all three season except seven sample where Mg2+and Na+ exceeds permissible limit during pre monsoon and monsoon season. Among the anions HCO3-, Cl- and SO42- were also below the permissible limit.

Enhancing nitrate and strontium concentration prediction in groundwater by using new data mining algorithm

Groundwater resources constitute the main source of clean fresh water for domestic use and it is essential for food production in the agricultural sector. Groundwater has a vital role for water supply in the Campanian Plain in Italy and hence a future sustainability of the resource is essential for the region. In the current paper novel data mining algorithms including Gaussian Process (GP) were used in a large groundwater quality database to predict nitrate (contaminant) and strontium (potential future increasing) concentrations in groundwater. The results were compared with M5P, random forest (RF) and random tree (RT) algorithms as a benchmark to test the robustness of the modeling process. The dataset includes 246 groundwater quality samples originating from different wells, municipals and agricultural. It was divided for the modeling process into two subgroups by using the 10-fold cross validation technique including 173 samples for model building (training dataset) and 73 samples for model validation (testing dataset). Different water quality variables including T, pH, EC, HCO3-, F-, Cl-, SO42-, Na+, K+, Mg2+, and Ca2+ have been used as an input to the models. At first stage, different input combinations have been constructed based on correlation coefficient and thus the optimal combination was chosen for the modeling phase. Different quantitative criteria alongside with visual comparison approach have been used for evaluating the modeling capability. Results revealed that to obtain reliable results also variables with low correlation should be considered as an input to the models together with those variables showing high correlation coefficients. According to the model evaluation criteria, GP algorithm outperforms all the other models in predicting both nitrate and strontium concentrations followed by RF, M5P and RT, respectively. Result also revealed that model's structure together with the accuracy and structure of the data can have a relevant impact on the model's results.

Groundwater quality evaluation for different uses in the lower Ketar Watershed, Ethiopia.

Groundwater quality samples from 33 wells were collected in the lower Ketar watershed (Ethiopia) to study its suitability for domestic and irrigation purposes. Samples were evaluated for major ions and physicochemical properties. In 58% of the samples analyzed, Ca2+ is the dominant cation and Na+ dominates the remaining 42% of the samples. Among the anions found during analyzation, HCO3- is the solo dominant ion in all the wells sampled. The order of the concentration of the major ions was Ca2+ > Na+ > Mg2+ > K+ for the cations and HCO3- > SO42- > Cl > NO3- for the anions. AquaChem analysis shows that Ca-HCO3 and Na-HCO3 are the major water types in the area. The analyses indicated that the dissolution of fluorite or fluorapatite is the possible source of the high fluoride concentration in the area. And, the interactions between water and rock and cation exchanges mainly determine the water quality. The suitability of the groundwater for use in irrigation was evaluated based on the salinity (EC), SAR, %Na, RSC, PI, KR, and the USSL Salinity diagram. The groundwater from most of the wells can be used for irrigation without any significant restriction except for a few of the wells downstream. Its suitability for domestic use was evaluated by comparing with the WHO standard limits. The parameters limiting the use of this groundwater for drinking purposes are F- (94%), HCO3- (45%), and Ca2+ (33%). All the remaining major cations and anions complied with the WHO standard limits for drinking.

Transforming Vulnerability Indexing for Saltwater Intrusion into Risk Indexing through a Fuzzy Catastrophe Scheme

Mapping vulnerability to Saltwater Intrusion (SWI) in coastal aquifers is studied in this paper using the GALDIT framework but with a novelty of transforming the concept of vulnerability indexing to risk indexing. GALDIT is the acronym of 6 data layers, which are put consensually together to invoke a sense of vulnerability to the intrusion of saltwater against aquifers with freshwater. It is a scoring system of prescribed rates to account for local variations; and prescribed weights to account for relative importance of each data layer but these suffer from subjectivity. Another novelty of the paper is to use fuzzy logic to learn rate values and catastrophe theory to learn weight values and these together are implemented as a scheme and hence Fuzzy-Catastrophe Scheme (FCS). The GALDIT data layers are divided into two groups of Passive Vulnerability Indices (PVI) and Active Vulnerability Indices (AVI), where their sum is Total Vulnerability Index (TVI) and equivalent to GALDIT. Two additional data layers (Pumping and Water table decline) are also introduced to serve as Risk Actuation Index (RAI). The product of TVI and RAI yields Risk Indices. The paper applies these new concepts to a study area, subject to groundwater decline and a possible saltwater intrusion problem. The results provide a proof-of-concept for PVI, AVI, RAI and RI by studying their correlation with groundwater quality samples using the fraction of saltwater (fsea), Groundwater Quality Indices (GQI) and Piper diagram. Significant correlations between the appropriate values are found and these provide a new insight for the study area.

Comparison of four learning-based methods for predicting groundwater redox status

Knowing the location where groundwater denitrification occurs, or by proxy the groundwater redox status (oxic, mixed, and anoxic), is valuable information for assessing and managing potential agricultural land-use impacts on freshwater quality. We compare the efficacy of supervised (Linear Discriminant Analysis LDA; Boosted Regression Trees, BRT; and Random Forest, RF) and unsupervised (Modified Self-Organizing Map, MSOM) learning-based methods to predict groundwater redox status in the agriculturally dominated Tasman, Waikato, and Wellington regions of New Zealand. Thresholds applied to regional groundwater-quality samples provide redox status variables and learn heuristics constrained by these variables and applied to spatial factors (climate, elevation, geologic, hydrology soils, and well depth) identify optimal sets of regional predictor variables. A split-sample approach is used to train and test the learning methods ability to predict redox status using the optimal predictor variables. Overall, the supervised methods demonstrate a prediction bias toward oxic conditions and inability to perform statistically well when using independent regional data; for example, consider kappa statistics for BRT (Tasman: 0.42, Waikato: 0.38, Wellington: 0.17), RF (Tasman: 0.42, Waikato: 0.47, Wellington: 0.17 and LDA (Tasman: 0.46, Waikato: 0.32, Wellington: 0.17). By contrast, the unsupervised method performs statistically well when predicting oxic, mixed, and anoxic conditions and corresponding depths when using independent regional data; for example, consider MSOM kappa statistics for Tasman: 0.78, Waikato: 0.80, Wellington: 0.76. The unsupervised learning method provides the added benefits of being (1) able to combine predictions into 3D regional anoxic probability plots for interpreting the spatial influence of paleosols and groundwater flowpaths on redox status, and (2) readily extended to map 3D redox status across New Zealand and other countries despite data bias and sparsity.

Spatial analysis of groundwater quality mapping in hard rock area in the Akola and Buldhana districts of Maharashtra, India

The study of groundwater quality parameters is most essential for irrigation and drinking water, and its quality is a serious problem around the study area. The spatial analysis of groundwater quality mapping is required and stimulated us to undertake a systematic work of groundwater quality parameters for suitable water exploration of crops and drinking purposes from bore wells and open wells in basaltic hard rock area. A detailed study of physico-chemical parameters composition of groundwater was performed from groundwater quality data of post-monsoon (December) in the year of 2013. The groundwater quality data were collected from 35 wells samples randomly distributed in area. GIS is a powerful tool for representation and analysis of spatial information related to groundwater resources management. To achieve this aim, the groundwater quality samples were analysed for the preparation of groundwater quality maps such as pH, electrical conductivity, TDS, Cl and Mg. The groundwater quality parameters were analysed for all the sampling locations using IWD interpolation techniques. In this study, groundwater quality values observed are minimum and maximum values of pH (6.2–8 on scale), electrical conductivity (348–1598 S/cm), total dissolved solids (268.32–707.95 mg/l), carbonate (0–30 mg/l), bicarbonate (0.9–58.9 mg/l), chloride (1.15–28.36 mg/l), sulphate (17.4–105 mg/l), nitrate (0.4–6.0 mg/l), calcium (2.35–7.24 mg/l), magnesium (2.88–3.73 mg/l), sodium (0.57–3.31 mg/l), potassium (0.26–1.2 mg/l), sulphate (0.5–4.64 mg/l), bicarbonate+ carbonate (1.07–11.16 mg/l) and carbonate (0–0.79 mg/l) in hard rock area. The spatial variation maps were derived and integrated through ARC GIS 10.3 software. The interpolation tool was used to obtain the spatial distribution of groundwater quality parameters in the basaltic hard rock area. Therefore, the result of groundwater analysis of large number of groundwater samples has been found to be suitable for drinking and irrigation purposes in the basaltic hard rock area.

Hydrochemical and environmental isotope analysis of groundwater and surface water in a dry mountain region in Northern Chile.

This case study examines the geological imprint and land use practices on water quality in the arid Huasco Valley against the backdrop of ongoing water conflicts surrounding competing demands for agriculture and mining. The study is based on a detailed analysis of spatial and temporal variations of monthly surface and bi-monthly groundwater quality samples measured during the Chilean summer of 2015/16. Additional information on source regions and river-groundwater interactions were collected using stable water isotopes. Regarding the geological impact on water quality, high concentrations of Ca2+, SO42- and HCO3- indicate a strong influence of magmatic rocks, which constitute this high mountain basin, on the hydrochemistry. Piper and Gibbs-diagrams revealed that all samples show a homogenous distribution dominated by rock-water interactions. Measured NO3- concentrations in surface water are generally low. However, groundwater aquifers exhibit higher concentrations. Mn is the only heavy metal with elevated concentrations in surface water, which are possibly related to mining activities. The results illustrate that both surface and groundwater can be classified as suitable for irrigation. In addition, groundwater has been found to be suitable as drinking water. High similarities in isotopic signatures indicate a strong connection between surface and groundwater. Isotopic analyses suggest a strong influence of evaporation. This combined approach of hydrogeochemical and isotopic analysis proved to be a helpful tool in characterizing the catchment and can serve as a basis for future sustainable water management.

Geographic Information System mapping of gross alpha/beta activity concentrations in ground water samples from Karnataka, India: A preliminary study

The activity concentrations of the gross α and β in ground water samples were determined for 178 bore wells of Karnataka state of India. The aim of this study was to develop a first insight regarding the radiological quality of ground water samples from Karnataka state. Sampling and measurements were carried out from 2013 to 2014. So far there has been no detailed study in the radioactivity measurements in drinking water of Karnataka state. TDS, pH and gross alpha and gross beta activity measurements have been performed according to standards. The gross alpha and gross beta activity concentrations in the bore water samples of Karnataka state have been found to lie between 0.69–15.26mBq/l with a mean of 5.66 ± 0.50mBq/l and 14.6–108.5mBq/l with a mean of 57.76mBq/l respectively. In general, the gross beta activity was higher than the alpha activity concentration. From the value of gross alpha and gross beta, it is clear that the water samples are investigated are acceptable for consumption, complying with the WHO recommendations for drinking water. The data obtained can provide information for to make decisions about potential future drinking water regulations.

At least 50 million in Pakistan at risk from arsenic contamination

The first-ever hazard map of arsenic contamination in Pakistan’s groundwater shows 50 million–60 million people are at risk, according to a new study (Science Advances 2017, DOI: 10.1126/sciadv.1700935). Swiss, Chinese, and Pakistani researchers worked together to make the first large-scale estimates based on a model that combined local geology and a set of 1,200 new groundwater quality samples, which had found contamination many times the World Health Organization’s recommended groundwater limits. This finding shows that more needs to be done to protect Pakistan’s people, including those in the major population centers of Lahore and Hyderabad. “This is an alarmingly high number, which demonstrates the urgent need to test all drinking water wells in the Indus Plain,” says lead author Joel E. Podgorski, a geophysicist at the Swiss Federal Institute of Aquatic Science & Technology. Some 150 million people worldwide were already estimated to be dealing with arsenic contamination of their

Extensive arsenic contamination in high-pH unconfined aquifers in the Indus Valley.

Arsenic-contaminated aquifers are currently estimated to affect ~150 million people around the world. However, the full extent of the problem remains elusive. This is also the case in Pakistan, where previous studies focused on isolated areas. Using a new data set of nearly 1200 groundwater quality samples throughout Pakistan, we have created state-of-the-art hazard and risk maps of arsenic-contaminated groundwater for thresholds of 10 and 50 μg/liter. Logistic regression analysis was used with 1000 iterations, where surface slope, geology, and soil parameters were major predictor variables. The hazard model indicates that much of the Indus Plain is likely to have elevated arsenic concentrations, although the rest of the country is mostly safe. Unlike other arsenic-contaminated areas of Asia, the arsenic release process in the arid Indus Plain appears to be dominated by elevated-pH dissolution, resulting from alkaline topsoil and extensive irrigation of unconfined aquifers, although pockets of reductive dissolution are also present. We estimate that approximately 50 million to 60 million people use groundwater within the area at risk, with hot spots around Lahore and Hyderabad. This number is alarmingly high and demonstrates the urgent need for verification and testing of all drinking water wells in the Indus Plain, followed by appropriate mitigation measures.

Assessment of Groundwater Contamination with Agricultural Chemicals in Upper Pampanga River Integrated Irrigation System, Philippines

Water used for domestic and drinking purposes in agricultural communities is still extracted from the groundwater using shallow tube wells. However, its quality is threatened by contamination due to chemical residues that were not fully utilized in a rice production system. These residues eventually go with the water as it is distributed in the whole area, with some amount reaching the groundwater. In this study, the rate of chemical fertilizers and pesticides applied by farmers and the possible level of groundwater contamination was determined. The information obtained maybe used in the formulation of strategies for future monitoring of the presence and level of concentration of chemical residues and regulation of the usage of agricultural chemicals in the Upper Pampanga River Integrated Irrigation Systems (UPRIIS). Results revealed that farmers in the UPRIIS service area used chemical fertilizers at the rate of 69-173 kg N per ha, 26-32 kg P per ha and about 30 kg K per ha. These application rates were high as compared to recommended rates, particularly in Districts IV and V of the UPRIIS service area. Similarly, majority of the farmers (60-80%) were using molluscicides, herbicides, insecticides and fungicides in preventing and controlling pests in their crops. Analysis of the quality of groundwater samples indicated that values obtained were within tolerable limits when compared to the standards for drinking water. The mean values of K concentration, which was found to be statistically different between the districts also exhibited strong relationships with PO43-, Na+ and NO3-. The other parameters of water quality showed no significant differences between and among the districts. While the observed values were within the tolerable limits, monitoring of their levels must regularly be done to safeguard the quality of groundwater.

Large Scale Electrical Resistivity Tomography Survey Correlated to Hydrogeological Data for Mapping Groundwater Salinization: A Case Study from a Multilayered Coastal Aquifer in Rhodope, Northeastern Greece

A large scale two dimensional electrical resistivity survey was carried out to investigate groundwater salinization phenomena of a multilayered coastal aquifer in south Rhodope area, northeastern Greece. The electrical resistivity tomography (ERT) profiles, calibrated with lithological, physicochemical and geophysical log data, were used to demarcate the geometry of the aquifer system and characterize the extent of the interface between saline and freshwater in a coastal groundwater system, which has been subject to overexploitation for the last 35 years. In total, 12 deep high resolution ERT profile lines, covering a distance of approximately 15 km were carried out at key locations across the downgraded part of the aquifer system. The resistivity sections were calibrated using a reference dataset of 45 information wells incorporating 28 lithological logs, 31 groundwater quality samples from a variety of screen placements and five gamma ray logs. Results revealed the presence of four major resistivity zones ranging in values between 0.1 and 150 Ωm at various depths and locations. A very low resistivity zone (0.1–5 Ωm) correlated with saline water saturated layers, a medium resistivity zone (5–15 Ωm) attributed to clays and silts, and two high resistivity zones generally representing freshwater saturated sediments of coarse grain size (15–40 Ωm) or alterations of thin marl and fine sand layers (40–150 Ωm). It is demonstrated that extensive use of high resolution deep geoelectrical sections, calibrated with a large number of hydrogeological data can successfully delineate aquifer geometry dimensions, identify hydraulic boundaries and clarify ambiguous field measurements, thus allowing the development of a thorough hydrogeological conceptual model.

Assessment of Groundwater Pollution and its Impact in and around Punnam Area of Karur District, Tamilnadu, India

Various samples of groundwater were collected from different areas in and around the Punnam village of Karur District, India and analyzed for their physicochemical characteristics. The results of this analysis were compared with the water quality standards of WHO and CPHEEO. In this analysis the various physicochemical parameters such as pH, electrical conductivity, turbidity, total dissolved solids, Cl-, F-, SO42-, NO3-, Na+, K+, Fe, Cr, calcium and magnesiumetc., were determined using standard procedures. The quality of groundwater samples were discussed with respect to these parameters and thus an attempt were made to ascertain the quality of groundwater used for drinking and cooking purposes in the sampling areas.