Majority Of Groundwater Research Articles

Risk Analysis of Groundwater Contaminant in Rural Areas Using Spatial Distribution

Background: Water is a very important material for the life of creatures in nature and its function for life cannot be replaced by other compounds. Groundwater is an important resource for humans, especially in rural areas that depend on Groundwaters as the main source of clean water. However, the quality of groundwater in many areas has decreased due to pollution from human activities, such as agriculture and industry. Method: This study aims to analyse the level of pollution risk of groundwaters in rural areas of Masama District, Banggai Regency using descriptive quantitative methods. Spatial analysis of pollution risk was conducted on 516 Groundwaters selected as samples. Spatial data is collected by recording the location of each well using GPS, which is then used to create a spatial map. The pollution risk analysis is based on the Sanitation Inspection results, using 11 key indicators. Result: The results showed that 4 Groundwaters (0.78%) were in the very high pollution risk category, 115 Groundwaters (22.29%) were in the high-risk category, 204 Groundwaters (39.53%) were classified as medium risk, and 193 Groundwaters (37.40%) had low pollution risk. The results indicate that most Groundwaters in the study area are at moderate to high risk. Groundwaters with high and very high risk are dominated by Groundwaters located in Minang Andala, Purwo Agung and Kembang Merta villages, which are agricultural areas with sufficient area and most of the people have livestock around their homes which could potentially be a source of contaminants. Conclusion: This study shows that the majority of Groundwaters in the study area have a moderate to high risk of pollution, with high and very high-risk categories found in villages that have agricultural and livestock activities. This emphasises the need for more intensive groundwater management and protection measures.

Groundwater quality assessment in different volcanic rocks using water quality index in the tropical area, Indonesia

Groundwater is the main water source that is most widely used in the world, one of which is in Indonesia. One of the uses of groundwater is for consumption needs. Therefore, the groundwater used should have good water quality. For this reason, this study aimed to determine groundwater quality in Indonesia during the dry season and make recommendations for groundwater management policies. A total of 211 groundwater samples taken from springs, drilled wells, and dug wells spread across volcanic areas on the islands of Sumatra, Java, Bali, and Sulawesi were collected to test their quality in this research. The method used in this research consisted of 4 analyses: WHO threshold analysis, Piper Diagram, Water Quality Index (WQI), and statistical correlation and regression. Based on the analysis, it was discovered that 47 K+ samples, 1 Na+ sample, 5 Ca2+ samples, 1 Cl- sample, 115 HCO3- samples, 3 TDS samples, and 3 pH samples exceeded WHO standards. The results of the Piper triangle diagram analysis showed that the majority of groundwater in Indonesia falls into the Unpolluted Groundwater classification (categories D and G), and the results of the WQI analysis also showed that 98% of the groundwater in Indonesia analyzed falls into the excellent and good water categories. The results of statistical analysis of the parameters K+, Na+, Mg2+, Ca2+, SO42-, Cl-, HCO3-, TDS, and pH showed that all these parameters are strongly and positively correlated with the WQI value.

Hydrochemical Characterisation of Groundwaters in a Crystalline Basement Environment: The Case of Fractured Aquifers in the Poni Watershed in the South-West Region of Burkina Faso, West Africa

The Poni watershed is located in the south-west of Burkina Faso. Its geology is made up of fractured crystalline and crystallophyllian basement, where fractured aquifers are the most exploited for water needs. The aim of this study is to determine the physico-chemical characteristics of the groundwater in the fractured aquifers of the Poni watershed in order to gain a better understanding of the mineralisation processes and hydrochemical properties of the groundwater in these aquifers. To do this, approaches based on the determination of Calcite Saturation Indices (CSI) and Dolomite Saturation Indices (DSI), Principal Component Analysis (PCA) and hydrochemical properties show that the majority of groundwater in the basin is undersaturated with respect to carbonates (79.37%) and divided into three families in relation to circulation speed: very slow circulation water (20.63%), slow circulation water (55.56%) and fast circulation water (23.81%). The approaches also show that the mineralisation of groundwater in the basin is governed by the acid hydrolysis of minerals in the surrounding rocks, residence time and surface inputs. They are characterised by calcic and magnesian bicarbonate facies (85.7%), calcic bicarbonate facies (6.35%), sodium and potassium bicarbonate facies (1.59%) and calcic and magnesian sulphate chlorides (6.35%).

Hydrogeochemical characteristic and water quality index of groundwater and streamwater at Nam Mu River basin, Lai Chau province in northwest Vietnam

Assessing the quality of groundwater and upstream water in regions experiencing water scarcity during the dry season, such as the mountainous districts of Northern Vietnam, holds immense significance in the management, utilization, and preservation of natural water resources. In this study, we collected and analyzed 54 samples of groundwater and upstream streamwater within the Nam Mu river basin in Lai Chau province during the dry season. These samples underwent thorough analysis for physicochemical parameters, major ion concentrations, and trace elements. Some results revealed a close relationship between streamwater and groundwater, indicating a similar chemical composition. These waters could be classified based on geological formations, yielding two primary water types in the area. The first type, characterized by Ca2+ - Mg2+ - HCO3 − is prevalent in Triassic terrigenous sediments. The second type is a mixed water type, ranging from Ca2+ - Mg2+ - Cl− to Ca2+ - Na+ - HCO3 −, primarily distributed in Permian felsic volcanic formations. These distinct water types are primarily the result of interactions between water and rock, precipitation processes, and ion exchange phenomena. Geochemical simulation results demonstrated the supersaturation of aragonite, calcite, and dolomite minerals, leading to the precipitation of carbonate minerals. Concurrently, the simulation indicated a tendency to dissolve minerals such as fluorite, gypsum, halite, and sylvite. The assessment of water quality using the WQI indicates that, in accordance with QCVN 01-1:2018/BYT 2018 standards, the majority of groundwater and streamwater are suitable for domestic use. However, exceptions exist in certain sample locations where water quality exceeds permissible standards, primarily due to elevated levels of Fe, Mn, and NO3 − concentration. Hence, it is important to implement water treatment processes for the water sourced from these specific locations before their utilization in daily activities to ensure the safety and well-being of the local population.

Hydrogeochemical appraisal of groundwater quality in Ngoua watershed (Douala-Cameroon): Implication for domestic purposes

Groundwater has been used for many purposes like domestic, agriculture, and industrialization in many regions of the world. Assessing groundwater quality and identifying pollutant risks are essential for managing groundwater resources. Ngoua watershed is located in sedimentary coastal zone of Douala. Groundwater is the major source of water for domestic purposes. Thus, the objective of this work is to assess groundwater chemistry and identify hydrochemical processes affecting groundwater quality of Ngoua catchment and its implication for domestic use. 30 groundwater samples were collected (23 wells, 4 springs and 3 boreholes) and physical-chemical parameters were analysed (T°, pH, TDS, EC), cations (Na+, K+, Ca2+; Mg2+ NH4+) and anions (Cl−, HCO3−, SO42− NO3−, PO43−, and F−) and calculation of groundwater quality index (WQI). The pH indicates that the groundwater in the study area is acidic to neutral. The temperature is similar to the ambient temperature of the study area (27 °C). The EC and TDS of the study area are average and the water are moderately mineralized. The order of mean abundance of the cation concentrations is as follows Ca2+˃Na+˃ Mg2+˃K+˃NH4+and the order of increasing classification of the anions is as follows NO3−˃Cl−˃SO42- ˃HCO3−˃PO43−˃F−The distribution of chemical facies of groundwater in the study area is as follows: 63.33 % Ca-HCO3, 23.33 % Ca-Mg-Cl and finally 13.33 % Na-Cl. The factors controlling groundwater chemistry are rock-water interaction, cation exchange, dissolution and anthropogenic activities may affect groundwater chemistry. Water Quality Index on this study varies between 2.12 and 187.21 with average of 29.67 and the majority of groundwater in the study area is acceptable in quality and can be used for domestic purposes such as drinking and irrigation. Nitrate and sulfate are the main contaminants of groundwater in the area. However, the high concentrations of NO3− in groundwater suggests than human activities (industrial and domestic activities) is intense and responsible factors for groundwater pollution in study area. Results of this study indicate importance of preventive measures to control groundwater contamination in Ngoua watershed.

Hydrogeochemical studies of groundwater in semi-arid areas of northern Ethiopia using geospatial methods and multivariate statistical analysis techniques

The present study focused on evaluating the groundwater hydrogeochemical of shallow aquifers in the semi-arid areas of northern Ethiopia, using geospatial modelling and multivariate statistical techniques. Physico-chemical parameters, including pH, major ions, electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH), pollution index (PI) and other parameters, from 22 samples have been used to assess water quality, sources of various ions, water types and factors controlling groundwater chemistry. Results showed that the spatial distribution of major ions, EC, TDS, TH and PI values in these samples significantly differ from one location to another due to geological variations and anthropogenic activities of the area. The quality of most groundwater is generally unfit for drinking due to their PI, EC, TH, calcium, potassium, total iron and bicarbonate (HCO3−) values that found to be above the permissible limits of WHO and Ethiopian standards. The parameters like sodium percentage, sodium adsorption ratio (SAR), residual sodium bicarbonate, permeability index, magnesium hazard and Kelly’s ratio revealed good quality of groundwater for irrigation utilization, whereas EC of irrigation water (ECiw), combined effects of ECiw − SAR and bicarbonate hazard values indicated that majority of groundwater are not suitable for irrigation use. Piper trilinear diagram classified majority of samples under temporary hardness with Ca–Mg–HCO3 type. Further, Gibbs diagram reveals that water–rock interaction is the major hydrogeochemical processes governing the water chemistry of the study area. Therefore, it is recommended to perform a constant water quality checking program and improvement of tangible management practices for sustainable utilization of groundwater resources.

Hydrochemical characterization, mechanism of mobilization, and natural background level evaluation of arsenic in the aquifers of upper Gangetic plain, India

Although arsenic (As) contamination has been extensively investigated in the aquifers of the lower and middle Gangetic plains, less attention has been given to the distribution and fate of As in the groundwater of the upper Gangetic plain, India. In the current study, groundwater samples (n = 40) were collected from Moradabad district in the upper Gangetic plain and analyzed for several physicochemical parameters to characterize the groundwater chemistry and evaluate various geogenic and anthropogenic factors controlling the occurrence, mobilization, and fate of As in the plain. Arsenic concentrations in groundwater ranged from 0.17 μg/L to 139 μg/L, with the majority of high-As groundwater associated with high Fe, Mn, and HCO3− and low NO3−, SO42−, and negative Eh values, implying that As was released via reductive dissolution of Fe and Mn oxyhydroxides in reducing conditions under the influence of organic matter degradation. Interrelationships between various geochemical variables and the natural background level (NBL) quantification of As suggested the influence of anthropogenic processes on the mobility of As in groundwater. Piper and Gibbs diagrams and various bivariate plots revealed that the majority of groundwater was of the Ca2+ − Mg2+ − HCO3− type and that the major ions in groundwater were derived from carbonate and silicate weathering, cation exchange and reverse ion exchange processes, and anthropogenic activities. Moreover, the results of principal component analysis (PCA), and hierarchical cluster analysis (HCA) also suggested geogenic and anthropogenic sources for the ion concentration in groundwater. The health risk assessment showed a higher non-carcinogenic risk for children and a higher carcinogenic risk for adults, respectively, due to the daily intake of As contaminated groundwater. Overall, this study represents the first systematic investigation of the distribution, geochemical behavior, and release process of As in groundwater in the study area and provides a strong base for future research in the alluvial aquifers of the upper Gangetic plain.

Geospatial Assessment of Ground Water Quality and Associated Health Problems in the Western Region of India

Groundwater constitutes a significant component of freshwater resources in India being vital for its economy and domestic water security. The quantity, quality and accessibility of water resources forms the basis of balanced socio-economic development and its optimum utilization cannot be sustained unless its quality is assessed. The current study tries to access the quality and suitability of groundwater for drinking purposes in western drier parts of India in the state of Rajasthan. Based on collected data, selected hydro-geochemical parameters, the quality of water has been determined and Water Quality Index (WQI) have been prepared using GIS applications. Applying the Inverse Distance Weighting method, WQI values for 89 villages in the area have been computed, which ranged between 71.23 and 447.39. While 68% of the region had “poor water quality”, only 32% is sustained as ‘good water’ for consumption. The fluoride content ranging between 1.66 and 8.60 mg/L and TDS > 1000 mg/L with average pH levels > 7 (8–9 pH) were found to be very high amongst all the 12 water quality parameters taken for the study. The northeastern region with a WQI value of >250 had the worst water quality. Furthermore, the existing water quality is also examined for influencing two water borne diseases, i.e., gastroenteritis and fluorosis in the region. The study thus establishes that the majority of groundwater in the region is beyond the permissible safer consumption limits, and a large population of the region, which is directly dependent on groundwater sources, is prone to water borne health hazards. A significantly high correlation was observed between Specific Water Quality Parameters in the region and prevalence of gastroenteritis (and fluorosis diseases with R2 = 0.530 and R2 = 0.813, respectively).

The Contribution of Groundwater to the Salinization of Reservoir-Based Irrigation Systems

This study evaluates the cause of salinization in an irrigation scheme of 100 ha supplied from a reservoir. The scheme is located in Gumselasa catchment (28 km2), Tigray region, northern Ethiopia. The catchment is underlain by limestone–shale–marl intercalations with dolerite intrusion and some recent sediments. Water balance computation, hydrochemical analyses and irrigation water quality analyses methods were used in this investigation. Surface waters (river and reservoir) and groundwater samples were collected and analyzed. The water table in the irrigated land is ranging 0.2–2 m below the ground level. The majority of groundwater in the effective watershed area and the river and dam waters are fresh and alkaline whereas in the command area the groundwater is dominantly brackish and alkaline. The main hydrochemical facies in the groundwater in the effective watershed area are Ca-Na-SO4-HCO3, Ca-Na- HCO3-SO4, and Ca-Na-Mg-SO4-HCO3. The river and dam waters are Mg-Na-HCO3-SO4 and HCO3-SO4-Cl types, respectively. In the command area the main hydrochemical facies in the groundwater are Ca-Na-HCO3-SO4 and Ca-Na-Mg-SO4-HCO3. Irrigation water quality analyses revealed that salinity and toxicity hazards increase from the effective watershed to the irrigated land following the direction of the water flow. The results also showed that the analyzed waters for irrigation purpose had no sodicity hazard. The major composition controlling mechanisms in the groundwater chemistry was identified as the dissolution of carbonate minerals, silicate weathering, and cation exchange. One of the impacts of the construction of the dam in the hydrologic environment of the catchment is on its groundwater potential. The dam is indirectly recharging the aquifers and enhances the groundwater potential of the area. This increment of availability of groundwater enhanced dissolution of carbonate minerals (calcite, dolomite, and gypsum), silicate weathering and cation exchange processes, which are the main causes of salinity in the irrigated land. The rising of the brackish groundwater combined with insufficient leaching contributed to secondary salinization development in the irrigated land. Installation of surface and subsurface drainage systems and planting salt tolerant (salt loving) plants are recommended to minimize the risk of salinization and salt accumulation in the soils of the irrigated land.

Groundwater Quality in Agricultural Lands Near a Rapidly Urbanized Area, South China.

Understanding the groundwater quality and its factors is a key issue in the context of the use and protection of groundwater resources in agricultural areas near urbanized areas. This study assessed the groundwater quality in agricultural areas in the Pearl River Delta (PRD) by a fuzzy synthetic evaluation method and determined the main factors controlling the groundwater quality by principal component analysis (PCA). Results showed that approximately 85% of groundwater sites in agricultural lands in the PRD were good-quality (drinkable). Drinkable groundwater was 95% and 80% in fissured aquifers and porous aquifers, respectively. Poor-quality groundwater in porous aquifers was controlled by four factors according to the PCA, including the seawater intrusion; the lateral recharge and irrigation of surface water and geogenic sources for As, Fe, NH4+, and Mn; the wastewater infiltration; and the geogenic sources for iodide. By contrast, another four factors, including the infiltration of wastewater and agricultural fertilizers, the geogenic sources for heavy metals, the geogenic sources for iodide, and the irrigation of contaminated river water, were responsible for the poor-quality groundwater in fissured aquifers. Therefore, in the future, the groundwater protection in agricultural lands in the PRD should be strengthened because the majority of groundwater in these areas was good-quality and suitable for drinking and agricultural purposes. In addition, poor-quality groundwater in agricultural lands in the PRD was a small proportion and negligible because the factors for poor-quality groundwater are complicated.

Assessment of groundwater potential and quality using geophysical and physicochemical methods in the basement terrain of Southwestern, Nigeria

An integrated approach involving geophysical and physicochemical methods was undertaken to assess the potential availability of groundwater and its quality was carried out at Akole, Abeokuta Southwestern Nigeria. A combination of electrical resistivity and natural electric field methods were used in delineating the sub-surface lithology, determining potential groundwater-bearing zones, and the potential availability of groundwater for a community water supply. Laboratory analyses of samples from existing wells in the area was also carried out to determine the groundwater quality index (GWQI). Four vertical electrical sounding (VES) stations and nine profiles were surveyed using the Omega Campus and PQWT 150 instruments, respectively. The VES results delineated a maximum of five geo-electric sub-surface layers. A sudden change in the stratigraphy view of the rock formation from soft to very hard formation was observed in profile map L2. Profile map L7 and VES 2 has the highest potential for future groundwater exploration. Areas under VES 3 and profile maps L2, L3, L4, L5, L6, L8 and L9 are categorized as having a “medium” groundwater potential while the low yield water potential are areas under VES 1 and 4 and, profiles maps L1 and L10. The majority of groundwater in the weathered/fractured aquifer of the study area is slightly acidic. The GWQI values were less than 100, an indication that the analysed water samples fall within the “excellent” and “good” quality categories, implying that the groundwater is fit for domestic purposes. A combination of geophysical and physicochemical techniques has been successfully used to provide useful information for the assessment of groundwater potential and quality of the community.

Assessment of groundwater quality in a semiarid region of Northwestern Algeria using water quality index (WQI)

The present paper aims at determining the status and trends of groundwater quality of 12 aquifers situated in Northwestern Algeria, especially under conditions of last drought that has affected the region using water quality index (WQI) over a period of 4 years. Multivariate statistical methods have been used jointly with conventional graphical methods, to classify the samples according to plausible levels of groundwater evolution. The computed WQI values range from 67 to 588 and therefore can be categorized into four categories: “good water” to “water unsuitable for drinking.” Overall, 36% of groundwater sites sampled in the study area had good water quality, while 53% were poor. Unfortunately, 6% of the samples indicate “very poor water quality” and 5% represent water “unsuitable for drinking purposes.” Results show that the majority of groundwater of Tafna basin fell under good water quality. Groundwater of poor and medium quality characterizes the majority of the studied aquifers of Macta basin. The result showed that the water quality at monitoring station “Ain Skhouna” fell under good water quality (Chott Chergui aquifer). Results also show that groundwater of Coastal Oranais basin showed poor water quality, very poor at some monitoring stations of Mléta Plain aquifer. It has been demonstrated that the water of some aquifers has degraded under water scarcity conditions and will continue to degrade given the ongoing and projected development in the study area. The analysis reveals that the water of some aquifers needs treatment before it is used for human consumption. The influence of salt water on the some freshwater aquifers in the study area needs special attention in terms of monitoring and for sustainable management.

Groundwater Quality Assessment in Urban Area of Baghdad, Iraq, Using Multivariate Statistical Techniques

An attempt has been made to assess the overall groundwater quality and identify major variables affecting the groundwater quality in the urban area of Baghdad, Iraq. Groundwater samples from tube wells of 66 sampling sites were analyzed for the major physicochemical variables during May 2010. From the Hill–Piper trilinear diagram, it is observed that the majority of ground water from sampling sites are Ca2+ -Mg2+ -Cl- -SO42- type and Na2+ -K+ -Cl- -SO42- type water. Multivariate statistical techniques such as factor analysis and cluster analysis were applied to identify the major factors (variables) corresponding to the different source of variation in groundwater quality of Baghdad. Factor analysis identified three major factors explaining 82.506% of the total variance in water quality; and the major variations are related to degree of mineralization of the geological components of soils, irrigation return flow, agricultural activities and mixing of wastewater. Hierarchical cluster analysis revealed three different groups of similarities between the sampling sites, reflecting different physicochemical properties and pollution levels in the groundwater quality.

Sand, salt and water in the Stampriet Basin, Namibia: Calculating unsaturated zone (Kalahari dunefield) recharge using the chloride mass balance approach

Estimating groundwater recharge rates in the Stampriet Basin is important for assessing the sustainability of the groundwater resource both within south-east Namibia, and across the borders of this transboundary resource into Botswana and South Africa. The 65 000 km2 basin contains a multi-layered aquifer system, of up to 9 superimposed aquifers, with a majorupper unconfined and 2 major artesian levels. The majority of water abstraction (66%) is from the unconfined Kalahari Aquifer. This research investigates the direct recharge pathway through the dune-sand cover of the southern Kalahari dunefield which overlies ~80% of the basin. This is undertaken using established chloride mass balance methods within 4unsaturated zone profiles (9 m to 11.5 m depth) from 2 regions of the basin. The results indicate that recent recharge rates are between 7 mm·y-1 to 46 mm·y-1, with profiles representing between 10 years and 30 years of rainfall infiltration. This is the first time that substantial direct (diffuse) recharge has been quantified for the Stampriet Basin, and this part of the southern Kalahari. These 4 profiles indicate potentially similar levels of spatial variability as seen in many other semi-arid, sand-rich unsaturated zones across the world. Further studies using the unsaturated zone should be employed in this region, to better inform our  understanding of recharge mechanisms across the basin. The chloride mass balance technique provides information about the unsaturated zone, and important insights about recharge in various sand-covered regions of the basin for which very little is known, or is possible to determine using conventional water balance approaches. Direct recharge rates estimated in this way constitute a vital part of constraining the water balance of the basin, and particularly of the Kalahari Aquifer from which the majority of groundwater abstraction occurs.

Hydrochemical profile for assessing the groundwater quality of Sambhar lake City and its Adjoining area

Quality assessment of water is essential to ensure sustainable safe use of it for drinking, agricultural, and industrial purposes. For the same purpose the study was conducted for the samples of water of Sambhar lake city and its adjoining areas. The standard methods of APHA were used to analysis 15 samples collected from hand pumps and tube wells of the specified area. The analytical results show higher concentration of total dissolved solids, electrical conductivity sodium, nitrate, sulfate, and fluoride, which indicate signs of deterioration but values of pH, calcium, magnesium, total hardness, and carbonate are within permissible limits as per WHO standards. From the Hill-piper trilinear diagram, it is observed that the majority of groundwater from sampling stations are sodium-potassium-chloride-sulfate type water. The values of sodium absorption ratio and electrical conductivity of the groundwater were plotted in the US salinity laboratory diagram for irrigation water. Only the one sample fall in C(3)S(1) quality with high salinity hazard and low sodium hazard. Other samples fall in high salinity hazard and high sodium hazard. Chemical analysis of groundwater shows that mean concentration of cation is in order sodium > magnesium > calcium > potassium while for the anion it is chloride > bicarbonate > nitrate > sulfate.

Groundwaters of Mt. Vulture volcano, southern Italy: Chemistry and sulfur isotope composition of dissolved sulfate

We report the chemical composition of groundwaters—including the first data on the sulfur isotopic composition of dissolved sulfate—from the volcanic aquifers of Mt. Vulture, one of the most important hydrological basins of southern Italy. A total of 27 water samples taken at different altitudes among drilled wells and springs were collected. The majority of groundwaters have a bicarbonate alkaline and bicarbonate alkaline-earth composition. High-salinity waters are sulfatebicarbonate alkaline in composition. The water-rock interaction process is mainly affected from uprising of CO2-rich gases which cause an increase of the water acidity promoting basalt weathering with an enrichment in certain chemical species (i.e., Na+, Ca2+, SO4 2–) and a high total carbon content. The δ34S values of dissolved sulfate ranging from +4‰ to +8.6‰ can be explained by leaching of volcanites. Higher δ34S values (from 9.6‰ to 10.4‰) detected in a few water springs can be ascribed either to the interaction with the pyroclastic layer rich in feldspathoids, such as hauyna, that have sulfur isotopic compositions up to +10.6‰ or animal manure contamination inducing localized bacterial sulfate reduction with an increase in the δ34S of sulfate. Taking into account that Upper Triassic evaporite deposits have higher δ34S values (from +13.5‰ to +17.4‰,) than those measured in all water samples the dissolution of these deposits could be excluded.

A hydrochemical profile for assessing the groundwater quality of Jaipur City

A study was conducted to evaluate the water quality of Jaipur City. Groundwater samples from hand pumps and tube wells of eleven sampling stations were analyzed during monsoon session with the help of standard methods of APHA. The analytical results shows higher concentration of total dissolved solids, electrical conductivity, total hardness and nitrate, which indicate signs of deterioration but values of pH, calcium, magnesium, sulphate and fluoride are within permissible limit as per WHO standards. From the Hill-Piper trilinear diagram, it is observed that the majority of ground water from sampling stations are calcium-magnesium-chloride-sulphate type water. The values of sodium absorption ratio and electrical conductivity of the ground water were plotted in the US salinity laboratory diagram for irrigation water. Most of the samples fall in C3S1 quality with high salinity hazard and low sodium hazard. Chemical analysis of groundwater shows that mean concentration of cation (in meq/l) is in order magnesium > sodium > calcium > potassium while for the anion (in meq/l) it is chloride > bicarbonate > sulphate > nitrate > carbonate > fluoride.

Fracture network characteristics of a deep borehole in the Table Mountain Group (TMG), South Africa

Core samples from an 800-m deep borehole at the Rietfontein Farm, 10 km west of Graafwater, Western Cape, South Africa, were examined and interpreted for the hydrogeological significance of the Table Mountain Group (TMG) in the area. A suite of fracture data was collected and analysed to characterize the aquifer and conceptualize flow in the vicinity of the hole. Based on these data, the hydraulic conductivity, and density and coating intensity (due to precipitation) of the fractures against depth were computed. The dependence of fracture density on depth is very weak, while the intensity of fracture coatings is closely linked to the distribution of hydraulically active fractures that represents the maximum number of fractures currently open to groundwater flow. Four scenarios of depth ranges reflecting the development of hydraulically active fractures are proposed as a depth model of groundwater flow, implying that the majority of groundwater exists above 400 m depth. The top of the hydraulically inactive fracture zone clearly indicates that no groundwater flow could take place below a depth of about 570 m. The depth model gives a better understanding of the properties of the aquifers in the area and improves conceptual models, considering the lower limit of aquifer depth in particular.