Precipitation controlled spatial variations in groundwater quality indices-suitability for drinking and irrigation purposes in the basalts of South India

Regional study on the impact of variations in input rainfall over groundwater quality and its suitability for utilitarian purposes is essential for its extraction and management. Water chemistry from 456 observations wells for 2007–2011 period in hard rock Basaltic terrain of Upper Godavari basin is supported with 8 field samples (in 2014) in this analysis. Based on mean annual rainfall (MAR), four narrow climatic zones are identified in the basin, defined as “humid” (MAR > 1600 mm), “sub-humid” (1600–1000 mm), “semi-arid” (1000–600 mm), and “arid” (MAR < 600 mm). NICB ratio (<±10%), and anionic percentages demarcated the polluted areas from rest “good data”, composing of 1818 samples. Hydrochemical facies are studied using Piper diagram, secondary alkalinity exceeded 50% and not one cation–anion pair exceeded 50%, and silicate–carbonate plot, arid zone nearer to silicate pole indicated the dominance of SiO₂ in Ca/Na vs Mg/Na plot. These geochemical variations emphasize a detailed study on role of climatic gradient on groundwater suitability for different purposes, for groundwater extraction, and its management. Suitability of groundwater for drinking based on water quality indices (WQI) indicated 98% of the samples as suitable (WQI < 50%). TDS in humid zone is 150–500 and 500–1000 mg/L in rest of the zones with ～68% in permissible range, 15% as hard water (TDS > 600 mg/L) and not acceptable for drinking. Suitability of groundwater for irrigation is studied using sodium percentage (Na %), Wilcox diagram, sodium absorption ratio (SAR), US salinity diagram, residual sodium carbonate (RSC), permeability index (PI), Kelly’s ratio (KR), ancd magnesium absorption ratio (MgAR). Na % in four zones is < 60% and permissible for irrigation. Very few water samples fall in “doubtful to unsuitable” and “unsuitable” category of Wilcox diagram. Region is observed to have SAR < 6, indicating that water would not cause any problem to the soil and crop. Humid and sub-humid zones belonged to C1S1 and C2S1 categories (low and medium sodium), while semi-arid extended to C3S1 category (salinity hazard zone) in US salinity plot. RSC for all the three zones ranged from 1 to 1.5 meq/L, with 90–95% of the area safe for irrigation. Out of 1818 samples, 1129 belonged to class 2 of PI classification (PI ranging from 25 to 75%) while rest 689 samples had PI >75% (class 1). KR varied from 0.05 to 12.81, with 70–80% of the area having KR < 1. MgAR ratio ranged from 67% to 96%, with sub-humid, humid zones having higher Mg concentrations (increased salinity). Thus, 90% of the samples indicated non-alkaline water with 1% of normal alkalinity. Hence, the current study systematically analyzed the effect of precipitation and geology on groundwater quality and on its usability for various purposes. This stepwise procedure categorized the regions, and the same can be adopted for any regional hydrogeochemical studies.     

Assessment of groundwater quality for drinking and irrigation purposes using hydrochemical studies in Nalbari district of Assam,India

The present work was carried out in Nalbari district of Assam (India) with an objective to assess the quality of groundwater and to check its suitability for drinking and irrigation purposes. Groundwater samples were collected from 50 different locations during pre- and post-monsoon seasons of 2016. Results of chemical analysis revealed that mean concentration of cations varied in the order Ca²⁺?>?Na⁺?>?Mg²⁺?>?K⁺, while for anions the order was HCO₃ ^??>?Cl^??>?SO₄^2??>?NO₃^2??>?F^? during both pre- and post-monsoon seasons. The suitability of groundwater samples for drinking purpose was assessed by comparing the results of physico-chemical analysis of groundwater with Indian Standards. Further, its suitability for irrigation purpose was assessed by evaluating several parameters like sodium adsorption ratio (SAR), sodium percentage (Na%), magnesium ratio, Kelly’s ratio and residual sodium carbonate (RSC). The SAR values obtained for all the samples were plotted against EC values in the US Salinity Laboratory diagram, and it was revealed that the most of the samples fall under water type C2-S1 indicating medium salinity and low SAR. Further, it was found that the majority of the samples belong to Ca–Mg–HCO₃ hydrochemical facies followed by Ca–Mg–Cl–SO₄, whereas only a few samples belong to Na–K–HCO₃ hydrochemical facies.     

An appraisal of groundwater quality for drinking and irrigation purposes in southern part of Bathinda district of Punjab, northwest India

Groundwater is being used for drinking and irrigation purposes in the agricultural dominated Indian state of Punjab. Fifty-six groundwater samples were collected from Bathinda, a south-western district of Punjab, during the pre-monsoon (March 2010) and post-monsoon (October 2011) seasons. These samples were tested for major cations, anions and contaminants. Various classification systems were used to study the groundwater quality with respect to drinking as well as irrigation purposes. Total dissolved solids (TDS) and total hardness (TH) are generally used to determine the suitability of groundwater for drinking purpose. Considering TDS as a parameter, 54 and 57 % groundwater samples were found to be unsuitable for use during the pre- and post-monsoon seasons. A wide range of TH values were observed in the pre-monsoon and post-monsoon waters samples (mean 250 and 270 mgL^?1). About 75 % of pre-monsoon and 79 % of post-monsoon samples exceeded the maximum permissible limit (MPL) of TH (150 mg L^?1) proposed by WHO. In terms of contaminant ions, 40 % and 55 % of the pre- and post-monsoon water samples were unfit for drinking purposes w.r.t. fluoride (MPL 1.5 mg F L^?1), 29 and 36 % were unfit w.r.t arsenic (MPL 10 μg L^?1) and 33 and 45 % were unfit w.r.t nitrate (MPL 45 mg NO₃ ^? L^?1), respectively. To determine the suitability of groundwater of Bathinda for irrigation purpose, three classification systems proposed by different research workers were used. The parameters electrical conductivity (EC), sodium adsorption ratio, and residual sodium carbonate (RSC) were calculated on the basis of chemical data. Considering EC and RSC together, 32 % samples collected during pre-monsoon season were fit, 19 % were marginal and 49 % were unfit for use. However, during post-monsoon, samples fit for irrigation decreased to 17 % and samples unfit for irrigation increased to 70 %. Increases in the percentage of unfit samples for irrigation after monsoon indicates addition of salts along with the rain water percolated into the groundwater. The other two classification systems, i.e. US Salinity diagram and Wilcox diagram also showed the similar results.     

Assessment of groundwater quality for drinking and irrigation purposes: a case study of Peddavanka watershed, Anantapur District, Andhra Pradesh, India

In India, the quantity and quality of water available for irrigation is variable from place to place. Assessment of water quality has been carried out to determine the sources of dissolved ions in groundwater. Quality of groundwater in a 398 km² Peddavanka watershed of a semi-arid region of south India is evaluated for its suitability for drinking and irrigation purposes. The middle Proterozoic Cuddapah Supergroup and Kurnool Group of rocks underlie most of the watershed. The main lithologic units consist chiefly of quartzite, limestone, and shale. Seventy-six water samples were collected from open-wells and bore-holes. Water samples were collected representative of the post-monsoon (winter) and pre-monsoon (summer). The quality assessment is made through the estimation of Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl⁻, SO₄²⁻, CO₃²⁻, HCO₃⁻, total hardness as CaCO₃, TDS, EC, and pH. Based on these analyses, parameters like sodium adsorption ratio, % sodium, residual sodium carbonate, non-carbonate hardness, potential salinity, Kelley’s ratio, magnesium ratio, index of base exchange and permeability index were calculated. According to Gibbs‘ ratio samples in both seasons fall in the rock dominance field. The overall quality of waters in the study area in post-monsoon season is high for all constituents ruling out pollution from extraneous sources.     

Evaluation of groundwater quality for irrigation and drinking using GIS and geostatistics in a peri-urban area of Delhi, India

Intensive agriculture by indiscriminate use of agrochemicals, sewage water, and polluted drain water has posed a serious threat to groundwater quality in some peri-urban areas of Delhi like Najafgarh block. The objective of the study was to determine the groundwater quality and to map their spatial variation in terms of suitability for irrigation and drinking purpose. Ordinary kriging method was used for preparation of thematic maps of groundwater quality parameters such as electrical conductivity, sodium adsorption ratio, bicarbonate, magnesium/calcium ratio, total dissolved solids, chloride, nitrate and hardness. Exponential semivariogram model was best fitted for all quality parameters except chloride and hardness, where spherical model fitted best. Pollution level was highest at south and south-eastern part of the study area. Better quality groundwater may be expected at the northern and western part. High salinity was due to high chloride concentration in the groundwater. Nitrate pollution level was found to be very alarming and need immediate interventions. High dissolved solids and hardness made the groundwater unsuitable for drinking. There were negligible sodium and bicarbonate hazard in the study area. The groundwater quality index was devised to analyse the combined impact of different quality parameters on irrigation and drinking purposes. The irrigation water quality index and drinking water quality index distribution maps delineated an area of 47.29 and 6.54 km² suitable for irrigation and drinking, respectively. These safe zones were found as a small strip along the northern boundary and a very small pocket at the western side of the study area.     

A comparative evaluation of groundwater suitability for irrigation and drinking purposes in two intensively cultivated districts of Punjab, India

Punjab is the most cultivated state in India with the highest consumption of fertilizers. Patiala and Muktsar districts are two agricultural dominated districts of Punjab located in extreme south-east and south-west of the state. This paper highlights temporal variations of the groundwater quality and compares its suitability for irrigation and drinking purpose in these two districts. Water samples were collected in March and September 2003, representing the pre-monsoon and post-monsoon seasons, respectively. Water samples were analysed for almost all major cations, anions, dissolved heavy metals and turbidity. Parameters like sodium adsorption ratio, % sodium, residual sodium carbonate, total hardness, potential salinity, Kelley’s ratio, magnesium ratio, index of base exchange and permeability index were calculated on the basis of chemical data. A questionnaire was also used to investigate perception of villagers on taste and odour. Comparison of the concentration of the chemical constituents with WHO (world health organization) drinking water standards of 2004 and various classifications show that present status of groundwater in Patiala is better for irrigation and drinking purposes except for a few locations with a caution that it may deteriorate in near future. In Muktsar, groundwater is not suitable for drinking. Higher total hardness (TH) and total dissolved solids at numerous places indicate the unsuitability of groundwater for drinking and irrigation. Results obtained in this forms baseline data for the utility of groundwater. In terms of monsoon impact, Patiala groundwater shows dilution and flushing but Muktsar samples show excessive leaching of different chemical components into the groundwater leading to the enrichment of different anions and cations indicating pollution from extraneous sources. No clear correlation between the quality parameters studied here and perceived quality in terms of satisfactory taste response were obtained at electrical conductivity values higher than the threshold minimum acceptable value.     

Evaluation of hydrogeochemical processes and groundwater quality for suitability of drinking and irrigation purposes: a case study in the Aosta Valley region,Italy

The present study aims to discuss the hydrogeochemical processes in the Aosta Valley region and assess the quality of its groundwater for suitability of drinking and irrigation purposes. One hundred twenty-two samples were collected from the Aosta Valley region in the years 2007 and 2008 (61 per year), and analysed for pH, electrical conductivity, total dissolved solids (TDS), total hardness, major cations and anions. The pH of the samples in both years indicated a near-neutral to alkaline nature of the groundwater. The cation and anion chemistry showed the general ionic abundance as: Ca²⁺ > Mg²⁺ > Na⁺ > K⁺ and HCO₃ ^?>SO₄ ^2?>Cl^?>NO₃ ^?>F^? in both years. Ca²⁺-Mg²⁺-HCO₃ ^? and Ca²⁺-Mg²⁺-Cl^?-SO₄ ^2? were the dominant hydrogeochemical facies. The computed saturation indices demonstrated that the groundwater was supersaturated with respect to dolomite and calcite in both years. The groundwater chemistry of the study area was mainly controlled by the dissolution of carbonate, sulphate and silicate minerals, as well as ion exchange processes. A comparison of the groundwater quality in relation to drinking water standards showed that most of the water samples were suitable for drinking and domestic uses. The computed water quality index (WQI) values of the study area groundwater ranged from 24 to 84 in the year 2007 and from 22 to 82 in the year 2008, and all the location fell under the Excellent to Good category. Quality assessment for irrigation uses revealed that the groundwater was good to permissible quality for irrigation; however, locally higher salinity, residual sodium carbonate (RSC) and magnesium hazard (MH) restricted its suitability for irrigation at a few sites. These results will be useful in implementing future measures in groundwater resource management at regional and national level.     

Impact of recharge from a check dam on groundwater quality and assessment of suitability for drinking and irrigation purposes

Assessment of surface water and groundwater quality is necessary as it controls their usability for drinking and irrigation purposes. This study was carried out to assess the suitability of groundwater for these purposes and to understand the impact of water stored in a check dam on groundwater quality near Chennai, Tamil Nadu, India. Water samples were collected from a check dam across Arani River and 13 nearby wells during October 2010, January 2011, and April 2011. These samples were analyzed for pH, electrical conductivity (EC), and calcium, magnesium, sodium, potassium, carbonate, bicarbonate, chloride, and sulfate concentrations. The World Health Organization and the Bureau of Indian Standards guidelines were used to assess the suitability of groundwater for the purpose of drinking. Suitability of water for irrigation was determined based on the EC, sodium adsorption ratio, US Salinity Laboratory diagram, percentage sodium, Wilcox’s diagram, Kelly’s index, and Doneen’s permeability index. About 38 % of the groundwater samples were suitable for drinking and 70 % were suitable for irrigational use. Water stored in the check dam and groundwater in the wells closer to the structure were suitable for both drinking and irrigation purposes. The study confirms that the check dam in this area improves the groundwater quality in its surroundings.     

Assessment of groundwater quality in and around Vedaraniyam,South India

Groundwater from 47 wells were analyzed on the basis of hydrochemical parameters like pH, electric conductivity, total dissolved solids, Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^?, CO₃ ^2?, HCO₃ ^?, NO₃ ^?, PO₄ ^3? and F^? in the Cauvery delta of Vedaraniyam coast. Further, water quality index (WQI), sodium percentage (Na %), sodium absorption ratio, residual sodium carbonate, permeability index and Kelley’s ratio were evaluated to understand the suitability of water for drinking and irrigation purposes. The result shows significant difference in the quality of water along the coastal stretch. The order of dominance of major ions is as follows: Na⁺ ≥ Mg²⁺ ≥ Ca²⁺ ≥ K⁺ and Cl^? ≥ HCO₃ ^? ≥ CO₃ ^2? ≥ PO₄ ^3? ≥ F^?. Na/Cl, Cl/HCO₃ ratio and Revelle index confirmed that 60–70 % of the samples were affected by saline water intrusion. WQI showed that 36 % of the samples were good for drinking and the remaining were poor and unsuitable for drinking purpose. The degradation of groundwater quality was found to be mainly due to over-exploitation, brackish aquaculture practice, fertilizer input from agriculture and also due to domestic sewage.     

Assessment of groundwater quality for irrigation purposes and identification of hydrogeochemical evolution mechanisms in Pengyang County, China

Groundwater is an important water source for agricultural irrigation in Penyang County. Some traditional methods such as irrigation coefficient, sodium adsorption ratio, total alkalinity, total salinity and total dissolved solids were employed to assess groundwater quality in this area. In addition, an improved technique for order preference by similarity to ideal solution model was applied for comprehensive assessment. The origin of major ions and groundwater hydrogeochemical evolution was also discussed. Groundwater in Penyang County contains relative concentrations of dominant constituents in the following order: Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ for cations and HCO₃ ^? > SO₄ ^2? > Cl^? > CO₃ ^2? for anions. Groundwater quality is largely excellent and/or good, suggesting general suitability for agricultural use. Calcite and dolomite are found saturated in groundwater and thus tend to precipitate out, while halite, fluorite and gypsum are unsaturated and will dissolve into groundwater during flow. Groundwater in the study area is weathering-dominated, and mineral weathering (carbonate and silicate minerals) and ion exchange are the most important factors controlling groundwater chemistry.     

Spatial variability of groundwater quality and its suitability for drinking and irrigation in the Amik Plain (South Turkey)

In this study, it is determined physicochemical properties of the groundwater and the spatial variability of physicochemical properties of the groundwater in the Amik plain and as well as assess its suitability for drinking and irrigation. A total 92 groundwater samples were collected from drilled well in June 2012. In addition, the 42 of 92 drilled wells were also sampled in September 2012 to evaluate the changes of groundwater properties. According to t test values, the mean Ca²⁺, SO₄ ^2?, Mg²⁺ and TH values in the June period were significantly lower than those of the September period. On the other hand, the mean (CO ₃ ^2?  + HCO₃ ^?) and RSC and MR values in the June period were significantly higher than those of the September period. The order of relative abundance of major cations in the groundwater (in mg L^?1) is in order Na⁺ > Mg²⁺ > Ca²⁺ > K⁺. The order of the anions abundance (mg L^?1) is SO₄ ^2? > Cl^? > HCO₃ ^? > CO₃ ^2? in this research. Log and square-root transformation were carried out for the most of the water properties before the calculation of semivariance. The nugget ratio showed all the variables were strongly spatial dependent except for K⁺ and Mg²⁺ and (CO₃ ^2? + HCO₃ ^?) which showed moderate spatial dependence (ratio ranging from 28 to 49.9 %). Spatial distribution analysis of groundwater quality indicated that The EC, TDS values and Na and Cl^? contents which is important water quality parameters increase from northern towards southern. The total hardness values increase also from northwestern towards southwestern.     

Mapping groundwater quality for irrigation in Punjab, North-West India, using geographical information system

The state of Punjab—a part of the Indus basin of the Indian subcontinent has an excellent net work of irrigation facilities. However, due to intensive cultivation it is facing a major problem with respect to quality of groundwater for irrigation. In the present investigation, geo-referenced groundwater samples were analysed to map water quality using geographical information system. Electrical conductivity varied from 0.418 to 5.754 dS m^?1 with an average of 1.365 dS m^?1. The carbonate ranged between 0 and 120 mg L^?1, whereas bicarbonate ranged from 5 to 1,000 mg L^?1. Chloride varied from 7 to 2,347 mg L^?1. Calcium plus magnesium ranged from 12 to 1,216 mg L^?1 with a mean value of 169 mg L^?1. Sodium adsorption ratio ranged between 0.0 and 34.78 with an average of 2.66 meq L^?1/2. Residual sodium carbonate varied from 0 to 21.30 meq L^?1 with a standard deviation of 2.24. The Geographic Information System (GIS)-based mapping indicated that water in suitable category spatially covered 45.7 % of the state which is located mostly in the sub-mountain (Siwalik Hills), north-eastern undulating and piedmont and alluvial plain agro-eco-subregions. Marginally suitable groundwater spatially covered 46.1 % in the central alluvial plain and south-western alluvial plain agro-eco-subregions. Unsuitable groundwater covered 8.2 % of the state, mostly in the erstwhile sodic soils areas in the central alluvial plain and south-western alluvial plain agro-eco-subregions. GIS-based maps are effective in identifying hot spots which need immediate attention and call for strategic planning for sustainable management.     

Evaluation of groundwater resources for drinking and agricultural purposes, Abar Al Mashi area, south Al Madinah Al Munawarah City, Saudi Arabia

A hydrogeochemical study was conducted on the groundwater of south Al Madinah Al Munawarah City, Saudi Arabia, to assess the quality of groundwater for drinking and irrigation uses. Groundwater samples have been collected and analyzed for major and some trace constituents from the study area. The nitrate concentration in most groundwater samples of the study area exceeded the safe limits for drinking purposes, whereas the concentrations of phosphate, boron, and trace constituents were below the maximum permissible limit for drinking purposes; Cr in two samples showed high content over the recommended limits of drinking purposes. Uncontrolled abstraction of groundwater in Abar Al Mashi area caused many environmental problems including water resource depletion and contamination. Correlations between chloride and major ions were positive and may be attributed to impact of agricultural activities on groundwater chemistry. Groundwater of the study area was classified into six water types. The chemical water types of groundwater in the study area contain CaHCO₃ in the eastern and southeastern parts and NaCl in western and northwestern parts, reflecting different land use characteristics and pollution sources. Piper diagram showed that almost all the samples fall in one zone, indicating similar chemical signature. Groundwater can be used safely for drinking with special treatments to eliminate the effect of increased concentrations of total dissolved solids, nitrate, and chromium. The groundwater of the study area can be used safely for irrigation on clay soil; however, specific crops should be selected according to their salt tolerance.     

Identification of the geochemical processes in groundwater by factor analysis in hard rock aquifers of Madurai District,South India

A study was carried out in the Madurai district of Tamil Nadu, India to identify the hydrogeochemical processes using factor analysis as a predictive tool. It also focuses on characterizing the samples of these factors with respect to standard geochemical plots. In order to obtain a synoptic view of the statistics and the geochemical processes, a total of 53 groundwater samples are collected representing the entire district. The major ions were analyzed; the order of ion dominance are Ca²⁺?>?Na⁺?>?Mg²⁺?>?K⁺?=?Cl^??>?HCO^? ₃?>?H₄SiO^? ₄?>?NO^? ₃?>?SO^2? ₄?>?P^3? ₄. The samples are classified according to three factors. Factor 1 shows strong positive loadings of Cl^?, Ca²⁺, Mg²⁺, and NO^? ₃ with 36.98 % of the total variance (TV); factor 2 accounts for 13.72 % of TV with high loadings of Na⁺, K⁺, and HCO^? ₃; and factor 3 shows strong positive loadings of PO^3? ₄ and SO^2? ₄ with TV of 13.1 %. In the Piper plot, few samples fall in the mix region as evidenced by the mixing proportion of two samples using AQUACHEM software. The results suggest that different hydrogeochemical processes, like weathering, ion exchange processes, and anthropogenic activities (like sewage infiltration and agriculture), has predominant impact in the study area. Thus, the study highlights the factor analysis technique as a predictive and effective tool for groundwater evolution.     

Evaluating groundwater suitability for the domestic,irrigation, and industrial purposes in Nanded Tehsil,Maharashtra, India,using GIS and statistics

Hydrogeochemical characteristics of groundwater and its suitability for domestic, irrigation, and industrial purposes were evaluated in Nanded Tehsil. A total of 50 representative groundwater samples were collected from dug/bore wells during post monsoon season 2012 and analyzed for major cations and anions. The order of dominance of cation and anions were Na > Ca > Mg > K and HCO₃ > Cl > CO₃ > SO₄ > NO₃, respectively. The rock weathering and evaporation processes are dominant in controlling the groundwater quality in the study area. Electrical conductivity (EC) and total dissolved solid (TDS) show high positive correlation with total Hardness (TH), Ca, Na, and Cl. As per the WHO and BIS standards for domestic water purposes, TDS, TH, Ca, Mg, Na, and Cl exceed the safe limits in 16, 22, 6, 18, 12, and 15 %, respectively; therefore, majority of samples show that the groundwater is suitable for drinking. The spatial distribution maps of physicochemical parameters were prepared in ArcGIS. The suitability of groundwater for agriculture purpose was evaluated from EC, TDS, sodium adsorption ratio (SAR), residual sodium carbonate (RSC), and %Na which ranges from excellent to unsuitable, so majority of the groundwater samples are suitable for irrigation. The U.S. Salinity Laboratory (USSL) diagram shows that most of the groundwater samples are characterized as in high salinity-low sodium hazard type water (C₃-S₁). All the groundwater samples are suitable for industrial use except sample numbers 44 and 48. Thus, most of the groundwater samples from this study confirm the beneficial use of aquifers in the area for domestic, agricultural, and irrigation purposes. However, sample numbers 44 and 48 identify the two aquifers in the study area which are problematic and need particular remedial measures if they are to have beneficial use.     

信阳市浅层地下水质量评价

为了保护信阳市浅层地下水资源环境,进一步合理开发该区浅层地下水,在对信阳市市区大量浅层地下水水样分析资料的基础上,从饮用水评价,农业灌溉用水评价,工业锅炉用水评价及综合评价等四个方面对该区浅层地下水质量进行了评价。评价结果表明：评价区内虽没有极差的Ⅴ级水,但在人口集中和用水集中的市区均为较差的Ⅳ级水,是人们生产和生活用水质量下降的主要原因;人口集中带来的生活污染是本区浅层地下水主要污染源,次要污染源为工业污染,这些理应引起高度重视,防止污染的进一步扩大。     

Assessment of hydrochemistry and groundwater quality in the coastal area of South Chennai,India

An attempt has been made to evaluate the water quality in the fast-growing coastal area of South Chennai. Groundwater samples were collected from selected locations and analyzed for major physico-chemical parameters. Experimental results show that the water has alkaline with pH varying from 7.2 to 8.2. Concentrations of Na and Cl were positively correlated with EC and elevated levels of these parameters near the coastal region, especially in the northern end of the study area, indicating the influence of seawater intrusion. Piper diagram identified Na–Cl as the dominant type of water in most of the samples. The presence of Ca–Cl facies in the groundwater suggests the possible ion exchange (Na with Ca) reaction in the aquifer. Molar ratios of Cl/HCO₃ and Mg/Ca showed a higher value (>1) in many samples, which confirmed the influence of seawater intrusion on water quality. The Water Quality Index (WQI) of the study area ranged between 8 and 116, the highest recorded being at Thiruvanmiyur and the lowest at Muttukkadu. However, total hardness values show that 64% of the samples were hard or very hard in nature. The results of SAR, Na%, and PI show that majority of the samples are suitable for irrigation purposes. A comparison of spatial distribution maps of water quality parameters with those of WQI shows that groundwater quality has highly deteriorated in the Thiruvanmiyur region, located on the northeast part of the study area. Good-quality water is found at the southeast part of the study area, namely, Muttukkadu. This study indicates that urbanization and seawater intrusion have heavily affected the groundwater quality of South Chennai coastal area.     

A GIS-index integration approach to groundwater suitability zoning for irrigation purposes

In recent decades, the high population growth has increased the demand for agricultural lands and products. Groundwater offers reliability and flexibility in access to water for irrigation purposes, especially in arid and semi-arid areas, such as Amol-Babol Plain, Iran. However, the quality and quantity of groundwater may not be suitable for irrigation purposes in all areas due to urbanizations, and intensive agricultural and industrial activities. Groundwater suitability zoning for irrigation purposes could be useful to improve water resources and land use planning, mostly in areas with water scarcity. Therefore, a GIS-based indices method is proposed to assess suitable zones for agricultural activities, integrating the irrigation water quality (IWQ) index and hydrogeological factors. IWQ index was utilized to assess groundwater quality based on salinity hazard, infiltration hazard, specific ions, and trace elements hazards, and miscellaneous effects such as pH, bicarbonate, and nitrate. The potential of the aquifer for irrigation water abstraction was investigated using hydrogeological surveys such as slope angle of the plain, hydraulic conductivity, and aquifer thickness. The groundwater suitability index classified most of the study area (more than 90 %) as “excellent” or “good” suitability zones for irrigation purposes. A limited area of around 5.6 % of the total area has moderate suitability for irrigation purposes due to the Caspian Seawater intrusion and the presence of fossil saline water. The proposed methodology provides useful information in order to allow irrigation management to prevent water and soil deterioration.     

东莞市地下水环境质量现状评价

对东莞市地下水环境质量现状进行了综合评价,简析本区的环境容量和地表水体与地下水体的相互关系.分析了近20年来地下水环境质量的演化趋势,并分析了造成地下水水质污染和水环境恶化的原因,在此基础上提出了有关地下水资源保护和水环境管理的几点建议.