Hydrogeological environment and groundwater occurrences of the alluvial aquifers in parts of the Central Ganga Plain, Uttar Pradesh, India

A detailed hydrogeological investigation was carried out in parts of the Central Ganga Plain, India, with the objective of assessing the aquifer framework and its resource potential. The area was studied because of its dual hydrogeological situation, that is water logging and soil salinization in the canal command areas and depletion of aquifers in the western part of the basin. A comprehensive investigation of the aquifer system between the Ganga River and Kali River revealed its lateral and vertical dimensions and hydrogeological characteristics. Moreover, study of the groundwater occurrences, movements and behaviour, in terms of water level fluctuation with time and space, confirms the coexistence of over exploitation as well as water logging in the area.

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Resumen Una investigación hidrogeológica detallada se llevó a cabo en partes de la Llanura de Ganga Central, India, con el objetivo de evaluar la estructura del acuífero y su potencial del recurso. El área fue estudiada por su doble situación hidrogeológica, es decir la saturación con agua y salinización de suelos en las áreas dominadas por el canal y vaciamiento de acuíferos en el la parte occidental de la cuenca. Una investigación completa del sistema acuífero entre el Río Ganga y el Río Kali, reveló sus dimensiones verticales y laterales y las características hidrogeológicas. Además, los estudios sobre la ocurrencia del agua subterránea, sus movimientos y comportamiento, en lo que se refiere al nivel de agua, y a su fluctuación en el tiempo y el espacio, confirma la co-existencia en el área de sobre- explotación así como de saturación con agua.

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Résumé L'objectif de cette étude hydrogéologique détaillée de portions de la Plaine Centrale du Gange est de déreminer la structure aquifère et la ressource potentielle. L'intérêt de la zone repose sur sa dualité du point de vue hydrogéologique, les zones influencées par le canal présentent une remontée de la nappe avec une salinisation des sols, la portion Ouest du bassin présente une baisse du niveau des aquifères. Par cette étude, le système aquifère compris entre la rivière du Gange et la rivière Kali révèle ses dimensions latérales et verticales ainsi que ses caractéristiques hydrogéologiques. De plus, l'étude des événements, des mouvements et du régime hydrogéologique affectant le niveau phréatique confirme la co-existence de surexploitation et de saturation des sols dans la région.

     

Groundwater vulnerability assessment of the SW Trans-Danubian Central Range, Hungary

 The most important karst water reservoir of Hungary is found in the SW Trans-Danubian Central Range, selected as test area for the proposed "system approach" and the application of GIS/ARC-INFO to vulnerability mapping. In addition, a case-study exemplifies the particularities of regional karst-aquifer vulnerability, and moreover the interpretation of data and maps from the very same point of view. The work has resulted in plotting an atlas to be a useful tool in the hands of land-users and waste-disposal managers, helping them to prevent groundwater deterioration. Received: 22 July 1996 · Accepted: 12 September 1997     

Role of monsoon rain on concentrations and dispersion patterns of metal pollutants in sediments and soils of the Ganga Plain, India

 Monsoon rain causes large scale sediment-water movement and reworking of sediments of the Ganga Plain which is one of the largest fluvial systems on Earth. Geomorphology and drainage type combined with sedimentation processes play a substantial role on dispersion and transport patterns of metals bound to sediments and soils. The study area of Kanpur-Unnao industrial region in the Ganga Plain has been divided into five independent geochemical domains on the basis of sediment-geomorphic, hydrological and geochemical characters. The monsoon hydrography and physico-chemical parameters (pH, conductivity) of the river and urban drain waters play a prominent role in regulating the concentrations and behaviour of the metals in the aquatic system of the Ganga Plain. Values of pH and specific electrical conductivity of the river water of the study area decrease whereas those of the urban drain water increase in post-monsoon period. The monsoon rain reduces the contents of Co, C-org, Cr, Fe and Ni and enhances the contents of Cd, Sn and Zn in sediments of post-monsoon period. In soils, it reduces the contents of Al, Co, Fe, Mn and Ni and enhances the contents of Cd, Sn and Zn in the post-monsoon period. These changes in concentrations vary from metal to metal and from one geochemical domain to the other. An increase in the concentrations of few metals in the soils from pre- to post-monsoon periods indicates that these metals were mobilized from the overflooding of metal rich waste-water onto the fields during high water stage and also by reworking of the soils through sheet floods during the monsoon time. Despite the changes in concentrations, metal dispersion patterns in each domain remain similar both in pre- and post-monsoon periods which indicate that the geochemical and sediment-geomorphic processes operating for the metal dispersion and mobilization in sediments are persistent even after large scale sediment-water movement and reworking of the sediments during the monsoon period. Received: 4 May 1998 · Accepted: 20 October 1998     

Status of anthropogenically induced metal pollution in the Kanpur-Unnao industrial region of the Ganga Plain, India

 The Ganga Plain is one of the most densely populated regions and one of the largest groundwater repositories of the Earth. For several decades, the drainage basin of the Ganga Plain has been used for the disposal of domestic and industrial wastes which has adversely affected the quality of water, sediments and agricultural soils of the plain. The concentrations of Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sn, Zn and organic carbon were determined in river sediments and soils of the Ganga Plain in the Kanpur-Unnao industrial region in 1994 and 1995 (pre-monsoon period of April–May). High contents (maximum values) of C-org (12.0 wt. %), Cr (3.40 wt. %), Sn (1.92 wt. %), Zn (4000 mg/kg), Pb (646 mg/kg), Cu (408 mg/kg), Ni (502 mg/kg) and Cd (9.8 mg/kg) in sediments (<20 μm fraction); and C-org (5.9 wt. %), Cr (2.16 wt. %), Sn (1.21 wt %), Zn (975 mg/kg) and Ni (482 mg/kg) in soils (<20 μm) in the pre-monsoon period of 1994 were found. From 1994 to 1995 the contents of Fe and Sn in sediments increase whereas those of C-org, Cd, Cu, Ni and Zn decrease. Considering the analytical errors, Al, Co, Cr, Mn and Pb do not show any change in their concentrations. In soils, the contents of Cd, Fe and Sn increase whereas those of Ni decrease from 1994 to 1995. Aluminium, Co, Cr, Cu, Mn, Pb and Zn do not show any change in their concentrations from 1994 to 1995. About 90% of the contents of Cd, Cr and Sn; 50–75% of C-org, Cu and Zn; and 25% of Co, Ni and Pb in sediments are derived from the anthropogenic input in relation to the natural background values, whereas in soils this is the case for about 90% of Cr and Sn; about 75% of Cd; and about 25% of C-org, Cu, Ni and Zn. The sediments of the study area show enrichment factors of 23.6 for Cr, 14.7 for Cd, 12.2 for Sn, 3.6 for C-org, 3.2 for Zn, 2.6 for Cu and 1.6 for Ni. The soils are enriched with factors of 10.7 for Cr, 9.0 for Sn, 3.6 for Cd, 1.8 for Ni and 1.5 for Cu and Zn, respectively. Received: 3 March 1998 · Accepted: 15 June 1998     

Groundwater quality and rural drinking-water supplies in the Republic of Moldova

 This paper describes the results of a groundwater quality assessment conducted in two pilot areas, Balatina and Carpineni, in the Republic of Moldova. Shallow groundwater is the main source of drinking water in rural areas, but reliable data on its quality are currently insufficient for developing rural water-supply systems with standard designs. The main components of the study included a field sampling program (including pesticides), an evaluation of the reliability of existing drinking-water data, an analysis of land use and groundwater-pollution risks using GIS, and the formulation of recommendations to reduce risks for public health. Microbiological, nitrate, and selenium contamination are most serious in the villages. These contaminants should be given priority in addressing drinking-water aspects for rural water-supply development in the two pilot areas. Pollution occurs mainly due to poor sanitary conditions. In a few shallow wells, traces of selected pesticides were observed, but the effect of these levels of pesticides on public health is still unclear. Limited resources of shallow groundwater of good quality occur outside the villages. Additional pilot studies should be implemented to prove the technical and institutional feasibility of developing and protecting these resources. Received, September 1997 Revised, September 1998 Accepted, March 1999     

Groundwater quality in the Niva River basin, Chittoor district, Andhra Pradesh, India

 This study was made to assess the groundwater quality in relation to agricultural and domestic uses in a part of the Peninsular Archean granite and gneissic complex of India. Water samples were collected from the existing wells in the Niva River basin, Chittoor district, Andhra Pradesh, India and analysed for major ions. The analytical data, processed and interpreted acoording to the WHO standards, reveal that, in general, the groundwater is suitable for both agricultural and domestic uses, exept in a few locations. High concentration of nitrates were observed in some of the wells (both agricultural and domestic) that are affected by the impact of industrial effluents. Multiple regression analysis was performed and used as a positive predictive tool in understanding the chemistry of the groundwater. Received: 2 May 1996 / Accepted: 14 October 1996     

Environmental fate and health exposures of the geogenic and anthropogenic contaminants in potable groundwater of Lower Ganga Basin,India

The study evaluated the sources and controlling factors of the groundwater contaminants in an agroeconomic region of Lower Ganga Basin using principal component analysis (PCA), multivariable linear regressions (MLR), correlation analysis, and hierarchical cluster analysis, and evaluated the public health risks using the Latin Hypercube Sampling, goodness-of-fit statistics, Monte Carlo simulation and Sobol sensitivity analysis based on the 1000 samples collected in two sampling cycles (N = 1000). The study reveals that the dissolution of fluoride-bearing minerals and semi-arid climate regulate the fluoride concentrations (0.10–18.25 mg/L) in groundwater. Extensive application of inorganic nitrogenous fertilizers and livestock manure mainly contributed to elevated nitrate levels (up to 435.0 mg/L) in groundwater. The health risks analysis indicates that fluoride exposure is more prevalent in the residents of each age group than the nitrate and both contaminants exhibited higher non-carcinogenic health risks on the infant and child (minor) age groups compared to adolescents and adults. Based on the cokriging interpolation mapping, the minor residents of 17.88%–23.15% of the total area (4545.0 km²) are vulnerable to methemoglobinemia whereas the residents of all age-groups in 38.47%–44.45% of the total area are susceptible to mild to severe dental/skeletal fluorosis owing to consumption of untreated nitrate and fluoride enriched groundwater. The Sobol sensitivity indices revealed contaminant levels, groundwater intake rate and their collective effects are the most influential factors to pose potential health risks on the residents. Artificial recharge and rainwater harvesting practices should be adopted to improve the groundwater quality and the residents are advised to drink purified groundwater.     

Sedimentation model of gravel-dominated alluvial piedmont fan,Ganga Plain,India

The Piedmont Zone of the Indo-Gangetic Plain contains numerous, laterally coalescing small alluvial fans. The Latest Pleistocene–Holocene 30 km long Gaula Fan can be divided into gravelly proximal fan (0–14 km down-stream), gravel-sand rich mid fan (14–22 km) and sand–mud dominated distal fan (22–30 km). The fan succession is composed of two fan expansion cycles A and B. Separated by an undulatory erosional contact of regional extent, cycle A is characterized by river borne clast-supported gravelly deposits, and the overlying fan expansion cycle B by matrix-supported gravely debris flows. The main process behind fan development has been lateral migration of channels over the fan surface probably due to rapid sedimentation caused by increased sediment supply, and the fluctuating water budget in response to changing climate. The water laid expansion cycle A represents a humid phase. The debris flow deposits of expansion cycle B suggest a dry phase. Approximately between 8 and 3 Ka, cycle B also indicates a phase of tectonic instability in the Siwalik Hills forming the mountain front. The tectonic activity caused incision of rivers into the fan surface, and in turn resulted in reduced fan-building activity. At present the fan surface is accreting by sheet flow processes.     

Arsenic Levels in Groundwater from Quaternary Alluvium in the Ganga Plain and the Bengal Basin, Indian Subcontinent: Insights into Influence of Stratigraphy

Late Quaternary stratigraphy and sedimentation in the Ganga Alluvial Plain and the Bengal Basin have influenced arsenic contamination of groundwater. Arsenic contaminated aquifers are pervasive within lowland organic rich, clayey deltaic sediments in the Bengal Basin and locally within similar facies in narrow, entrenched river valleys within the Ganga Alluvial Plain. These were mainly deposited during early-mid Holocene sea level rise. Arsenic was transported from disseminated sources as adsorbed on dispersed phases of hydrated-iron-oxide. These were preferentially entrapped as sediment coatings on organic-rich, fine-grained deltaic and floodplain sediments. Arsenic was released later to groundwater mainly by reductive dissolution of hydrated-iron-oxide and corresponding oxidation of sediment organic matter. Strong reducing nature of groundwater in the Bengal Basin and parts of affected middle Ganga floodplains is indicated by high concentration of dissolved iron (maximum 9-35 mg/l). Groundwater being virtually stagnant under these settings, released arsenic accumulates and contaminates groundwater. The upland terraces in the Bengal Basin and in the Central Ganga Alluvial Plain, made up of the Pleistocene sediments are free of arsenic contamination in groundwater. These sediments are weakly oxidised in nature and associated groundwater is mildly reducing in general with low concentration of iron (<1 mg/l), and thus incapable to release arsenic. These sediments are also flushed free of arsenic, released if any, by groundwater flow due to high hydraulic head, because of their initial low-stand setting and later upland terraced position.     

Chemistry of springwater in Almora, Central Himalaya, India

 A field study was conducted to assess variations in physico-chemical characteristics of water of the springs located within the boundary of a Central Himalayan town where the springwater is used for drinking purposes. Monitoring of 12 springs was carried out for three seasons (winter, summer and monsoon). The results indicate direct influence of unplanned sewage disposal on the springwater quality as reflected by significant regional variations in the concentration of nitrates, chlorides, sulfates, sulfides and electrical conductivity. Population density varies within the town from 3110 to 14 137 persons/km^–2 and has direct relationship with water quality. Springs located in the densely populated area had higher concentrations of all these compounds. Concentrations of nitrates up to 60 ppm were observed in some springs, making water unsuitable for human consumption. No significant changes were observed in springwater quality during different seasons. Received: 3 February 1995 · Accepted: 27 February 1996     

The Stream Sediment Geochemistry of the Walawe Ganga Basin of Sri Lanka - Implications for Gondwana Mineralization

A regional geochemical and mineralogical study aimed at investigating the mineralization in the western-part of the Walawe Ganga (river) Basin in Sri Lanka is represented in this paper. The river basin is the 3^rd largest in the country and has within it a boundary zone between two geologically different crustal blocks, which are marked by granulitic grade rocks and amphibolite grade rocks. Size fractions of stream sediments (< 63 μm; 63–125 μm; 125–177 μm and 177–250 μm) developed on the granulite-grade metamorphic terrain have been analysed at their source for their mineralogical and selected element compositions. Thirty-eight (38) sediment samples and 15 representative probable parent rock samples were chemically analysed giving special emphasis to the High Field Strength trace Elements (HFSE) including the Rare Earth Elements (REE). The granulite grade rocks in the study area is geochemically similar to that of post Archean upper crust. However the stream sediments developed from the high-grade rocks during the intense weathering, are markedly enriched with HFSE and REE. The enrichment of HFSE and LREE is accounted for by the presence of HFSE- and REE- rich accessory mineral phases such as zircon, monazite, apatite, garnet and rutile in the sediments. In some samples, the content of heavy minerals contributes as much as 50 wt. %. These minerals act as a source of elements in the sediments. However, extreme hydraulic sorting of HFSE- and REE-bearing minerals during the sediment deposition cannot be expected within a short distance from near the sources except from a mineralized occurrence. Therefore, the higher enrichment of these elements presumably indicates occurrences of scattered mineral sources such as highly differentiated granites and associated pegmatites within the Walawe Ganga drainage basin. These granitic pegmatites are probably intruded during or soon after the main granulite-facies metamorphic event and similar events are seen in other terrains of East-Gondwana.     

Groundwater pollution due to sugar-mill effluent, at Sonai, Maharashtra, India

 Analyses of 126 samples collected from 18 dug wells in the shallow basaltic aquifer over a period of 7 months have revealed spatial as well as temporal changes in the chemical properties of groundwater. While the temporal changes have been attributed to dilution and concentration phenomena governed by climatic factors, the spatial variations in the geochemical characteristics of groundwater appeared to be related to pollution due to effluents from the Mula Sugar Factory. The cause of groundwater pollution is the effluent carried by a stream flowing through the area. Fluctuations in the groundwater table, influent water quality character of the stream, less capacity to accommodate large volume of effluent and occurrence of zero base flow (under natural conditions) in the stream are the factors favoring infiltration of constituents of waste water into the underlying weathered basaltic aquifer. Pollutants have entered into the shallow aquifer by downward percolation through the zone of aeration to form a recharge mound at the water table and, further, lateral movement below the water table. The plume of polluted groundwater has a lateral extent of a few meters in the upstream area and more than 400 m on either side of the stream in the downstream part. The zone of polluted groundwater has an areal extent of more than 3.5 km². Groundwater is the only source available for drinking and agricultural purposes. It is recommended that the base of the lagoons and the stream used for release of plant effluent should be waterproofed for the protection of groundwater in the Sonai area. Received: 30 April 1997 · Accepted: 23 September 1997     

Major and trace element geochemistry in upper Ganga river in the Himalayas, India

Chemical weathering and resulting water compositions in the upper Ganga river in the Himalayas were studied. For the first time, temporal and spatial sampling for a 1 year period (monthly intervals) was carried out and analyzed for dissolved major elements, trace elements, Rare Earth Elements (REE), and strontium isotopic compositions. Amounts of physical and chemical loads show large seasonal variations and the overall physical load dominates over chemical load by a factor of more than three. The dominant physical weathering is also reflected in high quartz and illite/mica contents in suspended sediments. Large seasonal variations also occur in major elemental concentrations. The water type is categorized as HCO₃^––SO₄^2––Ca²⁺ dominant, which constitute >60% of the total water composition. On an average, only about 5–12% of HCO₃^– is derived from silicate lithology, indicating the predominance of carbonate lithology in water chemistry in the head waters of the Ganga river. More than 80% Na⁺ and K⁺ are derived from silicate lithology. The silicate lithology is responsible for the release of low Sr with extremely radiogenic Sr (⁸⁷Sr/⁸⁶ Sr>0.75) in Bhagirathi at Devprayag. However, there is evidence for other end-member lithologies for Sr other than carbonate and silicate lithology. Trace elements concentrations do not indicate any pollution, although presence of arsenic could be a cause for concern. High uranium mobilization from silicate rocks is also observed. The REE is much less compared to other major world rivers such as the Amazon, perhaps because in the present study, only samples filtered through <0.2 m were analysed. Negative Eu anomalies in suspended sediments is due to the excess carbonate rock weathering in the source area.     

Heavy metal pollution in freshly deposited sediments of the Yamuna River (the Ganges River tributary): a case study from Delhi and Agra urban centres, India

 The Yamuna River sediments, collected from Delhi and Agra urban centres, were analysed for concentration and distribution of nine heavy metals by means of atomic adsorption spectrometry. Total metal contents varied in the following ranges (in mg/kg): Cr (157–817), Mn (515–1015), Fe (28,700–45,300), Co(11.7–28.4), Ni (40–538), Cu (40–1204), Zn (107–1974), Pb (22–856) and Cd (0.50–114.8). The degree of metal enrichment was compared with the average shale concentration and shows exceptionally high values for Cr, Ni, Cu, Zn, Pb and Cd in both urban centres. In the total heavy metal concentration, anthropogenic input contains 70% Cr, 74% Cu, 59% Zn, 46% Pb, 90% Cd in Delhi and 61% Cr, 23% Ni, 71% Cu, 72% Zn, 63% Pb, 94% Cd in Agra. A significant correlation was observed between increasing Cr, Ni, Zn, and Cu concentrations with increasing total sediment carbon and total sediment sulfur content. Based on the Müller's geoaccumulation index, the quality of the river sediments can be regarded as being moderately polluted to very highly polluted with Cr, Ni, Cu, Zn, Pb and Cd in the Delhi and Agra urban centres. The present sediment analysis, therefore, plays an important role in environmental measures for the Yamuna River and the planning of these city centres. Received: 21 June 1999 · Accepted: 1 October 1999     

Groundwater pollution due to discharge of industrial effluents in Venkatapuram area, Visakhapatnam, Andhra Pradesh, India

 Hindustan Polymers Limited was established in the Venkatapuram area in the northwestern part of Visakhapatnam urban agglomeration. Untreated industrial effluent from the plant is discharged with total dissolved solids concentrations reaching up to 6500 mg/l. The groundwater pollution was identified as early as 1981 and a hydrogeologic and water-quality database is available from 1981. The groundwater quality in the plant environs is found to be in the range of 3500–4500 mg/l. Major chemical constituents of industrial-waste waters consist of Na, Cl, and SO₄. Some characteristic parameters of the aquifer were estimated. The available hydrogeologic and hydrologic data was analyzed to conceptualize the groundwater regime. A mathematical groundwater flow model was constructed to compute the hydraulic head at the center of finite-difference grid. The computed head distribution and effective porosity of the formations were used to calculate the groundwater flow velocity. The computed velocity field was ultimately used to prognose the pollutant migration in groundwater accounting for the advection and dispersion processes in the mass transport model and for determining the time-dependent pathlines of pollutant. Areal migration of pollutants from the source was predicted up to year 2002. Received: 23 December 1996 · Accepted: 9 September 1997     

Simulation of chloride migration rates in Paleo Pennar Delta Region, Coastal Andhra Pradesh, India

 Quaternary alluvial aquifers in the paleo Pennar delta region of Andhra Pradesh (Long. 80°0′ and 80°12′; Lat. 14°40′ and 14°20′) constitute an important coastal strip, with potential fresh groundwater resources and several well fields in operation. The lineament patterns and traces of paleo channels provide basic information on the configuration and boundaries of paleo delta and the possible neotectonic movements in the region. The paleo delta region is essentially characterized by freshwater aquifer systems at the near-surface depths, (up to 50 m from ground level) with transmissivity values in the system ranging from 1200 to 2500 m²/day. This groundwater system has been subjected to heavy draft situation over the last two decades, parlicularly near the outer rim of the delta where an unlined brackish-water canal runs parallel to the coast imparting chloride contamination to the adjoining fresh aquifers. A two-dimensional solute transport model solution was applied to assess chloride migration rates inland under different hydraulic stresses, combining finite difference solution of flow equation and the method of characteristic solution of solute transport equation. Groundwater flow and chloride migration patterns/rates were obtained for different simulated stress events in the delta system, and measures required to protect the freshwater resources ara outlined. Received: 2 January 1997 · Accepted: 4 November 1997     

Groundwater resources of the middle and upper Odra River basin, southwestern Poland

 The total amount of groundwater resources in the middle and upper Odra River basin is 5200×10³ m³/d, or about 7.7% of the disposable groundwater resources of Poland. The average modulus of groundwater resources is about 1.4 L/s/km². Of the 180 'Major Groundwater Basins' (MGWB) in Poland, 43 are partly or totally located within the study area. The MGWB in southwestern Poland have an average modulus of groundwater resources about 2.28 L/s/km² and thus have abundant water resources in comparison to MGWB from other parts of the country. Several types of mineral waters occur in the middle and upper Odra River basin. These waters are concentrated especially in the Sudety Mountains. Carbon-dioxide waters, with yields of 414 m³/h, are the most widespread of Sudetic mineral waters. The fresh waters of the crystalline basement have a low mineralization, commonly less than 100 mg/L; they are a HCO₃–Ca–Mg or SO₄–Ca–Mg type of water. Various hydrochemical compositions characterize the groundwater in sedimentary rocks. The shallow aquifers are under risk of atmospheric pollution and anthropogenic effects. To prevent the degradation of groundwater resources in the middle and upper Odra River basin, Critical Protection Areas have been designated within the MGWB. Received, January 1995 Revised, May 1996, August 1997 Accepted, August 1997     

A graphic expression of salinization and pollution of groundwater The case of Israel's groundwater

 Anthropogenic activities create various contaminated leachate, which can migrate downward from the vadose zone to groundwater, transferring contaminants, including some hazardous ones. When these various sources of contamination influence the groundwater aquifer simultaneously, the effects of contamination are enhanced. The major concern of this study has been to determine whether the shape of a groundwater chlorograph might be the result of such deterministic effects as accumulation of one or more particular processes of groundwater contamination, and how this might relate to specific hydrological situations. This study proposes a classification of groundwater contamination on the basis of properties of the main components of groundwater quality graphs and the corresponding hydrogeological/environmental situation. The study further suggests that contamination of groundwater in any hydrogeological situation (e.g. sea water) may be graphically expressed. A variety of chlorographs and nitrographs, representative of various groundwater aquifers sampled from a number of wells throughout Israel attest to this. The study thus indicates that groundwater quality graphs may be considered as a complementary tool for groundwater quality control and better understanding aquifer situations.     

Hydrogeochemical analysis of salinization processes in the coastal aquifer of Oropesa (Castellón, Spain)

 The coastal aquifer of Oropesa is affected by salinization processes undoubtedly associated with intense groundwater exploitation for agriculture supply. The aquifer corresponds geologically to a tectonic depression with Plioquaternary fill. Hydrogeologically, this aquifer is detrital, with intergranular porosity, which receives substantial recharge from adjacent Mesozoic aquifers. Contact with the sea, in addition to the presence of cultivated soil requiring extreme exploitation of groundwater, frequently give rise to processes of seawater intrusion. The present research is an attempt to understand the saltwater intrusion in this aquifer, using hydrochemical analyses of the behavior of certain minor ions that could help in the characterization process. In the case of the Oropesa sector, groundwater salinization does not appear to be attributable solely to the intrusion of seawater, but there are also anomalies related largely to the geology of the sector and its surroundings, the type of recharge, the hydrodynamic conditions in the specific area, etc. Received: 23 January 1995 · Accepted: 12 September 1995     

Modeling pollutant migration in the Upper Palar River Basin, Tamil Nadu, India

 Palar River Basin, a crystalline rock region in North Arcot District (Tamil Nadu), India, possesses vast groundwater potential along and near the river course and its lands are fertile. Serious contamination of both surface water and groundwater has been reported in this basin as a result of uncontrolled discharge of untreated effluents by the tanning industries for the last three decades. The health of the rural farming community and people working in the tanning industries has been seriously affected and they are suffering from occupational diseases such as asthma, chromium ulcers and skin diseases. About an 11000 hectares area of fertile land has lost its fertility. Total dissolved solids (TDS) concentration in groundwater at some pockets varies from 3000 to 10000 mg/l. As the discharge of effluents is continuing, a prognosis of further pollutant migration is carried out using a mathematical model. A numerical model of the Upper Palar River Basin was developed using the finite difference technique coupled with method of characteristics and used to predict TDS migration for the next 20 years. Sensitivity analysis was carried out to identify the parameters which are influencing the contaminant migration. Sensitivity analysis shows that advection and not dispersion is the predominant mode of solute migration in Palar Basin. Prognosis using the model confirms that the polluted area zone as well as the concentration of pollutants in the groundwater will continue to increase in future. The study also indicated that even if the pollutant sources are reduced to 25% of the present level, the TDS concentration level in the groundwater, even after 20 years, will not be reduced below 50% of its 1992 level. Received: 20 June 1998 · Accepted: 26 October 1998