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.

     

Surface and groundwater quality characterization of Deoria District,Ganga Plain,India

A water quality investigation was carried out in the Deoria district, Ganga plain, to assess the suitability of surface and groundwaters for domestic, agricultural, and industrial purposes. As much as 50 representative samples from river and groundwater were collected from various stations to monitor the water chemistry of various ions, comprising Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃ ⁻, SO₄ ²⁻, NO₃ ⁻, Cl⁻, F⁻, and trace metals, such as Fe, Cu, Mn, Zn, Cd, and Pb. The results showed that electrical conductance (EC), total dissolved solids (TDS), HCO₃ ⁻, Mg²⁺, Na⁺, and total hardness (TH) are above the maximum desirable limit, and apart from Fe and Mn all other trace metals are within the maximum permissible limit for drinking water. The calculated values for sodium absorption ratio (SAR), salinity, residual sodium carbonate (RSC), and permeability index (PI) indicate well to permissible use of water for irrigation. High values of Na%, RSC, and Mg-hazard (MH) at some stations restrict its use for agricultural purpose. Anthropogenic activities affect the spatial variation of water quality. Economic and social developments of the study area is closely associated with the characteristics of the hydrological network.     

Extensional tectonic activity in the cratonward parts (peripheral bulge) of the Ganga Plain foreland basin,India

Flexural subsidence of the Indian lithosphere created the foreland basin in front of the emerging Himalayan mountain belt. The continued northward push of the Indian plate and thrust sheet loading in the Himalayan orogen caused an up-warping along its cratonward margin, in the form of a regional gentle bulge. In the cratonward peripheral bulge small-scale to moderate size deformation features, e.g., gentle folds (up-arching of the sediment layers), extensional normal faults and uplifted tilted blocks, and incised river channels with 20-60-m-high cliffs, developed. Cliff sections of many rivers in this cratonward part of the foreland basin expose deposits of latest Pleistocene-Holocene age and show evidences of active tectonics in the last few thousand years: vertical uplift leading to deep incision of the river system, development of prominent fractures cutting through the sedimentary succession, bending and tilting of the strata, and tilted blocks. In the Late Quaternary relaxation phase of the Himalayan orogen-foreland, there is increased vertical tectonic activity in the region of the peripheral bulge. The vertical uplift in this part of the Ganga Plain foreland basin caused the rivers (including the axial rivers) to make further deep incision without shifting from their courses. During periods of increased tectonic activity in the Himalayan region, i.e., the addition of thrust slices more rapidly, probably caused the maximum down-bending in the proximal part of the Ganga plain foreland basin. The high amplitude and asymmetric nature of this foreland basin is partly controlled by extensional tectonism.     

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.     

Hydrochemical characteristics and seasonal variations in groundwater quality of an alluvial aquifer in parts of Central Ganga Plain,Western Uttar Pradesh,India

The present study was undertaken to assess major ion chemistry of groundwater in parts of the Central Ganga Plain and observe seasonal variations in its chemical quality. Systematic sampling was carried out during November 2005 and June 2006. The major ion chemistry of groundwater shows large variations, so much so that at times the meteoric signature seems to be completely obliterated. In many samples the concentrations of SO₄, NO₃ and F are above the permissible limit for human consumption. The graphical treatment of major ion chemistry helps in identifying four types of groundwater. All possible ionic species such as NaCl, KCl, NaHCO₃, NaSO₄, KNO₃, NaNO₃, CaHCO₃, MgHCO₃, MgSO₄ are likely to occur in groundwater system. The observed chemical variations may be attributed to sediment water interaction, ion exchange, dissolution mechanisms and anthropogenic influences such as application of fertilizers and effluents from sugar factories and paper mills. A general increase in TDS is observed in samples during June 2006. The increase in salinity is attributed to evaporation from water table, irrigation return flows, anthropogenic activities and below average rainfall in 2005 and 2006. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Evaluation of hydrogeochemical parameters of groundwater for suitability of domestic and irrigational purposes: a case study from central Ganga Plain,India

The study area is one of the most productive part of central Ganga Plain and fertile tract for sugarcane cultivation. Hydrogeochemical parameters of groundwater of the study area was evaluated to know the suitability of groundwater for domestic and irrigational purposes. Fifty-five groundwater samples from hand pumps in pre-monsoon 2007 were analyzed for physical and chemical groundwater parameters (electrical conductivity, pH, total dissolved solid, Na, K, Ca, Mg, HCO₃, Cl, SO₄, and NO₃). Three major groups of groundwater with distinct chemical compositions had been identified on L–L diagram, i.e., Ca⁺Mg-HCO₃ type, mixed type, and alkali bicarbonate type. All possible species, such as Na-Cl, K-Cl, Na-HCO₃, Na-SO₄, Ca-HCO₃, Mg-HCO₃, Ca-SO₄, and Mg-SO₄ occur in the groundwater system. Groundwater comes under the category of moderately hard to very hard, mildly acidic to slightly alkaline in nature. Majority of the sample are within the permissible limit when compared with drinking water standards in terms of electrical conductivity, pH, total dissolved solid, Na, K, Ca, Mg, HCO₃, Cl, SO₄, and NO₃. According to Gibb’s ratio, most of groundwater samples fall in the rock dominance field. Assessing the domestic uses, all the samples are considered fit, as they are neither acidic nor strongly alkaline. Based on analytical results, irrigational quality parameters like sodium adsorption ratio, residual sodium carbonate, and permeability index were calculated which indicate that the groundwater is also suitable for irrigational uses.     

Groundwater quality in parts of Central Ganga Basin, India

 This paper deals with the drinking water quality of the Ganga-Kali sub-basin which occupies 1300 km² over parts of Aligarh and Etah districts. Water samples were collected from shallow and deep aquifers and were analyzed for major ions and trace elements. The analytical data were interpreted according to published guidelines. Chemical analysis shows that the groundwater in the basin is alkali bicarbonate type. Trace element studies of water from the shallow aquifer show that the concentration of toxic metals Fe, Mn, Cd, Pb, and Cr⁺⁶ are above permissible limits which may present a health hazard. The water from the deep aquifer is comparatively free from contamination. The aquifers are subject to contamination due to sewage effluents and excessive use of fertilizers and pesticides in agriculture. Received: 7 December 1998 · Accepted: 2 March 1999     

Assessing groundwater vulnerability using GIS-based DRASTIC model for Ahmedabad district,India

The present research aims to derive the intrinsic vulnerability of groundwater against contamination using the GIS platform. The study applies DRASTIC model for Ahmedabad district in Gujarat, India. The model uses parameters like depth, recharge, aquifer, soil, topography, vadose zone and hydraulic conductivity, which depict the hydrogeology of the area. The research demonstrates that northern part of district with 46.4% of area is under low vulnerability, the central and southern parts with 48.4% of the area are under moderate vulnerability, while 5.2% of area in the south-east of district is under high vulnerability. It is observed from the study that lower vulnerability in northern part may be mostly due to the greater depth of vadose zone, deeper water tables and alluvial aquifer system with minor clay lenses. The moderate and high vulnerability in central and southern parts of study area may be due to lesser depth to water tables, smaller vadose zone depths, unconfined to semi-confined alluvial aquifer system and greater amount of recharge due to irrigation practices. Further, the map removal and single-parameter sensitivity analysis indicate that groundwater vulnerability index has higher influence of vadose zone, recharge, depth and aquifer parameters for the given study area. The research also contributes to validating the existence of higher concentrations of contaminants/indicators like electrical conductivity, chloride, total dissolved solids, sulphate, nitrate, calcium, sodium and magnesium with respect to groundwater vulnerability status in the study area. The contaminants/indicators exceeding the prescribed limits for drinking water as per Indian Standard 10500 (1991) were mostly found in areas under moderate and high vulnerability. Finally, the research successfully delineates the groundwater vulnerability in the region which can aid land-use policies and norms for activities related to recharge and seepage with respect to existing status of groundwater vulnerability and its quality.     

Natural hazards in the Ghaghara River area, Ganga Plain, India

The Ganga Plain is one of the most densely populated regions of the world due to its fertile soil and availability of water. The rivers of this plain are the lifeline for millions of people of this vast alluvial plain. All rivers of this plain are characterized by narrow channel confined within wide valley. Continuously increasing pressure of population on this plain has led to the intensification of settlement even into the valley of the river. This unplanned expansion has enhanced the damage due to flooding during high-discharge period and lateral erosion during low-discharge period. Flooding and lateral erosion are identified as fluvial hazards in the Ghaghara River area. Extensive studies have been carried out on flooding, but not much attention has been paid to the phenomenon of lateral erosion. However, it has been observed that lateral erosion is an independent fluvial hazard that operates during low-discharge period. Low degree of compaction due to the presence of sandy and silty facies in the river valley deposits, mass movement, palaeocurrent pattern, and fractures initiates and enhances the lateral erosion. The present paper deals with the fluvial hazards in the Ghaghara River area.     

Arsenic mobility in fluvial environment of the Ganga Plain,northern India

In the northern part of the Indian sub-continent, the Gomati River (a tributary of the Ganga River) was selected to study the dynamics of Arsenic (As) mobilization in fluvial environment of the Ganga Plain. It is a 900-km-long, groundwater-fed, low-gradient, alluvial river characterized by monsoon-controlled peaked discharge. Thirty-six water samples were collected from the river and its tributaries at low discharge during winter and summer seasons and were analysed by ICP-MS. Dissolved As and Fe concentrations were found in the range of 1.29–9.62 and 47.84–431.92 μg/L, respectively. Arsenic concentration in the Gomati River water has been detected higher than in its tributaries water and characteristically increases in downstream, attributed to the downstream increasing of Fe₂O₃ content, sedimentary organic carbon and silt-clay content in the river sediments. Significant correlation of determination (r ² = 0.68) was also observed between As and Fe concentrations in the river water. Arsenic concentrations in the river water are likely to follow the seasonal temperature variation and reach the level of World Health Organization’s permissible limit (10 μg/L) for drinking water in summer season. The Gomati River longitudinally develops reducing conditions after the monsoon season that mobilize As into the river water. First, dissolved As enters into pore-water of the river bed sediments by the reductive dissolution of Fe-oxides/hydroxides due to microbial degradation of sedimentary organic matter. Thereafter, it moves upward as well as down slope into the river water column. Anthropogenically induced biogeochemical processes and tropical climatic condition have been considered the responsible factors that favour the release of As in the fluvial environment of the Ganga Plain. The present study can be considered as an environmental alarm for future as groundwater resources of the Ganga–Brahmaputra Delta are seriously affecting the human–environment relationship at present.     

Implication of drainage basin parameters of Chhoti Gandak River,Ganga Plain,India

The drainage basin parameters of the groundwater-fed Chhoti Gandak River originating in the terai area of the Ganga Plain were analyzed using topographical sheets, satellite data, and field documentation with emphasis to its implication for flood mitigation and recharging of groundwater. The analyses indicate dominance of first order streams, gentle slope gradient, low surface run-off, low sediment production, high infiltration rate, and low value of basin relief. The low water storage capacity, spreading of water and concentration of peak discharge in the distal part of the river basin explain that whenever precipitation is high in the catchment area there is flood in the distal part of the basin. The bifurcation ratio value (4.34) of this basin describes that the drainage is carved naturally by slope and local relief and not influenced by geological structures like lineaments and faults.     

Mapping groundwater vulnerable zones using modified DRASTIC approach of an alluvial aquifer in parts of central Ganga plain,Western Uttar Pradesh

A detailed hydrogeological and hydrochemical study was carried out in Yamuna-Krishni sub-basin which is a part of the vast central Ganga plain. Groundwater is the major source of water supply for agricultural, domestic and industrial uses. The excess use of groundwater has resulted in depletion of water levels. The groundwater quality, too, has deteriorated in areas dominated by industrial activity. This has led to the preparation of a groundwater vulnerability map in relation to contamination. Groundwater vulnerability maps are valuable derivative maps that show, quantitatively or qualitatively, certain characteristics of the sub-surface environment that determine vulnerability of groundwater to contamination. The modified DRASTIC method was used to prepare vulnerability map. The parameters like depth to water, net recharge, aquifer media, soil media, impact of vadose zone, hydraulic conductivity and land use pattern, owing to its bearing on groundwater regime, were considered to prepare vulnerability map. The vulnerability index is computed as the sum of the products of weight and rating assigned to each of the input considered as above. The vulnerability index ranges from 140 to 180, and is classified into four classes i.e. 140–150, 150–160, 160–170 and 170–180 corresponding to low, medium, high and very high vulnerability zones respectively. Using this index, a groundwater vulnerability potential map was generated which shows that 7%, 40% and 53% of the study area falls in low, medium and high to very high vulnerability zones respectively. The map, thus generated, can be used as a tool for protection and management of aquifers from contamination.     

Environmental impact assessment in the Moradabad industrial area (rivers Ramganga-Ganga interfluve), Ganga Plain,India

Sediment samples collected in the Moradabad area, lying in the interfluve of the Ganga and Ramganga Rivers, were analysed for heavy metals, after studying the geomorphology of the area. Geomorphologically, the area can be divided into three terraces - the T₀, T₁ and T₂ surfaces. The rivers on these three surfaces show varying amounts of pollution depending upon the input from industries and urban settlements. The Ramganga River on the T₀ surface shows the highest amount of pollution. However, the pollution levels in all these rivers show a downstream dilution effect. The characteristic feature of the vast interfluve area (T₂ surface) is the presence of several, independent basins which are closed and rarely interact with each other or with any river. The sediments are redistributed and redeposited within the basin itself, and thus these basins serve as sinks. The sediments of one such basin in the study area show significant concentrations of arsenic, chromium, copper, nickel, lead, zinc and organic carbon. The concentrations of heavy metals in such a basin will show exponential increases with time, because there is no activity to funnel out the sediments and dilute the effect of pollution. This increase will pose more threats, as ultimately it will make its way laterally and vertically through the sediments, thereby polluting groundwater.     

Development of a GIS-based catastrophe theory model (modified DRASTIC model) for groundwater vulnerability assessment

This study developed a new paradigm for groundwater vulnerability assessment by modifying the standard DRASTIC index (DI) model based on catastrophe theory. The developed paradigm was called the catastrophe theory-based DI (CDI) model. The proposed model was applied to assess groundwater vulnerability to pollution index (GVPI) in Perak Province, Malaysia. The area vulnerability index was modeled by considering the DRASTIC multiple vulnerability causative factors (VCFs) obtained from different data sources. The weights and ranking of the VCFs were computed by using the inner fuzzy membership mechanism of the CDI model. The estimated vulnerability index values of the CDI model were processed in a geographic information system (GIS) environment to produce a catastrophe theory–DRASTIC groundwater vulnerability to pollution index (CDGVPI) map, which demarcated the area into five vulnerability zones. The produced CDGVPI map was validated by applying the water quality status–vulnerability zone relationship (WVR) approach and the relative operating characteristic (ROC) curve method. The performance of the developed CDI model was compared with that of the standard DI model. The validation results of the WVR approach exhibits 89.29% prediction accuracy for the CDI model compared with 75% for the DI model. Meanwhile, the ROC validation results for the CDI and DI models are 88.8% and 78%, respectively. The GIS-based CDI model demonstrated better performance than the DI model. The GVPI maps produced in this study can be used for precise decision making process in environmental planning and groundwater management.     

Evaluation of hydrogeochemical processes in the Pleistocene aquifers of Middle Ganga Plain, Uttar Pradesh, India

Evaluation of major ion chemistry and solute acquisition process controlling water chemical composition were studied by collecting a total of fifty-one groundwater samples in shallow (<25 m) and deep aquifer (>25 m) in the Varanasi area. Hydrochemical facies, Mg-HCO₃ dominated in the largest part of shallow groundwater followed by Na-HCO₃ and Ca-HCO₃ whereas Ca-HCO₃ is dominated in deep groundwater followed by Mg-HCO₃ and Na-HCO₃. High As concentration (>50 μg/l) is found in some of the villages situated in northeastern parts (i.e. adjacent to the concave part of the meandering Ganga river) of the Varanasi area. Arsenic contamination is confined mostly in tube wells (hand pump) within the Holocene newer alluvium deposits, whereas older alluvial aquifers are having arsenic free groundwater. Geochemical modeling using WATEQ4F enabled prediction of saturation state of minerals and indicated dissolution and precipitation reactions occurring in groundwater. Majority of shallow and deep groundwater samples of the study area are oversaturated with carbonate bearing minerals and under-saturated with respect to sulfur and amorphous silica bearing minerals. Sluggish hydraulic conductivity in shallow aquifer results in higher mineralization of groundwater than in deep aquifer. But the major processes in deep aquifer are leakage of shallow aquifer followed by dominant ion-exchange and weathering of silicate minerals.     

A new model (DRARCH) for assessing groundwater vulnerability to arsenic contamination at basin scale: a case study in Taiyuan basin,northern China

A modified DRASTIC model for groundwater vulnerability assessment (abbreviated as DRARCH model by combining the first letters of its six assessment indices) was proposed. It is essentially the specific application of DRASTIC model rather than a new model. Both natural hydrogeological conditions that prevent groundwater from contamination and important intrinsic hydrogeochemical properties of sediments in vadose zone that are related to the retardation of contaminants were considered as vulnerability indices. The DRARCH model consists of six indices: (1) Depth to the water table, (2) net Recharge, (3) Aquifer thickness, (4) Ratio of cumulative thickness of clay layers to total thickness of vadose zone, (5) Contaminant adsorption coefficient of sediment in vadose zone, and (6) Hydraulic conductivity of aquifer. The rating values and the weights of these vulnerability indices were obtained by contaminant transport simulation and factor analysis method respectively. Furthermore, the DRARCH model was applied to evaluate the groundwater vulnerability to arsenic contamination in Taiyuan basin, northern China, where groundwaters with high arsenic concentration occur in some localities. GIS-based mapping of groundwater vulnerability using this model indicates that the distribution of very high and high-vulnerability areas corresponds well to that of high-arsenic groundwaters. The DRARCH model is therefore reliable and useful for guiding groundwater environment management.     

A GIS-based DRASTIC model for assessing groundwater vulnerability in the Ordos Plateau, China

Groundwater plays a key role in arid regions as the majority of water is supplied by it. Groundwater pollution is a major issue, because it is susceptible to contamination from land use and other anthropogenic impacts. A study was carried out to build a vulnerability map for the Ordos Plateau using the DRASTIC model in a GIS environment. The map was designed to show the areas of the highest potential for groundwater pollution based on hydrogeological conditions. Seven environmental parameters, such as depth to water table, net recharge, aquifer media, soil media, topography, impact of the vadose zone media, and hydraulic conductivity of the aquifer, were incorporated into the DRASTIC model and GIS was used to create a groundwater vulnerability map by overlaying the available data. The results of this study show that 24.8 % of the study area has high pollution potential, 24.2 % has moderate pollution potential, 19.7 % has low pollution potential, and the remaining 31.3 % of the area has no risk of groundwater pollution. The regional distribution of nitrate is well correlated with the DRASTIC vulnerability index. In contrast to this, although the DRASTIC model indicated that the western part had no risk, nitrate concentrations were higher in some of these areas. In particular, higher nitrate concentrations were recorded along river valleys and around lakes, such as the Mulin River valley. This is mainly caused by the intensive agricultural development and favorable conditions for recharge along river valleys.     

Water quality of the Chhoti Gandak River using principal component analysis,Ganga Plain,India

Chhoti Gandak is a meandering river which originates in the terai area of the Ganga Plain and serves as a lifeline for the people of Deoria district, Uttar Pradesh. It travels a distance of about 250 km and drains into Ghaghara near Gothani, Siwan district of Bihar. It has been observed that people of this region suffer from water-borne health problems; therefore water samples were collected to analyse its quality along the entire length of Chhoti Gandak River.     

Geochemistry of groundwater in parts of Guntur district, Andhra Pradesh, India

Hydrogeochemical investigations, which are significant for the assessment of water quality, have been carried out to study the sources of dissolved ions in groundwaters of some rural areas of Guntur district, Andhra Pradesh, India. Groundwaters in the area are mostly brackish. High contents of SiO₂, and Na⁺ and Cl^- ions in groundwater, in comparison with those of seawater, suggests a meteoric origin of groundwater. The high concentration of SiO₂ and various geochemical signatures reflect the weathering of minerals. However, the Na⁺+K⁺ vs Cl^- ratio suggests weathering, has occurred only to some extent. The chemistry of groundwater favours the formation of clay minerals (montmorillonite, illite and chlorite), because of evapotranspiration. The positive saturation index of CaCO₃ and the high signatures of Ma²⁺:Ca²⁺ and Na⁺:Ca²⁺ reveals the occurrence of evaporation. The evaporation enhances the concentration of ions (which occurred originally in the water) in the soils during summer. The very high % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfKttLearuavTnhis1MBaeXatLxBI9gBae % bbnrfifHhDYfgasaacH8srps0lbbf9q8WrFfeuY-Hhbbf9v8qqaqFr % 0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8 % frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaqabeaadaaakeaacqqG % tbWucqqGpbWtdaqhaaWcbaGaeeinaqdabaGaeeOmaiJaeeyla0caaa % aa!2EC5! SO₄^{2 -} {\rm SO}_{\rm 4}^{{\rm 2 - }} and Cl^- contents in some groundwaters and the occurrence of kankar (CaCO₃) in the area suggest a long history of evaporation. Greater ionic concentration in the groundwaters of post-monsoon compared with pre-monsoon indicates the increasing addition of leachates into the groundwater from the soils in the monsoon and anthropogenic activities, which leads to a deteriorating quality of groundwater. According to the Gibbs' diagrams, rock weathering, to some extent, and evaporation are the dominant phenomena responsible for the higher ionic concentrations found in groundwater. Measures that benefit sustainable management of groundwater quality are suggested in this study.     

A proposed new approach for groundwater resources assessment in India

Assessment of groundwater resources in India is guided by National Water Policy (1987, 2002) which states that groundwater resources can be exploited only up to its recharge limit. The methodology for groundwater resources assessment in India is broadly based on Ground Water Resources Estimation Methodology, 1997 and it involves assessment of annual replenishable groundwater resources (recharge), annual groundwater draft (utilization) and the percentage of utilization with respect to recharge (stage of development). The assessment units (blocks/watersheds) are categorized based on stage of groundwater development (utilization) and the long term water level trend. The present methodology though useful in identification and prioritization of areas for groundwater management, falls short of addressing several critical issues like spatial and temporal variation of groundwater availability within the aquifer, accessibility of groundwater resources and quality of groundwater. This paper introduces a new categorisation scheme considering the above issues. The proposed scheme takes into account four criteria, viz. (i) stage of exploitation, (ii) extractability factor, (iii) temporal availability factor and (iv) quality factor. In comparison to the existing method used for categorisation, the proposed approach is more inclusive. The methodology is also equally suitable for both alluvial and hard rock terrain since it takes into consideration the variable characteristics of different types of aquifers and convergence of quantitative and qualitative assessment. The categorisation proposed here involves GIS based integration of different parameters/ themes. This allows better representation of spatial variability. The proposed methodology is demonstrated in this paper taking a case study from a hard rock terrain in central India.