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Saha D.,Central Ground Water Board | Sinha U.K.,Bhabha Atomic Research Center | Dwivedi S.N.,Central Ground Water Board
Applied Geochemistry | Year: 2011

Arsenic concentrations in groundwater extracted from shallow aquifers in some areas of the Ganga Plain in the states of Bihar and Uttar Pradesh, exceed 50μgL -1 and locally reach levels in the 400μgL -1 range. The study covered 535km 2 of active flood plain of the River Ganga, in Bihar where a two-tier aquifer system has been delineated in a multi-cyclic sequence of Quaternary sand, clay, sandy clay and silty clay all ≤∼250m below ground surface. The research used isotopic signatures (δ 18O, δ 2, 3H, 14C) and major chemical constituents HCO3-,SO42-,NO3-,Cl-,Ca2+,Mg2+,Na+,K+,Astotal of groundwater to understand the recharge processes and groundwater circulation in the aquifers. Values of δ 18O and δ 2 combined with 3H data indicate that the recharge to the As-enriched top 40m of the deposits is modern (<50a), predominantly meteoric, with some evaporation during infiltration, and partly from tanks and other surface water bodies. The lower part of the upper aquifer is vulnerable to mobilization of As with increasing groundwater extraction. The low As lower aquifer (max. 5μgL -1) is hydrologically isolated from the upper aquifer and is characterized by lower 14C concentration and lower (more negative) δ 18O values. Groundwater in the lower aquifer is ∼3ka old, occurs under semi-confined to confined conditions, with hydrostatic head at 1.10m above the head of the upper aquifer during the pre-monsoon. The recharge areas of the lower aquifer lies in Pleistocene deposits in basin margin areas with the exposed Vindhyan System, at about 55km south of the area. © 2011 Elsevier Ltd.

Reddy A.G.S.,Central Ground Water Board | Kumar K.N.,Kakatiya University
Environmental Monitoring and Assessment | Year: 2010

Hydrogeochemical studies were carried out in the Penna-Chitravathi river basins to identify and delineate the important geochemical processes which were responsible for the evolution of chemical composition of groundwater. The area is underlain by peninsular gneissic complex of Archaean age, Proterozoic meta-sediments, and strip of river alluvium. Groundwater samples were collected covering all the major hydrogeological environs in pre- and post-monsoon seasons. The samples were analyzed for major constituents such as Ca 2+, Mg2+, Na+, K+, CO3 -, HCO3 -, Cl-, SO2 -4, NO3 -, and F-. The groundwater in general is of Na+-Cl-, Na+-HCO3 -, Ca2+-Mg2+-HCO3 -, and Ca2+-Mg2+-Cl- types. Na+ among cations and Cl- and/or HCO3 - among anions dominate the water; Na+ and Ca2+ are in the transitional state with Na+ replacing Ca2+ and HCO3 - Cl- due to physiochemical changes in the aquifer and water-rock interactions. The Ca2+-Mg2+-Cl- HCO3 - type water in one third samples suggest that ion exchange and dissolution processes are responsible for its origin. Change in storage of aquifer in a season does not influence the major geochemical makeup of groundwater. Gibbs plots indicate that the evolution of water chemistry is influenced by water-rock interaction followed by evapotranspiration process. The aquifer material mineralogy together with semiarid climate, poor drainage system, and low precipitation factors played major role in controlling groundwater quality of the area. © 2009 Springer Science+Business Media B.V.

Senthilkumar M.,Central Ground Water Board | Elango L.,Anna University
Hydrogeology Journal | Year: 2011

Groundwater modelling is widely used as a management tool to understand the behaviour of aquifer systems under different hydrological stresses, whether induced naturally or by humans. The objective of this study was to assess the effect of a subsurface barrier on groundwater flow in the Palar River basin, Tamil Nadu, southern India. Groundwater is supplied to a nearby nuclear power plant and groundwater also supplies irrigation, industrial and domestic needs. In order to meet the increasing demand for groundwater for the nuclear power station, a subsurface barrier/dam was proposed across Palar River to increase the groundwater heads and to minimise the subsurface discharge of groundwater into the sea. The groundwater model used in this study predicted that groundwater levels would increase by about 0.1-0.3 m extending out a distance of about 1.5-2 km from the upstream side of the barrier, while on the downstream side, the groundwater head would lower by about 0.1-0.2 m. The model also predicted that with the subsurface barrier in place the additional groundwater requirement of approximately 13,600 m3/day (3 million gallons (UK)/day) can be met with minimum decline in regional groundwater head. © 2011 Springer-Verlag.

Naik P.K.,Central Ground Water Board
International Journal of Water Resources Development | Year: 2016

Water is an issue that relates to all aspects of human development in Africa, including health, agriculture, education, economics, and even peace and stability. But the perception that Africa has perpetual water scarcity and is heading towards water crisis is challenged by a significant number of water professionals. Although most agree that Africa suffers from economic water scarcity, physical water scarcity could possibly be controlled with better water management. The large amount of international aid granted annually to Africa is a subject of criticism. This article examines the water crisis in Africa, whether it is a myth or reality, and reasons thereof, and suggests remedial measures. © 2016 Informa UK Limited, trading as Taylor & Francis Group

Saha D.,Central Ground Water Board | Shukla R.R.,Central Ground Water Board
Water Environment Research | Year: 2013

Distribution and mobilization of groundwater arsenic from a 1580-km 2 area in the Gangetic Plain was studied. A two-tier aquifer system made up of Quaternary sand layers exists within 300 m below ground. Arsenic concentration exceeding .>50 μg/L is confined within the active floodplain of the Ganga River, affecting the top aquitard and upper 5- to 20-m slice of the underlying shallow aquifer. The genesis of arsenic was investigated by principal component analyses involving total dissolved solids, Ca+2, Mg+2, Na+, K+, HCO3-, Cl -1, SO4 -2, NO3-, Fetotal, and Astotal and analyzed for 57 groundwater samples, hydrochemical facies analyses, aquifer-aquitard configuration, and water-level behaviour. A 20- to 25-m thick deeper aquifer, appearing at 190 to 205 m below ground and separated from the shallow aquifer by a thick clay sequence, was low in arsenic load (<2 μg/L). Hydrostratigraphy and pumping tests revealed that the deeper aquifer can be used for community drinking in contaminated areas.

Reddy A.G.S.,Central Ground Water Board
Journal of the Geological Society of India | Year: 2012

The study on water level conditions of fractured aquifer system in northeastern part of Anantapur district is of immense importance as the area is covered by varied geological formations and has different irrigation patterns. The monthly groundwater level data of 154 observation wells for five year period (2001-06) is analyzed to decipher the behavior of water levels in different seasons and geo-environments. The hydrographs of the average water level data of each Mandal (group of villages) indicate steady declining trend ranging from 0.50 to 2.91m/yr. Yellanuru Mandal has both the shallowest and the deepest water levels among eight Mandals, highly undulating terrain could be one of the reasons for this contrasting condition. The pre-monsoon water levels show decline of 8.22 m in one year from May 2002 to 2003. A negative seasonal fluctuation of -1.49m has occurred in the year 2002 during which the area received 32% less than normal rainfall. The mean water levels are deeper by 42% in areas covered by sedimentary formations than those of granite terrain. Raise in water levels is significant where monthly rainfall is more than 200 mm. Due to erratic rainfall in space and time, deeper water levels are noticed even in post-monsoon period and shallow in February month at some locations. The water levels in command areas are deep and exhibit falling trend as the area forms the tail end part of the Tunga Bhadra High Level Canal. The deeper water level conditions and its declining feature is directly related to groundwater development in the form of increased agriculture activity, reduced area under rain-fed crops, high horticulture development. Arid climatic conditions, low precipitation and continuous exploitation of groundwater resources could be other factors contributing for steady decline in water levels in the area. The wide variations in groundwater levels could be due to uneven topography, heterogeneous and anisotropic conditions of granites and poor porosity - permeability of shales, lack of vegetation, and increased groundwater extraction. © 2012 Geological Society of India.

The assessment of hydrogeochemical processes that govern the water quality of inland freshwater aquifers in coastal environment, especially in Indian sub-continent, is occasionally attempted. To bridge the gap, a detail hydrochemical evaluation of groundwater occurring in coastal alluvium is attempted. Single set of high-density water sampling is done from a limited area to gain an in-depth knowledge of the processes that govern the water chemistry of the sandy aquifers. The water is of weak alkaline nature and less mineralized, EC being < 1,000 μS/cm in many samples. Major ion composition indicates that water is contaminated with excess concentration of nitrates. Ionic abundance is in the order of Cl- > Na+ > Ca2+ > HCO3- > SO42- > Mg2+ > NO3-. Na+ and Cl- are almost in similar proportions implying the influence of coastal climate on water quality. The water shows modest variation in their ionic assemblage among different sample points as evident from Schoeller scheme. Groundwater can be classified into three distinct facies viz. Cl--Ca2+-Mg2+, Na+-Cl- and Ca2+-Mg2+-HCO3- types. The ionic assemblages, their indices, ratios and cross-plots substantiate that multiple processes were involved in the evolution of the water chemistry. Among them, silicate weathering, halite dissolution, ion exchange and base exchange played prominent role in the ion enrichment of groundwater. The aquatic chemistry is further influenced and modified by marine environment, evapotranspiration and anthropogenic inputs which is authenticated by good correlation (r2 = 1) among the Na+-Cl-, EC-Mg2+, Na+ and Cl-. Gibbs plots established that evaporation is more responsible for contribution of minerals to the groundwater than aquifer material. Nitrate contamination can be attributed for poor sewerage disposal mechanism which is aggravated by fertilizer inputs, irrigation practices and agriculture activity. A contrasting correlation (r2 ≥90 to <0.40) among select pairs of ions reassures dissimilar source of those ions, involvement of multiple processes and limited interaction of formation water with aquifer material. © 2012 Springer-Verlag.

Hydrogeochemical controlling factors for high rate of groundwater contamination in stressed aquifer of fractured, consolidated rocks belonging to semi-arid watershed are examined. The groundwater in mid-eastern part of Prakasam district confining to Musi-Gundlakamma sub-basins is heavily contaminated with nitrate and fluoride. Distinct water chemistry is noticed among each group of samples segregated based on concentration of these contaminants. The nitrate is as high as 594 mg/l and 57 % of the samples have it in toxic level as per BIS drinking water standards, so also the fluoride which has reached a maximum of 8.96 mq/l and 43 % of samples are not fit for human consumption. Nitrate contamination is high in shallow aquifers and granitic terrains, whereas fluoride is in excess concentration in deeper zones and meta-sediments among the tested wells, and 25 % of samples suffer from both NO3 - and F- contamination. Na+ among cations and HCO3 - among anions are the dominant species followed by Mg2+ and Cl-. The NO3 --rich groundwater is of Ca2+-Mg2+-HCO3 -, Ca2+-Mg2+-Cl- and Na+-HCO3 - type. The F--rich groundwater is dominantly of Na+-HCO3 - type and few are of Na+-SO4 2- type, whereas the safe waters (without any contaminants) are of Ca2+-Mg2+-HCO3 -- and Na+-HCO3 - types. High molecular percentage of Na+, Cl-, SO4 2- and K- in NO3 - rich groundwater indicates simultaneous contribution of many elements through domestic sewerage and agriculture activity. It is further confirmed by analogous ratios of commonly associated ions viz NO3 -:Cl-:SO4 2- and NO3 -:K+:Cl- which are 22:56:22 and 42:10:48, respectively. The F- rich groundwater is unique by having higher content of Na+ (183 %) and HCO3 - (28 %) than safe waters. The K+:F-:Ca2+ ratio of 10:5:85 and K+:F-: SO4 2- of 16:7:77 support lithological origin of F- facilitated by precipitation of CaCO3 which removes Ca2+ from solution. The high concentrations of Na+, CO3 - and HCO3 - in these waters act as catalyst allowing more fluorite to dissolve into the groundwater. The indices, ratios and scatter plots indicate that the NO3 - rich groundwater has evolved through silicate weathering-anthropogenic activity-evapotranspiration processes, whereas F- rich groundwater attained its unique chemistry from mineral dissolution-water-rock interaction-ion exchange. Both the waters are subjected to external infusion of certain elements such as Na+, Cl-, NO3 - which are further aggravated by evaporation processes leading to heavy accumulation of contaminants by raising the water density. Presence of NO3 - rich samples within F- rich groundwater Group and vice versa authenticates the proposed evolution processes. © 2013 Springer-Verlag Berlin Heidelberg.

There are several Proterozoic sedimentary sequences in India, some of which are metamorphosed and deformed, whereas others, such as the Puranas, are not metamorphosed and are virtually undeformed. On the basis of U-Pb SHRIMP ages of zircons from the Sukhda tuff (in the Chhattisgarh basin), recently an age bracket of approximately 1650-1000 Ma has been assigned to nearly all Purana basins in India. Putting Purana sedimentation in an approximately Mesoproterozoic age bracket warrants a few explanations regarding metamorphosed and unmetamorphosed Proterozoic sedimentary successions and their chronostratigraphic relationship. Our drill hole data indicate that the stratigraphic position of the Sukhda tuff is in the Gunderdehi Formation, much lower than what has been proposed recently. If so, sedimentation in the Chhattisgarh basin continued well beyond 1000 Ma and into the Neoproterozoic. It is obvious that an unequivocal assignment of the stratigraphic position of the Sukhda tuff is vital for calibrating the chronostratigraphy of the Precambrians of the Central Indian Craton. © 2010 by The University of Chicago.

This study analyses 26.5 Ma record of deep-sea benthic foraminifera from 194 samples from Ocean Drilling Program Hole 757B (latitude 17°01.458' S, longitude 88°10.899' E, water depth of 1652.1 m) located on the Ninetyeast Ridge, southeastern Indian Ocean below equatorial divergence zone. The data documents important changes in benthic foraminiferal population at Hole 757B since the late Oligocene. The welloxygenated, oligotrophic species including Cibicides cicatricosus, C. pseudoungerianus and Oridorsalis umbonatus were dominant during the late Oligocene to the early Miocene. These species began to decline as site 757 moved northward into the influence of the Indonesian Throughflow (ITF) beneath surface and subsurface water masses from the Pacific Ocean. Cibicides cicatricosus and C. pseudoungerianus disappeared in the late Miocene (10-8 Ma) at Hole 757B. The lower bathyal to abyssal species Nuttallides umbonifera shows a major increase at ∼11.5 Ma coinciding with a significant increase in Neodymium (Nd) isotope values, indicating substantial transport of deep Pacific water to the Indian Ocean through the Indonesian seaway. Nuttallides umbonifera decreases drastically during 3-2.8 Ma, though the Nd isotope values do not show a decrease. We relate this change to a low sample resolution in the latter study. This event coincides with the final closure of the Indonesian seaway and a switch in shallow ITF source from warm, saline South Pacific to cool, fresh North Pacific thermocline water, which triggered global cooling and major expansion of Northern Hemisphere glaciation.

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