Central Ganga Basin Research Articles

Palaeoclimatic shifts in the Central Ganga Basin during the Middle- to Late Holocene: Exploring the 4.2 ka arid event and its implications in northern India

The Central Ganga Basin is one of the most densely populated regions of India. It is agriculturally diverse and contributes much to the Indian economy. The region has housed numerous ancient and mediaeval empires. This study presents a continuous record of the paleomonsoon from the Chandrika Devi lake, Lucknow district of Uttar Pradesh, India which is linked with paleo vegetational shifts over the last ~6000 years (5871–75 cal yr BP). The chronology of the lake core is based on three accelerated mass spectrometry (AMS) radiocarbon and two Optically Stimulated Luminescence (OSL) dates. The multiproxy data (grain size, major and trace element ratio, total organic carbon (TOC wt%), carbon isotopes (δ13Corg‰) and pollen), suggest that the lake was initially a part of the Gomti river that began to transform into a lake at ~5000 cal yr BP with weakening of the Indian summer monsoon (ISM) in the Central Ganga Basin. The lake formation was completed at ~4100 cal yr BP under the influence of the 4.2 ka arid event. This phase marks the beginning of human presence as well as agricultural activities in the lake region with the appearance of Cerealia pollen and other agricultural taxa. The agricultural activity surrounding the lake catchment peaked at ~3000 cal yr BP. The lake gradually shrank and became a marshy lowland at ~75 cal yr BP. Our study is significant because it is the first comprehensive multiproxy study from the Lucknow region in the Central Ganga Basin on paleomonsoonal variability and its relationship to human activity, agricultural practices during the Late-Holocene with a focus on the 4.2 Ka arid event. Also, pollen record suggests that the changes in agriculture and human activity began just after 4.2 ka arid event in the study area.

Basement and lithospheric structure of the central Ganga Basin between the Bundelkhand craton and the Sharda Deep by magnetotellurics

The geological and tectonic fabric of the Indian plate in the Ganga Basin is masked by alluvial sediments. Geophysical exploration of the basin for hydrocarbons yielded information on the presence of transverse basement ridges and Cenozoic as well as some pre-collision stratigraphy of the basin. However, the depth of the basement especially in the northern part of the basin and the nature of the underlying crust and mantle lithosphere is largely unknown. We have carried out a magnetotelluric (MT) study along a 300-km-long profile between the Bundelkhand craton (BC) and the Sharda Deep (at the Himalayan foothills) across the central Ganga Basin to delineate the basement and the lithospheric structure. The electrical resistivity image obtained by 2-D inversion of broadband MT data reveals significant lateral heterogeneity in the subsurface structure along the profile. The model yields a super-thick sedimentary basin in the Sharda Deep consisting of multiple stages of basin formation, including a Proterozoic paleo-rift, and a highly heterogeneous lithospheric structure of the Indian plate north of the BC. The model consists of two major upper mantle conductors connected to the conductors within the lower crust. It is surmised that enhanced conductivity could be due to the presence of fluids and the upper mantle conductors are feeding to the crustal conductors. However, an in-depth analysis of the genesis of these conductors would require other independent geophysical information which is not available at present. This is the first reporting of such a heterogeneous nature of the Indian continental lithosphere beneath the Ganga Basin at a regional scale. Our model further supports the presence of the electrical Moho in the BC and, together with earlier published MT results along another profile, suggests that the BC extends much farther north than its presently known northern limit.

Electrical Moho and upper mantle metasomatism in the Archaean Bundelkhand craton of the Indian peninsular shield

The Bundelkhand Craton (BKC), one of the Archaean nuclei in the north central part of the Indian shield, has a lesser surface exposure compared to other cratons. Recent magnetotelluric (MT) study in the Central Ganga Basin (CGB) showed NNE-SSW extension of the cratonic block as a transverse ridge and delineated a shear zone within the buried section of the BKC. In the present study, we extend the MT profile to further south with 19 broadband MT sites in the exposed BKC to complement the lithospheric electrical resistivity architecture. Two-dimensional (2-D) geoelectric structure down to 100 km is obtained from inverse modelling of the distortion corrected MT impedance tensors together with the 31 sites in the CGB. The resulting geoelectric model reveals a flat and sharp resistivity contrast at 40–42 km depth, the electrical Moho (e-Moho), separating highly resistive Bundelkhand massif and moderately conductive upper mantle. The 2-D model also brings out two shear zones represented by near-vertical moderately conductive zones within the massif, indicating zones of amalgamation of different fragments of the pre-Bundelkhand craton. In contrast to other major cratons of the Indian shield, the present MT study has delineated a moderately conductive upper mantle beneath the BKC. In view of the estimated low mantle heat flow along with relatively flat topography, we infer metasomatism of the mantle lithosphere by percolation of fluids. We hypothesize that infiltration of fraction of water (H2O) in nominally anhydrous mantle minerals as hydrogen (H) bonded to structural oxygen (O) originated from the subducted oceanic slab has altered the mantle rheology and metasomatized the lithosphere.

A novel weight-drop seismic energy source for subsurface characterization

Multichannel Analysis of Surface Waves (MASW) studies for subsurface characterization in Central Ganga Basin of India, where thick cover of alluvium absorbs most of the vibrations generated by a sledgehammer source, give low quality seismic data at large offsets and generally provide imaging depth lesser than 30 m due to low quality of dispersion curves at lower frequencies. Therefore, a novel seismic energy source is designed and developed to produce large amplitude surface waves even at longer offsets and for deeper depths of imaging using dispersion analysis of surface waves. The developed source for seismic data acquisition is low-cost, repeatable, portable, and easy to operate with no environmental impact. Unlike the sledgehammer source where the quality of surface waves generated also depends on the person hitting the metal plate, the seismic data quality from the novel weight-drop source is independent of the operator.The developed source is an impact type where a free-falling mass accelerated due to gravitational pull hits onto a base plate coupled with the earth generating vibrations in the ground. The performance of the source was evaluated in a field trial. A receiver array of 24-channel cabled geophones with 3 m spacing was planted on the ground. Seismic data were acquired using the source at 5 m negative offset inline from the first geophone. Seismic data were also recorded with the sledgehammer as a source for comparison. Five shot gathers for each source were acquired with the same acquisition geometry and source position.Shot gathers were analyzed and compared using trace attributes, 1D and 2D Fourier spectra, signal-to-noise ratio, relative energy, and dispersion images. The study shows that the developed source produces low frequency high amplitude signal and better dispersion image, notably in the lower frequency range, in comparison with the sledgehammer source. Therefore, the developed source is adapted to investigate deeper subsurface velocity structure with dispersion curve from high amplitude surface wave analysis. Moreover, the repeatability study suggests that the repeat shot gathers acquired from the developed source have remarkably high degree of similarity. Therefore, seismic data acquisition with the developed source does not require repeat shots for vertical stacking as often done in case of a hammer source. Sound pressure level measurement indicates that the developed source has no adverse environmental impact on the operator. From the field trial of the developed source, it is convinced that the source is cost-effective, portable, easy to operate and handle and is environmentally friendly.

A Comprehensive Evaluation of Gridded L-, C-, and X-Band Microwave Soil Moisture Product over the CZO in the Central Ganga Plains, India

Recent developments in passive microwave remote sensing have provided an effective tool for monitoring global soil moisture (SM) observations on a spatiotemporal basis, filling the gap of uneven in-situ measurement distribution. In this paper, four passive microwave SM products from three bands (L, C, and X) are evaluated using in-situ observations, over a dry–wet cycle agricultural (mostly paddy/wheat cycle crops) critical zone observatory (CZO) in the Central Ganga basin, India. The L-band and C/X-band information from Soil Moisture Active Passive (SMAP) Passive Enhanced Level 3 (SMAP-L3) and Advanced Microwave Scanning Radiometer 2 (AMSR2), respectively, was selected for the evaluation. The AMSR2 SM products used here were derived using the Land Parameter Retrieval Model (LPRM) algorithm. Spatially averaged observations from 20 in-situ distributed locations were initially calibrated with a single and continuous monitoring station to obtain long-term ground-based data. Furthermore, several statistical metrices along with the triple collocation (TC) error model were used to evaluate the overall accuracy and random error variance of the remote sensing products. The results indicated an overall superior performance of SMAP-L3 with a slight dry bias (−0.040 m3·m−3) and a correlation of 0.712 with in-situ observations. This also met the accuracy requirement (0.04 m3·m−3) during most seasons with a modest accuracy (0.059 m3·m−3) for the entire experimental period. Among the LPRM datasets, C1 and C2 products behaved similarly (R = 0.621) with a ubRMSE of 0.068 and 0.081, respectively. The X-band product showed a relatively poor performance compared to the other LPRM products. Seasonal performance analysis revealed a higher correlation for all the satellite SM products during monsoon season, indicating a strong seasonality of precipitation. The TC analysis indicated the lowest error variance (0.02 ± 0.003 m3·m−3) for the SMAP-L3. In the end, we introduced Spearman’s rank correlation to assess the dynamic response of SM observations to climatic and vegetation parameters.

Numerical groundwater modelling for studying surface water-groundwater interaction and impact of reduced draft on groundwater resources in central Ganga basin.

Water resources in India's Indo-Gangetic plains are over-exploited and vulnerable to impacts of climate change. The unequal spatial and temporal variation of meteorological, hydrological and hydrogeological parameters has created additional challenges for field engineers and policy planners. The groundwater and surface water are extensively utilized in the middle Gangetic plain for agriculture. The primary purpose of this study is to understand the discharge and recharge processes of groundwater system using trend analysis, and surface water and groundwater interaction using groundwater modelling. A comprehensive hydrological, and hydrogeological data analysis was carried out and a numerical groundwater model was developed for Bhojpur district, Bihar, India covering 2395 km2 geographical area, located in central Ganga basin. The groundwater level data analyses for the year 2018 revealed that depth to water level varies from 3.0 to 9.0 meter below ground level (m bgl) in the study area. The M-K test showed no significant declining trend in the groundwater level in the study area. The groundwater modelling results revealed that groundwater head is higher in the southern part of the district and the groundwater flow direction is from south-west to north-east. The groundwater head fluctuation between the monsoon and the summer seasons was observed to be 2 m, it is also witnessed that groundwater is contributing more to rivers in the monsoon season in comparison with other seasons. Impact of reduction in pumping on groundwater heads was also investigated, considering a 10% reduction in groundwater withdrawal. The results indicated an overall head rise of 2 m in the southern part and 0.2-0.5 m in the middle and northern part of the district.

Release of Fluoride in Groundwater from Various Rock Forming Minerals and Sandy Aquifer of Central Ganga Basin, India

Abstract Fresh and pure water has an important role to play for healthy life. Currently, in many studies higher concentrations of contaminants like calcium, sodium, nitrate, lead, chromium, arsenic, fluoride etc. have been reported that makes the water unfit for its direct consumption. Sources and release mechanism of many such pollutants is still not known. These sources can be anthropogenic or geogenic. This paper deals with one of such contaminants namely fluoride and emphasizes on its release from various minerals viz. Gypsum, fluorite, tourmaline, actinolite, plagioclase, biotite, quartz, kayanite, epidote and orthoclase under different pH environment. It has been noted that maximum fluoride has been released from the fluorite at all pH environment (acidic, normal and alkaline) of water while minimal fluoride was released from kayanite. However, orthoclase, tourmaline and biotite can release fluoride in considerable amount. The attempts were also made to compare the release of fluoride from modern sand (Ganga sediments) with ancient sand (from sandy aquifer) under different pH condition. Outcome of studies shows that maximum fluoride released from the sand at the pH range of 6.1 to 8.2.

Groundwater Quality Issues and Challenges for Drinking and Irrigation Uses in Central Ganga Basin Dominated with Rice-Wheat Cropping System

Increased population and increasing demands for food in the Indo-Gangetic plain are likely to exert pressure on fresh water due to rise in demand for drinking and irrigation water. The study focuses on Bhojpur district, Bihar located in the central Ganga basin, to assess the groundwater quality for drinking and irrigation purpose and discuss the issues and challenges. Groundwater is mostly utilized in the study area for drinking and irrigation purposes (major crops sown in the area are rice and wheat). There were around 45 groundwater samples collected across the study region in the pre-monsoon season (year 2019). The chemical analytical results show that Ca2+, Mg2+ and HCO3− ions are present in abundance in groundwater and governing the groundwater chemistry. Further analysis shows that 66%, 69% and 84% of the samples exceeded the acceptable limit of arsenic (As), Fe and Mn respectively and other trace metals (Cu, Zn, Pb, Cd) are within the permissible limit of drinking water as prescribed by Bureau of Indian Standard for drinking water. Generally, high As concentration has been found in the aquifer (depth ranges from 20 to 40 m below ground surface) located in proximity of river Ganga. For assessing the irrigation water quality, sodium adsorption ratio (SAR) values, residual sodium carbonate (RSC), Na%, permeability index (PI) and calcium alteration index (CAI) were calculated and found that almost all the samples are found to be in good to excellent category for irrigation purposes. The groundwater facie has been classified into Ca-Mg-HCO3 type.

Crustal structure of the Indian plate underneath the alluvial plains of the central Ganga basin by broadband magnetotellurics

The Ganga basin consists of thick Cenozoic sediments that mask the tectonic fabric of the underlying Indian plate. Despite the availability of fairly good information on the intra-basin structure, especially at the foothills of the Himalaya due to hydrocarbon exploration activities, very little is known about the basement and the crustal/lithospheric structure although composition and thermomechanical properties of the underthrusting Indian plate are expected to have a significant role in controlling the deformation and seismicity along the Himalayan arc. Here, we present a two-dimensional geoelectric model of the crustal structure along a 285-km-long profile across the central Ganga basin. The results were obtained by inversion of decomposed TE- and TM-mode impedance tensors derived from broadband magnetotelluric data recorded at 45 sites along the profile. The results reveal three main features: (i) the highly resistive Bundelkhand massif (BKC) extends northward beneath the sediments up to Lucknow; (ii) the massif is constituted of two blocks separated by a 10-km-wide moderately resistive nearly vertical zone; and (iii) a super-deep sedimentary basin constituted of highly conductive sedimentary succession exists in the northern segment of the profile. We report the presence of an electrical Moho at 40–45 km depth for the buried BKC and a crustal shear zone within the craton masked by the alluvial sediments. These results shall facilitate in furthering our understanding of the evolution of the BKC as well as the lithospheric/flexural deformation of the Indian continental lithosphere.

Paleomonsoonal shifts during ∼13700 to 3100 yr BP in the central Ganga Basin, India with a severe arid phase at ∼4.2 ka

We present a multiproxy record of grain size and stable carbon isotope from the Lilaur lake, Ganga Basin, India to understand the history of lake formation linked to changes in Indian monsoon precipitation during ~13714 to 3073 calibrated year before Present (cal yr BP). A comparison is made between Lilaur lake proxy record with those from other parts of South Asia as well as North Atlantic to understand extent and causes of monsoon variability and its influence on the fauna and flora of the region. Chronology of lake core was constrained using AMS 14C and optically stimulated luminescence (OSL) dates. This study suggests a transition from river to lake during ~5800 to 5189 cal yr BP which is supported by reduced precipitation with weakening of the Indian summer monsoon (ISM). This river to lake transition culminated in a severe arid phase during 4250 to 4050 cal yr BP (4.2 ka event), corresponding to enhanced El Niño activity, southward shift of the Inter-Tropical Convergence Zone, and aridification of India when the ISM was weak.

Electrical resistivity image of a basement ridge in the foreland central Ganga basin

The foreland Ganga basin is traversed by several transverse ridges and faults, buried beneath the thick alluvial cover, that are considered to be underthrusting the Himalaya. The Faizabad Ridge, assumed to be the NE-to-NNE extension of the Bundelkhand craton, is one such prominent transverse tectonic feature in the central Ganga basin whose exact extent up to the Himalayan front is not known. In order to delineate its extent beneath the sediments, we have carried out magnetotelluric (MT) study along a 335-km-long profile, starting from the Vindhyans in the south and reaching up to the Himalayan front in the north. MT data were acquired at 32 sites with average inter-station spacing of 10 km. The impedance tensors in the period band of 0.001–25 s were analyzed for distortion and decomposition yielding a dominant strike direction of N105°E, coinciding with the general strike of the Ganga basin in this region. The distortion corrected TE- and TM-mode decomposed data were inverted using a two-dimensional inversion algorithm. The geoelectric structure reveals a gradual increase in the depth to the top of the Ridge. At Faizabad, the basement depth is about 3.4 km, but it rapidly increases thereafter and reaches to more than 8 km at the northernmost part of the profile where the Ridge signatures are not seen. We infer that the Ridge does not continue to the Himalayan Foothills in this region. The results also suggest the presence of a near-vertical weak zone of moderate resistivity in the vicinity of the Yamuna River. This region is also the contact between the buried Faizabad Ride and the Vindhyan Supergroup.

Observations of ambient trace gas and PM10 concentrations at Patna, Central Ganga Basin during 2013–2014: The influence of meteorological variables on atmospheric pollutants

Atmospheric pollutants including ozone (O3), sulfur dioxide (SO2), oxides of nitrogen (NOx), carbon monoxide (CO), and inhalable particulate matter (PM10) were measured in the central Indo-Gangetic Basin (IGB) at Patna, India, from 1st March 2013 to 31st December 2014, and significant variability was observed in the temporal patterns of these pollutant concentrations. The mean O3, SO2, NO, NO2, CO (trace gases: TG), and PM10 (PM) concentrations were 14.5±4.8, 5.9±4.8, 23.1±22, 20.6±14.6ppb, 1.5±0.7ppm, and 192.0±132.8μg/m3, respectively, over the study period. The highest concentrations of these species were during the post-monsoon and winter seasons except O3 and SO2 that showed the highest concentrations during the pre-monsoon. The lowest concentrations of TG and PM were observed during the monsoon season as a result of scavenging by rain. NO and NO2 along with PM concentrations decreased by ~76, 19, and 63% when the wind speed (WS) was >0.5m/s. However, for O3, an opposite trend was observed with ~14% higher concentrations. The WS was negatively correlated with PM during the winter (−0.48) and post-monsoon (− 0.32) seasons. In order to investigate the source region of TG and PM, 5-day air mass back trajectories were computed. The dominance of the air masses (92, 53, and 49%) were from the IGB is highly polluted during the winter, pre-monsoon, and post-monsoon, respectively. The TG and PM were observed much higher during these periods. During the biomass burning period (post-monsoon), the trajectory analysis showed that the TG and PM concentrations were around three-fold higher (flow from the IGB ) than the other seasons. To improve air quality over IGB, the mitigation measures should be designed to reduce emissions from both local and regional sources.

Identification of groundwater potential zones considering water quality aspect

To evolve a proper management scenario for groundwater utilization, identification of groundwater potential zones is an important step. In the present study, an attempt has been made to identify possible groundwater potential zones both in terms of quantity and quality. A methodology is proposed for identification of groundwater potential index (GWPI) and a new water quality index (WQI) based on analytic hierarchy process. The proposed methodology has been applied to the shallow alluvial aquifer of central Ganga basin, Kanpur (India). Land use/land cover, soil, geology, recharge rate, drainage density, rainfall, slope, elevation, normalized difference vegetation index, groundwater depth or depth to groundwater table are used for GWPI calculation. Moreover, WQI considers alkalinity (as CaCO3), magnesium (Mg2+), total dissolved solids and fluoride (F−) as influencing attributes. Final integration of attributes yield GWPI and WQI map. The resulting GWPI map has been classified into three groundwater potential zones namely: good, moderate and poor covering 26.94, 43.76, and 29.30 %, area, respectively. The WQI map has been classified into five quality zones namely: above permissible limit, poor, moderate, good, very good covering 12.39, 7.63, 15.17, 38.18, and 26.64 % area, respectively. Monitoring data from well locations along with GWPI and WQI map reveals the proper potential zones. This analysis demonstrates the potential applicability of the methodology for a general aquifer system.

Stable Isotopic and Hydrochemical Studies in a Part of Central Ganga Basin

Abstract: Isotopic and hydrochemical studies of groundwater were attempted in a part of central Ganga basin to gain knowledge on recharge conditions, to outline the processes responsible for isotopic fractionation, to determine the surface-water groundwater interaction and to locate the sources of groundwater contamination in the area. In the present study, conjunctive use of isotopic and silica data is employed to make an assessment of residence time of water underground and to decipher the role of rock water interaction in isotopic variations. Although the aquifer in the area is isotopically heterogeneous in its lateral extension, but oxygen and hydrogen isotopic compositions of most of the samples in pre-monsoon and post-monsoon exhibited very similar ranges which point to the single source of recharge in both the seasons. However, during post-monsoon, evaporation effects can be observed in some groundwater samples which can be attributed to the irrigation return flow in the area. Various sources of groundwater contamination have been narrowed down and it has been found that agriculture plays a dominant role in groundwater contamination in addition to other domestic and industrial sources.

Thick sedimentary sequence around Bahraich in the northern part of the central Ganga foreland basin

We present the results of a magnetotelluric study along a 285km long profile between Hamirpur and Rupadia (Nepal border) across the central Ganga basin. The electrical resistivity image obtained by combining 1-D Occam inversion models for 39 sites reveals a significant contrast in the subsurface structure from south to north along the profile. At the southern end, the Bundelkhand massif is delineated as a high resistivity block buried beneath 250–300m thick sediments. The thickness of sediments gradually increases to about 500–600m at Kanpur, and to about 1.2km at Lucknow. Here, the basement depth increases to more than 2.5km within a profile distance of 20km, which could be attributed to the Lucknow fault. The underlying rocks also have moderate resistivity and possibly represent the Vindhyans. The sedimentary sequence at the northern end of the profile around Bahraich is more than 9km thick. Integrating the resistivity image with a published seismic velocity structure from the region and the lithology from the 3927m deep Matera-I well reveals that the top 4km succession is constituted of highly conductive Oligocene and younger rocks of the Matera Formation and the Siwaliks, and recent sediments whereas the underlying >5km section is composed of sedimentary rocks of the Bahraich Group overlying the Archean basement. The high conductivity of sediments in conjunction with the low seismic velocity and large Vp/Vs obtained by receiver function analysis implies poor consolidation of sediments and thus high seismic hazard potential. The present results have implications for hydrocarbon exploration, hazard potential scenario of the central Ganga basin, and flexural strength of the Indian Plate.

Evaluation of Recharge and Groundwater Dynamics of a Shallow Alluvial Aquifer in Central Ganga Basin, Kanpur (India)

Evaluation of recharge and groundwater dynamics of an aquifer is an important step for finding a proper groundwater management scenario. This has been performed on the basis of statistical Kendall Tau test to find a relationship between groundwater levels and hydro-meteorological parameters (e.g., precipitation, temperature, evaporation). Recharge to the aquifer was estimated for identification of critical areas/locations based on the analytical Soil and Water Assessment Tool. Moreover, spatiotemporal variability of groundwater levels has been quantified using space–time variogram. The overall characterization method has been applied to the shallow alluvial aquifer of Kanpur city in India. The analysis was performed using groundwater level data from 56 monitoring piezometer locations in Kanpur from March 2006 to June 2011. Groundwater level shows relatively higher correlation with temperature. Performance of the geostatistical model was evaluated by comparing with the observed values of groundwater level from January 2011 to June 2011 for two scenarios: “with limited spatiotemporal data” and “without spatiotemporal data.” It is evident that spatiotemporal prediction of groundwater level can be performed even for the unmonitored/missing data. This analysis demonstrates the potential applicability of the method for a general aquifer system.

Groundwater Quality in Parts of Central Ganga Basin, Aligarh City, Uttar Pradesh, India

Hydrochemistry of groundwater in Aligarh city of Uttar Pradesh, India was used to determine its suitability for drinking and irrigation purpose. Physical and chemical parameters of groundwater such as electrical conductivity, pH, total dissolved solids (TDS), Na+, K+, Ca2+, Mg2+, Cl–, HCO3 –, CO3 2– and SO4 2–, were determined in one hundred groundwater samples collected from open wells as well as hand pumps in 2010. Ionic concentrations of the groundwater vary spatially and temporarily and the water is alkaline in nature. The higher values of some parameters at certain locations indicate contamination of the groundwater, making it unsuitable for specific applications. Twenty five percent of the wells lie under the medium salinity zone (EC 750-2250 micro mhos/cm). The Sodium Absorption Ratio (SAR) values range between 0.26 to 15.5 indicating that some water samples fall under the category of medium salinity hazard and are not suitable for irrigation. The groundwater of the area has also been classified on the basis of the Piper diagram. Many of the samples fall in the magnesium and sodium or potassium type, and 50% samples fall in no dominant type. As per US Salinity Laboratory Classification for irrigation water, most of the water samples fall under C2-S1 class (medium salinity and low SAR), eighteen locations fall under the category C3-S2 class (medium salinity and low SAR) and one location Luxmi Nagar shows C3-S3 (high salinity and high SAR). The major reason for the decline in water quality is the dumping of large amount of acid wastes by illegal lock factories, and another important source of pollution is slaughterhouse where at least 2500 buffaloes are slaughtered daily.

Lithosphere, crust and basement ridges across Ganga and Indus basins and seismicity along the Himalayan front, India and Western Fold Belt, Pakistan

Spectral analysis of the digital data of the Bouguer anomaly of North India including Ganga basin suggest a four layer model with approximate depths of 140, 38, 16 and 7km. They apparently represent lithosphere–asthenosphere boundary (LAB), Moho, lower crust, and maximum depth to the basement in foredeeps, respectively. The Airy’s root model of Moho from the topographic data and modeling of Bouguer anomaly constrained from the available seismic information suggest changes in the lithospheric and crustal thicknesses from ∼126–134 and ∼32–35km under the Central Ganga basin to ∼132 and ∼38km towards the south and 163 and ∼40km towards the north, respectively. It has clearly brought out the lithospheric flexure and related crustal bulge under the Ganga basin due to the Himalaya. Airy’s root model and modeling along a profile (SE–NW) across the Indus basin and the Western Fold Belt (WFB), (Sibi Syntaxis, Pakistan) also suggest similar crustal bulge related to lithospheric flexure due to the WFB with crustal thickness of 33km in the central part and 38 and 56km towards the SE and the NW, respectively. It has also shown the high density lower crust and Bela ophiolite along the Chamman fault. The two flexures interact along the Western Syntaxis and Hazara seismic zone where several large/great earthquakes including 2005 Kashmir earthquake was reported.The residual Bouguer anomaly maps of the Indus and the Ganga basins have delineated several basement ridges whose interaction with the Himalaya and the WFB, respectively have caused seismic activity including some large/great earthquakes. Some significant ridges across the Indus basin are (i) Delhi–Lahore–Sargodha, (ii) Jaisalmer–Sibi Syntaxis which is highly seismogenic. and (iii) Kachchh–Karachi arc–Kirthar thrust leading to Sibi Syntaxis. Most of the basement ridges of the Ganga basin are oriented NE–SW that are as follows (i) Jaisalmer–Ganganagar and Jodhpur–Chandigarh ridges across the Ganga basin intersect Himalaya in the Kangra reentrant where the great Kangra earthquake of 1905 was located. (ii) The Aravalli Delhi Mobile Belt (ADMB) and its margin faults extend to the Western Himalayan front via Delhi where it interacts with the Delhi–Lahore ridge and further north with the Himalayan front causing seismic activity. (iii) The Shahjahanpur and Faizabad ridges strike the Himalayan front in Central Nepal that do not show any enhanced seismicity which may be due to their being parts of the Bundelkhand craton as simple basement highs. (iv) The west and the east Patna faults are parts of transcontinental lineaments, such as Narmada–Son lineament. (v) The Munghyr–Saharsa ridge is fault controlled and interacts with the Himalayan front in the Eastern Nepal where Bihar–Nepal earthquakes of 1934 has been reported. Some of these faults/lineaments of the Indian continent find reflection in seismogenic lineaments of Himalaya like Everest, Arun, Kanchenjunga lineaments. A set of NW–SE oriented gravity highs along the Himalayan front and the Ganga and the Indus basins represents the folding of the basement due to compression as anticlines caused by collision of the Indian and the Asian plates. This study has also delineated several depressions like Saharanpur, Patna, and Purnia depressions.

Multivariate analysis of hydrochemical data of the groundwater in parts of Karwan – Sengar sub - basin, Central Ganga basin, India

Ganga basin is one of the world’s biggest aquifer repositories. The thick alluvium of the basin hosts its three tier aquifer system. The aquifer of the basin is under high stress due to unethical human intervention in the natural system. This warrants the need to evolve the basic hydrochemistry of every bit of the basin to make a scientific planning followed by a pragmatic execution. A multivariate statistical analysis was carried in order to give the hydrochemistry of the shallow aquifer a new dimension which is easily understood at a glance. In the present paper an attempt has been made to study the hydro chemical analysis data of shallow groundwater in parts of Karwan – Sengar sub basin, Central Ganga basin. The study is made of shallow aquifer of the region in which the movement of groundwater is from northwest to southeast. The descriptive statistical analysis was done beside Pearson correlation, principle component and regression analysis. All these are synthesized here to decipher the dynamics involved in the hydrochemistry of the area. The principle component analysis identified five factors that are responsible for the data structure explaining 83.49 % of the total variance of the data set. Factor 1 to 5 explains variance of 31.23, 19.445, 13.131, 12.105 and 8.647% respectively. Regression analysis show that Electric Conductivity (EC) as an independent variable which can be used to measure Carbonate (CO3 2-), Chloride(Cl-), Sodium (Na+), and Total Dissolve Solids (TDS). Further Magnesium (Mg2+) can be used to calculate the Total Hardness (TH) directly in the area.

Fluvio–sedimentary response of the monsoon-fed Indian rivers to Late Pleistocene–Holocene changes in monsoon strength: reconstruction based on existing 14C dates

The primary objective of the present study is to identify major phases of alluviation in the Indian region since the abrupt Deglacial intensification of the monsoon (∼15 cal ka BP) on the basis of analysis of 68 radiocarbon dates from two major hydro-geomorphic regions of India: the Central Ganga Basin (CGB) and the Deccan Peninsula (DP). The recognition of main phases of alluviation and incision has been achieved by evaluating the temporal distribution and clustering of the radiocarbon dates from alluvial sequences. The clusters were detected on the basis of the interpretation of the summed probability distribution plots derived by using OxCal version 4.0.1 and CALPAL (version May 2006) software packages. The summed probability plots reveal that periods of alluviation in the CGB, represented by three clusters (13.9–12.3, 11.9–11.2 and 9.8–9.0 cal ka BP) occur roughly before the onset of Early Holocene monsoon optimum phase. Two other clusters occur in the intervals 3.6–2.8 and 1.1–0.9 cal ka BP. The peak monsoon period generally lacks clusters of radiocarbon dates implying fluvial erosion and channel incision. This period also shows clustering of radiocarbon dates of the abandoned channels. In comparison, 14C dates from DP alluvial units form clusters at 16.4–14, 12.8–11.2, 10.8–8.9, 8.1–6.7 and 5.1–3.9 cal ka BP, indicating an association with the Deglacial–Early Holocene humid phase. Alluviation in the DP appears to have continued, more or less, uninterrupted till the middle of the Holocene epoch. The beginning and end of the discernible gap in the radiocarbon dates of CGB (9.0–3.6 cal ka) broadly corresponds with the two well-established short-term events of the Holocene, 8.2 and 4.2 ka cal BP. In comparison, the prominent gap of DP radiocarbon dates (3.9–2.1 ka cal BP) approximately begins with the 4.2 ka cal BP short-term event (onset of aridity) and ends with the 2.0 ka cal BP enhanced monsoon event. Notwithstanding the inter-regional differences in the fluvio–sedimentary response in the India region, the clusters of radiocarbon dates indicate that the century to millennium scale variations in fluvial activity in the Indian subcontinent were intimately linked to long-term fluctuations in the monsoon strength during the Late Quaternary.