Ganga River System Research Articles

Climate-tectonic imprints on the Late Quaternary Ravi River Valley Terraces of the Chamba region in the NW Himalaya

• The present manuscript provides pristine OSL ages of the Ravi River Valley terraces, a tributary of the Indus River. • Aggradation events were mainly induced by climate, whereas the incisions phases were governed by both tectonic and climate. • Synchronous incision phases in Hinterland (Ravi River) and Indus plain suggest akin Late Quaternary climatic conditions. • Unlike Ganga River system, Ravi River system does not show any time lag for incision between the hinterland and the plain. • The first report on reactivation age (46 ka) of the MBT and the Chamba Thrust in NW Himalaya. An attempt has been made to reconstruct the landform evolution in monsoon-dominated the Ravi River Valley (a major tributary of the Indus River), Chamba Nappe, Lesser Himalaya based on detailed field mapping, supported by the Optically Stimulated Luminescence (OSL) dates. In the upper Ravi River Valley sediments are generated by glaciation-paraglaciation processes and accumulated in terraces and alluvial fan deposits in lower reaches north of the Main Central Thrust during deglaciation and periods of intensified monsoonal phases. Field study and OSL dating demonstrate aggradation of river terraces and debris-flow terraces occurred in two major phases: 73–46 ka and 39–23 ka and at least six minor phases between <23 ka and 7 ka. The incision was initiated shortly after 7 ka and ascribed to the decrease in overall monsoon intensity and simultaneous reduction in sediment flux. The first phase (73–46 ka) of aggradation was regional and occurred in a pre-existing river valley, whereas the later phases (39 ka onward) occurred as cut-and-fill and degraded terraces. The incision of the first major phase (220 m thick) accelerated between ∼46 ka and 39 ka due to reactivation of the Chamba Thrust and the Main Boundary Thrust (MBT). The study suggests that the fluvial dynamics and aggradation phases in the Ravi River Valley were regulated by monsoon variability, whereas both tectonic activity and climatic variables governed the incision of these deposits. The contemporaneous aggradation and incision in the hinterland and the Indo-Gangetic plains suggest that the Late Quaternary climate variability was the main factor in the evolution of fluvial landforms.

Changes in gradient and bed profile in geomorphological study: A case of the Kosi River in plain

Gradient of a river is developed by a continuous process of degradation and aggradation through dynamic action of discharge over a landmass in fluvial dominant areas. Initially when a landmass emerges due to internal forces or on the landmass already existing in areas when there is rainfall, fluvial processes are operational. The earth surface is sculptured by external process found in the area. Finally, it is the product of the balance between internal and external forces operating. In this study, fluvial process is referred with respect to the changing gradient of the Kosi River and its bed profile. The characteristics of precipitation over an area determine discharge of a river. Discharge is also impacted by several factors like slope, structure and composition of rocks, vegetative cove, porosity and permeability of the soils, available human footprints, land use and land cove change caused by human beings etc. All of them are affecting discharge and sediment yield, which ultimately makes changes over an area through which it is running. The chosen area is the Kosi River in the plain and it is characterized by enormous discharge due to torrential rainfall in association with snowmelt during summer days. It is one of the largest tributaries of the Ganga River system. It is notorious for bringing flood frequently in its plain and termed as “Sorrow of Bihar”. Due to huge sedimentation from its foothills, the plain is said to be an “Inland Delta” and also called as “Kosi Megafan”. The changing gradient and bed profile is an important topic of geomorphological enquiry. Therefore, an attempt has been made in this paper to (i) study the changes in gradient of the Kosi River, (ii) investigate the changing bed level, particularly, after construction of embankment in 1958, and (iii) find long term solution of channel stability and flood management.

Identification of Gangetic turtles based on species-specific variations on mitochondrial cyt b and nuclear Cmos genes

The freshwater turtles of the iconic Ganga river system are one such group of vulnerable turtles. Despite common knowledge of the severity of turtle trade in the region, Gangetic turtles continue being poached in large volume, evident from the numerous and extensive seizures across the Gangetic belt. The intensive wildlife trade in Gangetic turtles warrants immediate conservation and management attention. The genetic resource is a vital forensic tool to monitor the Gangetic turtle species to understand the pattern of illegal wildlife trade. We collected 64 softshell and hardshell turtles samples from the Ganga river and report species-specific variations among turtle species based on mitochondrial cytochrome b gene (1140 bp) and nuclear Cmos gene (602 bp). This genetic information will help augment the molecular database to identify Gangetic turtle species and lineages effectively. We identified unique species-specific variable sites, haplotypes, and Single Nucleotide Polymorphisms (SNPs) and analyzed genetic differentiation and phylogenetic relationships. The unique mitochondrial and nuclear signatures exhibited in this study will add to baseline information on the genetic relationship of turtles of river Ganga. It will be helpful in wildlife forensics characterization of the endangered turtles. It will also help in formulating in-situ and ex-situ conservation and management plan to improve the rescue and rehabilitation strategies.

Conceptualization and development of multi-layered groundwater model in transient condition

Effective management of water resource is essential in arid and semi-arid areas of India. In Bihar, for drinking purpose humans, livestock is dependent on the groundwater as well as in agricultural areas groundwater plays an important role in irrigation directly or indirectly. There is rise in the groundwater demand due to rapid population increase and fast industrialization. To meet this groundwater demand, excessive withdrawal of groundwater is a point of concern due to limited storage of it. Assessment of the groundwater was done by preparing a numerical model of the groundwater flow. This model is capable of solving large groundwater problems and associated complexity with it. In this study, a transient multi-layered groundwater flow model was conceptualized and developed for the Koshi River basin. In north Bihar plains, the Koshi River is one of the biggest tributaries of the Ganga River system. Koshi originates from the lower part of Tibet and joins the Ganga River in Katihar district, Bihar, India. After model development, calibration of the model was also done, by considering three model parameters, to represent the actual field conditions. For validation of the model, fifteen observation wells have been selected in the area. With the help of observation well data, computed and observed heads were compared. Comparison results have been found to be encouraging and the computed groundwater head matched with the observed water head to a realistic level of accuracy. Developed groundwater model is used to predict the groundwater head and flow budget in the concerned area. The study revealed that groundwater modeling is an important method for knowing the behavior of aquifer systems and to detect groundwater head under different varying hydrological stresses. This type of study will be beneficial for the hydrologist and water resource engineers to predict the groundwater flow behavior, before implementing any project or to implement a correction scheme.

Morpho-tectonic assessment of Central Northern escarpment of Peninsular India, based on tectonically sensitive geomorphic indices

ABSTRACT The morpho-tectonic characteristics of the study area were evaluated due to paleo-tectonic significance. The Upper Tons Basin is associated with the Ganga river system, originated over the fracture zones produced after the collision of Indian and Eurasian plates; hence, the study region has its tectonic importance with small-scale tectonic deformation. The relief, drainage and tectonic characteristics are analyzed by using digital elevation model and topographical maps, geomorphic indices, lineaments and transverse profiles. Result reveals that two-third areas are in declining from mature stage (H I < 0.50) or monadnock phase (H I < 0.40). The value of basin asymmetry factor is suggesting right-side tilting of the trunk stream due to the tributaries of the Tons river originating over the Bhander uplands being longer. Further, the comparison of the stream length gradient with normalized stream length gradient shows delineating tectonically anomalous regions, and the anomalous points are addressed in the longitudinal profiles. The scarps fronts of the plateau are more sinuous and highly eroded, while the straight Kaimur fronts indicate relatively sensitive fronts. The relative tectonic activity index helps to evaluate the potential tectonic activity of a drainage basin and drainage network developed over the tectonically pre-designed valley.

Implications of Physical Barriers on Longitudinal Connectivity in the Ganga River System through Morphological Assessment of Cirrhinus mrigala (Cyprinidae) Populations

Implications of Physical Barriers on Longitudinal Connectivity in the Ganga River System through Morphological Assessment of Cirrhinus mrigala (Cyprinidae) Populations

Diet components, dietary habits, resource and its use in the coexisting catfish species

In over last six decades fisheries of the Ganga river System in general and the Ganga R. in particular have witnessed a radical change in dominance from the carp to catfish and now to invasive exotic species. Has this happened due modified river environment (natural flows, pollution) or have the species modified the food-web of the river is an issue that should be addressed in deep earnest intent. Among many facets that need to be answered, we should know the food resources base available in the river environment, preferences of fish species, if it is selective and the extent of overlap among the sympatric and co-existing species. The present investigation precisely examines this for the co-existing catfish species, Rita rita and Bagarius bagarius. R. rita feeds with greater intensity than B. bagarius. In R. rita intensity was high in pre-monsoon (January to May) compared to B. bagarius where intensity was higher in post monsoon (October to December). R. rita showed +ve preference for chironomid-Diptera and variety of Trichoptera among insects.Others include crustaceans and gastropod molluscs. In contrast B. bagarius shows preferences for a consortium of Diptera (Simuliidae), Trichoptera (Glossosomatidae), Ephemeroptera (Heptageniidae), Coleoptera and Odonata among insect food. It has high preference for fish elements. Both species select these items. There is a biologically significant diet overlap but these species avoid competition not only by selecting different items from the common food resource base but also by seasonal variation in feeding intensity. Such studies need to be extended to fish within and among feeding guilds. Keywords Catfish, diet composition, co-existance

Assessment of relationship of braiding intensities with stream power and bank erosion rate through Plan Form Index (PFI) method: a study on selected reaches of the upstream of Ganga river near Malda district, West Bengal, India

River bank erosion is a hazardous and common phenomenon in diara region near Malda district of North East India during monsoon and post monsoon periods of every year. The left bank of Ganga river is texturally very weak along diara region of Malda district. The present work explores relations between stream power, braiding intensities and bank erosion in certain stretches of upstream of the Ganga river near Malda district of West Bengal in India. In the present study, we have tried to do a quantitative assessment of channel braiding process of the Ganga river by applying the Plan Form approach and equivalent measurement of stream power. A comparative study of discrete years has been done through braiding index to understand morphological behaviour of the channel. Beside its stream power of the selected stretches of the study area is estimated and compared with braiding intensity and bank erosion. This paper presents the dynamic behaviour of the channel pattern of the Ganga river system in Malda district over a time span of 40 years. This procedure addresses the selection of input parameters from digital satellite images comprising scenes for the years 1975, 1995 and 2015 with specific dates, from Rajmahal in Jharkhand district to Farakka barrage in Malda district. To obtain Plan Form Indices for the entire study area, required parameters were extracting through using GIS techniques. Stream power is measured through analyzing latest flood records and satellite images. The present study concluded that a wide spread and continuous braiding process has occurred in the study area due to aggradations of riverbed and temporal declination of stream power.

Determination of water quality of Ganga River System in Himalayan region, referencing indexing techniques

The Ganga River system is one of the most important water resources in North India by providing water for drinking and other purposes. This study aimed to determine the suitability of river water for drinking purposes in the Himalayan region by using a water quality index (WQI). The transformation of water quality data set into index value is understandable and usable by the public. To interpret the seasonal water quality, a total of 20 monitoring locations were selected to collect water samples from Gangotri to Roorkee, for various reasons. After applying the WQI, water quality was found in good condition in three seasons except during monsoon season. In winter, summer, and autumn seasons, the value of WQI was observed 41.69, 39.4, and 35.6, respectively, which indicates good water quality, but in monsoon season, the value of WQI was found 65.3 which showed the poor water quality. To assess the metal contamination, metal index (MI) and pollution index (PI) were applied for Fe, Pb, Zn, and Cu. The MI and PI values (MI: > 6 and PI: > 5) represent that the water quality is seriously affected condition which makes river water unfit for drinking purposes. Therefore, it is needed to evaluate the river water quality as well as the implementation and formulation of an integrated plan to control the contamination level.

Water quality assessment using NSFWQI, OIP and multivariate techniques of Ganga River system, Uttarakhand, India

Ganga River water is very much stressed with the rapidly increasing population, climate change and water pollution that increase domestic, agricultural and industrial needs. This study assesses the surface water quality of the River Ganga in India, using NSFWQI, OIP and multivariate techniques. During the current study, water samples from Ganga River were collected for the assessment of 19 physico-chemical determinants from 20 sampling locations. Water quality indices (WQIs) is used to classify the overall impact of different variables of water. Multivariate techniques were utilized to assess the water conditions for productive management of fresh water quality. The WQI results showed that surface water quality varied at the selected sampling sites among medium and good categories. The PCA generates the 6 principle components which highly contributes (80.3%) in influencing the hydro-chemistry of river water. Agricultural waste runoff, untreated effluents and many other anthropogenic activities were identified as main contributor in decreasing the water quality of the River Ganga. To maintain and protect this fresh water resources against contamination, the usage of stringent policies and rules are expected to preserve fresh water resources for people in the future.

Probabilistic seismic hazard assessment for some parts of the Indo-Gangetic plains, India

Indo-Gangetic plains are seismically most vulnerable due to the proximity of adjacent great Himalayan earthquakes and thick alluvium deposits of the Ganga River system. As the urbanization on this plain is increasing, there is a need to quantify seismic hazard in the Indo-Gangetic plains (IGPs). IGP also includes major cities with high population density. A probabilistic seismic hazard analysis (PSHA) plays an essential role in ensuring the safety of buildings, bridges and nuclear power stations. A seismic hazard analysis (SHA) was performed deterministically for most of the atomic power stations in India. An attempt has been made to perform PSHA of the part of Indo-Gangetic plains around Narora nuclear power plant (NNPP), accounting for a wide variety of uncertainties associated with SHA. Geological and tectonic features, as well as seismicity distribution around NNPP, are studied in detail, and four source zones are identified according to the geology, seismotectonics and diffuse seismicity. Mmax values for all the source zones based on 300-km distance around NNPP are 7.61 ± 0.54 for Himalaya zone (Zone 1), 6.12 ± 0.54 for Indo-Gangetic Peninsular India (IGPI) East zone (Zone 2), 6.29 ± 0.54 for IGPI Central zone (Zone 3) and 6.38 ± 0.64 for IGPI West zone (Zone 4). The b-value and return period of earthquakes in these zones are also estimated using Kijko–Sellevoll–Bayes model. The hazard curve for peak ground acceleration (PGA) and pseudo-spectral acceleration (PSA) at 0.2 s for the study region is obtained. Hazard map shows a PGA value of 0.0294 g for 100-year return period, 0.0616 g for 475-year return period design-based earthquakes, 0.1033 g for 2475-year return period maximum considered earthquakes, 0.1508 g for 10K-year return period and 0.2598 g for 100K-year return period level at PGA considering all source zones. Similarly, the hazard curve and maps for PSA at 0.2 s are also plotted. According to seismic zonation map of India, most of the study area lies in Zone 4, and the PGA values reported in seismic zonation map and Global Seismic Hazard Analysis Program for the study area range from 0.3 to 0.4 g. The obtained PGA values denote the maximum expected PGA at bedrock level in the study area.

Chronological variation in landing of Indian Major Carp (IMC) of Ganga River

AbstractDuring its course of 2,525 km, the River Ganga flows through the variant topography, ecological, and environmental conditions that harbor huge range of floral, faunal, and fish diversity. The ecological condition and biodiversity of upper, middle, and lower stretches of the river are different from each other. Increases in anthropogenic activities on Ganga have resulted in a decrease in quality and quantity of its water, which ultimately led to change in its biodiversity. Menon (1974) listed 141 fish species occurring in the Ganga River system belonging to 72 genera, 30 families, and 11 orders. Recent studies reported 143 fish species from the River Ganga (Das et al., 2014; Sarkar et al., 2011) including cold water, freshwater, and estuarine fishes. In this article, a critical comparison is made on the availability of an important fish group, the Indian Major Carp (IMC), of the Ganga River during different decades, starting from 1956 and annual yield between 2005 and 2018. Average annual IMC landing during 1955–1967 was recorded as 90.85 ton, with maximum (131.3 ton) during 1964–1965 and minimum (54.0 ton) in the year 1958–1959. There was generally an increasing trend of IMC landing during 2005–2018, but it has reduced to one‐third in comparison to the time period of 1956–1967. The analysis shows that catch as well as species composition of IMC had been changed over the period of time due to changes in hydrological regime and ecology of the river. The reason in totality of this change is a focused theme of this paper.

Pseudobranch mimics gill in expressing Na+K+-ATPase 1 α-subunit and carbonic anhydrase in concert with H+-ATPase in adult hilsa (Tenualosa ilisha) during river migration.

In hilsa (Tenualosa ilisha), pseudobranch comprises a row of parallel filaments bear numerous leaf-like lamellae arranged on both sides throughout its length. The purpose of this study was to elucidate involvement of pseudobranchial Na+, K+-ATPase (NKA) 1 α-subunit, and carbonic anhydrase (CA) in concert with H+-ATPase (HAT) compared to their branchial counterparts in freshwater acclimation of hilsa during spawning migration from off-shore of the Bay of Bengal to the Bhagirathi-Hooghly zones of the Ganga river system in India. Adult hilsa fish were collected from seawater (SW), freshwater 1 (FW1), and freshwater 2 (FW2) locations, where the salinity level was 26-28‰, 1-5‰, and 0-0.04‰, respectively. Hilsa migrating through freshwater showed a consistent decrease in the plasma osmolality, sodium (Na+) and chloride (Cl-) ion levels indicates unstable ionic homeostasis. The mRNA expression and activity of NKA 1 α-subunit in pseudobranch as well as in true gills declined with the migration to upstream locations. The pseudobranchial CA activity almost mirrors its branchial counterpart most notably while hilsa entered the freshwater zone, in the upstream river suggesting its diverse role in hypo-osmotic regulatory acclimation. Nevertheless, the H+-ATPase activity of both the tissues increased with the freshwater entry and remained similar during up-river movement into the freshwater environment. The results confirm that the pseudobranchial NKA 1 α-subunit mRNA expression and activity mimic its branchial counterpart in the process of ionoregulatory acclimation during migration through salt barriers. Also, the increase in the activities of pseudobranchial and branchial CA in concert with H+-ATPase (HAT) during freshwater acclimation of hilsa suggests their critical involvement in ion uptake.

STATUS, DISTRIBUTION AND HABITAT SPECIFICITY OF BENTHIC MACRO-INVERTEBRATES: A CASE STUDY IN FIVE TRIBUTARIES OF BUDDHIGANGA RIVER IN WESTERN NEPAL

Benthic macro-invertebrates are organisms that inhabit the bottom of substrates such as sediments, debris, logs, macrophytes and filamentous algae of streams, rivers and lakes for some span of their lifecycle. They are important part of food chain since they are source of food for different species of fishes and process organic matters. These organisms are considered vital tools to assess any environmental change caused by anthropogenic interference in the river ecosystems. In this study, we sampled macro-invertebrates from 5 different rivers across altitudinal ranges of 600- 800 m and 1500-1700 m above sea level. We observed that the macro-invertebrate diversity varied substantially across altitudinal ranges. The diversity of macro-invertebrates was higher in lower altitudinal range, where 11 families were found, more than the higher altitudinal range. Some rare and dominant families were also identified in our study. We also examined the substrate specificity of macro-invertebrates. Results revealed that Ephemeroptera,Tricoptera, Coleoptera, Diptera and Odonata were found in all seven substrates namely bedrock, boulder, cobble, stone, pebble, gravel and sand. The richness and abundance of macro-invertebrates were documented in cobble, stone and pebble substrates. Similarly we also investigated the ecological river quality class of rivers using Ganga River System Biotic Score-Average Score per Taxon (GRS-BioS/ASPT) system which indicated good status. The outcomes of this study serve as a baseline data since no prior research has been done in these rivers.

Taxonomic validation of five fish species of subfamily Barbinae from the Ganga river system of northern India using traditional and truss analyses.

Morphometric differences were investigated among five fish species of subfamily Barbinae from the Ganga river system through traditional morphometrics and the truss network system. Species taken into account were Puntius chola (Hamilton 1822), Puntius sophore (Hamilton 1822), Pethia ticto (Hamilton 1822), Pethia conchonius (Hamilton 1822) and Systomus sarana (Hamilton 1822). Although, taxonomists carefully examine external body features to discriminate these species, there is still a risk of misidentification during a visual assessment. In the present study, the traditional morphological analysis included 22 morphometric measurements and 10 meristic counts. Truss network system of 14 landmarks was interconnected to yield 91 distance variables. The principal component analysis (PCA), discriminant function analysis (DFA) and cluster analysis (CA) were employed in order to determine morphometric variations. In traditional analysis, 29 characters out of 32 were found significant (p<0.05). Eight principal components were extracted through PCA explaining 85.30% of the total variance in samples, DFA correctly classified 100.0% of original grouped cases and 100.0% of cross-validated grouped cases. Truss analysis showed that all the 90 characters were significant (p<0.05). PCA extracted four principal components explaining 96.45% of the total variance. DFA correctly classified 96.1% of original grouped cases and 92.1% of cross-validated grouped cases. The results acquired from the traditional as well as truss analyses indicate significant morphometric heterogeneity. However, variations are not the same for the two different methods (traditional and truss) employed for the analyses. Shape differences among species were evident from relative warps (RW) supporting truss network analysis. Geometric morphometric methods (GMM), but limited use of Procrustes methods revealed even very small dissimilarity between groups. In spite of determining the morphometric differentiation among species, the present study also provides a useful insight on the application and complementary role of truss analysis with traditional morphometric analysis in the correct classification of the selected species.

HPI appraisal of concentrations of heavy metals in dynamic and static flow of Ganga River System

Ganga River system is a life support system to sustain the people of northeast region, India, by providing freshwater resource. In this study, the seasonal heavy metal concentrations of Ganga River system at Haridwar region (India) have been characterised for metal pollution. The collection of water samples was done from 10 different locations and analysed for various metal parameters (Zn, Pb, Mn, Fe, Cu, Si, Al, Ni, Cd, Mg and Co) using a standard laboratory procedures. The pollution level was assessed from the observed concentrations by using Heavy Metal Pollution Index (HPI) for nine heavy metals. The observed values of HPI were found lower than the Critical Pollution Index value of 100 (average value 78.62 and 81.18) during the study period. The concentration of Fe and Mg is exceeding the desirable limits of the World Health Organization, Bureau of Indian Standards and US Environmental Protection Agency in all water samples throughout the study period. The levels of all the metals were higher in the monsoon season and lower in the winter season. The Karl Pearson’s correlation matrix was developed by using the mean values of all parameters and showed the light intensity positively correlated with biochemical oxygen demand (BOD) and sulphate which indicate good microbial activity. Dissolved oxygen and BOD is found negatively correlated. From this study, it is easy to understand the various harmful effects of metal pollution to irrigation water and health of local people.

Recent insights into the dissolved and particulate fluxes from the Himalayan tributaries to the Ganga River

The Ganga River plays a major role in the transfer of materials from the Indian sub-continent to the Bay of Bengal, both in dissolved and particulate forms. To understand the present elemental dynamics of the Ganga River system, it is important to assess the hydrogeochemical contribution of its tributaries. In this paper, we present an updated database on dissolved and particulate fluxes and denudation rates of the Himalayan tributaries of the Ganga River (Ramganga, Ghaghara, Gandak and Kosi). Dissolved trace element concentrations, their fluxes and suspended sediment-associated elemental fluxes of the Himalayan tributaries have been reported for the first time. Total dissolved flux of the Ramganga, Ghaghara, Gandak and Kosi was estimated as 4, 19.1, 10.3 and 8.8 million tons year−1 accounting for ~ 5.7, ~ 27.3, ~ 14.7 and ~ 12.6%, respectively, of the total annual dissolved load carried by the Ganga River. The total particulate flux of the Ramganga, Ghaghara, Gandak and Kosi was computed as 8.2, 81.6, 30.9 and 19.5 million tons year−1, respectively. Compared to earlier studies, we have found a significant increase in the total dissolved flux and chemical denudation rate of the studied tributaries. The estimated particulate fluxes were found to be low in comparison to the previous studies. We suggest that a significant increase in the dissolved fluxes and a decrease in the particulate fluxes are an indication of the increasing anthropogenic disturbances in the catchment of these tributaries.

Massive production of heavy metals in the Ganga (Hooghly) River estuary, India: Global importance of solute-particle interaction and enhanced metal fluxes to the oceans

The Ganga River System is a major contributor to the global sediment and water discharge to the oceans. The estuary of Ganga (Hooghly) River in India is under increasing influence of anthropogenic contributions via discharge of the industrial and urban effluents. Here we document, based on the investigation of water and suspended sediment samples collected during six periods over two years, that there is extensive production of heavy metals (Co, Ni and Cu) in the estuary such that the annual dissolved fluxes of metals from the Hooghly River are enhanced by up to 230–1770%. Furthermore, the estuarine dissolved metal fluxes, when normalized with water fluxes, are the highest among estuaries of the major rivers in the world. Our simultaneous data on the dissolved, suspended particulate and exchangeable phases allow us to identify the ion-exchange process (coupled adsorption and desorption) as the dominant contributor to the generation of heavy metals in the middle and lower estuary where the estimated anthropogenic contribution is negligible. The estimated contributions from the groundwater are also insufficient to explain the measured metal concentrations in the estuary. A strong positive correlation that is observed between the dissolved heavy metal fluxes and the suspended particulate matter (SPM) fluxes, after normalizing them with the water fluxes, for estuaries of the major global rivers imply that the solute-particle interaction is a globally significant process in the estuarine production of metals. Based on this correlation that is observed for major estuaries around the world, we demonstrate that the South Asian Rivers which supply only ∼9% of the global river water discharge but carry elevated SPM load, contribute a far more significant proportion (∼40 ± 2% Ni and 15 ± 1% Cu) to the global supply of the dissolved metals from the rivers.

Comparative study on seasonal variation in hydro-chemical parameters of Ganga River water using comprehensive pollution index (CPI) at Rishikesh (Uttarakhand) India

The assessment of the Ganga River System at Rishikesh was investigated at five different sites for three different seasons (summer, winter and monsoon) using comprehensive pollution index (CPI), considering 10 physicochemical parameters such as conductivity, turbidity, total dissolved solids, dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, total hardness, Cl, phosphate and sulphate. The CPI was found to be 0.54–2.47, which indicates the variation in pollution level of the River Ganga. The variation in pollution index value clearly shows that water quality was slightly polluted in winter (0.54–0.72) and summer (0.64–0.88) whereas high contamination (1.68–2.47) was observed during monsoon season. Among various sampling stations, Pashulok Barrage (Site 5) was more contaminated than other sites. All the studied parameters were under the permissible limit of W.H.O. (2011) except turbidity, total solids and suspended solids which were higher than the permissible limit. This study also illustrates the correlation between parameters by developing correlation matrix. The result of this study clearly elucidates that the water quality is getting contaminated as we moved from upstream to downstream of river and helps to understand the potential effects of water quality on drinking, irrigation and other purposes.

Vulnerability assessment through index modeling: a case study in Muriganga–Saptamukhi estuarine interfluve, Sundarban, India

The coastal regions, deltas, and estuaries are severely affected by the sea level rise and cyclonic activities and climate changes. Sundarban delta is one of the most mysterious landscapes in the world, which has successively evolved due to sediment accumulation by the great Ganga and Brahmaputra river system. The area is characterized by low-lying islands and a flat topography coupled with macro-tidal activities, powerful surges, and seasonal cyclonic events. All these conditions put together this landscape defenseless to frequent flood and erosion. Since the last hundred years, the face of Sundarban has been changed remarkably from wildest to human-occupied territory by protecting this low-lying flat plain from tidal inundation through artificial embankment. In this background, the current study attempts to highlight the spatial extent and magnitudes of internal risk factors of the region using the composite vulnerability index. Coastal vulnerability defines a system’s openness to flood and erosion risk due to hydrogeomorphic exposures and socio-economic susceptibility in conjunction with its capacity/incapacity to be resilient and to cope, recover, or adapt to an extent. Coastal vulnerability assesses the potential risk from erosion and flooding of any low-lying coastal region due to its physiographical and hydrological exposures, socio-economic and political susceptibility, and resilience capacity. A natural system affects the socio-economic scenario of any region. Hence, multidimensional databases can be more effective to understand the extent of exposure, susceptibility, and resilience of any system. To throw some light on the situation of vulnerability of western estuarine Sundarban, between Muriganga and Saptamukhi interfluve, the composite vulnerability index has been carried out to delineate the magnitude and spatial extent of vulnerability with the help of quantitative techniques and geospatial tools. The estuarine tracts and coastal parts of the Ganga delta are two of the most densely populated areas in the world. The study highlights the critical situation of the population under different potential risk classes residing in the study area with the intention of suggesting some proper course of action of planning and management to conserve coastal communities in their original habitat.