Peninsular Rivers Research Articles

Estimation of chemical weather indices of sediments using R program

For estimating major elemental geochemistry of sedimentary packages, various Weathering Indices (WIs) are utilized by researchers involved in geochemical evolution of sediments. Through developing a computer program, GeoChem, based on ‘R’ programming environment, we intend to simplify the evaluation and implementation of various Weathering Indices (WIs), including CIW, CPA, PIA, CIX, CIA, WIP, R, ICV, V, MWPI and STI. Additionally, it generates plots of input data used to quantify chemical weathering of clastic sediments in various compositional space diagrams, such as Al2O3 – CaO – Na2O, Al2O3 – K2O – CaO – Na2O, Al2O3 – CaO + Na2O – K2O, Al2O3 – CaO + Na2O + K2O – Fe2O3 + MgO and M – F – W compositional space diagram. Using GeoChem, one can do all the calculations and artwork associated with the finished report without having to use Microsoft Excel, CorelDraw or similar software. Input data source files and output calculations results data files are in CSV format. Data plots are produced in vector as well as in raster formats, providing additional flexibility to the user. Also, we are trying to figure out the associated statistical parameters, their correlation and specially restricting the major elemental geochemistry in a variety of compositional space diagrams to constrain sediment and rock composites, demonstrating chemical weathering profiles and mineralogical composition of the parent rock. By altering different arguments in the code, the ‘R’ programming environment allows the investigator to change the code, depending on the dataset under consideration and the user requirement to generate user-defined, customized plots. To demonstrate the applicability of the tool, its performance was tested, evaluating the major elemental geochemical data of diverse geological settings and sedimentary provenance different in kind. For the same, sediments selected include channel, suspended and overbank sediments of the Peninsular rivers of Ganga basin; Surma group and Barail group of sandstones; lake sediments of Manasbal, Kashmir; Mizoram Foreland Basin, India.

Freshwater discharge from the large and coastal peninsular rivers of India: Areassessment for sustainable water management.

This study offers an updated mean annual water discharge of 10 large and 11 coastal basins of the Indian Peninsula and looks into environmental parameters influencing the water flux and discharge trends. The mean annual discharge of large and coastal rivers is estimated to be 221 and 294 km3. Thus, despite draining 25% of the Indian Peninsula, coastal rivers deliver more than half of the annual flux, and west-flowing coastal rivers contribute 85% of it. This study demonstrates temporal changes in the water discharge of various river basins. The presence of dams regulates discharge regimes of large rivers. The construction of large dams resulted in a significant decline in the water discharge of the Krishna, Cauvery, and Narmada. Through this study, we demonstrate the role of rainfall, catchment size, water loss through evapotranspiration and infiltration, and societal use of water in determining the runoff of each basin. We recommend tapping the water resources of the west-flowing rivers for proper planning, development, and management to reduce the water stress in the peninsular region and promoting sustainable management.

Dynamics of streamflow and sediment load in Peninsular Indian rivers (1965–2015)

The streamflow and sediment load in natural rivers around the world are undergoing significant changes due to the present climate change and anthropogenic activities. Therefore, for the management of water resources, soil conservation practices, and regulating coastal erosion; it is crucial to identify spatio-temporal variability and dynamics of streamflow and sediment load in natural rivers. The inherent characters of the tropical rivers in Peninsular India are not extensively studied. This paper examines temporal variation in streamflow, sediment load, and sensitivity of landscape complexity in varying sediment yield in 12 major tropical rivers in Peninsular India. About half-century of daily time-series records have been assessed to compute annual variabilities, trends, and abrupt changes through Mann-Kendall and Pettitt tests. Partial least squares regression has been employed to determine dominant drivers of sediment yield from a large number of topographic and climatic variables. The results indicate that concerning the global river runoff and sediment flux, 12 major Peninsular Indian rivers contribute less than 1% water and little more than 1% sediment to the world oceans. During the past five decades, a significant decrease in streamflow is found in Krishna, Cauvery and Narmada rivers and the changes are associated with variation in precipitation. After 2000, sediment load in almost all rivers has declined more than 40%. Construction of numerous high capacity reservoirs and dams have a significant influence on the reduction of sediment load. Profile curvature, plan curvature, relief, average elevation, circularity ratio and average annual rainfall explain the most among numerous other topographic and climatic variables with relation to the sediment yield in Peninsular India. The present study is intended to elucidate the dynamics of streamflow and sediment load during the past five decades and bridge knowledge gaps of the dynamic nature of Peninsular rivers in India.

Single Genetic Stock Revealed by Microsatellite Markers Among Wild Populations of Cirrhinus mrigala from Peninsular India

Cirrhinus mrigala (mrigal) is one of the Indian major carps widely cultured in the whole Indian subcontinent. Population genetic structure of this species from Peninsular Rivers of India is lacking. Among DNA markers, microsatellites are excellent tools to evaluate genetic variation of populations. In this study, genetic variation of six peninsular riverine mrigal populations was evaluated using seventeen microsatellite loci. In analyzing 288 samples, the number of alleles ranged from 4 to 27; observed heterozygosity from 0.595 to 1.00, expected heterozygosity from 0.586 to 0.959 and inbreeding coefficient (FIS) ranged from -0.034 to 0.02. Exact test for Hardy Weinberg disequilibrium revealed that one locus was not in equilibrium across the rivers except one. The AMOVA analysis revealed the main source of genetic variation to be within the population (94.54%) than among the populations (5.46%). The Nei’s genetic distance and structure analysis depict river Narmada and Mahi populations are different from the four east coast rivers. The overall Fst (0.05462) data showed moderate differentiation among the six populations. The results of this study provide essential information to resource recovery and help in delineating populations for fishery management. Besides, the data will provide a valuable baseline for further investigations on the geographic distribution of this commercially important fish species.

Exploring prevalence of potential pathogens and fecal indicators in geographically distinct river systems through comparative metagenomics

Microbial communities are considered as vital members to reflect the health of a riverine system. Among them, pathogenic and fecal indicators imply health risks involved with potability of river water. The present study explores the diverse microbial communities, distribution pattern of potential pathogens, and fecal indicators between the geographically distinct Himalayan and Peninsular river systems of India. It also inquires into the environmental factors associated with community variance and distribution pattern of microbial indicators. The application of high-throughput amplicon sequencing approach unveiled significant demarcation (p < 0.004, Anosim R = 0.62) of samples suggesting unique microbial diversities in these two river sediments. Random forest analysis revealed Desulfobulbulus, PSB_M_3, and Opitutus in Himalayan, while DA101, Bacillus, and Streptomyces in the Peninsular as significant contributors to develop overall dissimilarity between the river systems. Permutational multivariate analysis of variance and co-occurrence network analysis were used to study the relationships between microbial taxa and environmental factors. Amongst the various studied environmental parameters, pH, K, Ca, Mg, Ba, and Al in the Himalayan and salinity, Na, temperature, and Th in the Peninsular significantly influenced shaping of distinct microbial communities. Furthermore, the potential pathogenic genera, including Flavobacterium, Clostridium, Arcobacter, Pseudomonas, and Bacillus were highly prevalent in both the river systems. Arcobacter, Clostridium, Acinetobacter, Bacteroides, and Caloramator were the prominent fecal indicators in these river systems. Our findings provide salient information about the crucial role and interplay between various environmental factors and anthropogenic influences in framing the microbiome of the distinct river systems in India. Moreover, assessing potential pathogenic and fecal indicators suggest the public health risk associated with untreated sewage discharge into these water sources. The detection of various F/S indicators and potentially pathogenic bacteria in Himalayan and Peninsular river systems emphasize the urgent need for future monitoring and management of major riverine systems in India.

Millennial-scale variability of Indian summer monsoon during the last 42 kyr: Evidence based on foraminiferal Mg/Ca and oxygen isotope records from the central Bay of Bengal

Studying marine sedimentary archives from the Indian Ocean have provided great opportunities to assess the forcing/response relationship between the Indian monsoons, millennial-scale climate variability as revealed in Greenland ice cores, and possible roles of the Atlantic meridional overturning circulation (AMOC) changes that are most likely responsible for driving both. Here we present new evidence of sea surface temperature (SST) estimates and δ18O of seawater (δ18Osw, presumably salinity-driven) from the paired data of Mg/Ca and δ18O measured from planktonic foraminifer Globigerinoides ruber (white) in core BoB-24 collected from the central Bay of Bengal (BoB), tropical Indian Ocean. Eleven accelerator mass spectrometry (AMS) radiocarbon dates on planktonic foraminifera Neogloboquedrina dutertrei from the core provide a reliable age model. Our results indicate a gradual surface warming with several short-lived fluctuations since ~42 kyr ago, and a ~3 °C cooling during the Last Glacial Maximum (LGM) and a ~3 °C warming from the last glacial to the Holocene. Our δ18Osw revealed an increased salinity during the Marine Isotope Stage (MIS) 2, which is likely attributable to a weakening of Indian Summer Monsoon (ISM) precipitation and associated river discharge in the BoB. Our record also indicates clearly a phase of strengthening ISM during the mid-MIS 3 (37.5–32 ka) as evidenced by low foraminiferal δ18Osw values of ~0.2‰. Lower than present δ18Osw values during the Bølling/Allerød (B/A) event (14.5–12.6 ka) and the early Holocene (10–5 ka) in core BoB-24 indicate lower salinity that in turn suggest enhanced ISM precipitation and increased freshwater output from the Ganges-Meghna-Brahmaputra-Irrawaddy (GMBI) rivers together with peninsular rivers and Irrawaddy-Salween rivers from Myanmar. This study brings data evidence that implies weakened ISM was linked with Northern Hemisphere cooling events, especially during the MIS 2. Furthermore, the millennial-scale hydroclimate changes in the BoB presented in this study support the dynamic role of AMOC in driving a teleconnection between the North Atlantic and Indian Ocean monsoon regions.

Sources of organic matter and tracing of nutrient pollution in the coastal Bay of Bengal

Stable isotopic composition of carbon (δ13CPOM) and nitrogen (δ15NPOM) in the particulate organic matter (POM) is used to identify sources of organic carbon and nutrients using monthly time-series observation in the coastal Bay of Bengal (BoB). The hydrographic structure indicates that the coastal BoB is influenced by coastal upwelling during March–May, advection of peninsular river discharge during June to September and glacial (Ganges) river discharge during October to December due to reversing of East India Coastal Currents (EICC). C/N ratios in POM were mostly higher values than Redfield ratio in the study region indicating possible contribution of terrestrial origin. Enriched δ13CPOM were found during March–May associated with coastal upwelling indicating major contribution of POM from the in situ production while lower values were noticed during June to September followed by October to December indicating influence of terrestrial sources. δ15NPOM displayed strong inverse relation with salinity and linear relation with Chl-a suggesting that anthropogenic nutrients from the land increased coastal phytoplankton biomass. δ15NPOM linearly decreased with increase in distance from the coast and reached to the typical offshore value of 6–6.5‰ indicating that terrestrial nutrients influence was spread up to a distance of 15 to 20 km from the coast in the study region. Our study suggested that coastal waters are influenced by terrestrial/anthropogenic nutrients and its impact can be noticed up to 15 to 20 km from the coast and its impact on Biodiversity Beyond National Jurisdiction may be negligible than hitherto hypothesized.

Rainfall Variation in Major River Basins in India and the Association with the Indo-Pacific Oceans

Varikoden, H.; Roja, C.; Revadekar, J.V., and Milind, M., 2020. Rainfall variation in major river basins in India and the association with the Indo-Pacific Oceans. In: Sheela Nair, L.; Prakash, T.N.; Padmalal, D., and Kumar Seelam, J. (eds.), Oceanic and Coastal Processes of the Indian Seas. Journal of Coastal Research, Special Issue No. 89, pp. 1-6. Coconut Creek (Florida), ISSN 0749-0208.The summer monsoon rainfall is the major water source for most parts of India and people depend on this water source for their livelihood. The rainfall during this season is highly variable over space and time. The rainfall during the southwest monsoon period is the main source of flow discharge in most of the rivers in India. In the present study, we made an attempt to explore the variability and trends in rainfall over the Ganges, Brahmaputra, Godavari and Krishna river basins. Northern river basins show a negative trend indicating the decrease of rainfall and increasing trends are observed in peninsular river basins. The Brahmaputra river basin shows a significant decreasing trend (-0.16 mm day-1 decade-1). Moreover, the variability in multi-time scale is also different for different basins. Among all the river basins considered in the study, the Brahmaputra river basin registered high average rainfall (15.11 mm day-1 with a standard deviation of 2.23 mm day-1) and the Krishna river basin the least (3.57 mm day-1 with a standard deviation of 0.87 mm day-1). Further, the large scale teleconnection of the rainfall with individual river basins has also been assessed. The Ganga river basin is one of the largest river basins and this region is highly influenced by the Arabian Sea and the west Pacific Ocean (Nino 3.4 region). However, the Brahmaputra basin does not show much connection with Sea Surface Temperatures (SST) over the west Pacific Ocean, the Arabian Sea or the Bay of Bengal. The rainfall in the Godavari and Krishna river basins have more influence on SSTs over the central Pacific Ocean.

Chemical weathering and atmospheric CO2 consumption in the semi-arid Swarnamukhi basin (Peninsular India) estimated from river water geochemistry

A small ephemeral Swarnamukhi River (hard rock) basin, more sensitive to climate change, was sampled and analyzed for various parameters. A total of 66 river water samples (22 of each season) were collected from different sampling stations covering the whole Swarnamukhi River basin in pre- and post- and monsoon seasons. Chemical weathering rate data of the Swarnamukhi River basin is integrated with the available data of other large perennial (Godavari and Krishna) and ephemeral (Kaveri and Periyar) hard rock river basins of Peninsular India. The Peninsular river basins, including Swarnamukhi River basin, are mainly dominated by granitic gneissic terrain. Contribution of inputs through forward modelling shows: silicate > evaporite > carbonate > atmosphere. The mean silicate and carbonate weathering rates in the river basin observed are 27.15 tonnes.km−2.yr−1 and 9.45 tonnes.km−2.yr−1 in pre-monsoon season, whereas 32.73 tonnes.km−2.yr−1and 45.90 tonnes.km−2.yr−1 in post-monsoon season, respectively. The Swarnamukhi river has lower silicate weathering rate (annual average: 30.57 tonnes.km−2.yr−1) than other published river basins data (Narmada: 33.9 tonnes.km−2.yr−1; Nethravati: 42 tonnes.km−2.yr−1; Godavari: 45.6 tonnes.km−2.yr−1) due to different localized geological setting. Mean annual CO2 consumption for the Swarnamukhi River is 6.9 × 105 mol km−2.yr−1 which is comparable to other Peninsular rivers such as the Godavari (6 × 105 mol km−2.yr−1) and Gad (5.7 × 105 mol km−2.yr−1) rivers. The study further provides the inventory for CO2 consumption on river basin scale, which is an important consideration from the global warming point of view.

Dissolved inorganic carbon export by mountainous tropical rivers of the Western Ghats, India

Large rivers that are known for carrying huge fluxes are few in numbers; nevertheless, the contributions of thousands of small mountainous coastal rivers to global biogeochemical cycles is also measured to be equally important. Small catchment sizes, high channel gradients yet high water discharge are prominent characters of the coastal rivers draining the Western Ghats (WG) of India. Three geo-tectonic divisions, namely, Southern Granulite Terrain (SGT) in southern, Western Darwar Craton (WDC) in central and Deccan Traps (DT) in the north constitute the entire Western Ghats. Based on the seasonal sampling of 70 coastal rivers draining into the Arabian Sea, this study provides a comprehensive discharge-weighted estimate of DIC for the Western Ghats (WG) region. The concentration of bicarbonate measured in-situ using gran plot method. Fluxes and yields were calculated using seasonal discharge and area of respective rivers. The discharge-weighted DIC concentration of WG region is 629 μM, which is slightly higher than the average global DIC concentration for the low latitude (< 30°) rivers. Despite, covering 113×103km2 area, this region yearly exports 175×109 mol DIC to the Arabian Sea. The DIC flux contributed by the WG region is among the highest in peninsular rivers and comparable with several large global rivers. DIC export rates suggest that within the region, the chemical weathering rate of DT is ∼4 times and WDC is ∼2.5 times higher than that of SGT region. The DIC flux of the WG region (covering 0.076% of global land area) is approximately 0.55% of the global riverine DIC flux to the ocean. Thus, in terms of global DIC export to seas, this region is the 28th largest contributor. Due to high annual DIC yield (1547×103 mol km−2) WG region ranks as the 9th most active region of the world. DIC yields of rivers draining granite-dominated (SGT and WDC) and basalt-dominate (DT) regions of WG are remarkably higher than the global rivers draining similar lithology from temperate and arctic regions. The WG rivers display a latitudinal gradient in DIC transport. Type of silicate rocks, rainfall-runoff, temperature range, and sediment yields control the variability in DIC fluxes and export rates of Western Ghats region.

Dissolved aluminium cycling in the northern, equatorial and subtropical gyre region of the Indian Ocean

Dissolved aluminium (hereafter, dAl) concentrations have been determined on 34 full vertical water column profiles, sampled along the two separate GEOTRACES-India transects (GI-01 and GI-06) to understand the biogeochemical controls on dAl distribution in the northern (the Bay of Bengal, the Andaman Sea and the Arabian Sea), equatorial and subtropical gyre region of the Indian Ocean. Al released due to the partial dissolution of and/or Al desorption from the suspended lithogenic sediments, supplied in a huge amount to the Bay of Bengal (BoB) waters by the Ganga-Brahmaputra (G-B) river system, Indian peninsular rivers and sediment resuspension from the continental shelf and slope, predominantly controls the dAl distribution in the BoB and results in an overall increase in the dAl concentrations throughout the water column towards the northern BoB and the eastern coast of India. Considering the steady-state balance between the dAl input from the lithogenic sediment flux in the upper water column and first-order scavenging removal of dAl, the fractional solubility of Al from the lithogenic sediments in the BoB surface waters is estimated to be in the range of 1.1–4.7%. Advection of Indonesian Sea surface waters through the Strait of Malacca and dAl input from the partial dissolution of resuspended terrigenous sediments, sourced from the insular shelf of the Nicobar Islands, set major controls on the dAl distribution in the surface and upper thermocline waters of the southern Andaman Sea and the southern BoB region near the Nicobar Islands. Rapid renewal of and vertical mixing in the deeper waters (>1000 m) relative to scavenging removal of dAl results in near-uniform dAl concentrations (∼3.7 nM) in the deeper waters at the center of the southern Andaman Sea. In the south-eastern Arabian Sea, the continental outflow of mineral dust and advection of dAl enriched Bay of Bengal surface waters control the dAl distribution in the surface water layer. dAl in the surface waters of the equatorial Indian Ocean, during the late winter sampling period of the GI-06 cruise, is predominantly determined by the mixing between dAl-rich surface waters of the southern BoB and relatively, dAl-depleted surface waters of the southern Arabian Sea under the influence of the Northeast Monsoon Current. The scavenging residence time of dAl in the deep waters of the equatorial Indian Ocean is estimated using a 1-D scavenging-advection–diffusion model and found to be in the range of 92–141 years. Deposition of Australian dust and advection of Indonesian Throughflow Water translates to the dAl enrichment in the upper water column (<500 m) at the northern end of the Indian Subtropical Gyre. Sediment resuspension near the Central Indian Ridge probably enrich the dAl in the ambient deep water depth (2000–3500 m) and this signal dampens as the deep waters progress north-westward in the Central Indian Ocean Basin. The bottom water (>3500 m) advects across the Ninety East Ridge from the Western Australian Basin to bring the dAl-rich waters to the northern end of the Central Indian Ocean Basin.

Length-weight relationship and relative condition factor of five Labeo spp. from river Cauvery in India

Length-weight relationship (LWR) of five species of the genus Labeo (Family: Cyprinidae) namely L. rohita (Hamilton,1822), L. calbasu (Hamilton,1822), L. bata (Hamilton,1822), L. dyocheilus (McClelland, 1839) and L. porcellus (Heckel, 1844), based on 214 specimens collected from Cauvery River in Peninsular India, were established. Sampling was carried out from December 2017 to December 2018 at around three months interval. The value of regression coefficient (b) ranged from 2.6147 (L. bata) to 3.2855 (L. dyocheilus). A new maximum length of 41 cm for L. porcellus has been recorded. For L. porcellus, LWR is established for the first time while for other species (except L. rohita); it is estimated for the first time from a peninsular river in India. Relative condition factor estimated for the five fish species did not show large scale variation (1.001 to 1.019).

Spatiotemporal variation in primary nutrients amassing in peninsular river sediment: India

Damodar is an important river of the industrial state Jharkhand, India. It menders through various coal mining regions is now under serious threats due to industrial and sewage discharge which is rich in TOC, available nitrogen, phosphorus and potassium (primary nutrient plants). Hence, present research work was formulated with the hypothesis of “river sediment possess high concentration of primary nutrients which can be used in mine site reclamation”. In this regard, spatiotemporal and seasonal variations in concentration of these nutrients were studied to know its sources. Nutrient index of the sediment was assessed to compare its fertility with soil for its utilization in mine site reclamation and pollution control of the river. Study area has momentous spatial variation; Garga river (site 12) carry sewage and effluent from Bokaro steel city having maximum concentration of TOC, available N, and P, while available K was maximum at Chandrapura thermal power plant (site 9). Substantial seasonal and temporal disparity in nutrient concentration was also found. In 2014, TOC (0.82 and 0.5)%, available N (12.3 mg/kg and 7.9 mg/kg), P (11.3 mg/kg and 6.2 mg/kg), and available K was (218 mg/kg and 201.7 mg/kg), respectively, in pre- and post-monsoon. These amplified to 39% for TOC, 19–29% for nitrogen, more than 35% for phosphorus and 2.9–3.9% for K by 2016. The nutrient index was medium for TOC and pH except low in 2014 post-monsoon. Nutrient index for nitrogen was low while high for phosphorus and potassium during the study.

Assessment of future water provisioning and sediment load under climate and LULC change scenarios in a peninsular river basin, India

ABSTRACTAssessment of the impact of changes in climate and land use and land cover (LULC) on ecosystem services (ES) is important for planning regional-scale strategies for sustainability and restoration of ES. The Upper Narmada River Basin (UNRB) in peninsular India has undergone rapid LULC change due to recent agricultural expansion. The impact of future climate and LULC change on ES in the UNRB is quantified and mapped using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST 3.3.0) tool. Our results show that water yield is projected to increase under climate change (about 43% for representative concentration pathway 4.5 for 2031–2040), whereas it is projected to decrease under the LULC change scenario. Sediment export is projected to increase (by 54.53%) under LULC change for 2031–2040. Under the combined effect of climate and LULC change, both water yield and sediment export are expected to increase. Climate change has a greater impact on projected water yield than LULC change, whereas LULC has greater impact on sediment export. Spatial analysis suggests a similar trend of variation in relative difference (RD) of ES in adjacent sub-basins. The quantified changes in ES provisioning will benefit future land management, particularly for operation of the Rani Avanti Bai Sagar Reservoir downstream of the UNRB.

Influence of river discharge on abundance and composition of phytoplankton in the western coastal Bay of Bengal during peak discharge period

To understand the influence of river discharge on phytoplankton composition along western coastal Bay of Bengal (BoB), surface water samples were collected during peak discharge period. River discharge from the Ganges influences northwest (NW) coastal BoB whereas peninsular rivers (Godavari and Krishna) discharge to the southwest (SW) coastal Bay. River discharge from the Ganges is an order of magnitude higher than peninsular river resulting in low saline, less suspended matter and lower nutrients concentrations in the NW and contrasting to that was observed in the SW. ~50%of the phytoplankton were composed of Thalassiosira spp., Nitzschia spp., Microcystis spp., Amphiprora spp. and Thalassionema spp. in the SW whereas Thalassiosira spp., Nitzschia spp., Chaetoceros spp., Merismopedia spp. and Peridinium spp. in the NW. Significant variability in phytoplankton composition was observed from coast to offshore. Our study revealed that river discharge and associated physico-chemical characteristics governed the phytoplankton community along western coastal BoB.

Last 42 Ky Sediment Chemistry of Oxygen Deficient Coastal Region of the Bay of Bengal: Implications for Terrigenous Input and Monsoon Variability

The discharge of terrigenous clastics by seasonal peninsular rivers is known to reach the upper slope of the eastern margin of India, which is presently impinged by the monsoon-sensitive intense oxygen minimum zone (OMZ); however, their mutual behaviour in response to changes in the intensity of past Indian summer monsoons (ISM) is not clear. The δ 18 O G.sacculifer time-series of a sediment core from the upper slope off Chennai exhibits distinct enrichment (~0.4‰) during the last glacial period (30–18 kiloyears BP: ka), and depletion (~-2.2‰) during the Holocene, suggesting a significant shift in ISM intensity. The monotonously increased terrigenous elements (Al, Ti and Mg) content and depleted δ 18 O G.sacculifer during the Holocene suggest tight-coupling between ISM and terrigenous sediment input. Highly depleted redoxsensitive Mn (<0.04%) (lesser than the source sediment content of 0.07%) throughout the last 42 kyr suggests well-sustained intense OMZ irrespective of ISM variation.

Additional Quaternary Faunal Remains from the Middle–Late Pleistocene Deposits of Purna Alluvial Basin, Maharashtra, Central India

One of the important fossiliferous localities being surveyed in recent years is the less known Purna Valley in Central India (Figure 1). However, the adjoining regions like the Central Narmada Valley have yielded numerous faunal remains in the past and these have been reported from time to time. In this context the Purna Valley assumes significant importance in the region. In fact, this area had remained less explored for a long time (Tables 1 and 2). Renewed efforts in this area have brought to light fossils from Bovidae, Equidae, Cervidae, Elephantidae and other groups like reptiles (turtles) and invertebrate fossils (molluscan shells) which are under study (Figure 2). In this study, the genus Elephas is reported from the Purna Basin. On the whole the material is well preserved and similar to that of the Narmada Valley. It throws enough light on the distribution pattern of these animals in Central and peninsular river valleys of India.

Geochemistry of sediments of the Peninsular rivers of the Ganga basin and its implication to weathering, sedimentary processes and provenance

Abstract Geochemistry of the Himalayan rivers has been a major point of contention in sedimentary geochemistry because of its global impact on ocean chemistry and climate. Among the Himalayan rivers, the Ganga and its Himalayan catchment have been studied extensively. However, the Peninsular rivers constituting a significant part of the Ganga basin have not received much attention, heretofore. In the present geochemical study of the Peninsular river's sediments, we have found that the initial chemical weathering of rocks in the catchment produces texturally, mineralogically and geochemically diverse sediments and fluvial processes further segregate them into the geochemically contrasting coarse channel and fine-grained suspended sediments. The overbank sediments possess an intermediate texture and geochemistry, but more towards the suspended sediments. The sediment geochemistry data indicates that the Peninsular river's sediments show an increase in the weathering intensity from the west (Banas river) to the east (Son river) along the climate gradient, i.e., from the arid-semiarid to the sub-tropical condition. The higher chemical index of alteration (CIA) values of the Peninsular river's sediments than the Yamuna and Ganga river sediments reflect the control of weatherable lithology in the tectonically stable, low relief and subtropical climate condition. The Yamuna and Ganga river sediments with lower CIA values show more physical weathering in the tectonically active Himalaya. The suspended and overbank sediments of the Yamuna and Ganga rivers show an increase in their CIA values after the confluence of the Peninsular rivers, indicating the contribution of more weathered materials by the Peninsular rivers. It has been found that there is a geochemical split between the channel and suspended sediments of the Peninsular rivers for sharing different sources, i.e., the dominant contribution of felsic sources to the channel and mafic sources to the suspended sediments. The weathering geochemistry, trace element systematics, and REE patterns suggest that the dominant sources of the channel sediments of the Peninsular rivers are the felsic crystallines and sedimentary lithologies of the Aravalli range, Bundelkhand and Chhotanagpur granite and gneisses, and Vindhyan sandstones. Whereas, the mafic lithologies such as the Deccan traps and mafic components of the felsic lithologies appear to be the major sources of the suspended sediments. Within the range of intermediate composition, the overbank sediment chemistry reflects more contribution of the mafic sources except for the Ken which shows a higher contribution of the felsic sources. The geochemical split between the channel and suspended sediments of the Peninsular river's sediments for the different provenances indicates differential weathering of the Deccan basalts, Bundelkhand crystalline, and Vindhyan sedimentary rocks; and also the hydrodynamic control of the Peninsular rivers during erosion, transport, and deposition. However, the Himalayan rivers do not show such contrast between the channel and suspended sediments because of the higher physical weathering and sediment mixing in the high gradient topography of the Himalayan catchment.

River Rejuvenation

India is in the midst of a water crisis and is now considered to be a water-scarce country. The Indian Himalayan and Peninsular rivers are fast depleting. To address the water crisis in India, initiatives to rejuvenate Indian rivers have been taken up by both Government and non-Government organizations.

Influence of river discharge on the distribution and flux of methane in the coastal Bay of Bengal

Abstract Rivers are known to be strong sources of methane (CH 4 ) to the atmosphere and their discharges may also enhance its flux from the coastal ocean. In order to examine this, CH 4 fluxes to the atmosphere were examined along the coastal Bay of Bengal during peak discharge period. The saturation of CH 4 in the Ganges river was relatively lower (208 ± 7%) than that of Indian peninsular rivers (907 ± 136%). The Ganges discharges into the northwestern (NW) while the peninsular rivers discharge into the central and southwestern (SW) regions of the coastal Bay of Bengal and influence the concentration and saturations of CH 4 in the western coastal Bay of Bengal. Methane was higher (4.4 ± 0.9 nM) and more supersaturated (208 ± 37%) in the SW coastal Bay of Bengal than in the NW region (2.5 ± 0.1 nM and 116 ± 2.6% respectively). The higher concentrations of CH 4 in the SW region were also influenced by mild coastal upwelling. The efflux of CH 4 is estimated as 57.4 ± 19.3 and 14.5 ± 2.3 μmol m − 2 d − 1 from SW and NW regions, respectively, and an average of 38.9 ± 11.3 μmol m − 2 d − 1 . Our study suggests that the western coastal waters of the Bay of Bengal act as strong source of CH 4 to atmosphere. The total flux from Indian coastal waters (estuaries, mangroves and coastal waters) is estimated as 21.9 × 10 9 g CH 4 y − 1 out of which ~ 70% is from the coastal Bay of Bengal and 20% from estuaries.