scholarly journals Downstream and seasonal changes of lithium isotope ratios in the Ganges‐Brahmaputra river system

2017 ◽  
Vol 18 (8) ◽  
pp. 3003-3015 ◽  
Author(s):  
Takuya Manaka ◽  
Daisuke Araoka ◽  
Toshihiro Yoshimura ◽  
H. M. Zakir Hossain ◽  
Yoshiro Nishio ◽  
...  
Keyword(s):  
Seasonal Changes ◽  
River System ◽  
Isotope Ratios ◽  
Lithium Isotope ◽  
Brahmaputra River ◽  
The Ganges

scholarly journals Stable Strontium Isotopic Compositions of River Water, Groundwater and Sediments From the Ganges–Brahmaputra–Meghna River System in Bangladesh

2021 ◽  
Vol 9 ◽  
Author(s):  
Toshihiro Yoshimura ◽  
Shigeyuki Wakaki ◽  
Hodaka Kawahata ◽  
H. M. Zakir Hossain ◽  
Takuya Manaka ◽  
...  
Keyword(s):  
River Water ◽  
Chemical Weathering ◽  
Drainage Basin ◽  
Dissolution Kinetics ◽  
River System ◽  
Ganges River ◽  
Brahmaputra River ◽  
Terrestrial Water ◽  
Stable Strontium ◽  
The Ganges

The Sr isotopic composition of rivers and groundwaters in the Bengal Plain is a major contributor to the global oceanic Sr inventory. The stable strontium isotope ratios (δ88Sr) provide a new tool to identify chemical weathering reactions in terrestrial water. In this study, we investigated the spatiotemporal variations of δ88Sr in samples of river water, bedload sediment, and groundwater collected from the Ganges–Brahmaputra–Meghna drainage basin in Bangladesh, which is known to strongly influence the 87Sr/86Sr ratio in seawater. The average δ88Sr values of waters of the Ganges, Brahmaputra, and Meghna rivers were 0.269, 0.316, and 0.278‰, respectively. Our data showed little difference between seasons of high and low discharge. The δ88Sr values measured in sequential leaching fractions of sediments varied from –0.258 to 0.516‰ and were highest in the silicate fraction, followed in turn by the carbonate fraction and the exchangeable fraction. Both 87Sr/86Sr and δ88Sr of these waters are primarily controlled by the inputs of Sr in weathering products from the Bengal Plain and Sr from the Himalayan rivers (Ganges and Brahmaputra). Values of δ88Sr and Sr/Ca were higher in the Brahmaputra River than in the Ganges River, a difference we attribute to greater input from silicate weathering. The variations of δ88Sr and 87Sr/86Sr were greater in groundwater than in river waters. Mineral sorting effects and dissolution kinetics can account for the large scatter in 87Sr/86Sr and δ88Sr values. The depth profile of δ88Sr showed wide variation at shallow depths and convergence to a narrow range of about 0.31‰ at depths greater than 70 m, which reflects more complete equilibration of chemical interactions between groundwater and ambient sediments owing to the longer residence time of deeper groundwater. We found that δ88Sr values in the groundwater of Bangladesh were almost identical to those of river water from the lower Meghna River downstream of its confluence with the Ganges–Brahmaputra river system, thus confirming that the δ88Sr composition of the groundwater discharge to the Bay of Bengal is very similar to that of the river discharge.

Subaqueous delta of the Ganges-Brahmaputra river system

1997 ◽  
Vol 144 (1-3) ◽  
pp. 81-96 ◽  
Author(s):  
Steven A. Kuehl ◽  
Beth M. Levy ◽  
Willard S. Moore ◽  
Mead A. Allison
Keyword(s):  
River System ◽  
Brahmaputra River ◽  
The Ganges

scholarly journals Magnetic fabric of Bengal fan sediments: Holocene record of sedimentary processes and turbidite activity from the Ganges-Brahmaputra river system

2020 ◽  
Vol 430 ◽  
pp. 106347
Author(s):  
Eva Moreno ◽  
Fabien Caroir ◽  
Lea Fournier ◽  
Kelly Fauquembergue ◽  
Sébastien Zaragosi ◽  
...  
Keyword(s):  
River System ◽  
Magnetic Fabric ◽  
Sedimentary Processes ◽  
Brahmaputra River ◽  
Bengal Fan ◽  
Holocene Record ◽  
The Ganges

scholarly journals Ore Genesis of the Takatori Tungsten–Quartz Vein Deposit, Japan: Chemical and Isotopic Evidence

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 765
Author(s):  
Yuichi Morishita ◽  
Yoshiro Nishio
Keyword(s):  
Oxygen Isotope ◽  
Early Stage ◽  
Isotope Ratios ◽  
Equilibrium Temperature ◽  
Granitic Rocks ◽  
Granitic Magma ◽  
Lithium Isotope ◽  
Vein Deposit ◽  
Pressure Independent ◽  
Isotope Equilibrium

The Takatori hypothermal tin–tungsten vein deposit is composed of wolframite-bearing quartz veins with minor cassiterite, chalcopyrite, pyrite, and lithium-bearing muscovite and sericite. Several wolframite rims show replacement textures, which are assumed to form by iron replacement with manganese postdating the wolframite precipitation. Lithium isotope ratios (δ7Li) of Li-bearing muscovite from the Takatori veins range from −3.1‰ to −2.1‰, and such Li-bearing muscovites are proven to occur at the early stage of mineralization. Fine-grained sericite with lower Li content shows relatively higher δ7Li values, and might have precipitated after the main ore forming event. The maximum oxygen isotope equilibrium temperature of quartz–muscovite pairs is 460 °C, and it is inferred that the fluids might be in equilibrium with ilmenite series granitic rocks. Oxygen isotope ratios (δ18O) of the Takatori ore-forming fluid range from +10‰ to +8‰. The δ18O values of the fluid decreased with decreasing temperature probably because the fluid was mixed with surrounding pore water and meteoric water. The formation pressure for the Takatori deposit is calculated to be 160 MPa on the basis of the difference between the pressure-independent oxygen isotope equilibrium temperature and pressure-dependent homogenization fluid inclusions temperature. The ore-formation depth is calculated to be around 6 km. These lines of evidence suggest that a granitic magma beneath the deposit played a crucial role in the Takatori deposit formation.

scholarly journals Are General Circulation Models Ready for Operational Streamflow Forecasting for Water Management in the Ganges and Brahmaputra River Basins?

2015 ◽  
Vol 17 (1) ◽  
pp. 195-210 ◽  
Author(s):  
Safat Sikder ◽  
Xiaodong Chen ◽  
Faisal Hossain ◽  
Jason B. Roberts ◽  
Franklin Robertson ◽  
...  
Keyword(s):  
Water Management ◽  
River Basins ◽  
Hydrologic Model ◽  
Streamflow Forecasting ◽  
Management Decisions ◽  
Brahmaputra River ◽  
Ganges Basin ◽  
Monthly Scale ◽  
Brahmaputra Basin ◽  
The Ganges

Abstract This study asks the question of whether GCMs are ready to be operationalized for streamflow forecasting in South Asian river basins, and if so, at what temporal scales and for which water management decisions are they likely to be relevant? The authors focused on the Ganges, Brahmaputra, and Meghna basins for which there is a gridded hydrologic model calibrated for the 2002–10 period. The North American Multimodel Ensemble (NMME) suite of eight GCM hindcasts was applied to generate precipitation forecasts for each month of the 1982–2012 (30 year) period at up to 6 months of lead time, which were then downscaled according to the bias-corrected statistical downscaling (BCSD) procedure to daily time steps. A global retrospective forcing dataset was used for this downscaling procedure. The study clearly revealed that a regionally consistent forcing for BCSD, which is currently unavailable for the region, is one of the primary conditions to realize reasonable skill in streamflow forecasting. In terms of relative RMSE (normalized by reference flow obtained from the global retrospective forcings used in downscaling), streamflow forecast uncertainty (RMSE) was found to be 38%–50% at monthly scale and 22%–35% at seasonal (3 monthly) scale. The Ganges River (regulated) experienced higher uncertainty than the Brahmaputra River (unregulated). In terms of anomaly correlation coefficient (ACC), the streamflow forecasting at seasonal (3 monthly) scale was found to have less uncertainty (>0.3) than at monthly scale (<0.25). The forecast skill in the Brahmaputra basin showed more improvement when the time horizon was aggregated from monthly to seasonal than the Ganges basin. Finally, the skill assessment for the individual seasons revealed that the flow forecasting using NMME data had less uncertainty during monsoon season (July–September) in the Brahmaputra basin and in postmonsoon season (October–December) in the Ganges basin. Overall, the study indicated that GCMs can have value for management decisions only at seasonal or annual water balance applications at best if appropriate historical forcings are used in downscaling. The take-home message of this study is that GCMs are not yet ready for prime-time operationalization for a wide variety of multiscale water management decisions for the Ganges and Brahmaputra River basins.

scholarly journals Modulation of the Ganges‐Brahmaputra River Plume by the Indian Ocean Dipole and Eddies Inferred From Satellite Observations

2017 ◽  
Vol 122 (12) ◽  
pp. 9591-9604 ◽  
Author(s):  
S. Fournier ◽  
J. Vialard ◽  
M. Lengaigne ◽  
T. Lee ◽  
M. M. Gierach ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
River Plume ◽  
Satellite Observations ◽  
Brahmaputra River ◽  
The Indian Ocean ◽  
The Ganges
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