This study gives an insight into the source of organic carbon and nitrogen in the Godavari river and its tributaries, the yield of organic carbon from the catchment, seasonal variability in their concentration and the ultimate flux of organic and inorganic carbon into the Bay of Bengal. Particulate organic carbon/particulate organic nitrogen (POC/PON or C/N) ratios revealed that the dominant source of organic matter in the high season is from the soil (C/N = 8-14), while in the rest of the seasons, the river-derived (in situ) phytoplankton is the major source (C/N = l-8). Amount of organic materials carried from the lower catchment and flood plains to the oceans during the high season are 3 to 91 times higher than in the moderate and low seasons. Large-scale erosion and deforestation in the catchment has led to higher net yield of organic carbon in the Godavari catchment when compared to other major world rivers. The total flux of POC, and dissolved inorganic carbon (DIC) from the Godavari river to the Bay of Bengal is estimated as 756 × 10 9 and 2520 × 109 g yr-1, respectively. About 22% of POC is lost in the main channel because of oxidation of labile organic matter, entrapment of organic material behind dams/sedimentation along flood plains and river channel; the DIC fluxes as a function of alkalinity are conservative throughout the river channel. Finally, the C/N ratios (?12) of the ultimate fluxes of particulate organic carbon suggest the dominance of refractory/stable soil organic matter that could eventually get buried in the coastal sediments on a geological time scale. © Springer 2005.
(Organic carbon transport and C/N ratio variations in a large tropical river: Godavari as a case study, India) Balakrishna, K.; Probst, J.L.
2005
Nine major rivers have been sampled around the Indian subcontinent to give an overview of the surface water characteristics. Both 18O and deuterium have been measured to determine the origin of the water and the possible evapotranspiration process. The major ions have also been analysed to obtain complementary information. Although some basins have been studied previously (mainly in the north), this is the first attempt at a wider investigation of major Indian rivers. The results are discussed from the perspective of the hydroclimatological, geographical and geological specificity of the river basins. ? 18O values vary from light-isotope-enriched Himalayan rivers to heavy-isotope-enriched peninsular Indian rivers in a northwest-southeast gradient across the subcontinent. There is more evapotranspiration, leading to heavy isotope enrichment, in the peninsular (southern Deccan) rivers compared with the light-isotope-enriched snow- and glacier-melt-derived waters of the Himalayan rivers. The ?18O values of Indian rivers correspond roughly to the ?18O values of the rains falling over the subcontinent. However, the influence of tributaries is dominant over rainfall in rivers like the Narmada and Tapti. The Cauvery and Krishna rivers show maximum evapotranspiration and sodium pollution, as indicated by the ?18O values, deuterium excess and major ion data. Copyright © 2005 John Wiley & Sons, Ltd.
(Oxygen and hydrogen isotopic composition of major Indian rivers: A first global assessment) Lambs, L.; Balakrishna, K.; Brunet, F.; Probst, J.L.
2005

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