Major ion chemistry of the Ganga–Brahmaputra river systems, India

Abstract

Rivers are the main pathways by which continental weathering products are transported to the oceans so that the chemistry of river waters and the flux of elements transported by them to the oceans are central to our understanding of the exogenic cycles of elements. There have been several detailed studies of major rivers^1–5 and we now report the major ion chemistry of another, the Ganga–Brahmaputra. These are two of the large rivers which drain the Indian subcontinent and they transport annually ∼10¹⁵ l of water and ∼2×10¹⁵ g suspended matter to the Bay of Bengal^6,7. On a global scale, these rivers rank fourth in terms of flow, and first in terms of sediment transport^6,7. Studies on the continental denudation rates and the budgets of major elements in the ocean, would, therefore, be incomplete without good geochemical data on these rivers. Our studies show that the Ganga–Brahmaputra system transports some 118 million tons of dissolved solids annually to the Bay of Bengal and that their water chemistry is dictated by the weathering of carbonates and contributions from soil salts and/or saline groundwaters.