Geochemical characteristics of water and sediment of the Indus river, Trans-Himalaya, India: constraints on weathering and erosion

Abstract

The Indus river carries a huge amount of chemical and sediment load while traversing the Himalayas. The present study deals with the chemistry of major ions (Ca, Mg, HCO₃, Na, K, Cl, SO₄, SiO₂ ) and trace metal contents (Ba, Sr, Zn, Ni, Cu, Co, Mn) of the river Indus, one of its major tributaries, the river Beas, many adjoining hot and cold water springs and the high altitude lake (~5700 m) Kyung Tso. Although anthropogenic activities like farming, grazing and tourism have started in large parts of this terrain, our study indicates that chemistry of Indus water is influenced mostly by the lithology of the basin and most of its ionic concentration appears to have been derived from weathering of carbonates and silicates in the catchment area. For the first time, bed and suspended sediments of the river Indus have also been studied and compared with average Post Archean shale (PAS) and greywacke. The sediments of the Indus river in its headwater region closely reflect the exposed portion of the crust in its catchment area. The headwater part of the Indus Basin in Ladakh and Karakorum is characterised by rapid uplift and, therefore, subject more to intense physical weathering than chemical weathering, as is evidenced by the suspended and dissolved load carried by the river. Physical weathering and erosion is expected to have major controls on the grain size and therefore the chemical nature of the sediments.