Chemical weathering rates in the Alaknanda-Bhagirathi river basins in Himalayas, India

The Alaknanda and Bhagirathi rivers flow through the Higher and Lesser Himalayas and confluence at Devprayag, which represents the origin of the Ganga (or Ganges) river. In the present study, a vast number of temporal and spatial samples of the river waters were collected and analyzed for major cations and anions. In addition, more recent and time series water flow data have been obtained and based on these inputs, a more refined dissolved flux rates have been estimated. The Alaknanda and Bhagirathi rivers show significant variations in chemical compositions during different seasons. Carbonate rock weathering is responsible for more than 70% of the chemical compositions in the river waters. The chemical weathering rates show seasonal variations and are much higher during non-monsoon season. The dissolved flux of Alaknanda river is much higher (1.80 × 106 tons yr−1) as compared to the Bhagirathi river (0.34 × 106 tons yr−1). The chemical weathering rates in the basin vary between 85 and 155 tons km−2 yr−1, which is significantly higher compared to the global average of ∼24 tons km−2 yr−1.