Controls on the major-ion chemistry of the Dokriani glacier meltwaters, Ganga basin, Garhwal Himalaya, India

A detailed study of the major-ion chemistry of the Dokriani glacier meltwat ers, feeding the Bhagirathi river, Ganga basin, Garhwal Himalaya, India, ha s been carried out to assess the role of active glaciers in the higher chem ical-denudation rate(CDR) in this area. The CDR of the Dokriani glacier cat chment is 321.6 t km(-2) a(-1), higher than in other glacierized catchments of the world, indicating intense chemical erosion in the glacierized catch ments of the Himalaya. The dominance of Ca2+, HCO3- and SO42- in meltwaters throughout the 6 month (May-October) ablation period suggests that the che mical weathering is dominated by coupled reactions involving sulphide oxida tion and carbonate dissolution. Good positive correlation between SO42- and suspended-sediment concentration during July and August (r(2) = 0.72 and 0 .67, respectively) suggests that the southwest monsoonal rainfall enhances the weathering of supraglacial moraine and contributes significant amounts of sulphate to the high meltwater discharges. The sulphate flux as a propor tion of combined (SO42- + HCO3-) flux, also increased from 45% at 2 m(3) s( -1) to 63% at 10 m(3) s(-1).