Meltwater characteristics of Garhwal Himalayan glaciers

A comparative study of the meltwater chemistry from the Gangotri, Satopanth -Bhagirathi. Dokriani, and Bagni glaciers has been done for the late ablati on period in October from 1991 to 1994. This late ablation period is charac terized by low atmospheric input and lean flow in the glacier streams due t o less availability of solar energy for supraglacial melting. During this p eriod subglacial melting has played a dominant role in determining the wate r chemistry of glacier meltwater. In all studies, the dominant controlling factor on meltwater chemistry has been rock weathering processes. The pH an d electrical conductivity of the meltwater from these Himalayan glaciers ra nged between 6.9-8.12 and 43-134.8 mu S/cm, respectively. The concentration ranges of major cations and anions recorded in the meltwaters of Himalayan glaciers are Ca+2 (166-800) mu eql(-1), Mg+2 (25.8-344.5) mu eql(-1), Na(11.1-124.2) mu eql(-1), K+ (80-677.6) mu eql(-1), HCO3- (381-2349.85) mu e ql(-1), SO42- (192-2234) mu eql(-1), and Cl- (0.72-53.25) mu eql(-1). The o rder of anion concentration in the meitwater is HCO3- > SO4-2 > Cl-. Howeve r, the order of anion concentration in meltwater of Gangotri, Bagni is SO4- 2 > HCO3- > Cl-. The order of cation concentration is Ca+2 > Mg+2 > K+ > Na + in all studies, except in the Satopanth and Bhagirathi glacier which show ed cation concentration of Ca+2 > Na+ > Mg+2 > K+ type. The purpose of this comparative study is to explain the geological control on the hydrochemist ry of the meltwater draining from four different glaciers in the Garhwal Hi malaya and to establish the relationship between meltwater hydrochemistry a nd the basement rock type.