Hydrograph Separation by Measurement of Electrical Conductivity and Discharge for Meltwaters in the Ganga Headwater Basin, Garhwal Himalaya

Water quality of meltwater streams in the Higher Himalaya is mainly controlled by precipitation (snowmelt, icemelt and monsoon rainfall), geology and land use patterns in the region. In response to increase in population growth and acidification of the Asian atmosphere, the quality of stream water in one of the pristine environments of the world viz. the Himalaya has been affected. The quality of water in these streams of the glacier region is controlled by mixing of the surface and subsurface waters. Hence, hydrographic study was carried out to quantify the proportion of glacier meltwater in the two different types of water sources in the stream viz. surface and subsurface. The hydrograph was separated into surface and subsurface component sources using a mixing model, and the electrical conductivity (EC) was used as a tracer for mixing of the surface and subsurface component. The results show that high variability in the temporal variation in the surface and subsurface component of water source in the stream. Average subsurface water contribution to stream water was 37 % of the total runoff. The subsurface water was rapidly flushed out from the system during the initial stages of snowmelting. During the rising limb, surface and subsurface flows contribute about 5 1 % and 48% of the total runoff respectively. Surface water was estimated to be the dominant component of streamflow on the falling limb of the hydrograph and constitutes about 77% of total flow. It constitutes however about 64% of total runoff for the whole water year.