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3 Methodology
3.1 Discharge Measurement
Measurements of the glacier runoff during the ablation seasons of the years 2000 to
2008 and 2010 was undertaken on hourly basis, in a 12 m wide channel, on Hamtah
glacier melt stream. The discharge-measuring site is located at about 600 m downstream of the glacier snout. As the channel has a near laminar flow of melt water at
the discharge site, it was considered ideal for recording of the glacier discharge
using area velocity or float method (Fig. 3). A stretch of 10 m was selected, for this
purpose, where the discharge was measured using area velocity method. A stream
gauge was fixed each year, after undertaking necessary repairs of the channel
embankments and plugging the seepage or percolation between the boulders.
The rating curve was prepared from a number of spot observations of varying
gauge heights and the corresponding stream discharges were measured by the area–
velocity method. The measured surface float velocities have been multiplied by a
factor of 0.70, for flows in reasonably smooth streams, as per the Water Measurement
Manual of the U.S. Department of the Interiors (2001) (considering the average
depth of water in the stream as ~3 feet). The product of the corrected velocities and
the cross-sectional area of the corresponding stream segments gave the segment
discharges. The sum of the segment discharges was the total discharge, at the observation time in m
3
/s.
Fig. 2 Emergence of Hamtah glacier meltwater stream from the snout
Glacier Melt Water Characteristics of Hamtah Glacier, Lahaul and Spiti District…
3 Methodology
3.1 Discharge Measurement
Measurements of the glacier runoff during the ablation seasons of the years 2000 to
2008 and 2010 was undertaken on hourly basis, in a 12 m wide channel, on Hamtah
glacier melt stream. The discharge-measuring site is located at about 600 m downstream of the glacier snout. As the channel has a near laminar flow of melt water at
the discharge site, it was considered ideal for recording of the glacier discharge
using area velocity or float method (Fig. 3). A stretch of 10 m was selected, for this
purpose, where the discharge was measured using area velocity method. A stream
gauge was fixed each year, after undertaking necessary repairs of the channel
embankments and plugging the seepage or percolation between the boulders.
The rating curve was prepared from a number of spot observations of varying
gauge heights and the corresponding stream discharges were measured by the area–
velocity method. The measured surface float velocities have been multiplied by a
factor of 0.70, for flows in reasonably smooth streams, as per the Water Measurement
Manual of the U.S. Department of the Interiors (2001) (considering the average
depth of water in the stream as ~3 feet). The product of the corrected velocities and
the cross-sectional area of the corresponding stream segments gave the segment
discharges. The sum of the segment discharges was the total discharge, at the observation time in m
3
/s.
Fig. 2 Emergence of Hamtah glacier meltwater stream from the snout
Glacier Melt Water Characteristics of Hamtah Glacier, Lahaul and Spiti District…