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0468 Southern Tibet : vol.2
Southern Tibet : vol.2 / Page 468 (Grayscale High Resolution Image)

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doi: 10.20676/00000263
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OCR Text

being 1.03m.ยน The average velocity measured at 32 points, at the surface, in the
middle, and near the bottom, was 0.50sm. a second. The breadth of the branch was
54m.; and the volume amounted to 21.38cub.m. a second.

The second branch had an average depth of 0.40m., an average velocity of
1.39m. a second, a breadth of 15.30m., and a volume of 8.54cub.m. a second. The
whole Dok-chu therefore carried 29.92cub.m., or in round figures, 30cub.m. a second.

The Tsangpo itself presented some difficulties on account of the very great
depth and the slow current. At the place where the rope was spanned across the
river and the boat held at equal distances for measuring depth and velocity, the
breadth was only 46m. The depth measured at 10 places along this line was on
an average 2.8m., the deepest being 4.67m. The average velocity was 0.578m. a
second, and the volume 74.98cub.m., or in round figures 75cub.m. a second. To
this is, however, to be noted that the velocity instrument could not be held steady
any deeper than 2m.; therefore I calculated a regular diminution of velocity towards
the bottom, and perhaps in reality the current may be stronger somewhere near the
bottom. The following measurements on the river will prove, however, that the value
of 75cub.m. was very likely correct.

The whole Tsangpo, below the junction with the Dok-chu-Raga-tsangpo had
thus a volume of 105 cub.m., and must have increased on its way to Shigatse to
at least 125cub.m., after having received several tributaries, the greatest of which
were Soo, Shab and Ta-nakpo-chu.

Below the point where the Dok-chu was measured it splits up in several delta
branches spread over the gravelly bed and rushes murmuring down to the quiet
and silent Tsangpo, which sweeps immediately along the rocks at its right bank.