IIIF Color HighRes
National Institute of Informatics - Digital Silk Road Project
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| IIIF Color HighRes |
| Scientific Results of a Journey in Central Asia, 1899-1902 : vol.4 |
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Citation Information
ICE AND SOUNDINGS IN THE TSO-NGOMBO. 305
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winter from the Tsanger-schar and other rivers plus what they derive from the innumerable springs which issue on its banks or in the bottom of the lake. Our Tibetans indeed asserted that the river in this section remains pretty constant all the year round, the only exception being a slight rise after rain. How far that is true can of course only be determined after continuous investigations on the spot. On the one hand we have to assume, that the outflow is considerably greater in the summer than in the winter, in consequence of the rainfall and the melting of the snows; but on the other hand the evaporation should be far more active in the summer than in the winter, when it is prevented by the ice. At the spot where we measured the river, we observed marks on the banks, which told us that not very
Fig. 212. UPWARDS FROM CAMP CXLIV.
long before the river had been 44 cm. higher than it was then, which would mean a volume three times as great as that which we measured. At that time the difference of level between the Tso-ngombo and the Panggong-tso could not amount to many centimeters. Farther down the erosive energy of the stream was more active. It looked as if the Panggong-tso were shrinking at a relatively more rapid rate than the Tso-ngombo, and thus accentuating the difference of level between the two lakes, with the consequence that the erosion in this section of the river will move backwards up it owing to the fall being increased in its lower part. In the upper part of the same section the fall is quite insignificant, and the river is deep and broad. It is however eating its way in deeper in consequence of the constant fall of level in the lakes occasioned by the alteration of climate, a fact of which we noticed many proofs in the interior of Tibet, as also in the old strand-terraces of the Tso-ngombo; and at this camp, No. CXLIV, we soon discovered beach-lines at a very much higher level. If we start from the fact, that both lakes are shrinking, we can easily conceive the following course of events as happening. In the begin-
He d i n, Tourney in Central Asia. IV. 39
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