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0265 Scientific Results of a Journey in Central Asia, 1899-1902 : vol.1
Scientific Results of a Journey in Central Asia, 1899-1902 : vol.1 / Page 265 (Grayscale High Resolution Image)

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[Figure] Fig. 149. Marginal Lakes

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doi: 10.20676/00000216
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5

B

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THE STRUGGLE BETWEEN THE RIVER AND THE SAND.   179

alone, we may infer how immense is the influence which all the lakes together exercise upon the volume of the river. The action of the Ullugh-köl may possibly

appear to be to some extent in conflict with the argument which has been set forth

above. If at a given point of time in the spring all the marginal lakes are full, and the river is already dropping steadily lower, the water ought of course soon to

flow back into the river; whereas we find, on the contrary, a strong current running into the Ullugh-köl. But, rightly considered, this is precisely a proof of the correctness of my reasoning. In the first place, it must be borne in mind that the loss of water in these marginal lakes, which, like the Ullugh-köl, are situated amongst the sand, is enormous, and that their evaporation increases as the summer advances.

The accompanying sketch will enable us to see the facts in the proper connections. If, say, the Tarim measures above a given number of lakes A, B, C,

D, E, and F Iob cub.m. in the second, and if each of these lakes requires to be fed at the rate of 5 cub.m. in the second, in order that their several levels may coincide with the level of the river, then the river, by the time it reaches the inflow canal of lake G, will have dropped to 7o cub.m. Suppose now that all these lakes

down to and including F are full, so that they no longer   100k:.b.m.

exercise any drain upon the river, this last, when it reaches   5

the canal of lake G, will be once more running mo cub.m.   5

strong. The consequence is that the inflow into lake G is   — - 5
livelier than before. The longer the upper lakes are in fil-

ling, the later does the river rise in spring over against lake   c - '_—   -= _ 70 huh.m

G. As a matter of fact, the outflow and equilibrium of level

are established between the river and each lake in turn,   F

and owing to the immense length of the river no serious

disturbance results. If however it should happen that several

lakes fill simultaneously, the effect would make itself felt to

a very marked degree lower down the river. So far as I was able to ascertain,

something of the kind appeared to have indeed taken place between the 16th and the 23rd May, the consequence of which was an otherwise inexplicable rise of 12.5 cub.m. in the level of the river.

May 24th. At Junus-ottogho and Kosch-kotan, immediately below Boba-uktusu, yet another old river-bed with reedy margins leads off to the right of the existing

channel; but, except for a mere trickle of water in its deepest part, it was on 6th

May quite dry and bare. Although the main current began to leave this bed about 6 years ago, it is only two or three years since that it finally made up its mind to

give the definitive preference to the existing channel. That is to say, the river was

here for the space of three or four years split into two arms; and the stretch between Kosch-kotan and Tarim-kirdi is consequently without forest. Indeed there

appears to be no forest beside the southern, abandoned arm either — a significant

fact, proving that the river must previously have pursued a more northerly course. On the left bank stands the village of Tuvekteki-uj, inhabited thirty years ago;

perhaps even as early as that some little rivulet groped its way towards the present channel. At the sharp bend of Tarim-kirdi stands the village of Tägirmändake-uj, consisting of four huts; this was inhabited in 1898, but not in 1900. In fact, the

Fig. 149.