IIIFカラー高解像度
国立情報学研究所 - ディジタル・シルクロード・プロジェクト
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| IIIFカラー高解像度 |
| Scientific Results of a Journey in Central Asia, 1899-1902 : vol.2 | |
| 1899-1902年の中央アジア旅行における科学的成果 : vol.2 |
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引用情報
520 GENERAL HYDROGRAPHY OF THE TARIM SYSTEM.
precisely the same as in the beginning of March, though the latter measurement was made a considerable distance below the former: the 19 cub.m. were obtained about
23o km. below Korla, whereas the 14 cub.m. were 28o to 290 km. below the same
town. From oral information I ascertained, that this diminution would continue all
the summer, although at a slow rate. Even when the river is at its lowest, it is
said to contain so much water that it is not possible to ford it on horseback; but
it is evident, that what there is flows excessively slowly. The reason why the river
decreases so rapidly in spring between Korla and Tikenlik and the Bos-ilek is that
all the canals in the district of Korla are then kept open for the purpose of irrigating the cultivated fields. Add to that the quantity of water which is naturally absorbed into the ground, and disappears through evaporation and the formation of . the marginal lakes. But even the artificial decrease, caused by irrigation, may be regarded as a constant factor; indeed it seems likely that the region around Korla was in former times more extensively cultivated than it is now, and consequently there was then an even heavier drain upon the Kontsche-darja than there is now. If we suppose the Kontsche-darja to be completely independent of the Tarim, and to flow entirely in its own bed all the way down to the Kara-koschun, then the volume of 33 cub.m. which we find at distances of 23o and 2 8o km. from Korla would not be able to get down to Kum-tschapghan, which lies 240 and 190 km. respectively still lower down; for the farther the water advances the greater the drain that is made upon it by the surrounding dry, torrid deserts and by the sandstorms with their extraordinarily arid winds, each as desiccating as its predecessor. And it would only be in autumn, after all the irrigation channels are closed, that a thin trickling ribbon of water would be at all likely to reach the terminal lake, and possibly the same thing might be repeated when the ice thaws in the spring. Indeed, when we call to mind how rapidly the Tarim shrinks in the lowest part of its course, it becomes extremely doubtful whether the Kontsche-darja alone would be able to get down as far as the Kara-koschun at all. Anyway it is from this stream that the Tarim receives its last impulse but one towards the maintenance of its powers of resistance; the very last impulse coming from the Tschertschen-darja.
The reasoning just adduced leads to yet another interesting conclusion. If the distance between Korla and Kum-tschapghan amounts to 47o km., and if it is only occasionally that the Kontsche-darja is able to travel the full distance down to the terminal lake, it may be certainly assumed, that the same thing happened in the Kuruk-darja, the distance by it between Korla and the place where it emptied itself into the Lop-nor being 410 km. The distance in the case of the latter stream is indeed somewhat less, but on the other side we have to set the fact that its banks were certainly inhabited in places, because one of the roads to Korla ran beside it,
, and it is safe to assume that the people who dwelt on its banks also utilized its water for irrigation. If now the stream of the Kontsche-darja, which we may safely say had, sixteen hundred years ago, about the same volume that it has now, for the Baghrasch-köl played then the same regulative and distributive part that it does now, and if the entire river flowed as one stream through the bed of the Kuruk-darja, then, it may argued, the river (1) would never have been able to get down to its terminus south-west of Altmisch-bulak, and (2) even snjj5osing it did get down as far
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