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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| 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
526 GENERAL HYDROGRAPHY OF THE TARIM SYSTEM.
darja. As a consequence of this, as also of the relative proximity of the latter stream to the main artery of the system, the Tschertschen-darja occupies a more favourable situation than the Kerija-darja does, and seeing that it not only reaches all the way to the main river, but also possesses its own terminal lake, namely the Kara-buran, it gives the impression of being the greater of the two streams. And yet this impression is not warranted by the actual facts. The Kerija-darja is, from Kerija to the point where it terminates, almost as long as the Tschertschen-darja from the town of Tschertschen to the Kara-buran. Several parasites however prey upon the first-named, and it loses its flood not only through irrigation but also because it adventures itself out amongst the destructive agencies of the dry sandy desert, where it becomes exposed to the effects of the drift-sand to a far greater extent than the Tschertschen-darja does, the position of which, running parallel to the prevailing wind, favours it still further.
Similarly, the Ak-su-darja has a more favourable position than the Jarkentdarja : the distance which the former travels to reach the Tarim is so short, whereas the latter is forced to cross over a large desert before it can join the main stream. The same is true of the Chotan-darja. In the end of June I found that the Jurunkasch carried an extraordinarily big flood, so big in fact that it was impossible to ford it on horseback; but in the beginning of the same month I forded on horseback both the Ak-su and the Tauschkan-darja, although not very easily. The catchment-area of the Ak-su-darja amounts to 42,000 sq. km., and that of the Chotan-darja to 37,000 sq.-km.; the difference therefore between the two rivers in this respect also is not particularly great. What makes the Ak-su, upon reaching the Tarim, incomparably so much greater than the Chotan-darja when it reaches the Tarim is simply and solely its geographical position, coupled with the fact that the oasis of Chotan is far better cultivated than the oasis of Ak-su. The distance from the junction of the two large headwaters of the Ak-su to the point where the united stream falls into the Jarkent-darja (Tarim) amounts in round numbers to 95 km.; from the confluence of the Kara-kasch and the Jurun-kasch to the point where the Chotan-darja issues into the Tarim the distance is 290 km., or three times as long. This last confluence lies however a good long way out in the desert, so that it would be better to compare the distances of the two belts of oases from the principal river. This in the case of the Ak-su amounts to I i 5 km., but in the case of the Chotan-darja it is 435 km., or nearly four times as great. It is in this part of
its course, whilst making its long journey across the desert, that the Chotan-darja becomes so exhausted that it is only with difficulty it does succeed in making its
way to the Tarim, whereas the northern stream is scarcely drawn upon at all be-
fore it reaches the same goal. If the two streams be compared from their respective belts of oases upwards to their sources, then the Ak-su-darja is unquestionably
a more powerful river than the Chotan-darja. Not only is there probably a heavier
precipitation over its catchment-area, but its snowfields and glaciers are more directly exposed to the midday sun, so that a relatively greater amount of snow and
ice is converted into water than in the source-region of the Chotan-darja, where, again, on the other hand evaporation appears to play a relatively more important rôle. One thing is however certain, namely that if the deepest part of the basin
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