804 KUCHA AND SOME OF ITS ANCIENT SITES [Chap. XXIII
In view of the extensive archaeological work undertaken by the numerous scholars who had preceded me in the area of Kuchâ, there was but limited scope for further antiquarian investigation during my own short stay. But I was particularly glad of the opportunity thus afforded of carrying out surveys likely to throw light on certain geographical factors which must have exercised a lasting influence all through historical times upon the economic and political fortunes of Kuchâ.. The geographical conditions I refer to are of additional interest when they are compared with those affecting the oasis of Khotan. It will be convenient to review these briefly, so far as they result directly from the position of Kuchâ in relation to the chief physical features of the Tarim basin, before I record such detailed observations as I was able to make in the course of my surveys.
Kuchâ, owes its comparatively large area of cultivable land, and the ample economic resources derived from it, to its situation at the point where two considerable rivers, the Muz-art and the Kuchâ.-daryâ, debouch close together from the Tien-shan foot-hills into the trough of the Tarim. The Muz-art-daryâ, by far the greater of the two, is fed mainly from the large glaciers which descend from the eastern slopes of the ice-clad Khan-tengri massif, the highest in the whole T`ienshan system. Before it breaks through the outermost hill range west of Kuchâ town in the gorge below Kizil (Map No. 17. B. 1), it passes through the subsidiary basin of Bai (Map No. 12. c, D. z), containing large stretches of fertile soil occupied by flourishing oases. Owing, probably, to the great amount of sediment which the Muz-art and its several large tributaries deposit here, the wide fan formed by the river where it issues from the basin is covered by a layer of fertile alluvium stretching right up to the point of its outflow above Kum-tura.
Just as in the case of the two rivers of Khotan, this favourable circumstance greatly facilitates the full use of the abundant water-supply for purposes of irrigation ; for where no wide barren glacis of gravel intervenes between the outflow of the river and the belt of fertile soil, many of the difficulties of irrigation, such as loss through evaporation, shifting of channels at canal heads, and similar troubles, are avoided. There is reason to believe that at the present time the irrigation facilities thus assured to Kuchâ are far from being completely utilized. But even so it is worthy of note that the area of practically continuous cultivation irrigated from the Muz-art-daryâ attains a maximum extent, from west to east, of close on fifty miles, as seen in Map No. ,17, while from north to south, if the Shahyâr tract is included, it measures over thirty miles.4
Irrigation In the case of the Kuchâ river, conditions are somewhat less favourable. It, too, is fed by
from glaciers on the main range towards Yulduz, but the volume of water is far smaller, On May 5th,
daryâ. according to measurements taken by Surveyor Afrâz-gul where the river debouches at Su-bâshi,
it amounted to about 32o cubic feet of water per second. The stretches of bare gravel ` Sai ' over which the canals taking off at Su-bâshi have to be carried reduce the supply actually available for the cultivated belt of ground east of Kuchâ, town. The consequent limitation of irrigation facilities is particularly felt in spring. Fortunately, however, recourse is then possible in this area to kara-su from springs fed by subterranean drainage, just as it is in the case of Keriya and the smaller oases east of Khotan. Thus the water of the Kuchâ river adds to the arable land of the oasis a stretch of ground about twenty miles long and six miles wide, which, owing to its position, could not be reached by irrigation from the Muz-art-daryâ.
The importance derived by the oasis of Kuchâ from an ample supply of water for irrigation is much increased by the advantages it draws from its position in relation to two dominant features in the geography of the Tarim basin—the mountain rampart of the Tien-shan rising above it to the north, and the great desert of drifting sands to the south. We shall readily perceive the
4 For details of the discharge of the several canals from the Muz-art-darya, as measured above Kum-tura, see below, ii. pp. 8o8 sq.