'Handbook of Mesopotamia. Vol. I. 1918' [‎23] (32/568)

BOUNDAETES AND PHYSICAL FEATURES 23
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southern slopes of the Qarajeh Dagh hill-country and Tur Abdin
plateau, which overlook that plain from the north. Below its
junction with the Khabur, 280 miles by river above Hit, the
Euphrates receives no tributary river: there are only wadis (water
courses), which from time to time bring down to it a part of the
rainfall of the Syrian and southern Jezlreh deserts.
The Tigris drains, first, the southern side of the Armenian plateau
through a number of streams, the most important of which is the
Batman Su; secondly, the mountains of central Kurdistan through
the Bohtan, the Kohsur, the Hazil, the Khabur, and the Great Zab ;
and thirdly, the western side of the Persian plateau through the Great
Zab and Lesser Zab, the 'Adheim, the Diyaleh, and the Karkeh.
Of these tributaries the Great Zah rises on the Persian frontier east
of Lake Van and cuts its way right through the high eastern ranges
of the central Kurdish mountains, taking their drainage ; in the
southern part of its course, below the neighbourhood of Amadiyeh,
it is fed by streams from the eastern side of the Persian plateau and
from the lower hill-country E. of Mosul; it joins the Tigris 35 miles
below Mosul. The Lesser Zah rises on the Persian plateau, not far
from the south-west corner of Lake Urmia, and, after flowing south
wards for some 80 miles, breaks through the mountain-barrier S. of
Ser Desht and Kaniyeh, and drains the hill-country between Raniyeh
and Altun Koprii ; it enters the Tigris 100 miles below Mosul, under
the Jebel Hamrln. Just below the point where the Tigris begins to
flow over an alluvial bed, the 'Adheim river comes in from the north;
this stream, which drains the lower hill-country between Kirkuk,
Suleimaniyeh, and Kufri, carries in the dry season little or no water
in the lower part of its course. A few miles S. of Baghdad the
Tigris is joined by the Diyaleh, known in its upper course as the
Sirwan. This river brings water from the provinces of Ardelan and
Kirmanshah on the Persian plateau ; most of its supply in the low-
w^ter season is used for the irrigation of the country NE. of Baghdad.
Below the Diyaleh a number of stream-beds descend into the plains
from the hills of the Pusht-i-Kuh. Most of these are dry in the
low-water season, but the southernmost of them is the channel of a
large river, the Karheh, which drains a considerable area of Luristan.
The greater part of the water that descends from the Pusht-i-Kuh
towards the Tigris is lost in swamps before it reaches that river, but
a certain proportion of the Karkeh water finds its way into the Tigris
or into the Shaft el-Arab a few miles below Kurna.
High and Low-water Seasons: —The volume of
water in the Euphrates and Tigris varies considerably during the
year. This variation has most important effects on irrigation and