'Handbook of Mesopotamia. Vol. I. 1918' [‎25] (34/568)

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BOUNDARIES AND PHYSICAL FEATUEES 25
the low-water discharge 7,700. At Kurna the river discharges about
28,000 cusecs in flood.
In northern Irak the Euphrates has a smaller discharge than the
Tigris in the flood months ; the average for the Euphrates on the
section Hit—Hindiyeh is about 87,000 cusecs against 100,000 for
the Tigris at Baghdad. Moreover the Euphrates in its most violent
flood does not rise here much beyond 160,000 cusecs. On the other
hand in the months of low water the discharge of the Euphrates in
northern Irak is somewhat greater than that of the Tigris (about
14,000fcusecs against 10,600 cusecs).
Both rivers bring down a great quantity of sediment in the high-
water season. In lower Mesopotamia part of this sediment forms
shifting banks in the channels, part is deposited in marshes or lakes
or in irrigation-channels. By the time the two rivers meet at
Kurna both have lost most of their silt, the Euphrates especially
being comparatively clear in its lower course.
Effect oft loods in IraJc, —In upper Mesopotamia the floods of the
Euphrates and the Tigris are contained in their valleys or troughs.
They flood low foreshores in the bottom of their troughs, but do not
spread very far. In the alluvium of lower Mesopotamia on the
other hand the water of the rivers spreads out in great inundations,
and has been known to change its main channel. Here the river
beds are not nearly capable of taking all the flood-season discharge ;
the soft alluvial soil is easily penetrated, and the ground-levels, which"
are below the high-flood levels of the rivers, fall gradually away from
the banks. Moreover, since the former irrigation-system was de-
stroyed in the Middle Ages, the slight and partial attempts to control
the flow of the water have not only been inadequate, but have often
made matters worse. Before the present war the Turkish authori
ties tried by means of bunds (dykes and dams) to limit the floods
round Baghdad, and they had the Hindiyeh Barrage and Hilla
Regulator built for the distribution of the water between the two
main branches into which the Euphrates divides below Museyib.
Elsewhere the only protective works were small and weak earthen
dykes along the river-banks. The Arabs were left to cut canals,
build dams, and reclaim land along the river-banks to suit their
private and local needs, and their work often had disastrous effects.
Only by the construction of a system of barrages and escapes at the
head of the alluvial plain (that is, between Hit and Eellujeh on the
Euphrates and in the neighbourhood of Samarra on the Tigris) can
excessive flooding be effectively prevented in Irak.
The amount of spill which occurs at this point or that, and the
position and extent of the inundations, vary more or less from vear