'IRAQ AND THE PERSIAN GULF' [‎25v] (55/862)

22 GEOLOGY AND DESCRIPTION OF THE LAND
estuary of the Karkheh and Katun entered the gulf at Sulaymanan.
The site of the latter is now lost, but Abadan is well known as the
oil-port of the Anglo-Iranian Oil Company below Mo ammera
and is now more than 25 miles from the head of the gul he
Karun sediments, unable to bar the outlet of the Tigris and Euphrates,
are carried seawards, and the combined delta is being reclaimed at
the rate of 2 miles a century. Much of this built-up land is under
marsh or lagoon, fed indifferently by the overflow of the tides or of
the inland waters; but the Khor Abdulla and the Khor as Sabiya,
fed by the Khor Zubair, used to drain the extensive marshlands west
and north-west of Basra, and even the Hammar lake, when all these
became a single sheet of water in high-flood season (p. 61).
Behind this growing barrier the two great rivers of Iraq, the
Euphrates and the Tigris, with considerable help from the tributaries
of the latter, have poured their waters since Tertiary times and with
their sediments have built up the Mesopotamian plain. It is calculated
that rather less than 10 per cent, of the sediment brought down by
these rivers in flood time passes on into the Shatt al Arab.
The Euphrates rises far away in north-east Turkey near Erzurum
and, after collecting the greater part of the drainage of eastern Turkey,
breaks through the Kurdish I aurus north-west of Diyarbekir.
Deflected westwards by the Karacali volcano, it flows through Syria,
turns south and then south-east about 120 miles from the Syrian
shore of the Mediterranean, and enters Iraq immediately below Abu
Kemal, where it is cutting its bed in the Tertiary rocks near the edge
of the Arabian escarpment. It enters its delta below Hit, about 200
feet above sea-level, and about 35° rml es i n a direct line up-river from
Basra. Except for the water of occasional rainstorms and an insignifi
cant trickle of water brought down by rare spring-fed wadis, it
receives no tributaries on either side in Iraq, though the flood waters
of the Tigris reach it at Nasiriya and below (p. 39). On the contrary,
from Hit downwards great quantities of water are drawn off for
irrigation purposes, and vast expanses of water extend on either bank
in the flood season. It is here that the greater part of the silt is
deposited. Moreover, the river and its distributaries have many times
changed their courses, as is shown by tels of ancient cities that once
stood on their banks. Two of its ancient channels, now the Hilla
and the Hindiya branches, are to-day regulated by the Hindiya
barrage, but both break up into a number of subsidiary streams and
canals before uniting again near Samawa, and much water is dissi
pated before the river reaches the extensive Hammar lake, from which,