Investigations into the Soils and Agriculture of the Lower Diyala Area of Eastern Iraq

Abstract

sometimes even causing serious floods, but in summer it is so reduced that only a small area can be cropped. The Iraq Development Board initiated the building of the Derbendi-Khan dam on the upper in 1951 to control these variations, in order to extend the limits and intensify the use of the present cultivated area in summer, and prevent flooding in the winter. A firm of consulting engineers, Sir Murdoch Mac? donald and Partners, was commissioned to advise on the irrigation development of the whole river basin. They employed Hunting Technical Services Limited to study and map the soils, to assess their value for irrigation, and to study agricultural methods both in the irrigated areas and the upper catchment. The and its tributaries drain an area of 11,800 sq. miles in the Cretaceous, Eocene and Oligocene fold ranges of western Persia and eastern Iraq. They fall rapidly from heights of over 12,000 feet to the Miocene gypsum, marl and red sand? stone hills of the Fars Series and the Pliocene Bakhtiari gravels which outcrop at the edge of the Mesopotamian lowland. The breaks through these parallel fold ranges transversely in a series of discordant gorges. As the hills decrease in height westwards, the lateral alluvial basins increase in size until the river finally emerges from the Jabal Hamrin on to the Mesopotamian plain. The Diyala Scheme concerns the whole river valley and catchment area, but has been divided for convenience into the Upper Diyala, the hilly country lying north of the gorge at Jabal Tuna Charkana; Middle Diyala, the undulating country of parallel ridges and intermontane troughs between Jabal Tuna Charkana and Jabal Hamrin; and Diyala, which is defined as that area which is commanded by gravity irrigation canals drawn off at Weir. This weir is situated where the river emerges from the Jabal Hamrin near the town of Muqdadiya (Shahraban). From it flow five canals on the left bank and one on the right bank which command a large well-defined area bounded on the north-east by the mountains, on the west by the river Tigris, and on the north-west and south by deserts (Plate 1). The Lower area History.1?The history of settlement of the Lower area is very ancient, going back to the Ubaid and Warka periods when some irrigation from small local canals was practised. The first flourishing came in the Proto-Literate and Early Dynastic Periods (c. 3600-2300 b.c.) when major canal systems were created, and brought a prosperity which lasted until after the Gutian invasion when some con? traction of cultivation took place (c. 2150 b.c). The region prospered again, however, under the Third Dynasty of Ur, and continued in fair stability under more or less independent local governors at Eshnunna (Tel Asmar) for half a millennium. There was a general decline after about 1700 B.c, accompanied by a considerable abandon? ment of settlement. The ancient sites of Tel Asman, Tel Agrab and Khafaji are marked with small circles on the map facing p. 392. Little is then known about the region for a long period. It was a route for armies under the Kassite, Assyrian and Neo-Babylonian empires. It entered a new era of growing prosperity under the Achaemenian Persians in 537 B.c, which was to continue 1 Derived from information given by Professor T. Jacobsen of Chicago University.