Irrigation in Iran covers 89,930 km2 making it the fifth ranked country in terms of irrigated area.[1]
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The Abadan Island (Fig. 1) in Khūzestān Province is situated between the Arvand and Bahmanshir rivers. The Arvand river (in Arabic: Shatt al-Arab) forms the boundary between Iran and Iraq and collects the waters from the Euphrates and Tigris rivers.
On the island extensive orchards of date palm are found thriving on tidal irrigation in the desert climate, although many date palms were destroyed during the Iraq-Iran war.
The palm tree belt stretches along the Arvand River from Abadan south-east over a distance of about 40 km and is bounded in the interior by a road.
The width of the belt varies from 2 to 6 km, and on average it is 4 km. The width is greater in the concave parts of the river bends and smaller in the convex parts. The convex parts have higher river levees and topography.
The total area of the belt is about 16000 ha. The tree spacing is around 6x6 m. There are roughly 300 trees per ha. The maximum yield is about 200 kg/tree and 60 t/ha.
A sketch of the system of tidal canals [2] is shown in figure 2. They are 2 to 6 km long depending on the topography and spaced at 50 to 60 m.
The tidal canals cut through and serve the levee soils along the river (Fig. 3) and they stop where the basin soils of the backswamps begin.
Between the tidal canals additional lateral ditches have been dug perpendicularly at a spacing of 50 to 60 m to further promote the distribution of the irrigation water.
Field channels originate from the lateral ditches at a spacing of 10 to 12 m and the date palms are planted along these (Fig. 4).
The typical properties of the levee soils are shown in figure 5. There is a well-developed topsoil with a thickness of more than 1 m through which the subsurface irrigation water can move in and out with relative ease.
The tidal movements are 2 m on average. A simulation of tidal fluctuations in the ditches is shown in figure 6 for an average and a high river discharge at various distances from the sea. The simulations were made with the Duflow [3] model.
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