Iraq has more water than most Middle Eastern nations, which led to the establishment of one of the world's earliest and most advanced civilizations. Strong, centralized governments--a phenomenon known as "hydraulic despotism"--emerged because of the need for organization and for technology in order to exploit the Tigris and Euphrates rivers. Archaeologists believe that the high point in the development of the irrigation system occurred about 500 A.D., when a network of irrigation canals permitted widespread cultivation that made the river basin into a regional granary. Having been poorly maintained, the irrigation and drainage canals had deteriorated badly by the twelfth and thirteenth centuries, when the Mongols destroyed what remained of the system.
About one-fifth of Iraq's territory consists of farmland. About half of this total cultivated area is in the northeastern plains and mountain valleys, where sufficient rain falls to sustain agriculture. The remainder of the cultivated land is in the valleys of the Euphrates and Tigris rivers, which receive scant rainfall and rely instead on water from the rivers. Both rivers are fed by snowpack and rainfall in eastern Turkey and in northwest Iran. The rivers' discharge peaks in March and in May, too late for winter crops and too early for summer crops. The flow of the rivers varies considerably every year. Destructive flooding, particularly of the Tigris, is not uncommon, and some scholars have placed numerous great flood legends, including the biblical story of Noah and the ark, in this area. Conversely, years of low flow make irrigation and agriculture difficult.
Not until the twentieth century did Iraq make a concerted effort to restore its irrigation and drainage network and to control seasonal flooding. Various regimes constructed several large dams and river control projects, rehabilitated old canals, and built new irrigation systems. Barrages were constructed on both the Tigris and the Euphrates to channel water into natural depressions so that floods could be controlled. It was also hoped that the water could be used for irrigation after the rivers peaked in the spring, but the combination of high evaporation from the reservoirs and the absorption of salt residues in the depressions made some of the water too brackish for agricultural use. Some dams that created large reservoirs were built in the valleys of tributaries of the Tigris, a measure that diminished spring flooding and evened out the supply of water over the cropping season. When the Euphrates was flowing at an exceptionally low level in 1984, the government was able to release water stored in reservoirs to sustain farmers.
In 1988 barrages or dam reservoirs existed at Samarra, Dukan, Darband, and Khan on the Tigris and Habbaniyah on the Euphrates. Two new dams on the Tigris at Mosul and Al Hadithah, named respectively the Saddam and Al Qadisiyah, were on the verge of completion in 1988. Furthermore, a Chinese-Brazilian joint venture was constructing a US$2 billion dam on the Great Zab River, a Tigris tributary in northeastern Iraq. Additional dams were planned for Badush and Fathah, both on the Tigris. In Hindiyah on the Euphrates and in Ash Shinafiyah on the Euphrates, Chinese contractors were building a series of barrages.
Geographic factors contributed to Iraq's water problems. Like all rivers, the Tigris and the Euphrates carry large amounts of silt downstream. This silt is deposited in river channels, in canals, and on the flood plains. In Iraq, the soil has a high saline content. As the water table rises through flooding or through irrigation, salt rises into the topsoil, rendering agricultural land sterile. In addition, the alluvial silt is highly saline. Drainage thus becomes very important; however, Iraq's terrain is very flat. Baghdad, for example, although 550 kilometers from the Persian Gulf, is only 34 meters above sea level. This slight gradient makes the plains susceptible to flooding and, although it facilitates irrigation, it also hampers drainage. The flat terrain also provides relatively few sites for dams. Most important, Iraq lies downstream from both Syria and Turkey on the Euphrates River and downstream from Turkey on the Tigris River. In the early 1970s, both Syria and Turkey completed large dams on the Euphrates and filled vast reservoirs. Iraqi officials protested the sharp decrease in the river's flow, claiming that irrigated areas along the Euphrates in Iraq dropped from 136,000 hectares to 10,000 hectares from 1974 to 1975.
Despite cordial relations between Iraq and Turkey in the late 1980s, the issue of water allocation continued to cause friction between the two governments. In 1986 Turkey completed tunnels to divert an estimated one-fifth of the water from the Euphrates into the Atatürk Dam reservoir. The Turkish government reassured Iraq that in the long run downstream flows would revert to normal. Iraqi protests were muted, because Iraq did not yet exploit Euphrates River water fully for irrigation, and the government did not wish to complicate its relationship with Turkey in the midst of the Iran-Iraq War.
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