HISTORICAL DEVELOPMENT OF ENGINEERED WATERWAYS IN THE TIGRIS-EUPHRATES VALLEY, IRAQ

Drainage systems have been engineered in the Tigris-Euphrates valley, the “Cradle of Civilization,” for more than six millennia. The first canals were constructed by the Sumarians for irrigation in the southern valley. Because of the high degree of administrative control required to develop, maintain, and defend complex irrigation systems, Sumarian city-states essentially became “irrigation cities.” The system was expanded as populations moved northward and the requisite centralized administrative skills became available. The establishment of Baghdad in the upper valley around 750 AD by the Abbasid Caliphate led to development of an even more extensive system of canals for irrigation, flood control, and swamp drainage. Remnants of this system still exist and are functional today. The waterway system continued to expand until administrative and political weakness in the Caliphate allowed it to fall into disuse in the 13th century. The Mongol invasion of the late 13th century ensured decline in the waterway system because the invaders lacked the desire and administrative skills to maintain the complicated system. Plans for rebuilding were initiated early in the 20th century by the British and repair of old systems and construction of new are ongoing. Most new construction has occurred in the delta along the Shatt al Arab to drain the marshes. Engineered waterways serve three purposes - irrigation, flood control, and drainage. Irrigation structures occur throughout the valley, whereas drainage structures are most common in the delta of the two rivers, south of An Nasiriya. Flood control structures, mostly in central Iraq, tend to consist of off-river overflow basins in non-irrigated areas. The Euphrates, slightly higher in elevation than the Tigris, functions as the water source, and the Tigris serves as the drain. We will show examples of engineered waterways to include ancient canals once used for shipping but now restricted to irrigation purposes, older local canal systems, overlays of modern canal systems on older systems, examples of salt intrusion, and modern flood control systems in the area between Baghdad and An Nasiriya using high resolution satellite imagery.