Changes

Probably one of the most important developments to enable more advanced water technologies was the development and use of iron. In fact, the increasing sophistication of mathematics and engineering by the 1st millennium BC, along with iron technology, enabled the next major phase of development for irrigation technologies to occur. With the use of iron, rock could be excavated more easily. This facilitated the development of more sub-surface irrigation features, including tunnels and qanat systems(Figure 2), which were essentially tunnels with access holes that brought water from highland regions to lowland areas. These qanats also required a large amount of engineering, as channels had to be cut across mountains or difficult hilly areas, while channels were sometimes even cut from different areas and were met some place in the middle. Surface channels cut into mountain rock were now also developed, which allowed the capture of water from elevated regions. These technologies appear to have developed perhaps in Anatolia, Iran, or Arabia, although the origins are not completely clear. During the Iron Age (early 1st millennium BC), another important development occurred. That is, the development of aqueducts began to appear. In fact, the first aqueduct we know of developed in northern Iraq, just north of the city of Mosul. This aqueduct, part of a large canal system bringing water to the city of Nineveh, enabled water to be brought over different watersheds. In other words, it now allowed societies to build irrigation features that crossed natural elevation change that would have restricted where you could irrigate. [[File:Qanat.jpg|thumbnail|Figure 2. Qanata system (arrows) showing the access holes. Underneath lies a tunnel that would have carried water to agricultural fields.]]