Water in Iran: Fragmentary Thoughts on Qanat
Irrigated land in Iran, according to the CIA: 75,620 sq km (1998 est.) For comparison, irrigated land in the entire European Union in 1998 from the same source: 115,807 sq km.
Much of Iran is basically a desert plateau. The mountain areas get precipitation, but without intervention, that precipitation translates into flashfloods with little water table, a geological reality which makes sustained agricultural development rather difficult. So, for the past couple of thousand years, Iranians have built and maintained a crazy-cool system of what they call Qanat.
As this site explains, a Qanat is essentially a manmade underground river running from an aquifer in the mountains to a lower-altitude farm or population center: "The trick is to make the angle of the qanat not too steep, because in that case, the water will grind itself down into the bottom and create pools that will make the qanat collapse; on the other hand, if the angle is not steep enough, the water will be tainted. Everything depends, therefore, on the correct angle." The longest Qanat in Iran, according to that source, is supposedly 70 kilometers.Here's another explanatory diagram. The underground part is necessary to minimize evaporation under the Iranian sun, but someone needs to crawl down the regular shafts every spring to clear out the debris that accumulates naturally.
Qanat systems are an effective--albeit fragile--solution for moving water from upland wettish areas to lowland arid areas. According to this proposal, Iran is discovering the hard way that drilling wells simply increases desertification. Favorite quote from that source: "In the past few years, due to lowering of water table levels and increasing salinity, the Ministry of Agricultural Jihad has started to revive the Qanat systems. Although these efforts have been so organised, but they have proven to be relatively effective." According to this source, some 30,000 Qanats are active in Iran today.
Besides being totally cool on its own merit and thus worth knowing about, the Qanat system would probably go to hell immediately upon any bombing campaign, even one that aimed for military targets.
[Edited for clarity.]