In some parts of the Atacama desert it has not rained for at least 400 years. Someone told me it is the driest place on earth and given how much the inside of my nose was itching the whole time we were there I have no reason to disagree with them. However, just outside the village of Toconao, about 50km from San Pedro de Atacama is one of the most curious things I have ever witnessed – an incredibly fertile valley maybe 60m across, bounded on each side by incredibly steep walls of pressed sand.
The reason for this is that they are blessed in that place by a small stream that flows out of the Andes down into the plain below. This stream of course never meets the sea, it is used in full by the people who live there. Interestingly the Atacama desert was not always so dry, when the land was first colonised about 12000 years ago the area was significantly wetter than it is now and since then the population have had to employ increasingly ingenious methods to cope with the drier and drier conditions.
The stream is maybe 1.5m across and is extensively canalized as it comes down through the valley. Small stone and clay channels snake off from the valley floor to the most amazing gardens of peach, grapes, chirimoya (custard apples), pomegranates and oranges as well as a whole load of indigenous plants I forget. There was one tree that was apparently growing something akin to alfalfa which they use to make some local moonshine.
Critically, no-one owns the water that flows down the valley. Instead there are a series of rules that determine who has access to it, for how long and when. A series of sluice gates control the flow of the water and it is a criminal offence to touch them if you are not an official from the local government – water monitors I guess.
Each person receives a share of the water flowing down according to the size of the garden they own, at an appointed day and time. If there is a drought, everyone's share is commensurately less. Taking water at a time not allocated to you will earn you a trip to see the popinjay Caribinieri, which I imagine you would not want.