They wondered how much water a particular tree could collect. In this way they were able to select the trees suited to be used in reforestation. In the end they succeeded in creating ten hectares of forest able to survive by itself - and there are plans for bigger projects. Ultimately they hope to make the forest big enough to produce more water than it needs for itself. The surplus will create little streams which can be used to drink and other purposes.
Water is never just a meteorological problem.
It is never just a shortage of water. In the desert too there is water and nature knows how to make use of that. Even in the driest spot on earth you can find water. And with that water you can break the vicious circle. If you don't have QuickTime, use the link below and download Quicktime from the Apple site.