JERUSALEM (Jan. 27)
Trees are growing in the Negev desert in areas where they have never grown before, thanks to the efforts of Hebrew University Prof. Aharon Yair.
Yair has developed a method of “water harvesting” that allows trees to be grown in areas where there are only four inches of rain a year.
Water harvesting is not new. It was used extensively by the ancient Nabatean people who farmed the Negev 2,000 years ago. They planted their crops in the small areas of soil at the foot of hills using runoff water that they directed through channels from the rocky hill tops.
Yair and his colleagues at the Hebrew University and at the Blaustein Institute of Desert Research at the Ben Gurion University in the Negev found that more water is in fact caught in the middle of slopes, in a “fertile belt,” where most of the runoff water from the rocks at the top of the ridge is absorbed and held at depth without evaporating.
The water collected in this belt is equivalent to some 10-12 inches of rainfall, and would suffice to grow trees in areas with only four inches of rain a year.
Four years ago, the Jewish National Fund helped Yair conduct an experimental planting of carob and pine saplings in basin-like furrows he designed in the fertile belt below a rocky ridge near Sde Boker, David Ben Gurion’s kibbutz.
The first two years of the experiment were drought years and the runoff was the sparsest in 25 years, yet the saplings developed well without irrigation, and grew as well as trees planted in more northerly and wetter regions.
The JNF is planning to unveil Yair’s grove of trees as part of the Ben Gurion centenary celebrations, and is planning to use the technique for growing several thousand trees, including trees of economic value such as olive trees, on hitherto uncultivated slopes in the Negev.