Soil Ecology Restoration Group

last update October 28, 2000

Rainfall Catchments Improve Survival of Container Transplants at Mojave Desert Site


Abstract

Deserts of the southwestern United States experience infrequent thunderstorms that bring large quantities of rainfall. This limits soil moisture, with favorable conditions for plant establishment typically occuring in only one out of five years (Cox and others, 1982). Lack of water is usually a limiting factor for restoration efforts in these areas and irrigation costs may more than double project costs. Ancient desert civilizations often did not have the resources to transport water over long distances, but they did develop systems for utilizing local water supplies (Shanan, 1979). Over 2,000 years ago, the Nabateans used dams and diversion channels to guide runoff from flash floods to irrigate crops (Evenari and others, 1982). Similar techniques were also used by other peoples in ancient Arabia, North Africa and pre-Columbian America. The rainfall catchment, using soil and stone berms to channel water into a simple basin, is one of the most useful techniques developed by these ancient farmers. These systems provide many advantages over other irrigation techniques. They are simple, inexpensive to construct, and can be built rapidly using local materials and manpower. Runoff water has a low salt content and, because it does not have to be transported or pumped, is relatively inexpensive. It was with this in mind that we set up an experiment to determine whether rainfall catchments could be adapted to a restoration setting, whether they increased survival rates for container out-plantings of native species, and which native species were best suited for the technique.