Water harvesting by wax-treated soil surfaces: Progress, problems, and potential

Abstract

Water-harvesting techniques can increase the useable water supplies of arid and semiarid areas. A relatively new water-harvesting treatment is the application of paraffin wax to soils to create a water-repellent catchment surface. The first two such catchments were installed at the Granite Reef test site in 1972 by applying ground paraffin wax (0.7 kg/m 2 average rate) atop smoothed, rain-compacted soils. Solar energy melted the wax into the soil. The catchments are still operational after 7 years of natural weathering. Average runoff efficiency (yearly runoff/yearly rainfall) for the two catchments averaged 87% for the 7 years. Year 7 averages were 85%, i.e., only 2% less than the 7-year average. Also, the 7-year average runoff efficiency of the two catchments was only 10% less than that of a plastic membrane, but was more than four times greater than that of a simple, cleared and smoothed soil surface and nearly six times greater than that of a small untreated, natural desert watershed. Several operational wax-treated catchments have been built to supply water to livestock on arid rangeland. Ranchers are pleased with them — equating them to permanent springs. Both laboratory and field tests indicated that the wax treatment is most successful on sandy soils containing less then 20–25% clay plus fine silt.