Microcatchment Water Harvesting for Olive Production in Water-scarce Environments

Abstract

Since time immemorial, people in dry environments have harvested water from rainfall for drinking, washing, livestock watering, and crop production. Motorized drilling equipment and pumps, as well as government-controlled dams, reservoirs, and pipelines, have greatly replaced this sustainable practice. Still, the establishment of small earthen dikes, in a v-shape or semi-circle just down-slope of the tree, allow the harvesting of a critical water supplement for olive production in water-scarce environments. To provide recommendations for the development of farmer-based micro catchment water-harvesting systems, research was conducted in a recently established (1999), untilled olive orchard on the limestone hill slopes of Khanasser Valley, Syria. Long-term average winter rainfall in the valley is low (210 mm), but events that produce runoff on these stony slopes occur regularly. Small and large micro catchments (50 and 70 m2) were established on 8% slopes (S8 and L8) and 50-m2 catchments on 15% slopes (S15). Soil moisture measurements were taken with a neutron probe in the tree basin and in the catchment area every week during the rain season. The average amount of water harvested during the wet 2002/03 season (302 mm) was 121 L for L8, 140 L for S15, and 150 L for S8. The benefits of water harvesting for these young trees were reduced by the limited depths of the soil profile (45-120 cm). The research activities and discussions with olive growers in the valley have motivated a number of farmers to apply water-harvesting techniques in both tilled and untilled orchards on the slopes.