Water - Harvesting Designs for Fruit Tree Production in Dry Environment
Water scarcity and increasing demand coupled with climate change require maximizing the use of avail-able resources. Water harvesting (WH) systems are currently being used in many areas to sustain crops and increase water productivity. This study investigated the effect of three treatments (S15: 50-m2catch-ment area with 15% slope, S8: 50-m2 catchment area with 8% slope, and L8: 70-m2 catchment area with8% slope) on the amount of water harvested in tree basin for young olive (Olea europaea L.) trees from November 2002 to July 2003. Soil moisture was monitored weekly during the rainy season and bi-weekly afterwards. To determine moisture changes in the catchment and target areas and amount of water harvested (in liters) for each tree, volumetric soil moisture content was measured at three or four pointsalong the slope using a neutron probe down to a maximum depth of 120 cm, as soil depth allowed. WH structures increased soil moisture content in the root zone compared to the catchment area. The rainfall threshold for runoff generation was less than 15 mm. Land slope was more important than micro-catchment size for increasing the amount of water harvested. Compared to the 8% slope, the 15% sloperesulted in larger harvested amounts for small storms, but the two were comparable when storms werelarge. The large micro-catchment size resulted in higher amounts of harvested water only in the presenceof storms greater than 26 mm. After adding the amounts lost by evapotranspiration, the net amount ofwater harvested in the tree basin of each tree for the 2002–2003 rainy season reached 722 and 688 l(or 361 and 344 mm) for treatments S15 and S8, respectively. Deeper soil profiles (i.e., >90 cm) wereimportant to ensure longer storage periods. By early July, soil moisture content in the tree basin fortreatments S15, L8 and S8 was still higher by 38, 13, and 5% respectively, than the levels recorded atthe onset of the experiment. WH increased soil moisture content during the spring and early summer, acritical period for olive production.