Capability of Rainwater Harvesting Systems to Provide Water Requirements in Hillside Orchards of Semi-Arid Regions

The present research has been executed in order to investigation of rainwater harvesting systems capability in runoff generation for supplying part of water required for hillside orchards. It is an innovative effort to establish a close link between watershed management activities and the production of horticultural products with a food security approach. Towards this attempt, in Chaharmahal and Bakhtiary province, 9 rectangular rainwater harvesting systems with dimensions of 4 × 3 m2 and 3 different managerial treatments (insulator surface, removed surface and natural vegetation cover) with 3 replicates and completely randomized design were made on a slope of 20 percent. At the end of each system, a reservoir has been installed to collect runoff coming from the plot. Rainfall amounts are estimated using a rain-gauge nearby and runoff volume was measured in the reservoir. Compare of the mean of treatments indicated that the system with insulator surface has generated the maximum runoff volume. The runoff volume generated by insulator surface was 5 times that of removed surface and 17.5 times that of natural vegetation cover. The results showed that the mean runoff coefficient derived from the systems with insulator surface, removed surface and natural vegetation cover were respectively 64.3, 7.7 and 1.8 percent. Also, the results showed that rainfall less than 5 mm has generated runoff only at insulator surface. Therefore, the other advantage of using insulator surfaces can be considered in the production of runoff in minimum rainfall. This issue, due to the frequency of rainfall events with values less than 5 mm in arid and semi-arid regions, makes it more necessary to use the insulator surfaces for harvesting of rainwater in these areas. So the use of insulator surfaces along with the installation of a runoff storage system and distribution of stored water in dry months is recommended to supply part of the water needed for hillside orchards.