rainwater harvesting for supplementary irrigation of rainfed wheat in mashhad region

abstract rainwater harvesting (rwh) is one of the most effective water resources management techniques for confrontation with water shortage condition. rwh which is basically known as a traditional method, has been developed rapidly and being used widely in dryland countries throughout the world. rwh is defined as collecting and storing rainwater from nearby catchment and delivering it to planting area during critical stages of plant requirement. rwh can be divided into two main categories which is known as micro and macro catchment methods. many factors such as rainfall amount and distribution, ground topography, soil type, economical and social aspects are important for selecting a specific rwh category. in the present paper, design and performance of a real size macro catchment rwh project located in a semi arid region (n-e of iran), is described. the project is comprised from a 5000 m2 plastic covered catchment, 500 m3 ground reservoir and an experimental cultivation area located next to runoff catchment which is planted with dryland wheat. planting area is consisted of 8 scaled plots with dimension of 6m by 85 m. following a randomized completely blocks design, four plots were considered for supplementary irrigation and the rest four replications were accounted as control (without irrigation). in an effort to conserve more water, drip irrigation system was used with 4 lit/hr/m discharge capacity. the results of two years study indicated that, compared to the conventional dry land farming undertaken in the control plots, wheat grain yield was increased by 70% and 87% respectively. during the study period, 35% and 70% of wheat water requirement was supplied from rwh system during plant growth period respectively. the result showed that it would be possible to have productive wheat cultivation in the regions with 250 mm annual precipitation (in average), if one can employ an effective rwh system.