Capability of rainwater harvesting systems in semiarid area for establishment of plant coverage

Making rain water harvesting micro catchments systems for hoarding rainwater is one of the forward ways to supply water. Performance of these systems is affected by climate specially intensity, duration and frequency of rainfall events, time distribution and their technical specifications such as figure, area and runoff coefficient. By this means rainwater plots built with dimensions of 4m×5m with surface treatments of impediment, semi impediment and natural (undisturbed) with 4 blocks that located on eastern hillside with slope of 15 to 25 percent. Daily rainfall and likes produced runoff for period of 4 years and totally 68 daily rainfall events that caused runoff (at least at 1 plot of impediment treatment from 4 repetitions) were measured. Results showed that in semiarid climate, for average frequency of daily rainfalls with depth of equal or more than 1 and 5 mm for warm months (season of plants growth and production) include July, August and September were 1 for every 1 year and 1 for every 3 years respectively. So the threshold of daily rainfall for runoff occurrence due to treatments of impediment, semi impediment and natural respectively nearly were 2.1, 3 and 5 mm and average percentage of runoff coefficients 34.93, 3.81 and 0.68 for period of May to November of every year. Conclusion is that application of impediment rainwater catchments associated with runoff reserve systems from rainy months (April and May) and reserved water distribution systems in more water needy months of plants (July, August and September) is recommended.