Potential assessment of runoff harvesting in rock outcrop catchments (Case study: Qohestan park watershed, Qaen, Southern Khorasan, Iran)

Valuable studies have been conducted in recent years to collect water from impermeable urban levels in some parts of the country. Nevertheless, the background of the studies in this field has been poor in south Khorasan province, Iran. This study aims to help urban planners and managers to recognize the potential of water harvesting. The purpose of this study is to identify and prioritize the sub-catchment covered by the rock outcrops playing an important role in runoff production. This work was carried out via the modeling of runoff by empirical methods and the SWMM model in Qaen urban watershed. Accordingly, it is possible to determine the amount of water available for supplemental irrigation of the urban green space and thereby provide a suitable extension pattern for similar areas. The irrigation in the urban park is done by well, which is a major problem for Qaen, as an arid area. About 54% (248.4 ha) of the basin surface has been populated by the 90% rock outcrops that has high runoff potential and can be useful in planning in terms of high potential of runoff production. Considering the existing facilities and the number of park trees, an approach is needed. The water shortage for supplemental irrigation of this park will compensate, if only 10% of the annual runoff equivalent to 11800 m3 can be harvested and stored during the months with no precipitation.