Water harvesting using runoff is one of the approaches that reduces risk factors in the country and leads to a stability and sustainability in agricultural activities of arid and semi-arid regions. This work aims to assess the potential of rock outcrops (more than 90% of rock fragment) for supplementary irrigation in the Zoshk-Abardeh watershed. Results showed that runoff volume extracted from rock outcrops with an area of 433 ha in only four month (June, July, August, and September) will be around 866000 m³, which would decrease the reliance on watershed groundwater resources and compensate a significant part of water deficiency in dry season. Ecosystem function of rainwater harvesting in the studied watershed was estimated to be 650$/ha, which can establish the economic justification of these techniques.