The use of rainwater harvesting systems, through improved irrigation timing, increases crop growth and, consequently, improves wheat yield. Accordingly, this study was conducted with the aim of technical feasibility and evaluating the potential of rainwater harvesting for use in supplementary irrigation of rainfed wheat fields in Ramhormoz County. By analyzing rainfall patterns and water requirements of wheat, critical times of water shortage were identified. Areas susceptible to the construction of water storage structures (earth dam, earthen/concrete pool) were estimated using GIS and considering rainfall, soil permeability, evapotranspiration, land slope, land use and waterways. The volume of water that can be extracted was calculated by considering rainfall during the rainfed wheat growing season and by separating surface runoff and upstream basins based on area, rainfall amount, and runoff coefficient. The results showed that in terms of zoning, more than 72.5 percent of rainfed agricultural areas are concentrated in low-slope plains, which provide suitable conditions for the construction of runoff storage ponds due to low to medium soil permeability. The maximum volume of water that can be extracted from runoff produced during the growing season is 1396 cubic meters per hectare. Considering the volume of water consumed due to infiltration and the volume of water that can be supplied from the upstream basin runoff, it is possible to provide 89.3 percent of the total water required to convert rainfed wheat to irrigated wheat in all cultivated areas of Ramhormoz County. From the perspective of crop yield and based on water-dependent productivity indices, the use of runoff from the field and upstream catchments can potentially increase the yield of rainfed wheat by about 3.8 tons per hectare. The results also showed that rainwater harvesting from the upstream catchment is more efficient compared to rainwater harvesting from the cultivated area.