Prospective of the utilization of rainfall in coastal regions in the context of climatic changes: case study of Egypt

Changes in climate drivers are projected to have a considerable impact on coastal freshwater supply and demand systems in future decades. The utilization of rainfall in coastal regions to secure sufficient freshwater to satisfy the rising demands of socioeconomic development has become a critical duty for decision-makers. This article assesses the present state of rainwater utilization in the water resources system for the coastal regions in Egypt. Volumes of annual rainfall that precipitate in 11 coastal Egyptian cities are estimated using ArcGIS maps and the run off rational equation. A future vision of using the estimated rainwater harvesting (RWH) from urban coastal cities in the water resources system is presented. Several scenarios are suggested and analyzed for using these volumes of water in the total water resources system in Egypt and also in the water resources system corresponding to each selected coastal governorate. The results indicated that over the areas under consideration, the annual maximum total amount of precipitation is limited to 1.8 km 3 . However, it is anticipated that 1 km 3 of the average annual quantity of rainfall water is efficiently used for agriculture. These findings are intended to help managers, planners, and decision-makers to choose locations, invest in water resources, and employ RWH as a substitute for traditional water sources.