Development of an isopluvial atlas for Egypt using statistical and GIS-based methods

Rainfall across various climatic zones of Egypt, including arid coastal and semi-arid inland regions, exhibits significant temporal and spatial variability. Precise estimation of effective rainfall depths is essential for design engineers, hydrologists, and consultants involved in the construction of hydraulic structures such as dams, lakes, culverts, and diversions. Moreover, rainfall depth plays a crucial role in the design of urban drainage systems, small-scale irrigation projects, and broader water resource management initiatives. To address this need, an atlas of isopluvial maps for Egypt was developed using statistical methodologies and Geographic Information System (GIS) tools. This study employed short-duration rainfall data from various climatic zones of Egypt to create an empirical formula for estimating short-duration rainfall depths. Maximum annual daily rainfall data from 54 stations were analyzed to estimate short-duration rainfall values. The analytical process used Gamma distributions to determine maximum rainfall depths for various return periods and durations. The derived empirical formula and daily rainfall data were then incorporated into a GIS framework for spatial interpolation and the generation of isopluvial maps. The resulting atlas provides isopluvial maps for return periods ranging from 2 to 200 years and durations from 5 minutes to 24 hours. These maps serve as a valuable resource for decision-makers and design engineers, providing reliable rainfall estimates for specific locations or regions across Egypt. Additionally, the methodology presented in this study offers practical guidance for understanding and modeling the temporal and spatial distribution of rainfall in diverse climatic regions; its potential for improving the design of hydraulic structures is highlighted. Further validation of the atlas using independent datasets is recommended.