Operational management of Nile water intakes: assessing safe submergence against ship and wind-induced vortexing

Abstract

Water intakes in navigable rivers like the Nile face significant risks of air-entraining vortices due to ship- and wind-induced surface fluctuations, which conventional static submergence criteria fail to address. This study evaluates these dynamic effects and develops an integrated framework for determining Safe Minimum Submergence Depth (SMSD) in the Aswan-Esna reach (158 cross-sections). Traditional Froude-number-based formulas (e.g., Hydraulic Institute [28]) were combined with Schijf’s primary drawdown, Kelvin wake secondary waves, and fetch-limited wind wave models (USACE, Young &Verhagen). New Excel VBA macros automate cross-section hydraulic properties, blockage ratios, and submergence calculations, while a Python framework (using Geopandas and Shapely) computes effective fetch via ray-casting for accurate wind wave hindcasting. Results indicate that vessel and wind waves necessitate SMSD values of 2.60-2.80 m (versus ~ 1.06 m under static conditions) under worst-case scenarios. The developed tools provide practical decision-support for resilient intake design and operation. This work advances river hydraulic engineering by bridging vessel hydrodynamics, wind wave mechanics, and intake design.