Hydrological Analysis of Flooding Wastewater Lake in Jeddah, Saudi Arabia

Wastewater Lake, known as Almisk Lake, has been the dumping site of Jeddah’s sewage for the last ten years. The lake was created as a stopgap measure to deal with the increasing amounts of wastewater in the growing city. It is located along wadi Bani Malek; the biggest wadi in east Jeddah (302 km^2). The lake covers an area of 2.88km^2 at a site 130 m above the mean sea level. A non-engineered earthen dike was built to prevent the wastewater polluted by toxic industrial wastes from flowing back to the city. About 40,000 m^3 of wastewater are transported to the lake every day and expanding significantly. Water levels are continuously rising. With winter rainfall, dangerous environmental consequences from wadi Bani Malek floods arise. Residents in the east of the Jeddah highway are in fear over the dam collapsing. Fears of Sewage Lake could overflow and flood Jeddah city are growing strongly. The purpose of the present paper is to simulate the floods of wadi Bani Malek at the lake site for various return periods to evaluate the threats on the lake, to develop conceptual model to evaluate the impacts on the subsurface flow to Jeddah city. Hydrological conditions for the study area were sought. The Watershed Modeling System (WMS) and Hydrological Modeling System (HEC-HMS) models were used. Water budget components for the lake were calculated. Proposed measures to alleviate the threats of the lake have been recommended. Results of the paper will promote ongoing solutions for sewage disposal in the city of Jeddah.