Impact Assessment of Radial Channels Project on Water Quality Status in Lake Manzala, Eastern Nile Delta, Egypt

Abstract

Lake Manzala lies on the eastern north coast of Egypt and is considered as the largest Egyptian coastal lakes. Economically, Lake Manzala is considered as one of the most valuable fish sources in Egypt. The water quality status of the lake has been degraded due to the progressive increasing of industrial, municipal and agricultural wastewater discharge from six main drains. The lake has three main effective outlets, one to Suez Canal and the others to the Mediterranean Sea. A new project has been started in Lake Manzala to improve the sea-lake water exchange by dredging the two main lake outlets to the sea and constructing two radial channels from the lake to the sea passing through the two main outlets. In this work, a hydrodynamic, advection dispersion and water quality model for Lake Manzala was developed, based on MIKE21 modelling system. Eight water quality parameters were simulated (BOD, DO, Chll_a, NO 2 , NO 3 , NH 3 , PO 4 , and TP), in addition to three hydrodynamic parameters (water depth, water temperature and salinity). The model results show good agreement with the observed water depth, water temperature, salinity and water quality records. The calibrated model was used to investigate the impacts of radial channels on Lake Manzala hydrodynamic and water quality characteristics. The results show a significant improvement in the lake water quality status. Significant decreases in the average concentrations of some water quality parameters were noticed, comparing to the original calibrated status of the lake (-21%,-14%,-13% and-10% for PO 4 , NO 2 , NH 3 and Chll_aas examples). While an increase in the average concentration of DO in the lake by about 1% was noticed. Other water quality improvement scenarios for the lake should be investigated, in addition to the investigated scenario of radial channels, using the lake developed model.

Maximize the Benefits of ElBoghdady Outlet in Water Quality Status of LAKE MANZALA, EGYPT

“…The aim of this work is to make ElBoghdady outlet useful to water exchange between lake and sea by connecting the outlet directly to the sea and then connecting the outlet to the middle sector of the lake. The proposed project is to dredge two radial channels, one from ElBoghdady outlet to the sea with 2.8 kilometers long and 200 m bottom width [19]. And the other radial channel from ElBoghdady outlet to inside the lake with 10 kilometres long and 200 m bottom width passing between big islands based on Lake Bathymetry to let sea water arrives to the middle and the south sectors of the lake where there is a high level of pollution, Figure (3).…”

“…Figure (5): Water levels stations in Lake Manzala for EEAA [15]. Hydrological records and drain discharges were collected by National Water Research Center (NWRC), Egypt.…”

“…Also Elshemy et al [13 -14] used MIKE21 modelling system to build a Lake Manzala Mediterranean Sea hydrodynamic and water quality model for Lake Manzala in 2016 to study the future impacts of climate change on the lake. Finally, A Elhamaimi in 2018 developed a hydrodynamic and water quality model for Lake Manzala using MIKE21 code to assess water quality status of the lake and to test ten water quality management scenarios on Lake Manzala, [15]. The Lake has indirect and ineffective connection to the sea called ElBoghdady outlet.…”

“…The Lake has indirect and ineffective connection to the sea called ElBoghdady outlet. The main objective of this research work is to maximize the benefits of ElBoghdady outlet by developing a radial channel project on ElBoghdady outlet and using the calibrated model for Lake Manzala, Hassan et al [16] to assess the impact of this project on water quality status of Lake Manzala.…”