International Conference on Civil and Environmental Engineering
Hurghada, Egypt, November 24-26, 2018
ASSESSMENT OF THE CURRENT SITUTION OF LAKE MANZALA,
EGYPT
O. M. Shalby1, M. R. Soliman2, H. M. Moghazy3, W. R. Elsayed4
1
Coastal Research Institute (CoRI), Alexandria, Egypt
e-mail: omniamahmoud24@yahoo.com
2 Irrigation Engineering and Hydraulics, Alexandria University, Alexandria, Egypt
e-mail: rera_hydro@hotmail.com
3 Irrigation Engineering and Hydraulics, Alexandria University, Alexandria, Egypt
e-mail: hossam_moghazy@yahoo.com
4
Coastal Research Institute (CoRI), Alexandria, Egypt
e-mail: walidelsayd@yahoo.com
Abstract: Lake Manzala has undergone significant recent changes, particularly in recent years, due to
the regulation of freshwater flows, land reclamation and increase of BOD and nutrients effluents. It is
located in the northeast quadrant of the Nile Delta, between 31o 00`-31o 35` N latitude and 31o 45` - 32o
15` E longitude. The lake is 35 km length from northwest to southeast and 30 km width. Lake Manzala is
shallow; ranging from 0.7 to 1.5 m in depth. The lake receives about 6.8 billion cubic meters per year of
drainage water. The flushing of the lake through the three inlets (boughaz) is not sufficient to improve the
water circulation and quality inside the lake. Delft 3D model has been applied to simulate the present lake
circulation and water quality parameters. Through simulation, the lake was divided into 6 zones according
to water quality. Both the developed hydrodynamic and water quality models were calibrated to examine
flushing drains’ effects on different water quality substances inside the lake. The salinity, dissolved
oxygen (DO), Biological Oxygen Demand (BOD), ammonium (NH4) and nitrate (NO3) during (2013-
2014) were used for the analysis and estimation of the water quality for the lake. Results indicated that the
numerical simulations were in good agreement with measurements values. For the regional variations, the
recorded measurements showed that the lake is, in general, brackish. The lake has high salinities in the
northern region of the lake due to impact of the sea. The salinities are slightly lower in the other regions,
which are strongly affected by drain effluents. The simulation results reveal that the salinities values in
the summer season are higher than in the winter season. The values of DO in winter are higher than in
summer. Simulation demonstrates that the southern east of the lake is the most zones have deteriorated in
water quality, which have dramatically decreased the rate of dissolved oxygen and high increase for
ammonium (NH4) and nitrate (NO3). This is attributed to the fluent comes from Bahr El-Baqar drain
which is considered highly polluted.
Key words: lake Manzala, Drains, DelWAQ, Hydrodynamic model, Water Quality, Bahr El-Baqar drain.
International Conference on Civil and Environmental Engineering
Hurghada, Egypt, November 24-26, 2018
1. Introduction: -
There are four large lakes (Idku, Burullus, Manzala and Bardawil) and one lake (Maryut) of
relatively shallow water bodies known as the Northern Egyptian lagoons. These lakes are
connected to the Mediterranean Sea by narrow openings, termed Boughaz except for Lake
Maryut, which is a closed lake. The first four lakes receive drainage water through agricultural
drains of freshwater from the Nile River [1]. The Lakes are an important natural resource for fish
production in Egypt. Until 1991, these Lakes have continuously contributed more than 40% of
the country's total fish production, on the contrary at present this has dramatically decreased to
less than 12.22% [2] , [3].
In the meantime, the lakes were exposed to a gradual reduction during the past few decades due
to land reclamation and alteration of significant parts of the lakes into fish farms, particularly
alongside the southern regions. In addition, large parts of the lakes are badly affected with
aquatic vegetation, which reduces the water body to nearly half of its total area, speeding up the
process of land transformation [2].
This study presents results of numerical simulating of the hydrodynamic and water quality
present state of lake Manzala using Delft-3D software [4], [5].
2. Materials and methods
2.1. Study area
Lake Manzala is the largest northern lake in Egypt, it is located in the northeast quadrant of the
Nile Delta, between 31o 00`-31o 35` N latitude and 31o 45`- 32o 15` E longitudes. It is bounded
by the Mediterranean Sea at the north, Suez Canal at the east, Damietta province in the North
West, and Dakahlia province in the southwest. The lake is 35 km length from northwest to
southeast and 30 km width, narrowing in the middle to only 15 km where the peninsula of Al-
Shabul protrudes. The lake depth is shallow; ranging from 0.7 to 1.5 m in depth, being composed
of about 30 basins varying in their depthes and water qualities [6].
The lake is connected to the Mediterranean Sea by the straits of El-Gamil, Ashtoum Al-Gamil,
Al-Baghdadi, El-Deiba and recently Al-Burg at the northwest corner of the lake. The lake
reaches the Suez Canal through a small navigating channel known as Al-Qabouti. These six
openings supply the lake with marine water.
It is an extremely dynamic aquatic system that has undergone significant physical, chemical
and biological variations during the past century. The lake has been gradually changed from a
largely marine or estuarine environment to a eutrophic fresh water system. This was an effect of
different features of human impacts of which: closing and opening of straits, construction of the
High Dam, silting of the lake, continuous drying processes for land cultivation sake and
pollution due to wastewater discharged into the lake. Drainage water contributes about 98% of
International Conference on Civil and Environmental Engineering
Hurghada, Egypt, November 24-26, 2018
the total annual inflow to Lake Manzala. Six drains are found to be carrying the fresh and
drainage water to the lake as shown in Fig. 1. Following are the mentioned drains with
comparative impact of the total flow in the lake as listed in table (1) [7]:
Table: 1. Contributions of drains to the Lake Manzala
Drain’s name Serving area contributes of the total inflow
Hadous drain 790000 feddans 49%
Bahr EL Baqar drain 536000 feddans 25%
Serw drain 68700 feddans 13%
Faraskour drain 20000 feddans 4%
Matareya drain 50000 feddans 2%
Fig. 1. location map of Manzala lake showing sampling stations.
2.2. Data collection
The data collected for building the hydrodynamic and water quality models can be represented in
three main sections, geometric data, hydrodynamic data and water quality data.
The geometric data was determined using remote sensing technique by investigating new
satellite image acquired from Coastal Research Institute (CoRI). This can be considered as the
International Conference on Civil and Environmental Engineering
Hurghada, Egypt, November 24-26, 2018
most important building block that defined the shape of El-Manzala Lake numerical model
because it was used by all other modules within the modeling process. The hydrodynamic
section included all the data responsible for simulating the water circulation and water level
conditions and variance between inside and outside the lake. In this paper, the authors have used
full one-year water levels and wind field measurements of the study area acquired by CoRI.
While the water quality section covers all the data required to simulate different water quality
processes for different substances inside the lake and investigated the effect of the drainage
effluents. All water quality measurements were determined by Egyptian environmental affairs
agency annual reports and source data [8], Drainage research institute (DRI) reports [9]which
was compared to data measured data by DHI in 2014 [10]. Khatita, Shaker and Shetaia collected
about Sixty-four water samples (30 cm depth) (16 samples every season) from 16 stations as
shown in Fig. 1 during 2014 [11].
2.3. Model setup
The model covers the study area and extends 16Km offshore reaching to depth of 18m. The
curvilinear grid cells vary from 200*400m to simulate the inside islands turned to be
concentrated and narrowed in the inlets to be 40*40m to get more accurate simulation of the
discharged water from and in the lake regarding that the difference between each two cells must
not exceed 20% of their minimum length as shown in Fig. 2. Bathymetric data was used for
meshing depth into the grids using grid cell averaging process in Delft3D for interpolation as
shown in Fig. 2. The model is forced by four open boundaries with water levels annual data
measured by CoRI, three for the sea and one to simulate the small channel connected with Suez
Canal as shown in Fig. 2. The time step of the model was calculated to be 5 minutes for the
hydrodynamic and 1 hour for the water quality module to keep the model structured and
unbreakable.
International Conference on Civil and Environmental Engineering
Hurghada, Egypt, November 24-26, 2018
Fig. 2.Model layout, grid and bathymetry.
2.4. Hydrodynamic calibration
The model was calibrated in two different steps. The first is the hydrodynamic process which
were conducted using comparison of the modelled and measured water levels as shown in Fig. 3.
Water velocity was compared in two main measured points, onshore sea station with current
variation between 0.2 to 0.4 m/sec and inside ashtom elgamil inlet with variation between 0.4 to
1.2 m/sec. It is clear that the model is highly calibrated with the last mentioned parameters.
Fig. 3.Modelled and measured water levels comparison
2.5. Water quality calibration
The water quality module was calibrated using DO, NH4, NO3 and Salinity data measured by
Khatita, Shaker and Shetaia [11] and Egyptian environmental affairs agency annual reports [8] as
shown in Fig. 4, Fig. 5, Fig. 6,andFig. 7 to show the DO, NH4, NO3 and salinity, respectively.
International Conference on Civil and Environmental Engineering
Hurghada, Egypt, November 24-26, 2018
The model shows particularly good attitude dealing with the last mentioned parameters and can
be relied on to conclude the water quality major state of the lake.
Fig. 4. Comparison of modelled and measured DO data
(A) Modelled Winter& (B) modelled Spring& (C) modelled Summer& (D) modelled Autumn&
(E) measured Winter& (F) measured Spring& (G) measured Summer& (H) measured Autumn
International Conference on Civil and Environmental Engineering
Hurghada, Egypt, November 24-26, 2018
Fig. 5. Comparison of modelled and measured NH4 data
(A) Modelled Winter& (B) modelled Spring& (C) modelled Summer& (D) modelled Autumn&
(E) measured Winter& (F) measured Spring& (G) measured Summer& (H) measured Autumn
International Conference on Civil and Environmental Engineering
Hurghada, Egypt, November 24-26, 2018
Fig. 6. Comparison of modelled and measured NO3 data
(A) Modelled Winter& (B) modelled Spring& (C) modelled Summer& (D) modelled Autumn&
(E) measured Winter& (F) measured Spring& (G) measured Summer& (H) measured Autumn
International Conference on Civil and Environmental Engineering
Hurghada, Egypt, November 24-26, 2018
Fig. 7. Comparison of modelled and measured Salinity data
(A) Modelled Winter& (B) modelled Spring& (C) modelled Summer& (D) modelled
Autumn& (E) measured Winter& (F) measured Spring& (G) measured Summer& (H)
measured Autumn
International Conference on Civil and Environmental Engineering
Hurghada, Egypt, November 24-26, 2018
3. Results
It is clear from the model that the western south zone of the lake is almost affected by the
islands’ existence as shown in Fig. 8 which presents the particles’ tracking of 16 particles in
different locations. The figure demonstrates that almost points where is close by the sea have
great circulation so it was the best part according to the water quality. It shows that part of Bahr
El-Baqar drain is discharged to Suez Canal by a small channel connecting the lake with the
canal. The western south part of the lake, the point couldn’t withdrawal the lake, consequently
the zone has bad circulation. From Fig. 8, the input data, model outputs and literature review, the
lake division into six zones according to the water quality properties as shown in Fig.
9. Zone (6)
is found to be the most polluted due to the influence of Bahr El-Baqar and Hadous drains. Lake
Manzala receives about 4000 million cubic meters of untreated industrial and domestic annually
into the lake through Bahr El-Baqar Drains so it has a large effect on the water quality of the
lake. Zone (4) is the second most polluted because the fragile water circulation as a result of
islands’ existence where the maximum velocity is 4 cm/sec. On the contrary, zones (1, 2 and 3)
are found to be better in water quality conditions due to interaction between the sea and the lake
with average velocity ranges from 20 to 35 cm/sec.
Fig. 8.Water particles tracking.
International Conference on Civil and Environmental Engineering
Hurghada, Egypt, November 24-26, 2018
Fig.
9.Divisions of water quality in lake Manzala
4. Conclusions
Lake Manzala is affected by different external factors especially, the advanced increase of
industrial and agricultural wastewater discharges. Bahr El-Baqar drain is most likely
contaminated with agricultural, industrial and domestic sewage. Hadous drain is contaminated
with agricultural chemicals. This study provides a clear evidence of water circulation decay rate
in the lake and the importance of new modifications into the lake body. The results from the
model indicated that the numerical simulations were in good agreement with measurements
values. Based on the results lake can be divided into six zones according to the water quality
properties, and accordingly, determine the characteristics of each zone. Hydrodynamic
improving solutions would be a very recommended as ray channels, new inlets or delivering part
of the drainage wastewater outside the lake such as Bahr El- Baqar drain. Dredging of western
islands would be considered very helpful solution to improve the water circulation in the western
zone of the lake.
5. Acknowledgement
The authors prescribe their acknowledge of the support given by Coastal Research Institute
(CoRI) for this study under the CoRI project of studying the future of Lake Manzala. Sincere
thanks are due to Engineer. Ahmed Mohamed Khalifa (Assistant Researcher, CoRI, Alexandria)
for his support, help in model creation and help with data gathering.
International Conference on Civil and Environmental Engineering
Hurghada, Egypt, November 24-26, 2018
6. References
[1]
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[2]
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WATER AND SEDIMENTS AND THEIR EFFECT ON OREOCHROMIS NILOTICUS
IN THE NORTHERN DELTA LAKES, EGYPT," in International Symposium on Tilapia in
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[3]
Y. Hamed, A. S. T. , M. A. E.-R. Hassan and R. Berndtsson, "Assessment of Heavy Metals
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[4]
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[5]
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[6]
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2008.
[7]
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[8]
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[9]
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[11]
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