Operational hydrodynamic model for the lagoon of Nador (Morocco)

Project leaders

Georg Umgiesser, Karim Hilmi

Agreement

MAROCCO - CNRST - Centre National pour la Recherche Scientifique et Technique

Call

CNR/CNRST biennio 2018-2019 2018-2019

Department

Earth system science and environmental technologies

Thematic area

Earth system science and environmental technologies

Status of the project

Extended

Report for renewal

joint-report-mbj2-ggu-fm-firmato.pdf

Research proposal

1 Introduction and project motivation
The Nador lagoon, located on the coast of Morocco to the E-NE of the city of Nador, is one of the most important water bodies of the Mediterranean and it is classified as site of biological and ecological interest (SIBE). Nador is the largest lagoon of Morocco with an area 115 km² and is separated from the sea by a dune ridge 25 km long, elongated parallel to the coast in the N-S direction. It communicates with the open sea through an inlet, known locally as "Bokana" and the bathymetry values are between 1 and 8 m, with a maximum located in the central part of the lagoon (Houssa & Abdellaoui, 2002). In the past, the lagoon of Nador was connected with the sea by one of approximately 80 m wide channel, but in the late 1970s this channel was closed because of increased sedimentation and a new 300 m channel was dug. Faced with bad environmental situation, the government decided to build a new wastewater treatment plant (WWTP) and a new navigation channel, not far from the old inlet, to allow a better water exchange between the lagoon and the open sea, improving the lagoon water quality.

Due to its socio-economic importance for the region, this lagoon has been the subject of various studies focused to investigate its hydrological behaviour with impacts on sediment transport, fisheries and aquaculture aspects (Abdellaoui et al., 2005, 2006, 2015; Arid and al., 2005; Guelorget et al., 1987; Hamoumi, 2012; Lefebvre et al., 1997, Malouli et al., 2003). Studies on the Nador lagoon hydrodynamics and physical processes, connected with the old morphological configuration with the old inlet, are few (Hilmi 2005; Hilmi et al., 2003, 2005, 2007; Orbi et al., 2006; Umgiesser et al., 2003, 2005, 2014) and almost nonexistent in the configuration of its new inlet (Hilmi et al., 2015). For this reason the main objective of this project is to create a decision support tool allowing the Nador lagoon management by means of a three-dimensional circulation model (3D) in near real operating mode. This will allow to understand better the hydrodynamic of the lagoon and to study the impact of water exchange of the new inlet on the Nador lagoon ecosystem.

We propose to renew this project for a period of two more years (2018/19) where we can use the data collected in order to thoroughly validate the model developed in the last two years. We also propose to apply a sediment transport model to study the sediment re-distribution inside the lagoon and the sediment dispersion from the lagoon into the open sea. This new process study is especially important in view of the new inlet installed in the Nador lagoon, where higher discharge is going through the inlets.

2 Materials and Methods
The three-dimensional hydrodynamic model SHYFEM, which is a state of the art finite element based numerical tool, will be implemented in the Nador lagoon. The hydrodynamic model SHYFEM consists in a 3D shallow water hydrodynamic model, coupled with a wind wave model and with a sediment transport, water quality and lagrangian model. SHYFEM has been developed at ISMAR-CNR (Institute of Marine Sciences - National Research Council; Umgiesser et al., 2004) and been already and successfully applied to several coastal environments (see Umgiesser et al., 2014 for a complete list). The model resolves the shallow water equations in their formulations with water levels and transports. The finite element method permits to reproduce complex morphologies and bathymetries.
In the past (before 2011), the 3D hydrodynamic models, developed and implemented for the Nador lagoon (Hilmi et al., 2005 a, b, Umgiesser et al., 2003, 2009 and 2014) provided information on the parameters of tide and current.
For the new inlet configuration of this project, the (3D) three-dimensional model for the lagoon of Nador will focus on the physical parameters of the lagoon (tide, current, temperature, salinity) in operational mode using its new inlet configuration.
The model will be also applied to simulate the sediment transport inside the lagoon and the sediment loss from the lagoon to the sea. This application should give some insight in the process of sediment dispersion and re-distribution, an important process for the Nador lagoon.

3 Impacts scientific, technological and/or socio-economic
This project contributes to the preservation of the Nador lagoon environment, a site great biological interest and a major Mediterranean challenge for biodiversity and the environment.
The project results will provide relevant information for the decision-makers and follow-up with local authorities, governments, and also to the various lagoon stakeholders (fishermen, fish farmers, community of scientific research).
The socio-economic benefits are important in the short, medium and long term. This project will create databases and management positions at the university to provide training to operational oceanography students who are very useful profiles and occupations of the future for Morocco. Two doctoral students will be involved in this project for these aspects.
Finally, in addition to its innovative character due to the establishment of a coordinated approach between all the local actors and tools for managing and sharing information, this project will provide a best practice example in the Mediterranean Sea, particularly for the countries of the southern shore.
This follow up project will allow the thorough validation of the model with data that have been collected in the last project and interpret the renewal times of the lagoon with the new inlet. It will especially allow to prepare the model for an operational computation of hydrodynamic parameters as well as salinity and temperature. The sediment transport module will give new insights in the sediment dynamics, an important process for all lagoons in Morocco.

Research goals

o Adapt a mathematical modeling tool and implement it for the Nador lagoon

o Study the exchange of the lagoon with the sea in order to better understand its ecosystem

o Apply a sediment transport module to study the re-distribution inside the lagoon and the dispersion of sediments to the open sea

o Better understand the issues of the Nador lagoon

o Better understand the new hydrodynamics of the lagoon after the installation of its new inlet

o Provide essential information to the government for decision-making processes

o Through this project, contribute to the coherence of public policy around the development of the management and protection of the lagoon

o Create a website platform for the dissemination of the results generated from the 3D model and the project

o Organize seminars and training for Moroccan students in Master / PhD and produce scientific publications

Last update: 12/10/2024