Solution

SMEC deployed a multidisciplinary team working in close collaboration to develop a sophisticated yet practical engineering solution that addresses the multifaceted challenges of water management in northern Mauritius. After a thorough assessment of various options, including new river diversions and upgrades to existing infrastructure, the team developed a comprehensive approach to enhance both the storage capacity and the efficiency of the water supply system:

• Enlargement of the La Nicoliere Dam to 34 metres: A critical component of the project is the proposed raising of the dam height by up to 20 meters, which will significantly increase the reservoir’s storage capacity from 5.2 million cubic meters (Mm³) to 16.0 Mm³. This expansion is essential to maximise inflows and boost resilience of the water supply during dry periods. The decision to raise the dam using a homogeneous embankment is supported by rigorous geotechnical investigations. Extensive lab testing was undertaken to identify any variations in the volcanic soils. Further research was undertaken to understand availability of earth fill downstream and availability of local stone for the production of concrete.
• Upgrades to water transfer: The project includes upgrading the La Nicoliere Feeder Canal (LNFC), which transports water from the Midlands Reservoir to La Nicoliere. This will involve a new 3km diversion, enhancing intake structures, and replacing outdated infrastructure, such as the Vacoas Siphon, with a new aqueduct. New river diversions from the Riviere du Poste and River Francoise will increase water inflow to the reservoir by approximately 15 Mm³ per year. A new concrete spillway weir and outlet structures will efficiently manage increased water volumes and prevent flooding.
• Innovative Water Management Strategies: Extensive hydrological analysis was undertaken to deliver a robust water balance model which assessed the optimum water quantity available. Training was undertaken with local operations teams in use of the water balance model to support sustainable, long term water management.
• Advanced Digital Engineering: The design for the new concrete spillway weir and outlet structures, combines the latest digital technologies with critical thinking. The Vacoas Siphon, a critical bottleneck in the system, will be replaced with a more efficient aqueduct. Additionally, three key sections of the feeder canal will be upgraded to enhance flow capacity. These tailored solutions are customized to meet the unique requirements of the project, ensuring resilience against future climatic uncertainties.
• Safety and Environmental Management: Throughout the project, SMEC sought to mitigate impacts on the community and environment, employing a robust dam safety management program, and ensuring the safety and stability of the dam structure. The project also focuses on transferring technical expertise to local staff, enhancing capacity building and sustainable management of water resources in the region.

Impact

The Enlargement of La Nicoliere reservoir study is a testament to SMEC’s commitment to delivering innovative and sustainable solutions that address the complex challenges of water scarcity. By combining technical expertise with a deep understanding of local needs and environmental considerations, SMEC is helping Mauritius secure its water future and pave the way for a more prosperous and resilient future.

By optimising water storage capacity, reducing water losses and improving the efficiency of the distribution network, the project will ensure a more resilient water supply. This will support agricultural activities, boost tourism, and promote industrial growth, contributing to the island’s economic prosperity.