Jay R.S. Doorga, Earth and Ocean Lab, Université des Mascareignes
Ryan Tannoo, École nationale supérieure d’architecture de Versailles,
Université Paris-Saclay, Orsay, France
Sum Yue Chung, Center for Policy Research on Energy and the Environment,
Princeton University, Princeton, USA
Anthony Odongo, African Institute of Environmental Research and Geospatial
Technology. Kakamega County, Kenya
EXECUTIVE SUMMARY
The article explores adaptive water management solutions in Mauritius, A Small Island Developing States (SIDS) increasingly exposed to the effects of climate change.
It underscores critical challenges, including a long-term decline in rainfall, growing water demand driven by population and economic expansion, and significant losses within water distribution systems. These pressures underline the urgent need for flexible, inclusive, and sustainable water management solutions.
A central recommendation of the study is the development of small reservoirs to harvest and store surface runoff. Designed using a multi-criteria framework that integrates environmental, engineering, and socio-community factors, these reservoirs represent a practical, locally tailored response to water scarcity. While immediate financial returns may be modest, their long-term value lies in enhancing climate resilience, supporting agricultural productivity, and promoting social equity.
The study also emphasizes the importance of integrating multidisciplinary expertise, participatory governance structures, and sustainable financing partnerships. By promoting decentralized water infrastructure and empowering local communities, this approach seeks to build systemic resilience to drought and water scarcity.
The case of Mauritius also offers a scalable and replicable model that other island nations facing similar water and climate challenges can benefit from.
Introduction
Mauritius, like many Small Island Developing States (SIDS), is grappling with the increasing severity and frequency of drought events caused by climate change. Despite contributing minimally to global greenhouse gas emissions, small islands face some of the most immediate and severe impacts of climatic shifts. This article summarizes key insights and recommendations from a recent technical study that explores adaptive water management strategies tailored to the Mauritian context, with an emphasis on the construction of mini reservoirs to enhance water resilience.
Context and Challenges
Groundwater and surface sources are the main sources of water in Mauritius, with approximately 50% coming from groundwater via 163 boreholes, and the remaining 50% from surface sources, including seven major reservoirs. In this context, data from 1931 to 2020 reveals a significant decline in annual rainfall, with some regions experiencing reductions of up to 22.3% in surface water recharge and 24.7% in groundwater recharge. These changes are attributed to rising temperatures, increased evapotranspiration, and climate variability driven by the Indian Ocean Dipole (IOD) and the El Niño–Southern Oscillation (ENSO). Population growth and economic development have added further stress. By 2020, nearly 60% of water distributed through the national system was lost due to leakage and inefficiency. Although Mauritius receives about 3,700 million m³ of rainfall annually, only 8% of this runoff is effectively harvested, with the rest lost to the sea.
Research Objectives and Methodology
This study aims to enhance water security by identifying optimal locations for small off-channel reservoirs. Using a Multi-Criteria Decision-Making (MCDM) framework supported by the Analytic Hierarchy Process (AHP), the study assessed hydrological, geospatial, and socio-economic variables to evaluate the feasibility of capturing untapped runoff.
Key site selection criteria included:
- Proximity to water stressed regions
- Nearness to rivers
- Land elevation and slope
- Proximity to human settlements
Advanced modeling techniques such as GIS-based interpolation (IDW) and QGIS tools were used to simulate rainfall trends and potential capture volumes
Key Findings
Rainfall Decline and Recharge Stress
Long-term precipitation data revealed a sustained decline in both surface and subsurface recharge, particularly in the North and South, with areas like Grand Sable, Isidore Rose, and Souillac identified as high-risk drought zones. In this context, harnessing surface runoff emerges as a critical strategy, as surface water flowing toward the sea represents a valuable freshwater resource. However, the island’s geography causes rapid surface runoff after rainfall, resulting in low or no flow shortly afterward, leading to the loss of this water to the sea. This rapid conveyance of freshwater to the sea means that the residence time of surface water on the island is very short. The hydrographs of streams and surface water bodies in Mauritius exhibit sharp peaks and rapid recession limbs, indicating a fleeting period of high flow followed by a swift return to baseflow conditions, which can often be negligible or even zero shortly after a rainfall event.
The geographical constraints of the island inherently lead to a low efficiency in retaining precipitation as readily available freshwater. Harnessing the initial pulse of surface runoff becomes critical because this ephemeral resource represents a substantial, albeit short-lived, component of the island’s water budget that would otherwise be lost to the sea.
All major reservoirs in Mauritius are located in zones where rainfall has decreased significantly. For example, the La Nicolière reservoir in the North, which is critical for potable, agricultural, and industrial use, is under pressure.
Rising Demand and Infrastructure Pressure
The population of Mauritius has increased by over 160% since 1950, substantially raising water demand. The domestic sector alone accounts for 78% of total usage. Seasonal shortages are common, especially in December, February, and July.
However, addressing this growing demand faces significant challenges. Aging infrastructure and poor maintenance contribute to major water losses, over 60% of water is lost through leaking and faulty pipes. Tackling the substantial water losses from aging infrastructure is a necessary step, but it must be coupled with strategies to augment the overall water supply to effectively meet increasing demands. .
Moreover, expanding reservoirs is largely unfeasible due to limited land availability, environmental concerns, and high financial costs, making it a less viable long-term solution.
Potential of Mini Reservoirs
The study proposes the construction of ten mini reservoirs, each with a capacity of 50,000 m³, to store a total of 0.5 million m³ annually. These would be strategically located in the South, East, North, and West, including Camp-Levieux and L’Escalier.
The reservoir design incorporates natural flow integration, sediment traps, cylindrical structures, and dual-barrage micro-dams to preserve water quality and minimize siltation. Water management strategies can be further enhanced through three complementary interventions.
First, the construction of mini reservoirs in strategically selected water-stressed areas can help capture seasonal peak flows and improve water availability during dry periods.
Second, a dual-barrage system offers an effective option for improving the efficiency of water collection and distribution, ensuring continuity of supply in vulnerable regions.
Third, the adoption of nature-based solutions, such as reforestation, wetland restoration, and managed aquifer recharge, is recommended for their role in enhancing natural water retention, supporting ecological balance, and strengthening resilience to drought and climate variability.
Economic Considerations
Although the initial capital cost of USD 102 million for the ten reservoirs is significant, it remains far less than the USD 4.5 billion needed to replace the entire leaking pipe infrastructure . The project’s Benefit-Cost Ratio (BCR) was calculated at 0.0853, reflecting low short-term financial returns due to water pricing at USD 0.38/m³.
However, broader socio-economic and environmental benefits justify the investment. Blended finance models, public-private partnerships, and international grants (e.g., Green Climate Fund) are recommended to improve viability
Policy and Governance Recommendations
The study advocates for Integrated Water Resource Management (IWRM) that blends infrastructure with nature-based and community-led solutions. Recommended strategies include:
- Restoration of wetlands and catchments to enhance recharge [1]
- Legal frameworks to support rainwater harvesting
- Tiered pricing to incentivize conservation while protecting low-income users
- Innovative Design: Developing geometric cylindrical mini reservoirs and dual-barrage systems tailored to Mauritius’ rugged terrain, optimizing structural strength and ease of replication.
- Improved coordination between agencies such as the Central Water Authority and Water Resources Unit
Broader Implications and Future Research
This case study aligns with global best practices in Integrated Water Resource Management (IWRM), emphasizing diversified water storage solutions to enhance resilience and offers a replicable model for other SIDS facing climate-induced water stress. Its integrated use of climatic, geographic, and socio-economic data exemplifies holistic drought adaptation planning.
Future efforts should include:
- Field validation of model outputs
- Community engagement for social acceptance
- Deployment of digital monitoring technologies
Conclusion
Mauritius stands at a critical juncture where the intensifying impacts of climate change, coupled with growing water demands, require bold yet practical solutions. The island’s future water security hinges on the country’s ability to adopt adaptive and inclusive strategies that prioritize resilience, equity, and long-term sustainability. In this context, the mini reservoir proposal emerges not only as a technically feasible intervention but also as a socially responsive one—bridging environmental needs with the realities of local communities.
If supported by robust planning frameworks, interdisciplinary collaboration, and reliable funding mechanisms, mini reservoirs can play a transformative role in decentralizing water storage, enhancing agricultural productivity, and empowering marginalized regions. Though the immediate financial gains may appear modest, the investment offers broader dividends in terms of climate adaptation, poverty reduction, and reduced vulnerability to extreme weather events.
Ultimately, this proposal reflects a shift from reactive crisis management toward a forward-thinking, preventive approach. It emphasizes the importance of inclusive governance and the co-creation of solutions with communities most affected by climate stress. Mauritius has an opportunity to position itself as a model for other small island developing states by embracing this kind of integrated, people-centered water strategy. The time for action is now—before the window for low-cost, high-impact solutions begins to close.
OTHER RESEARCH BY THE AUTHORS:
Doorga, J.R., Deenapanray, P.N. and Rughooputh, S.D., 2023. Geographic carbon accounting: The roadmap for achieving net-zero emissions in Mauritius Island. Journal of Environmental Management, 333, p.117434. [https://www.sciencedirect.com/science/article/pii/S0301479723002220]
Doorga, J.R.S., 2022. Climate change and the fate of small islands: The case of Mauritius. Environmental Science & Policy, 136, pp.282-290. [https://www.sciencedirect.com/science/article/pii/S146290112200199X]
Doorga, J.R., Hall, J.W. and Eyre, N., 2022. Geospatial multi-criteria analysis for identifying optimum wind and solar sites in Africa: Towards effective power sector decarbonization. Renewable and Sustainable Energy Reviews, 158, p.112107. [https://www.sciencedirect.com/science/article/pii/S1364032122000363cle/pii/S2212420921006440]
Original article: Adaptive water management in small islands amidst climate change: Addressing drought and harnessing river runoff in Mauritius
This article has been co-written by Ibrahim Elhatimi
Main photo from Pexel
Charles Telfair Centre is an independent nonpartisan not for profit organisation and does not take specific positions. All views, positions, and conclusions expressed in our publications are solely those of the author(s).