The Western Indian Ocean (WIO) islands are separated by large expanses of ocean and do not share any freshwater resources. Freshwater resources vary considerably across the islands.

Madagascar can be divided into two major basins – one draining to the west into the Mozambique Channel and the other draining to the east into the Indian Ocean. Water in Madagascar, Mauritius and the Seychelles is primarily extracted from rivers on the main inhabited islands through the construction of dams and reservoirs, while the islands of Comoros are heavily dependent on groundwater resources. The islands are subject to tropical storms or cyclones with heavy rainfall from November to May giving rise to periodic flooding. Despite the relative abundance of rainfall, the islands also experience periods of water shortage.

There are large variations in rainfall across the countries and this has implications for available freshwater resources. All the countries experience extended dry seasons with periods of heavy rain, torrential at times, which present technical problems for storage, treatment and distribution. Climatic patterns are discussed in Chapter 2: Atmosphere.


Wetlands occur throughout the island states. These wetlands are important habitats that provide breeding grounds for large numbers of waterfowl. These natural assets make the island states ideal tourist destinations.

On the Mauritius island of Agalega, 1 000 km north of Mauritius main island (Government of Mauritius 2005), the use of groundwater is declining for domestic or agricultural purposes, because of saltwater intrusion and land pollution; rainwater harvesting from pitched roofs is proving a problem because of faecal contamination from birds.

In the areas of public awareness and information, and economic measures, such as metering and charging for water use, there are opportunities to further curtail the demand for freshwater.


Projections for the WIO islands place Mauritius in the category of water-stressed countries and Comoros in the category of water-scarce countries by 2025 (see Figure 2). Comoros is currently on the threshold, with just 1 700 m3 available per person per year (UNEP 2005a). Water availability is a problem across the sub- region (UNEP 2005a):

  • Precise figures for the Seychelles, where most water comes from rivers, are not available, but water shortages were so severe during 1998, partly as a result of the very extreme El Niño event, that the brewing and fish canning industries were forced to close;
  • Mahé, which is part of the Seychelles, is under increasing threat of water shortages as a result of wilt disease that is damaging a tree species, Pterocarpus indica, important for watershed management; and
  • Water supply in the Comoros on the islands of Grande Comore, Mohéli and Anjouan is threatened by the fragile equilibrium between freshwater and seawater.

In the Comoros, seawater intrusion reaches as far as 2 km inland due to the high water table around the coast (UNEP 2004). There are also problems of contamination of groundwater through seepage from septic tanks, substandard equipment and an insufficient number of water pumps.

The Intergovernmental Panel on Climate Change’s (IPCC) projected worst-case scenario of a 1 m sea-level rise by 2100 would result in loss of coastal land, agricultural opportunities, groundwater resources (due to salinization), biodiversity critical to community support, and in loss of livelihoods (IPCC 2001). The social impacts of a sea-level rise will cause migration and displacement of people, water-related diseases and water supply problems.

In the Seychelles, high fertilizer use means that rivers have fertilizer loads of up to 25 kg per day (UNEP 2005b). Wells in Mauritius have high nitrate levels reaching 50 microgrammes per litre, which is up to the World Health Organization defined safety limits (UNEP 2005b). Mauritius uses, on average, 57 500 tonnes of fertilizer annually, representing 600 kg per hectare, or three times the rate in western Europe (UNEP 2005b).

For many people in many of the WIO islands, waterborne and tropical communicable diseases are widespread, as a result of contamination of water supplies by human waste. The Comoros, for example, suffered cholera epidemics in 1975, 1998 and 2001. Two recent outbreaks were associated with poor sanitation and pollution of freshwater. Poor disposal of waste, particularly containers, is also generating increased risk of malarial infections, especially in Madagascar and the Comoros. The containers, ranging from old plastic bags to paint tins, accumulate rainwater, which is an ideal breeding ground for disease-carrying insects. Both Mauritius and the Seychelles have developed organized waste management schemes. In the Comoros, collection and disposal of waste is poorly managed.

In the Comoros, malaria is one of the principal causes of morbidity and mortality, being associated with 25 per cent of hospital admissions and 10-25 per cent of deaths in children under five years old (WHO/UNICEF 2003). Diarrhoea is a significant cause of morbidity in children in the Comoros and is associated with poor water quality.

Madagascar has health problems associated with stagnant water in irrigation canals in rice fields which promote mosquito breeding and are host to the spread of the parasites producing bilharzia. Mauritius and the Seychelles are relatively free from diseases affected by poor quality of water. Malaria has been successfully eradicated in Mauritius, although in the past it was responsible for over 2 000 deaths per year. Tourist areas throughout the sub-region have yet to introduce quality controls on water in bathing areas, although the adoption of the Blue Flag schemes of western Europe is being considered.


The role of the private sector in financing water projects and infrastructure is increasing, although more so in Mauritius and the Seychelles than in Madagascar and Comoros (UNEP 2004). In the Seychelles, the role and importance of NGOs in sustainable development has increased since 1996.

In January 2005, the Mauritius Strategy was adopted, by the Small Island Developing States (SIDS) and the international community, to ensure the successful implementation of the 1994 Barbados Programme of Action (BPoA). The BPoA focuses on problems SIDS face related to climate change and sea-level rise, natural and environmental disasters, freshwater resources, and capacity- building. Selected challenges and actions related to freshwater resources are listed in Box 18. The next step is to outline a road map for the implementation of the strategy.

Box 18: Mauritius Strategy – freshwater challenges and actions
  • Small Island Developing States continue to face water management and water access challenges, caused in part by deficiencies in water availability, water catchment and storage, pollution of water resources, saline intrusion and leakage in the delivery system. Sustained urban water supply and sanitation systems are constrained by a lack of human, institutional and financial resources;
  • Further action is required, with the necessary support from the international community, to meet the MDGs and the World Summit on Sustainable Development (WSSD) 2015 targets on sustainable access to safe drinking water and sanitation, hygiene, and the production of IWRM and water efficiency plans;
  • Seek international support to build self-reliance and implement agreed priority actions, namely: IWRM, water demand management, water governance, capacity-building; and regional and inter-small island developing states water partnerships.

Sources: UN 2005

Box 19 illustrates the progress made with disaster management in one of the island states, the Seychelles.

Box 19: Disaster management in the Seychelles

For about twenty years after independence, the Seychelles were fortunate in escaping major environmental and natural hazards. That situation changed when the 1997 El Niño floods struck the Seychelles, raising public and government awareness about the necessity of strategic disaster management. In 2004, a National Strategy for Risk and Disaster Management was drafted. In October of the same year, Seychelles created a National Disaster Secretariat. The Secretariat acts as the operational arm of a National Disaster Committee.

Mahé, the largest island of the Seychelles, took the full force of the tsunami on 26 December 2004. The seawater was driven hundreds of metres up into the city drainage system, blocking pipes with silt and flooding roads, shops and houses.

Source: UNEP 2005a