Solar Powered Reverse Osmosis in the Caribbean

Special Programme for Adaptation to Climate Change (SPACC) Implementation of Adaptation Measures in Coastal Zones

TECHNICAL NOTE 5C/SPACC-12-05-01 (15 May, 2012)

Implementation of adaptation measures to address the absence of fresh water and coastal vulnerabilities in Bequia, St. Vincent and the Grenadines

The Special Program for Adaptation to Climate Change (SPACC) pilot project “Implementation of adaptation measures to address the absence of fresh water and coastal vulnerabilities in Bequia, St. Vincent and the Grenadines”, was implemented in Bequia, Saint Vincent and the Grenadines by the World Bank, acting as the implementing agency for the Global Environment Fund (GEF), and the Caribbean Community Climate Change Centre (CCCCC), acting as the executing agency.

Background Bequia is the largest of the Grenadines islands, approximately 7 square miles in size, with a population of 4,874 (1991 census). Due to its size and geology, the island has no surface water and no known underground source. Approximately 30% of the island is covered with scrub vegetation of no market significance. The livelihood of the people of Bequia is tied to the surrounding coastal sea. Most natives are fisher folks or sailors. Given the absence of surface water and the calciferous nature of the soil, fresh water resource is a major issue for Bequia. Bequia’s need for water Bequia’s very limited water resources are being threatened by climate change. For people living in Bequia it is clear that dry spells are becoming unusually long, or that the pattern of the rainy season has changed. Water availability to key critical ecosystems is at greater risk as the limited water available is tapped or harvested by households due to the rain water supply systems that no longer meet their water needs. At present, there is no water distribution system in the island of Bequia. Each household has traditionally solved its water supply needs by building individual rain collection systems. It is indicated that up to 30% of the construction cost of a house in Bequia is allocated to the rain harvesting system.

The community and climate change

Of particular concern is the Paget Farms community (Figure 1) where the least wealthy population of the island lives. The entire community relies exclusively on rain water harvesting as the source of potable domestic water. In fact, many of the households in the Paget Farms community, the population targeted by this pilot, are equipped with underground storage that fill during the rainy season. The others utilize one or more glass reinforced plastic tanks that do not always satisfy their needs throughout the season and water supplies have sometimes had to be supplemented by purchase of water transported by barge from Kingstown. Current trends in precipitation confirm what Global Circulation Models predict: there are longer periods of drought, followed by shorter, more intense precipitation events. Moreover, sea level rise is threatening coastal aquifers through saline intrusion. Both factors are already threatening water supply stability for already stressed populations, which in turn Figure 1 : Paget Farm community in Bequia, with Fisheries Complex in the foreground leads to over-exploitation of aquifers and natural resources, endangering the fragile ecosystems and associated biodiversity.

The project: building a carbon neutral reverse osmosis desalination plant

The pilot project in Bequia was aimed at exploring an integrated, sustainable solution to face these challenges: the combination of a renewable, carbon-free energy generation source (photovoltaic system), with a reverse osmosis desalination plant whose input is inexhaustible sea water. The low-maintenance renewable energy source offsets the high energy demand of the plant by providing all the energy required plus some excess energy for the island, with the additional revenue generated covering operation and maintenance costs. This combination has been proven to be both technically and economically viable, and showcases a robust, sustainable approach to the issue, with a very strong replication potential elsewhere in the Caribbean, where similar zones are suffering similar stress. Download PDF

As the report above states that 'Current trends in precipitation confirm what Global Circulation Models predict: there are longer periods of drought, followed by shorter, more intense precipitation events. Moreover, sea level rise is threatening coastal aquifers through saline intrusion.', all Small Island Developing States (SIDS) should be implementing Plan B. A Plan B is necessary from the perspective of energy security. Should the geo-political situation in the Persian Gulf deteriorate the price of petroleum (oil) could rise dramatically making water unaffordable to residents of islands wholly dependant on fossil fuel produced electricity for their water production. The Cayman Islands has no Plan B. The response from the Water Authority, when questioned what their options were if the was a spike in the cost of diesel stated that they would have to raise their cost to the consumer. Editor

 

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