Desalination for augmenting domestic rainwater harvesting in the Grenadines

Abstract

In the past, the islands of Carriacou and Petite Martinique in the Grenadines have depended on domestic rainwater harvesting (RWH) for their water supply. Although the availability of water from this has increased over time, there is a growing gap between water demand and availability, driven mainly by growth in tourism. Closing this gap is essential, particularly in the context of adaptation to climate change. In this regard, solar-driven water desalination plants have been installed on the islands to augment RWH supplies, thus creating a hybrid system. Although, the desalinated water (DW) is highly subsidised, there is a general reluctance to embrace its availability and to pay for it. In Carriacou, the borehole supply that was used to augment rainwater in the urban area was replaced by DW, resulting in increased use of the public supply. The potential of augmenting rainwater with DW is restricted by concerns about quality, a general unwillingness to pay for the water, the strong preference for rainwater and the inability of the utility company to recover costs. The initial lessons learnt from this hybrid system can be important for developing appropriate water policies for islands that have traditionally been dependent on RWH.