ABSTRACT
Ibo Island, located in northern Mozambique, is a coral atoll, less than 10 km in length and nowadays featuring a growing tourism industry and business market. A hydrogeological study has been carried out with the aim of providing tools for sustainable water-resource management. The existing aquifer is recharged from rainwater infiltration and characterised by a double porosity through the main unaltered rock and well-developed karst channels, with the associated high risk of water pollution. As a general pattern, groundwater flows from the centre of the island to the coastline, through submarine discharges with increasing seawater intrusion and bacteriological contamination. The freshwater/seawater interface is characterised by a mixing zone depending on annual seasonality but also on tide periodicity. Renewable fresh groundwater resources were quantified using an aggregated water-balance model for the island and calibrated to obtain an annual aquifer recharge of 146 mm/yr. Freshwater usable thickness was estimated to be up to 5 m concluding that it is feasible to extract up to 0.6 Hm3/yr taking into account the extreme vulnerability of the Ibo Island aquifer to prolonged drought episodes. Final recommendations for sustainable development were elaborated to institutions at different government levels responsible for implementing the sustainable development goals.
