In the Mediterranean islands, limited water supplies combined with highly developed tourism and irrigation agriculture lead to extreme pressures on water resources. ISLA project has produced an application to support water managers in their decision-making activities, providing them with specific and up to date information obtained from Earth Observation data. Resulting of this project, water managers will be able to address their most typical and urgent problems in land and water management; to plan viable solutions for water use reduction; to know how much water is potentially available; to exploit alternative sources of water; and to have an overview of the total water supply. ISLA project is geographically focused on the islands of Mallorca (Spain) and Crete (Greece), and the target users of ISLA system are river basin organisms, regional authorities, local development agencies and hydroelectric companies.