Many touristic islands around the world are facing a threat to the availability and the quality of the water resource because of problems in common like water scarcity during low precipitation seasons, overexploitation of the aquifers, intrusion of the sea water into the aquifers and lack of wastewater treatment plants. Because of the increasing tourism population, the water management requires improvements in order to address this environmental problem. San Andres is a Colombian Island located in the Caribbean Sea with and extension of 26 km2. It has a population of 72.000 inhabitants with a fluctuant population of 1.000.000 tourists per year. The main water source is the groundwater from two aquifers (82%), which are recharged naturally. However, because of the increasing tourism industry, the exploitation of the water resource is higher than the natural recharge, which results in the intrusion into the aquifers. In addition, there are around 5.000 water wells and 10.000 septic tanks. These issues have created an environmental, social and economic problem which has been under discussion by the local and national authorities in the last years. The goal of this research is to evaluate the eco-efficiency of the water resource management in the island, in order to identify processes feasible to be improved to decrease the risk of lack of availability of the water resource and the decrease of its quality. In order to reach this goal, a first phase was proposed to make a characterization of the water management system based on the material flow analysis methodology, taking into account the different processes involved, like water extraction, water treatment, water distribution, and wastewater treatment. The main parameter studied was the water flow between all the processes in the water management system and its fluctuation in the time. A second phase consisted of the study of the social and ecological interactions in the water resource management system and the influence of stakeholders and environmental policies in the system. This phase allows identifying the processes and flows feasible to be improved and the potential strategies to be implemented in order to increase the eco-efficiency in the water resource management in the island. The results of this research not only help to give recommendations to the stakeholders to improve the sustainability of the water resource management, but also, it helps to create a research framework to study other case studies about the water management in islands in developing countries worldwide. This research is funded by the Research Unit and the Faculty of Civil Engineering of the “Universidad Santo Tomas Seccional Tunja, Colombia”.