David Garcés Córdoba
Regional Corporation for the Sustainable Development of the Archipelago of San Andrés, Old Providence and Santa Catalina, Colombia
E-mail: dgarce@coll.telecom.com.co

In rural areas far away from urban centers and on the very small islands (less than 100 km²), where underground water is very limited and the geologic conditions for storing surface water are not favorable, rainwater harvesting is the only available alternative to supply drinking water. In my paper I will present a methodology to find the best storage capacity of a rainwater cistern taking into account the hydrological, harvesting and consumption variables. While small cisterns help to save water, big cisterns are cheaper.