The island of Santa Cruz, the most populated of the Ecuadorian Galápagos Islands, is currently experiencing extreme pressure on its water resources due to exponential increase in tourism and corresponding growth of the local population. Because of that, the municipal water supply system has not been able to provide reliable and continuous service of safe drinking water. This study aims to describe the current situation related to the scarcity of water, by analysing and quantifying the total supply as a first step towards further development of a water balance for Santa Cruz. It elaborates on three different water sources, the differences between the two main urban settlements and constraints which the Municipal Department of Potable Water and Sanitation have been dealing with. The conclusions include among others, that the specific demand supplied from different sources is ±370 lpcpd, which is surprisingly high figure for a water scarce area.@en