In the developing countries of Latin America, population growth and high levels of marginalization and poverty lead people to migrate and seek places to live. In general, this population has no information to make better decisions on which geographic areas could be settled without any risk, therefore, that in the case of countries like El Salvador, we see an increasing number of banks of rivers, ravines and foothills areas of the volcanoes are increasingly populated. Likewise, local or municipal governments have not implemented the concept of land management, not implemented mechanisms to transmit information on threats and vulnerabilities to support the planning and development of their communities safer, reducing the potential impacts that may cause the natural phenomena. Hence the need to develop Early Warning Systems (EWS), with principal support network of local observers, as a tool that can help the residents of an area of risk awareness of their situation and provide informed and information in case of events of potential harm. This document will briefly explain the history of birth and description of Early Warning Systems (EWS) located in El Salvador and the type of prognosis associated with each SAT, the types of flooding affecting the country. Finally, the concept, creation and the role played by key players called "Social Network of Local Observers."