Geographic Information Systems (GIS) have been widely used as a tool to support decision making in the management of river basins and their resources. A GIS is a system composed of: data, computer programmes, equipment, people and procedures. When choosing these components, some issues must be observed and carefully planned, such as: the available resources, the profile of the users and the products to be created. Planning increases the chances of successful implementation and utilisation of the MIS. To assist managers of organisations active in water resources management - Basin Committees, Water Agencies and Non-Governmental Organisations - in the planning stage of the Geographic Information System, this Manual was developed. The material presented here is the result of the master's thesis in Water Resources Management and Regulation (ProfÁgua - UERJ), defended by the author in August 2018.