Countries, which have implemented for the first time or reformulated their domestic water management policies after the 1970s-1980s, have had the opportunity to choose from a series of water management models around the world. Brasil is one of these countries. In 1997, the Brazilian Federal State defined (Law 9,433) the new water management model to be implemented throughout the country. The model is based on the integrated management of multiple water uses, defining the river basin as its unit of analysis and management. These principles reflect a trend towards decentralization and participation, which requires a close collaboration and negotiation among the different government levels ? federal, state and municipal, as well as between these and water users and civil society organizations. This collaboration and negotiation is to be developed within River Basin Committees, where representatives from all the above mentioned sectors participate. Despite this legislative and implementation dynamics at the federal level, since the 1988 Federal Constitution, several Brazilian States had approved state legislation (re)organizing their water management systems. Most of them already encompassed the basic principles later adopted at the federal level. The result is a mosaic of water management institutions, which, in some river basins, arguably hold overlapping functions and responsibilities. Why have these overlapping water management models persisted? Why have not they been consolidated in one or just replaced one by another? The answers to these quesitons may shed some light over governments’ choices of water management models and the paths which the implementation of these models have followed (and are following). The Watermark Project ? Projeto Marca D’Ãgua ? is a long-term study (5-10 years), which seeks to investigate the institutional and social aspects of the water management decentralization in diverse physical, social, and organizational contexts across Brasil. The project strives to better understand the decision making process used by emerging river basin organizations and how factors such as the type of water related problem and the level of social organization, influenced their creation and their management activities. The Watermark Project research team has currently over 30 collaborators from institutions in Brasil and the United States of America, representing a diverse group of universities, governmental agencies, and non-governmental organizations. During 2001-2002, baseline and follow-up studies were conducted in 27 basins throughout Brasil. The Piracicaba, Capivari and Jundiaà River Basin (PCJ) is one of the case-studies researched and being followed within The Watermark Project. The paper will analyze the Piracicaba, Capivari and Jundiaà River Basin case, where a distinct water management model was implemented in the 1980s ? PCJ Consortium. This water management model was subsequently followed by the implementation of a second model of water management as a result of the State of São Paulo Water Law (1991) ? PCJ State Committee ? and recently, by the implementation of yet a third water management model as a result of the Federal Water Law (1997) ? PCJ Federal Committee. The reasons for choosing one water management model over another and for their overlapping existence and functioning will be discussed. [ABSTRACT FROM AUTHOR]