Decreasing water availability per capita in more and more countries is the result of bad management over the past centuries. The 'world water crisis', however, is not inevitable. The concept of Integrated Water Resources Management (IWRM) has been promoted over the last ten years as a possible way of reversing such a trend. One of its most fervent promoters is the Global Water Partnership, according to which "IWRM is a process which promotes the co-ordinated development and management of water, land and related resources, in order to maximize the resultant economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems" (GWP, 2000: 22). A number of authors are critical of an appropriation of the IWRM concept by the Global Water Partnership devoid of its historical evolution over more than 70 years (Biswas, 2005; Mollard and Vargas, 2005a). As a result of this omission, these authors question the applicability and usefulness of the concept and call for assessing the effectiveness of IWRM implementation. The difficulties of practical IWRM implementation are manifold and include issues of scale, as well as institutional, political, and social constraints to sectoral and environmental integration (Tortajada, 2005; Duda and El-Ashry, 2000; Mitchell, 1990), that can be more or less specific to developing countries (Thioubou, 2002). The 1992 Mexican Water Law, amended in 2004, explicitly refers to IWRM as a national objective. As a result, there has been fairly extensive research on the implementation of IWRM in Mexico at the national level. This study assesses the implementation of IWRM efforts in the municipality of El Grullo (Jalisco), to identify the local and necessary conditions to enhance these. We first recall the innovative aspects of the IWRM concept, as compared to more traditional water management. Ambitious, integrated water resources management is a holistic approach that includes both the natural system (water and its diverse components –surface water/groundwater, quantity/quality– but also all other environmental resources such as land, forests and biodiversity in general) and the human system, including all the different uses (domestic, agricultural, industrial, etc.) (Mitchell, 1990). Integrated water management is an indicator of what Gleick (2000) qualifies as a change in paradigm between the 20th century –where infrastructure development enabled to better exploit resources, perceived as unlimited– and the 21st century, where finite resources are to be managed in order to maintain ecological integrity. Integrated water resources management is necessary to realise this 'blue revolution' (Calder, 2005). It requires, on the one hand, a participative and negotiation-oriented institutional framework and, on the other hand, water pricing tools, so as to balance demand and supply (Meublat, 2001). At the level of a municipality, implementing IWRM efforts translates, on the one hand, in ensuring good quality municipal water and sanitation services without impacting surrounding ecosystems and, on the other hand, participating –with other municipalities and institutions– in coordination activities at the level of the basin or sub-basin (Smits and Butterworth, 2006). Seven months of fieldwork over a three-year period enabled to realise a number of interviews, both with households in the El Grullo municipality (in four urban neighbourhoods and three villages) and with key informants (the local authorities of El Grullo and five neighbour municipalities, members of the Ayuquila-Armería Watershed Commission and researchers from the partner institution IMECBIO). These interviews were complemented by direct observation as well as secondary sources of information. Our results show that in spite of being well endowed in water resources, the municipality of El Grullo does not manage to provide good quality potable water services. Water distribution is irregular and forces households to resort to appropriate social practices (e.g. use of various storage methods and alternative water sources). The inequity of the variable water service quality is reinforced by a fixed water fee system, in the absence of meters. Further, the lack of any wastewater treatment station impacts riparian villages and aquatic ecosystems located downstream from the wastewater discharge. Efforts are currently underway to address these issues: the municipality wishes to have water meters installed, and is also negotiating a concession with a private company for a constructed wetland to treat municipal wastewaters. At the regional level, the Ayuquila-Armería Watershed Commission, which was established in 1998, is criticised for the poor effective participation it generates and its lack of means and concrete results. Created in reaction to finance local priorities, the Inter-municipal initiative of the lower Ayuquila watershed, a negotiation platform that convenes ten municipalities, is in comparison relatively successful. Developed through a ten year trust-building process by the researchers from the University of Guadalajara and the directorship of the Sierra de Manantlán Biosphere Reserve, it has enabled the Ayuquila River to regain its original state, as well as set up a series of measures to protect the environment (e.g. the establishment of fire brigades and solid waste separation and recycling programmes). The Ayuquila-Armería Watershed Commission wishes, in turn, to replicate this model throughout the whole watershed. Although the management plan is still to be designed at the basin scale, these inter-municipal initiatives are indeed judged more flexible and better adapted to IWRM implementation. These results show that in order for the El Grullo municipality to enhance its efforts in terms of IWRM, important changes must take place. More specifically, decentralisation must be reinforced, at the level of both the municipal water board and the Ayuquila-Armería Watershed Commission. First, the potable water tariffs should be set independently by the municipal water board, on the basis of its operating costs –and not on that of political calculations, as is actually the case by the Jalisco State Congress. This would contribute to put an end to the vicious circle entailed by the municipal board's insufficient financial capacity (i.e. lack of staff, limited infrastructure maintenance, heterogeneous water services, lack of meters, non-payment of fees, etc.), along with other factors at stake (like encouraging a culture of payment). The Ayuquila-Armería Watershed Commission should also benefit from more freedom and means, in order to increase its credibility among the municipalities its territorial borders encompass. The effective transcription of the 2004 reform of the Water Law, which seems to point in that direction, is awaited by all those interested in this issue. This thesis thus confirms previous analyses of problems surrounding IWRM implementation in Mexico (Mollard and Vargas, 2005b; Tortajada, 2005; García, 2004; Centro del Tercer Mundo para el Manejo del Agua, 2003; Martínez et al., 2002b). It also highlights the importance of finding country-specific ways for ensuring effective IWRM implementation. In particular, this may mean considering other scales than that of river basins.