Background Located in the Transdanubian region of Western Hungary, the Lake Balaton Resort Area (LBRA) is an area of 3780 km² that lies almost entirely in the watershed of the lake. Lake Balaton itself is the largest freshwater lake in Central Europe – it has a surface area of 593 km2, is 78 km long, is 7.6 km wide and has an average depth of 3.3 m. However, the Lake Balaton area has a particularly sensitive ecosystem and mass tourism is having a negative impact, particularly in the summer months. The number of people in the LBRA can increase from a permanent population of 250,000 to a peak summer population of nearly one million. The pressures from tourism mean that it is particularly difficult to maintain a good water quality during the summer months. The most important environmental problem is the eutrophication of the lake caused by the excessive load of plant nutrients such as phosphorus and nitrogen. The sources of nutrients are municipal sewage effluents, agricultural runoff and urban runoff. Some efforts had been made over the previous two decades to reduce the load from sewage and agricultural runoff through measures such as sewer development, the Kis-Balaton reservoir construction and a sharp fall in fertiliser application. Objectives The project sought to avoid the emerging risks of an environmental and socio-economic disaster in the Lake Balaton region and create a model for sustainable tourism. It aimed to tackle the still serious problem posed by the urban runoff because of its high nutrient concentration and the high content of suspended solids, pathogenic and other micro-organisms, as well as toxic, carcinogenic and mutagenic chemicals such as PAHs, metals and humic substances. Specifically, the project sought to establish an environmental and socio-economic monitoring system looking at on-line traffic and water quality with an array of other relevant monitoring instruments. It intended to develop an action programme based on an innovative and integrated Decision Support System to promote sustainable tourism, regional development and rehabilitation of the region. Results The project succeeded in developing an innovative Decision Support System (DSS), integrating multidimensional environmental and socio-economic monitoring. This system offers a tool to support sustainable environmental and tourism policies based on an understanding of the interrelation between the natural and human spheres. A key success of the project was that its results were taken into account by the Government when preparing its National Development Plan. The project started by engaging with end-users, conducting environmental and socio-economic surveys and analysing earlier decisions and policies to provide background static data. It then developed or integrated monitoring tools including tourist counting units, vehicular traffic measuring units, speed monitoring, traffic hazard signals, equipment to monitor water quality and water quantity, storm information stations and road-side screens to provide real-time information on a variety of key factors. It created a special GIS database which collects, maintains and manages all the information from the on-going monitoring sources and makes it available together with the static data on the internet. A prototype identifies risks or real-time changes in the environment from the received data and suggests policy options. The information produced by the project was incorporated into the region’s official development plans allowing for improved planning and response activities in the face of environmental threats, such as algae proliferation. By combining environmental and socio-economic information, it has specifically allowed planning towards more sustainable tourism and the improved management of traffic in the region to reduce their environmental impact. The DSS, prototype and the action programme created during the project offer innovative potential solutions for many other European regions that encounter similar problems. The modular format makes the project a good candidate to be copied in other locations. The technical aspects of the project are also easy to transfer as they use widely-available technology and are not tied to any specific brand or supplier. What is most necessary for the transferral of the project is know-how and experience. To share information on the project and its results, the project has developed an extensive web site, which the beneficiary will continue to up-date and develop beyond the LIFE project. Meanwhile, to ensure the sustainability of these results, the LBDCA has already undertaken a commitment to continually develop the GIS systems to ensure the databases are updated.