Background Changes taking place at global level are expected to affect the availability and/or quality of surface, ground, marine and continental waters as well as the frequency and strength of extreme meteorological events. Climate change is a key issue in this context. A progressive increase of atmospheric temperature would likely change the amount, frequency and intensity of precipitation. These changes would in turn modify the water cycle, including run-off, infiltration and aquifer recharge. Moreover, additional factors may have even more impact on water availability than climate change. Changes in land use – such as abandonment of crops, growing urbanization, destruction of forests or deforestation – are affecting the ground’s capacity to absorb water. Increases in population and greater demand for water from people in developing countries as they increase their quality of life are also starting to put water resources under even greater pressure. It is important to assess the potential impact of these global changes on water resources, so that water companies and other stakeholders can adapt management strategies and infrastructure appropriately. Water policies related with river basin management, marine environment, water quantity (floods, droughts, water scarcity), water and health (drinking and bathing water) and water pollution (water treatment) should be based on a good understanding of the changes taking place. Objectives The WATER CHANGE project aimed to provide the tools and methodology necessary to model the impact of Global Change on water resources and infrastructure. Global change is defined as all the anthropic-related changes affecting directly or indirectly the water quantity and the water quality, influencing the sustainable management of the water resources in a river basin; Future scenarios aimed to cover both climatic and anthropogenic medium and long-term changes. Ultimately, the project sought to provide a means of adapting effectively to the global changes taking place and ensuring adequate quantity and quality of future water resources. Specifically, the project sought to: Develop a methodology for medium and long-term modelling of water resources in a river basin, taking into account future scenarios of climate change, land use and water consumption, based on socio-economic evolution; Develop a modelling system capable of predicting the evolution of water resources within a river basin, by connecting input data, models and output data, and allowing the user to visualize and analyse the results; Apply the methodology and tool to a case study: the Llobregat river basin, which is highly affected by human activity; Assess the impacts of global changes on water resources and associated infrastructures in the Llobregat basin and to determine the vulnerability of different sectors; Propose appropriate adaptation measures for the case studied, based on an evaluation of their economic and environmental costs and benefits.Results The WATER CHANGE project successfully developed a methodology and tool that allows users to assess the impacts of Global Change on water resources and inform adapted policies accordingly. The Water Change Modelling System is useful for river basin agencies and water companies to develop long term planning in compliance with future scenarios of climate, land use and water demand. The project worked throughout with key stakeholders in water resources management to conduct the following actions towards delivering the final tool: Definition of the modelling system, including three integrated sub-models covering hydrology, water management and water quality; Definition of the input parameters, including temperature, precipitation and land cover as well as management rules; Definition of outputs, including water resources, system performance, water quality, water withdrawal and improved management rules; Design of a tool to use the selected models for the modelling system, including system architecture, software and functional design; Programming of the modelling system to integrate the different models and process the available data; Adaptation of the selected hydrological and water management models to the Llobregat case study; Collection and inputting into the system of the following data for the Llobregat river basin: - topographical and geometrical data - past climate data - soil, vegetation and aquifer data - water quality and use. Calibration of the models based on optimising algorithms and validated against historical data; Definition of future scenarios and analysis of the combination of scenarios affecting climate, land use and water use; Estimation of the consequences of global changes in water supply and water demand together with the degree of uncertainty; Identification of adaptation strategies for the impacts on water and analysis of the economic and environmental costs and benefits. The Water Change Modelling System allows the handling of a large quantity of data and the integration of already existing user's models inside a modelling platform. The system stores the models input and output files in a central data base and allows comparison of scenarios via graphs, tables and maps of the river basin. It supports decision-making regarding which strategies are likely to be most effective in terms of avoiding the costs and impact of events such as droughts or floods. The project shows how to combine the results of the simulations with a cost-benefit analysis thus enably to adopt the most efficient strategy in terms of avoided drought costs and financial resources needed for its implementation.The project highlighted the need for long-term planning in the Llobregat river basin since the tested scenarios revealed an important risk of future water deficits. In general, the results of the Water change project have shown the importance of considereing Global Change in long term planning, since deficits in water demand could be greater than today and the socio-economic impact quite considerable. The WATER CHANGE project was also awarded as Winner for the Planning Category of the 2012 IWA Europe and West Asia Regional Project Innovation Award. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).