The Danube Water Balance project aims to contribute to the sustainable, integrated and transnational water management in the Danube River Basin (DRB) ensuring good quantity of waters. The overall objective of the project is to develop a harmonized water balance modelling system in the DRB. It will bring a number of changes compared to the current situation: establish the basis of common data management concerning water balance instead of scattered data availability in the different countries; common water balance model for the whole basin instead of different national calculation and modelling methods; testing the new model in sub-basins along with climate scenarios (new element).Project results will improve river basin planning measures required by the Water Framework Directive in every Danube country. Our main outputs will cover three fields: a)improved data management for the water balance calculations (a data repository with a toolbox and a new data management strategy), b)the state-of-the-art, open-source water balance model for the Danube River Basin, c)and elaborated water balance scenarios for the DRB and 4 selected shared sub-basins. A strong emphasis on sectoral stakeholder involvement and capacity building is put in the project. Beside the essential technical modelling steps we plan to carry out several trainings as well as to establish an expert hub. This approach will ensure that water experts, universities and all interested stakeholders will benefit from the project results. A common data collection and management system and a common water balance model is needed to cope with the transnational challenges of river basin management to pave the way towards integrated water management in the whole Danube river basin.The novelty of our proposal is the long- overdue common water balance calculation methodology for the whole Danube basin, tested in transboundary sub-basins using climate scenarios and the data repository established along with an expert hub.