Abstract. Web services support the integration and interoperability of Web-based applications and enable machine-to-machine interaction. The concepts of web services and open distributed architecture were applied to the development of T-DSS, the prototype customised for web based hydro-information systems. T-DSS provides mapping services, database related services and access to remote components, with special emphasis placed on output flexibility (e.g. multilingualism), where SOAP web services are mainly used for communication. The remote components are represented above all by distant data and mapping services (e.g. eteorological predictions), modelling and analytical systems (currently HEC-HMS, Modflow and additional utilities), which support decision making in water management.