Hydrological studies, both observation and modelling, cover a broad range of spatial scales, from a few cm in the lab up to the global scale. The question of the "right" scale is what links and at the same time what separates researchers across the entire hydrological community. This sessions aims at federating key experts to provide an update on the state-of-the-art on this central question and to stimulate a discussion on what are the appropriate scales for specific questions of water resources management. We further want to have a special focus on how hydrologic prediction at different scales can provide relevant information for water resources management in a changing world, the central theme of the current IAHS scientific decade Panta Rhei (www.iahs.info/pantarhei).

This is an invited-only session with five invited speakers organized by spatial scales:

1. Hans Jörg Vogel (small scale), Centre for Environmental Research - UFZ

2. Theresa Blume (small scale to meso scale), GFZ German Research Centre for Geosciences

3. Thorsten Wagener (meso scale), University of Bristol

4. Jenc C. Refsgaard (meso scale), Geological Survey of Denmark and Greenland

5. Lena Tallaksen (macro scale), University of Oslo

These invited presentations will be completed by an open poster session to stimulate a wide exchange on the question of relevant scales for water resources management.