Water flows from Sources in the highest mountains to the deepest oceans through river basins to the Seas that span the earth system from top to bottom. Starting from highest mountains to the depths of the seas, all people depend directly or indirectly on the multitude of ecosystem services this water provides. 

The Science Policy panel, organized by UNESCO during the COP-25 in Madrid, Spain, emphasized the importance of scientific cooperation, and connecting scientific research, policy development and action, and developed a set of recommendations to enhance interface and interconnections among different components of the Source-to-Sea flow pathway.

IHP provides the knowledge base to develop a comprehensive scientific understanding of the Source-to-Sea phenomena incorporating the cryosphere, the terrestrial hydrological water cycle, water quality, sediment and erosion processes and deposition in littoral zones, deltas and coasts.