To all hydrologists of the world: A Call to Arms!
What are the 23 Unsolved Problems in Hydrology that would revolutionise research in the 21st century?

At the IAHS Scientific Assembly in Port Elizabeth in July 2017 the then President of IAHS, Günter Blöschl, outlined his vision for a new initiative to generate a list of unsolved problems in hydrology.

Progress in hydrology is currently hampered by the rather fragmented research and we need stronger harmonisation of research efforts.  At the beginning of the 20th Century, mathematician David Hilbert set out 23 unsolved mathematical problems which have greatly stimulated focused research in mathematics and we can use this as a model for the IAHS initiative.

IAHS will facilitate the compilation of a list of unsolved scientific problems in hydrology to revolutionise research in the 21st Century and raise the level of excitement for the science.

The video outlining the new IAHS initiative is available on the IAHS YouTube channel.

Discussion is encouraged via the LinkedIn Group IAHS – International Association of Hydrological Sciences. All IAHS members are invited to join, and so are all sister associations and partners, and all hydrologists.  The IAHS Commissions and Working Groups are tasked with streamlining the discussion and coming up with 3 unsolved problems each. 

During Winter 2017/2018 we discussed the procedures for selecting the most important problems and come up with a short list of problems. In April 2018, the final selection of questions was made based on the discussion outcomes. That meeting was open to all hydrologists.

Once established, the list will be used within IAHS to align symposia planning and other events. It can of course also be used by everybody in hydrology for supporting project proposals and more generally conducting focused research. The vision is for the list of unsolved problems in hydrology to better link hydrological research around the world, and to make more tangible, coherent progress in hydrology. The list of questions can be found at here 

The dedicated meeting was held on 14 April 2018, just after the EGU Assembly, at TU Vienna in the frame of the VCSS series. Details are available here 

Meeting Schedule.
How to contribute to UPH (pdf presentation)
List of questions after 14 April 2018 plenary

Attendees of the VCSS meeting on 14 April 2018

UPH meeting 13 April 2018
PowerPoint presentation as pdf
Full list of questions as pdf
Meeting Report

The first UPH paper was published as an author accepted manuscript in the Hydrological Sciences Journal in June 2019. ‘Twenty Three Unsolved Problems in Hydrology – a Community Perspective’ is now available open access on T&F Online 

A follow up UPH meeting was held during the IUGG General Assembly in Montreal on 10 July 2019.

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