We explore how to address the challenges of adaptation of water resources systems under changing conditions by supporting flexible, resilient and low-regret solutions, coupled with on-going monitoring and evaluation. This will require improved understanding of the linkages between biophysical and social aspects in order to better anticipate the possible future co-evolution of water systems and society. We also present a call to enhance the dialogue and foster the actions of governments, the international scientific community, research funding agencies and additional stakeholders in order to develop effective solutions to support water resources systems adaptation. Finally, we call the scientific community to a renewed and unified effort to deliver an innovative message to stakeholders. Water science is essential to resolve the water crisis, but the effectiveness of solutions depends, inter alia, on the capability of scientists to deliver a new, coherent and technical vision for the future development of water systems.

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Editors of several journals in the field of hydrology met during the Assembly of the International Association of Hydrological Sciences - IAHS (within the Assembly of the International Union of Geodesy and Geophysics - IUGG) in Prague in June 2015. This event was a follow-up of a similar meeting held in July 2013 in Gothenburg (as reported by Blöschl et al. [2014]). These meetings enable the group of editors to review the current status of the journals and the publication process, and share thoughts on future strategies. Journals were represented in the 2015 meeting through their editors, as shown in the list of authors. The main points on fostering innovation and improving impact assessment in journal publications in hydrology are communicated in this joint editorial published in the above journals.

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This paper introduces the Water Resources Research special section on Uncertainty Assessment in Surface and Subsurface Hydrology. Over the past years, hydrological literature has seen a large increase in the number of papers dealing with uncertainty. In this article, we present an overview of the different sources of uncertainty and the different types of problems associated with uncertainty assessment. It is argued here that clarity about which part of the large field of uncertainty research is addressed by a given research activity would already help guide discussions within the hydrological community. We present an introduction to the differences between the more classical frequentist approach to uncertainty and Bayesian approaches and between probabilistic and nonprobabilistic approaches. Bayesian approaches allow for inclusion of more subjective expert knowledge and would be more appropriate where less "hard" data are available. Any underlying assumptions need to be made very clear to the end user. Finally, a brief classification of the articles of the special section is presented.@en