**3. Conclusions**

The papers in this Special Issue are, of course, not reflecting all the recent developments in water sciences. However, it provides a snap-shot of important scientific developments required to support water managers in their endeavor to deal with increasing complexity and uncertainty. As such, Arjen would be proud of the result of this Special Issue, as all articles contribute to the much needed debate around the fair and sustainable allocation of fresh water resources [14].

**Acknowledgments:** All acknowledgements for making this special issue a success are for the late Arjen Hoekstra, gues<sup>t</sup> editor of this Special Issue, and a devoted and inspiring researcher.

**Conflicts of Interest:** The author declares no conflict of interest.
