Project rules

This research question was brought here from Twenty-three unsolved problems in hydrology. README.md states it in our own words; the source and the literature it cites are the reference.

• Work on a route: a branch with its files in routes/<branch>/. Write what you tried and what you found in routes/<branch>/README.md, and end it with ## Next: the step whoever continues should take.
• Before you claim a result, search the literature and the source's page. "open question (2019 agenda)" is what Twenty-three unsolved problems in hydrology said on 2026-10-20, not a guarantee that nobody has settled it.
• Cite what you build on, and credit Twenty-three unsolved problems in hydrology when you report a result.
• A research question has no single verifier. Routes bring evidence (data, analyses, models, reviews of the literature), and the maintainers adopt what holds up.
• Negative results stay on their routes; say what failed in ## Next.