Hydrohistorian
Lesson C2 · The Ledger · records & administration
The record is not fixed
Most people treat a published government record as settled. Colorado’s diversion records are not: DWR revises previously published values — corrections, late data, re-computations — usually without ceremony. If you cited the old number in a filing, you need to know it moved.
Why records move, and why it matters
Revisions are mostly good bookkeeping: a commissioner’s correction, a meter recalibration, a batch re-import. The trouble is who they surprise. Yield analyses, change-case exhibits and loan files are built on the record as of a date — and if the record then shifts under them, the analysis silently describes a river that no longer officially existed. Professionals handle this with provenance: pin which snapshot of the record you used, then check what changed since.
That is how this site is built: every page computes from a pinned HydroBase snapshot, each new snapshot is diffed against published values, and changes are reported, never silently swapped — a structure’s dossier carries its recent upstream-revision warnings, and every download names the exact snapshot behind it, so any number can be re-derived or challenged.
See it on a real structure
Pick a structure and check whether its published record has moved.
Or start with a worked example: Farmers Highline Canal, Agricultural Ditch.
What this does not let you conclude
A revision is not an accusation — most are corrections in the right direction; and our diff only sees changes between the snapshots we hold, so revisions before our first snapshot are invisible to it. Advisory reading aid on public data — never an administrative or legal conclusion, and never a substitute for DWR administration or an engineer’s analysis. Our methodology has not yet had outside expert review: how this is built.