Hydrohistorian
A century of Colorado water, finally readable.
Colorado’s water record is public, enormous, and effectively unreadable — decrees, admin numbers, diversion histories, and daily calls scattered across systems built for specialists. Hydrohistorian turns it into something you can actually use: flow networks you can follow, legal context in plain language, and the record running back to 1899 — with the source shown on every page.
Visit hydrohistorian.comAsk about a basin
Free for everyone during the open beta — every district unlocked, no account needed.
What’s in it
Every water district, mapped
All 78 of Colorado’s water districts on one map with real boundary geometry and river centerlines — searchable by name or number, each one opening onto its own basin page. Coverage runs deepest in the South Platte, Boulder Creek, and Clear Creek.
The river as a flow network
Each basin page draws the stream and its structures as a schematic you can trace headgate by headgate, with a topology review checklist so you can see where the network is confident and where it isn’t.
Priority, in plain view
Decreed rights, administration numbers, call analysis, and a what-if curtailment cascade — plus the historical call record back to 1950. The daily in-priority calculation agrees with DWR 95.5% of the time across 85,822 structure-days, and that number is published rather than assumed.
The long record
469 gages at full period of record — Clear Creek alone holds 546,515 daily values starting 1 April 1899, DWR’s own earliest entry. Mass-balance reconstruction and a basin evolution animation show how the system got to where it is.
Trends, drought, and snow
Mann-Kendall with Sen slopes and Pettitt changepoints, paleo-drought reconstruction alongside the modern Drought Monitor record, SNOTEL and gridded snow, and an in-house runoff forecast that keeps a public scorecard against the NRCS.
Groundwater and wells
598,010 well permits with a township atlas, water-table trends by well, and a 3D “x-ray” of the Denver Basin aquifers for anyone trying to picture what’s underneath them.
My Water
Type an address: which district you sit in, whether the ground is mapped irrigated parcel, which ditches serve it, and the nearest ditches, wells, reservoirs, and gages — each linking straight into its record.
Learn the system
Two dozen lessons across five tracks, built on the same live data as the rest of the site, for anyone who has to understand prior appropriation well enough to work in it.
Why you can check it
A site whose whole claim is “here is what the record actually said” has to be auditable, so the provenance is part of the product rather than a footnote.
- Every page carries its sourcesWhich HydroBase snapshot the numbers came from, when it was imported, which engine version and commit produced them, how many daily values, and where the record starts and ends.
- Revisions are logged, not silently appliedWhen DWR changes a historical value, the change is recorded per structure — so the record has a history of its own.
- Cross-checks are shown, not hiddenHydroBase-against-cache and DWR-against-USGS both run, and their verdicts are published either way.
- Advisory by designOutputs are reading aids over public DWR and USGS data — not administrative or legal conclusions, and never a substitute for DWR administration. Methodology review status is stated on every basin page.
Where it stands
Hydrohistorian is free right now: the paywall is switched off for the open beta, so all 78 districts are open to everyone with no account. When the beta ends, Clear Creek stays free in full and a $29/month plan opens every basin. An account is worth making either way — it’s what My Water uses to remember your structures.
Open HydrohistorianTalk about your basin
Built and operated by True Ascent Labs on Colorado DWR/CDSS (HydroBase and REST) and USGS NWIS data. Interested in the same engine for another state’s record? That conversation is open.
