# Hydrohistorian

> Colorado water data, basin by basin: flow networks, water rights and seniority, reservoir storage, groundwater, and 125 years of gage history for all 78 water districts, built from public DWR, HydroBase and USGS records. Free to use.

Hydrohistorian is a map first: each of Colorado's 78 water districts has a page, and every decreed ditch, reservoir, well and gage in the public record has its own. Pages are server-rendered HTML with the figures in the text; there is no separate data API for agents. Please cite the page URL, and where a page states the date its record was built, cite that too. Measured values and decrees are shown as filed and name their source; forecasts and derived figures are labelled as such; each page says what it does not know.

## Start here

- [The map](https://hydrohistorian.com/): every district, with what is calling and flowing now
- [Water districts](https://hydrohistorian.com/gages): browse gages, [ditches](https://hydrohistorian.com/ditches), [reservoirs](https://hydrohistorian.com/reservoirs), [wells](https://hydrohistorian.com/wells) and [springs](https://hydrohistorian.com/springs) by district
- [Groundwater](https://hydrohistorian.com/groundwater): the monitoring network and the well-permit file, including the Driller's Atlas of Division 1
- [Interstate compacts](https://hydrohistorian.com/compacts): what Colorado owes downstream, and how it is doing
- [Water providers](https://hydrohistorian.com/providers): every public water system, its source, counties, water district, and who it buys from or sells to
- [Water quality](https://hydrohistorian.com/water-quality): every USGS sensor reporting temperature, conductance, oxygen or turbidity now; the same readings sit on each gage's page
- [Instream flows](https://hydrohistorian.com/instream-flows): every reach and lake level the CWCB holds a right for, by district; [designated groundwater basins](https://hydrohistorian.com/designated-basins); [the water courts](https://hydrohistorian.com/water-court)
- [Colorado River status](https://hydrohistorian.com/colorado-river): Powell and Mead against the elevations that decide operations, and the rule in force
- [Snowpack](https://hydrohistorian.com/snow), [long-term trends](https://hydrohistorian.com/trends), [transbasin diversions](https://hydrohistorian.com/transbasin)
- [Everything on this site](https://hydrohistorian.com/everything): every public page, grouped by what a reader is doing
- [Methods](https://hydrohistorian.com/methods): sources, definitions and what each figure means
- [Terms](https://hydrohistorian.com/terms)

## Reference (every entry with its source and a trust chip)

- [Glossary](https://hydrohistorian.com/reference/glossary): Colorado water terms, one cited definition each
- [Statutes and cases](https://hydrohistorian.com/reference/law): the constitution, Title 37 article by article, and the decisions
- [Institutions](https://hydrohistorian.com/reference/institutions): who does what, with founding dates and homepages
- [Timeline](https://hydrohistorian.com/reference/timeline): dated events from 1852 to today

## Learn (short lessons on how Colorado water works)

- [A right is a place in a queue](https://hydrohistorian.com/learn/place-in-line)
- [Paper water and wet water](https://hydrohistorian.com/learn/paper-water)
- [Why downstream can beat upstream](https://hydrohistorian.com/learn/priority-line)
- [When the call does not stop you](https://hydrohistorian.com/learn/when-the-call-stops)
- [Reading an administration number](https://hydrohistorian.com/learn/admin-number)
- [The line above the line](https://hydrohistorian.com/learn/interstate-compacts)
- [Reading a hydrograph](https://hydrohistorian.com/learn/reading-a-hydrograph)
- [Where water goes between two gages](https://hydrohistorian.com/learn/gains-and-losses)
- [The season is the system](https://hydrohistorian.com/learn/the-season)
- [Trend or noise?](https://hydrohistorian.com/learn/trend-or-noise)
- [Water that crossed the divide](https://hydrohistorian.com/learn/water-across-the-divide)
- [Reading a runoff forecast](https://hydrohistorian.com/learn/reading-a-runoff-forecast)
- [Anatomy of a drought](https://hydrohistorian.com/learn/anatomy-of-a-drought)
- [How to read a diversion record](https://hydrohistorian.com/learn/reading-a-diversion-record)
- [The record is not fixed](https://hydrohistorian.com/learn/the-record-moves)
- [Anatomy of a call](https://hydrohistorian.com/learn/anatomy-of-a-call)
- [Is the river getting harder to divert from?](https://hydrohistorian.com/learn/tightening)
- [Tributary groundwater is the river](https://hydrohistorian.com/learn/wells-are-the-river)
- [Reading a well, reading an aquifer](https://hydrohistorian.com/learn/reading-a-well)
- [Pumping now, depletion later](https://hydrohistorian.com/learn/pumping-now-depletion-later)
- [Three things called “well”](https://hydrohistorian.com/learn/three-kinds-of-well)
- [What a right actually yields](https://hydrohistorian.com/learn/what-a-right-yields)
- [Who objects, and why](https://hydrohistorian.com/learn/who-objects)
- [Augmentation plans](https://hydrohistorian.com/learn/augmentation)

## Machine-readable

- [Sitemap index](https://hydrohistorian.com/sitemap.xml): core pages, every gage, and every decreed structure in chunks
- [robots.txt](https://hydrohistorian.com/robots.txt): the same paths are open to every agent; AI training crawlers are paced with 429 + Retry-After rather than blocked