Learn Colorado water

Short lessons on how water actually works in Colorado — rights, administration, rivers and records. Every lesson teaches the general rule, then shows it on a real structure with its real record, because the gap between reading about seniority and watching your own ditch go out of priority is the gap between information and fluency.

Free, no account, and it stays that way. Lessons are written by people and the numbers are computed from the public record — the same figures, provenance and caveats as everywhere else on this site. The methodology has not yet had outside expert review; each lesson says what it cannot tell you, and corrections are wanted — especially from people who administer, litigate or engineer this for a living.

The Line · prior appropriation

A right is a place in a queue

Not a quantity of water. Where one real structure stands in its district's line, and what that has meant week by week.

Lesson A1 · 4 minutes · works with real data

Paper water and wet water

A right's decreed amount is not the water it gets. The most consequential misunderstanding in Colorado water.

Lesson A2 · 4 minutes · works with real data

Why downstream can beat upstream

Priority runs by date, not geography. Set a hypothetical call on Clear Creek and watch who shuts off.

Lesson A3 · 5 minutes

When the call does not stop you

Futile calls, free river, and augmentation — the three ways "senior calls, junior stops" gets more interesting.

Lesson A4 · 5 minutes · works with real data

Reading an administration number

The one number that ranks every right in Colorado, decoded digit by digit — try any admin number.

Lesson A5 · 3 minutes · works with real data

The River · hydrology

Reading a hydrograph

What "normal" means for a river, and why an average year barely exists.

Lesson B1 · 4 minutes

Where water goes between two gages

A river is a running ledger: diversions out, returns in, and the reach that gains or loses to the ground.

Lesson B2 · 4 minutes

The season is the system

Headgates open in spring and close in fall. A century of that rhythm, animated, with a narration to watch it by.

Lesson B3 · 4 minutes

Trend or noise?

Why a slope needs a p-value, why short records lie loudest, and how this site ranks its own trend claims.

Lesson B4 · 4 minutes

The Ledger · records & administration

How to read a diversion record

What DWR actually publishes for a headgate, column by column, on a structure you pick.

Lesson C1 · 5 minutes · works with real data

The record is not fixed

DWR revises published values. What that means, and how to see whether it has happened to a structure you care about.

Lesson C2 · 3 minutes · works with real data

Anatomy of a call

Who places a call, what it says, and what it does — read from the district's real call record.

Lesson C3 · 4 minutes · works with real data

Is the river getting harder to divert from?

Every ditch rider says it. Days under call per year puts a number on it, for one real district.

Lesson C4 · 4 minutes · works with real data

Under the Ground · groundwater

Tributary groundwater is the river

On a delay — which is the whole difficulty, and why 1969 changed everything for wells.

Lesson D1 · 4 minutes

Reading a well, reading an aquifer

Why a datum matters, why units must never mix, and which aquifers answer to a different body of law.

Lesson D2 · 4 minutes

Pumping now, depletion later

The stream feels a well months or years after the pump starts. Timing, not volume, is the argument.

Lesson D3 · 4 minutes