Last verified Jul. 2026

Colorado's water supply picture

What "over-appropriated" actually means

It does not mean the state is running dry. It means the paper exceeds the water: if every decreed right on a stream diverted its full decreed amount at once, the stream would not supply them. That is not a defect in the system — it is the expected result of 170 years of appropriation under a rule that never stops issuing rights as long as unappropriated water exists at the moment of claiming.

The consequences are structural rather than dramatic:

• A new right in most basins is junior enough to be nearly worthless in a dry year.
• New wells generally require an augmentation plan to replace their depletions C.R.S. § 37-92-103(9).
• Cities that need supply buy senior agricultural rights rather than appropriating — which moves water off farmland permanently.
• Seniority, not need, decides who goes short.

The five structural pressures

1. The paper-versus-wet gap

173,056 decreed records exist statewide. Nothing like that many are in priority at once. Understanding that gap is most of what separates people who make good water decisions from people who buy a decree and expect water.

2. Agriculture-to-municipal transfer

Front Range growth is supplied substantially by purchasing senior irrigation rights and moving them, through a change case, into municipal use. Because only the historical consumptive use transfers, the transaction retires irrigated acreage permanently — the pattern usually called buy-and-dry. It is the single biggest ongoing shift in Colorado water, and it is a market process rather than a policy one.

3. Geography: headwaters with obligations

Colorado receives no water from upstream and owes water downstream under compacts on the Colorado, South Platte, Arkansas, Rio Grande and Republican. Those obligations sit above in-state priority — see the Colorado River Compact. Much of the Front Range is supplied by transmountain diversion from the West Slope, which makes basin politics an intra-state matter as much as an interstate one.

4. Groundwater catching up with surface water

Tributary groundwater was pulled into the priority system in 1969, decades after wells proliferated. In parts of the South Platte and Arkansas that reconciliation is still working through, and it is why well augmentation requirements are strictest there.

5. Aging infrastructure and imperfect measurement

Ditches dug in the 1870s are still the delivery system in much of the state, and administration depends on measurement that is better than it was and still uneven.

Where the calls actually are

The distribution of active calls is a useful map of pressure. On July 22, 2026:

Read it as a snapshot, not a ranking of scarcity — call counts reflect how many separate stream reaches are being administered, which depends on basin structure as well as on how dry it is. The divisions page explains what each covers.

What the system does well, and badly

Well: it is predictable. A right's yield is a function of a date, and that date is public. It makes water a transferable asset, which lets supply move to where the demand is without expropriation. And it has functioned for 150 years with remarkably little violence, in a place where water is the binding constraint on everything.

Badly: it takes no account of need, efficiency, or environmental value except where the legislature has bolted those on — instream flow rights, recreational in-channel diversions, and the conservation programs that protect fallowing from counting as abandonment C.R.S. § 37-92-103(2). And it can push owners to divert water they do not need in order to protect a right, which is the least defensible thing about it.

What it means if you own or are buying

Nothing on this page changes the practical advice: seniority is the asset, verify everything in the state’s records, and price a right by how often it has actually been in priority rather than by what the decree says. What rights are worth works through that, and the basics covers the system itself.