Water Rights Priority Dates: What They Mean for Your Property

A water right's priority date is the date the right was established, typically the date a formal application was filed with the state, though for historic rights it may be the date beneficial use began.

Under prior appropriation, every water right on every stream in a given state has a priority date. When the stream runs low and can't supply everyone, rights are satisfied in priority order: the oldest date first, down through progressively newer dates until the water runs out. Rights that are too junior to receive water during a shortage are curtailed.

Think of it as a queue. The 1880 right is first. The 1920 right is somewhere in the middle. The 1965 right may be fifty-seventh. If the stream runs dry after the forty-second user has been served, rights forty-three through one hundred receive nothing.

Consider Cache Valley, Utah. Dozens of farms divert water from the Logan River and its tributaries. In a dry year, the river simply can't meet all the demand.

A farm with an 1895 irrigation right may irrigate without interruption from April through September, every year, regardless of conditions. The water is senior enough that the stream satisfies it before most other users.

A farm on the same stream with a 1955 right may irrigate freely in wet years, but in any dry year will receive a notice from the watermaster: priority call in effect, junior rights curtailed. That farm may receive no water for weeks or months at a time.

The difference in farm viability between those two properties can be enormous, even if every other characteristic is identical.

Curtailment (also called a priority call) is the formal process by which junior water users are required to stop diverting so that senior rights can be filled.

The mechanics vary by state. In Utah, the State Engineer issues administrative calls. In Idaho, district watermasters manage curtailment within their districts. In Colorado, the division engineer issues curtailment orders.

If your water right receives a curtailment notice, you must stop diverting immediately. Continuing to divert in defiance of a call is a serious legal violation. A curtailment doesn't eliminate the water right. It only restricts diversion during the shortage period. When conditions improve, junior users can resume.

This isn't about seniority in abstract terms. In many Mountain West basins, 1880s rights represent the earliest large-scale irrigation development. By the time rights were established in the 1950s through 1970s, most reliable water had already been claimed.

An 1880 right on the Snake River may be "almost always wet": it receives its full allocation in nearly every year, including drought years. A 1955 right on the same river may be "frequently dry", curtailed in any below-average water year.

Water professionals quantify this as reliability: the percentage of years a right can expect to receive its full allocation. A right with 95% historical reliability commands a dramatically higher price per acre-foot than one with 60% reliability, even at identical volumes.

Over a 30-year farming horizon, the difference translates to fundamentally different crop revenue, insurance costs, and underlying land value.

Priority within a state is only part of the picture. Most major river systems in the Mountain West are subject to interstate compacts that allocate water between states.

Under the Colorado River Compact, the upper basin states (Colorado, Utah, Wyoming, New Mexico) collectively cannot deplete the river below a certain amount passing to the lower basin. When the upper basin is behind on its compact obligations, this can constrain water use throughout the system, regardless of individual state priorities.

Similar compacts govern the Snake River, the Bear River (Utah-Idaho-Wyoming), and others. For buyers in interstate basins, compact status is a background risk worth understanding, especially as climate change puts increasing pressure on long-established allocations.

Priority dates appear on the main record in each state's database:

• Utah: Listed as "Priority Date" in the DWRi portal record at waterrights.utah.gov
• Idaho: Listed as "Priority Date" in the IDWR record at idwr.idaho.gov
• Colorado: Listed as "Appropriation Date" in the CDSS record at cdss.state.co.us

For canal company shares, the underlying company holds state water rights with specific priority dates. Ask the company for documentation of its decrees and the associated priority dates.