Water in Idaho: Prior Appropriation Basics

Water in Idaho does not belong to the person whose land it crosses. It does not belong to the county. It belongs, in the language of Article XV of the Idaho Constitution, to the public, and a person or company holds a right to use a measured amount of it. That right is property. It can be bought, sold, inherited and lost. But what you hold is a right to divert and use, not title to a river.

Everything else in this course follows from that one fact. When you read about a call on the river, a protest of a transfer, a domestic well in a new subdivision or a canal company assessment, someone is working out who holds which right, how old it is, how much it covers and what it is used for.

Who owns the water

Article XV, section 3 of the Idaho Constitution says the right to divert and appropriate the unappropriated waters of any natural stream to beneficial uses "shall never be denied." The same section sets the rule for shortages: as between those using the water, the one first in time is first in right. It also ranks the kinds of use when a natural stream cannot supply everyone. Domestic use comes first, subject to limits set by law. Agricultural use ranks above manufacturing. In an organized mining district, mining and the milling that goes with it rank above manufacturing or agriculture.

Idaho Code 42-201 adds the working rule: rights to divert and use the waters of the state are acquired and confirmed through the application, permit and license process in Title 42, and the Idaho Department of Water Resources (IDWR) has the authority over appropriating the state's surface and ground water. Rights that were started by actual diversion and use before the permit system took effect can still be recognized, which is why many old rights show up in court decrees rather than in permits. Lesson 6 covers how those older rights were gathered in the Snake River Basin Adjudication.

So there are two layers. The public owns the resource. Individuals, farms, cities, districts and companies hold rights to use pieces of it, and each piece has a date, an amount, a place and a purpose.

First in time, first in right

The idea is simple enough to say in a sentence. Whoever first diverted water and put it to a beneficial use gets to keep using that amount before anyone who came later. The date a right was established is its priority date. A right from 1895 is senior to a right from 1962. In a year with plenty of water, none of that matters; the ditch is full and everyone is served. In a dry year it decides everything.

Picture a creek with three diversions. The rights are for 6 cubic feet per second (cfs) dated 1893, 4 cfs dated 1921 and 3 cfs dated 1977. When the creek carries 15 cfs, all three are filled, with 2 cfs left in the creek. When it drops to 10 cfs, the 1893 and 1921 rights take their 10 cfs total and the 1977 right gets nothing. When it falls to 5 cfs, only the 1893 right is served, and it still lacks a cfs. Nobody splits the shortage evenly. The most junior user absorbs it first, and the newest rights can be shut off entirely.

The picture matters for money too. A farm with a 1977 right on that creek might have the same acres, the same soil and the same machinery as its neighbor, yet be worth far less in a dry year because its water is the first to go. A junior right can still be valuable if the source is reliable or if the farm holds a stored-water contract or a well as a second supply. That is a fact about the water supply, not a flaw in the right.

Beneficial use: the measure of a right

A water right is not a right to flood a field with as much water as the ditch can carry. It covers the water actually put to a beneficial use, and it extends only as far as that use. Idaho recognizes irrigation, stock watering, domestic use, municipal supply, commercial and industrial use, power generation, fish and wildlife, recreation and others. The right is described by what it is used for, how much, and where.

The use-it-to-keep-it side of this is the reason Idaho Code 42-220 limits an irrigation license to no more than one cubic foot per second for each 50 acres irrigated. It is also the reason a right that goes unused for five years can be forfeited, with specific exceptions, which lesson 3 covers in detail. In practice beneficial use keeps the water from being held for speculation or wasted: you hold what you use, and you use what you hold.

Prior appropriation compared with riparian rights

Eastern states grew up with riparian rights. If your land touches the water, you may make reasonable use of it, and neighbors along the same stream share. The right comes with the land and depends on the stream being there.

The reason for the difference is geography. Idaho's farmland sits in dry country, often miles from a river, so the system had to let a person move water to where it was needed and protect the person who built the canal. A rule that required land to touch the stream would have made most of the Snake River Plain unfarmable.

Where Idaho's water comes from

Most of Idaho's water begins as snow. Mountain snowpack builds through winter and melts in spring, filling rivers like the Snake, the Salmon, the Boise and the Clearwater. Reservoirs on those rivers hold part of the runoff for the irrigation season. Some of it soaks into the ground and moves through aquifers, coming back out as springs and as gains in the river. Winter storms, spring melt, summer heat and the timing of all three set the year. A low snowpack year is a short water year, and people in the irrigation business talk about it in the winter, not in July.

Water is also moved around by people. Canals divert from rivers and carry water to fields. Return flows from irrigation, called seepage and drainage, find their way back to streams and aquifers, and downstream users depend on them. That makes one person's efficiency another person's loss, a point that comes up again in lessons on irrigation districts and the Eastern Snake Plain Aquifer.

Ground water and surface water

Ground water is water in the pores of soil and rock below the surface. Surface water is in streams, lakes and canals. In Idaho both are covered by the same appropriation system, and ground water rights have priority dates too. The two are not separate worlds. Where an aquifer feeds springs or flows into a river, pumping can reduce that supply, sometimes with a delay of months or years. So a well drilled in a field can affect a senior surface right miles away. Idaho's Conjunctive Management Rules, covered in lesson 7, exist because of that link.

For a rural lot owner the practical point is smaller: a domestic well does not float outside the system. For a farmer on a well the point is larger: a well right has a priority date, and in some areas that date decides whether pumping continues in a dry year.

Why this matters to residents

• Buying land. Land with a water right is a different asset than land without one. The right's priority date, amount and place of use are on record at IDWR and can be checked before purchase. Lesson 6 shows how.
• Subdivisions. When farmland becomes lots, the water right that served it may be changed, split, kept by the seller or lost. Residents on new lots are often surprised to find the irrigation water stays with the old ditch company or the old owner.
• Local officials. County commissioners and planning commissioners do not decide water rights, but their land use decisions put people on wells and change where water is needed. Knowing which decisions belong to IDWR and which to the county prevents a lot of wasted testimony.
• Local news. Calls on the river, protests of transfers and curtailment orders are covered by notices and orders anyone can read. Water stories are paper-trail stories.

Questions and answers

Is a water right the same as owning water?

No. The public owns the water in the state's sources. A water right is the right to divert and use a stated amount, for a stated use, with a stated priority. It is property and it can be sold, but it is a right of use.

What is a priority date, and where do I find mine?

It is the date a right was established, and it appears on the water right record. IDWR's online water right search lists the priority date for each right. Lesson 6 walks through the search step by step.

Do I need a water right to water my lawn and garden from a creek?

In general, diverting water from a natural watercourse without a right is not allowed under 42-201, and the exceptions in that section are narrow (fire fighting, forest practices and hazardous spill cleanup, for example). Domestic exemptions from wells are separate and covered in lesson 5. If you are unsure about a specific diversion, call the IDWR regional office.

What is the difference between a cfs and an acre-foot?

A cfs is a rate, like miles per hour. An acre-foot is a volume, like miles traveled. One cfs for one day is about 1.98 acre-feet.

Why can a junior right be shut off while a senior right keeps running, even on the same canal?

Because priority, not equal sharing, decides who is served. The watermaster follows the priority dates of the rights in the district.

Does Idaho law ever put one kind of use ahead of another?

Yes. Article XV, section 3 ranks uses when a natural stream is short: domestic first, subject to limits set by law, then agriculture above manufacturing, with a special rule for mining districts. The ranking works alongside priority dates, and how the two fit in a specific case turns on the statutes and decrees.

Is ground water really connected to rivers?

In many places it is. Aquifers feed springs and river reaches. How strong the connection is and how fast pumping effects travel are studied basin by basin, and lesson 7 covers the Eastern Snake Plain.

Who can I call with a question about water in my area?

The IDWR regional office for your county, or the watermaster if your source is in a water district. Lesson 2 explains both.

Hard questions

"First in time, first in right is unfair. Why should the oldest right win when a newer user needs the water more?"

The system rewards the person who built the ditch and took the risk early, and it gives everyone certainty about whether the water will be there. The tradeoff is that it does not weigh need. Some water users argue that rigidity can leave a high-value or high-need use without water while a lower-value use is served; defenders say certainty is the point and that rights can be bought, sold and leased (lesson 4) so water can move to higher value uses by agreement. Idaho has also used water banks and leasing for that reason. Both views rest on real features of the system.

"Isn't it a taking if the state limits or forfeits a right that someone has used for generations?"

The law treats a water right as property, and also as a right of use conditioned on beneficial use. Forfeiture requires proof of long non-use, with statutory exceptions, and a person has the chance to be heard first. Disputes over whether a specific limit crosses a line are decided in court on the facts of the case, so this lesson does not give an answer for any one case.

"Why should I care if I only have a small domestic well?"

Because the number of wells in a basin adds up, and because a domestic well sits in the same aquifer as larger rights. It also matters if you buy or build, since local rules about water supply for new lots reach you through the county and IDWR. Lesson 5 covers what a domestic well can and cannot do.

"Isn't water law just too complicated for a normal resident to follow?"

Parts of it are. But the key facts about any right are five items on one record: priority date, quantity, source, purpose and place. Learn to read those and most local news makes sense. The rest of this course builds from there.