TWIN FALLS — For decades, groundwater and surface-water users have played a delicate game of give and take.

Now the game is tug of war.

On Friday, the Idaho Supreme Court will hear an expedited case that will likely decide the future of Idaho water law. At stake is how Idaho’s most precious resource is distributed — for irrigation, industry and consumption.

Ramifications from this case are far reaching: If you use water in this state, this decision will affect you.

“This case couldn’t be more important,” said Lynn Tom-inaga, director of the Idaho Ground Water Appropriators. “It’s going to decide who stays in business and who doesn’t.”

The case arises after 5th District Court Judge Barry Wood decided on June 2 that the Idaho Department of Water Resource’s rules for applying conjunctive management are unconstitutional.

Conjunctive management is a system of legal guidelines the IDWR director follows to administer water between ground and surface water-right holders. It gives the IDWR director, a governor-appointed position, a liberal amount of discretion when it comes to deciding who gets water.

The district ruling came in response to a lawsuit filed by a coalition of surface water users — including the Twin Falls Canal Co., the Burley Irrigation District and the Minidoka Irrigation District — challenging the constitutionality of conjunctive management.

Here’s the back story:

In spring 2005, IDWR Director Karl Dreher responded to a call for water from senior-right surface users who wanted junior users curtailed. Dreher allocated some water for the call but not as much as was asked for. In response, senior users filed suit in district court.

Senior users cited prior appropriation — a doctrine that says the holders of older water rights should get water before junior-right holders.

Essentially, Wood’s ruling upheld the prior-appropriation doctrine and rendered conjunctive management obsolete but not for the reasons the surface-water coalition’s attorneys asserted. Wood ruled that conjunctive management is unconstitutional because the system lacks tenets and procedures he viewed as constitutionally mandated.

Who gets hurt?

“Anyway you cut the cards,” Wood said in August, “there’s going to be harm to somebody.”

He’s right.

Without conjunctive management, Dreher would be forced to shut down junior groundwater users — nearly 7,000 wells and 1.2 million acres of irrigated land — and water supplies for several municipalities and the thousands of citizens who use water every day. That, groundwater users say, would cripple Idaho’s agricultural economy and have devastating effects on towns across southern Idaho.

Tominaga, a groundwater supporter, said that if junior users don’t have guaranteed access to water, banks won’t finance their operations.

He also said curtailment doesn’t always mean more water for surface users. Because groundwater moves much slower than surface water, the effects of curtailment sometimes aren’t seen for years.

Doesn’t matter, say surface-water users. They say they’re being harmed under the current system — they want water they’re entitled to under prior appropriation, and they worry the system is moving away from that doctrine.

“I think the state of Idaho is asking the court to depart from administering by prior appropriation,” said Tom Arkoosh, an attorney who will argue the case. “And first and foremost, the aquifer needs to be administered through prior appropriation.”

How do water rights work?

In his 127-page decision, Wood quoted numerous times the water-rights debate of the 1889 constitutional convention when Idaho’s legal framers, he implied, sought a system of permanence and stability.

Their system operated relatively efficiently until the 1940s, when farmers realized they could irrigate rights-free by pumping water from the Eastern Snake Plain Aquifer. Pumpers continued to irrigate without water rights until 1951. The new groundwater rights were administered separately from surface rights until the 1990s, when scientists determined that groundwater and surface water are connected.

That’s when the state began using conjunctive management. Senior water-right holders could make a water call requiring the IDWR director to shut down, or curtail, groundwater users so that senior holders could get their water in times of drought.

Pumpers who could not afford to stop pumping could pay senior-right holders for the lost water or lease water from other users.

Under conjunctive management, senior holders had to prove injury — that crops suffer — for a water call to work. But that’s hard to do.

Making things more complex is a 2003 law that states if a water-right holder shifts management techniques that require less water — like many farmers did when they switched from flood irrigation to sprinklers in the 1970s — the user still retains the larger water right.

In recent years, water users have worked (mostly) together to distribute a resource of which there is simply not enough. Recent data show a declining water level in the aquifer, and Idaho experienced its worst drought in nearly 100 years from 1999 until 2005. Some experts say the drought isn’t yet over.

Progress derailed?

The Supreme Court case calls into question the future of recently proposed deals and programs meant to prevent the legal battle the sides now find themselves in. A Conservation Reserve Enhancement Program that pays groundwater pumpers for idling their land is in danger unless more farmers sign up. CREP requires farmers to prove access to water before joining the program, and if the Supreme Court upholds the Wood decision and groundwater pumpers are curtailed, they won’t be able to prove access and the program might fail.

Ripples from the decision also may affect an aquifer-recharge plan now being assembled by the IDWR board. The plan is slated for presentation to the 2007 Legislature, but the Supreme Court decision will likely affect how, and if, the Legislature executes the board’s recommendations.

Also proposed are plans to recharge the aquifer through injection wells and by running extra water through canals so it can seep into the aquifer; plans to line canals in the Thousand Springs area to increase efficiency for spring-water users; and plans to transfer some groundwater rights to senior rights.

But, at least for now, the fate of these plans — and the fate of Idaho water law as users now know it — hangs in the balance. With virtually no one willing to predict how the court will decide, Idahoans can only tread water until the court decides just who will sink and who will swim.

Those close to the case expect a decision within two months.

Times-News staff writer Matt Christensen covers natural resources. Contact him at 735-3243 or at matt.christensen@lee.net.

Meet the players The Supreme Court decision that will decide the constitutionality of conjunctive management — rules that tell Idaho Department of Water Resources Director Karl Dreher how to jointly manage groundwater and surface-water right holders — will affect nearly every water user in Idaho. Here are the five major players in the issue and what they have at stake: 1. Groundwater users Those who pump water rather than use surface water will be affected more than any other interested group. If the court upholds an earlier court decision declaring conjunctive management unconstitutional, thousands of wells could be shut down. 2. Surface-water users Irrigators who rely on canals and springs for water largely support the prior-appropriations doctrine that states that water-right holders with older rights get their water before junior water-right holders. Surface-water users want the earlier court’s decision to stand so that junior-water users, who are largely groundwater pumpers, will be curtailed and surface users can have their full water rights fulfilled. 3. Municipalities Many Magic Valley cities — including Wendell, Gooding, Jerome and Shoshone — rely on groundwater. Although these cities will likely weather a curtailment (Jerome rarely reaches 50 percent of its total water capacity), ag-related businesses in those communities might not. The cities mostly fear economic fallout. 4. Environmental groups Environmentalists are worried about two things: the aquifer and salmon. The court’s upcoming decision will likely affect how, and if, the Eastern Snake Plain Aquifer is recharged. Most environmentalists oppose injection-well recharge because of water-quality concerns. Another concern is salmon. The outcome of this case may affect how much water is diverted to rivers to aid spawning fish. 5. Spring users Water users who rely on springs — water that bubbles to the surface from the aquifer — are mostly senior, surface-right holders in the aquiculture business. For the most part, they advocate the prior-appropriations doctrine and blame groundwater users for depleting the aquifer.

Liquid dictionary A dictionary of Idaho water words Adjudication: A proceeding in court that determines water rights. Aquifer: Underground water that moves through permeable rock. Call: When a senior water user demands junior users stop using water so he can get his legally entitled share. Conjunctive management: A system of guidelines to manage groundwater and surface-water rights jointly. Curtailment: When a water user’s rights are withheld to supply water to a more senior user. Futile call: A call that shuts down a junior user, even though that curtailment may not result in more water for a senior user. Groundwater: Water, usually pumped, from the aquifer. Junior user: Someone who holds a junior water right. Junior water rights are not as old as senior water rights. Recharge: Act of returning water to the aquifer. Spring: Groundwater that flows from the aquifer to the surface. Surface water: Water flowing through rivers, streams, lakes, canals and springs. Senior user: Someone who holds a senior water right. Senior water rights are older and, in most cases, more valuable than junior water rights. Water right: A legal authority to divert water.

Important dates in Idaho water history 2006 The Idaho Supreme Court hears a case on the constitutionality of conjunctive management. 2003 Legislature passes a law that states that even if a water-right holder doesn’t use all the water in a right, he is still entitled to that water. Also this year, salmon advocates sue after demanding more water from federal reservoirs be released to help salmon. 1995 Legislature approves a plan that allows groundwater users to jointly manage groundwater pumping. This established the precedent of junior users leasing or paying surface-water users. 1993 The Idaho Department of Water Resources orders a moratorium on new wells. 1987 Snake River Basin Adjudication established to reconcile water-right disputes. 1985 Idaho Power Co. and the state reach a compromise in the Swan Falls Agreement that sets minimum water flows in rivers the company uses for hydroelectricity. 1965 The Idaho Water Resource board is created. 1947 The first groundwater pump is built. 1913 The Foster Decree determines water rights and expands state watermaster authority. 1905 With construction on Milner Dam under way, I.B. Perrine starts the Twin Falls Land and Water Co. 1902 Reclamation Act grants federal aid for irrigation projects. 1894 U.S. Congress passes the Carey Act that gives federal land to anyone willing to develop it. The Magic Valley is born.