LANDER - Since his first year in the Wyoming Senate seven years ago, Sen. Cale Case, R-Lander, has pursued an elusive quarry - a revision to Wyoming water law that would allow greater flexibility for instream flow, or leaving water in streams as a benefit to fisheries.

"I've tried a lot of different things," Case said last week, "and I'll keep at it in the future."

Like most of the western United States, Wyoming operates under the doctrine of "prior appropriation," which gives those with the earliest water rights the first right to water. This "first in time, first in rights" doctrine means that in a year when there isn't enough water to satisfy all water rights, the early water right holders get water, followed by junior water right holders until the water runs out. When there's a drought, many junior water right holders go without water.

In addition, the "use it or lose it" rule means that if a senior water right holder doesn't use the water for a beneficial use (irrigation, industrial or municipal), then that water can be lost to a junior water right holder who will put the water to work.

In 1986, the Wyoming Legislature passed a law which recognized leaving water in the stream for fisheries as a beneficial use. Case has spent much of his legislative career trying to broaden what he called a very narrow law.

"I think it might have to be done by ballot initiative," Case said. He said there's more than enough votes in the state House and Senate to pass an instream flow bill, but his proposals just don't get past the powerful agricultural committee chairmen in the House and Senate.

Case is floating the idea of a citizen initiative with the help of various groups and organizations that like the idea of instream flow as a beneficial use.

Ballot initiatives are fairly difficult to pull off in Wyoming, he said, compared to other states. Here, not only do you need 20 percent of the electorate to sign an initiative petition, but you need to hit that 20 percent threshold in every county - no exceptions.

"You can't just go to Cheyenne, Casper and Laramie and get all your signatures for a statewide initiative," he said.

He said it might be possible to get his bills assigned to committees other than agriculture panels, but that would mean asking fellow legislators to go against decades of tradition and long-established practice.

While he's certain he has the votes to pass instream flow legislation overall, he's much less certain of votes to remove instream flow bills from the agriculture committees.

Case emphasized that he's not being critical of the ag committee chairmen.

"They just don't see the benefit of instream flow," he said.

And there are more than fish that can benefit from instream flow, such as public health and water quality.

"You can have a low-water situation where the E. coli counts go right through the roof, and it is dangerous to public health. More water would flush the stream and dilute the E. coli to where the water was safe," Case said.

Case tries to keep up with evolving water law in neighboring states, but is somewhat resigned to the fact that Wyoming is inherently more conservative than its neighbors when it comes to water.

For example, Montana has successfully found a way for water right holders to voluntarily lease their water to second parties such as Trout Unlimited, yet retain ownership of those water rights. In one case on the North Fork of the Blackfoot River, Trout Unlimited replaced a leaky irrigation canal with a more efficient center-pivot irrigation system and a solar powered stock-watering tank.

"Old Montana ranch families have learned that they can keep their water rights while getting paid to lease the water to others," said Laurie Goodman, water director for Wyoming Trout Unlimited. She added that the Montana Farm Bureau and Republican Party support the concept of allowing water right owners to benefit from leasing their water.

Goodman recognizes that Wyoming might not be prepared to lease water to instream uses. A better and perhaps more comfortable approach might be to expand temporary change of use definitions, to allow instream use.

"We'd have the same effect either way," Goodman said, "an economic opportunity to be paid money to leave water instream."

She said State Engineer Patrick Tyrell has approved more than 900 temporary changes of use since 2002 - everything from oil and gas, to irrigation and even snow-making.