Over the past century the Okanagan River has been badly degraded, and in the process trout and salmon runs have virtually been wiped out.

The river once meandered through a series of marshes and verdant ox bows as it ran south from Okanagan, Skaha and Osoyoos Lakes, before linking with the Columbia River in north-central Washington State.

But when fruit growing and other agriculture flourished in the Okanagan Valley, provincial authorities straightened the river and put in a number of structures to control its flow, bringing an end to flood threats.

"They basically created a canal," said Ian McGregor of the B.C. Ministry of Environment, which is playing a key role in the restoration project.

Mr. McGregor said the combined impact of habitat destruction in the Okanagan Valley and dams on the Columbia, dramatically reduced sockeye and chinook runs. Now only a handful of native salmon spawn in the river. Big rainbow trout, which used to move into the river in the spring and fall, have also largely vanished.

But Mr. McGregor said the desert river has a tremendous potential.

The project is being worked on by the provincial Ministry of Environment, the Okanagan Nation Fisheries Commission, the federal Canadian Department of Fisheries and Oceans, and the Douglas County Public Utilities Commission, in Washington State.

"It is a huge project," said Mr. McGregor.

Feasibility studies are still underway, but the first real work on habitat restoration may take place as early as this summer.

Mr. McGregor said one key aspect of the project is to restore the river to its natural bed wherever possible.

"There was a series of ox bows from Okanagan Lake to the U.S. border. They were taken out for flood control," he said. "The ox bows are a mecca for wild life. They're sitting there with some water in them, either spring water or seepage from the river, but they're not all that productive.

"Is it feasible to put the river back in there? That's the question we're looking at right now, and it seems that there are some real opportunities to do that."

A classic example exists just above Osoyoos Lake, where the Okanagan River runs in a straight line, between raised, canal-like banks. Just over those banks, however, lie a series of stagnating marshes, surrounded by thick willows. If it was possible to divert the river back through there, it would open up a rich area of habitat, restoring flow to the marshes and linking the river to extensive rearing areas for fish.

To improve conditions in the river itself, the Okanagan Basin Technical Working Group plans to install a series of Newbury Riffles, structures that dissipate energy and create fish habitat.

"Newbury Riffles are basically V-shaped structures. It looks like a natural river once you've got them in," said Mr. McGregor. "They create a bubbling effect in the current. On the upside, spawning gravel will accumulate, on the downside the eddy helps create a pool."

Basically the man-made riffles slow down the river, creating places for fish to spawn, feed and rear. As it stands now the once-rich Okanagan River pretty much runs through the desert like a flume.

"It's a pretty sterile environment, but the potential is there," said Mr. McGregor. "It once produced some big rainbows."

With Newbury Riffles in place, it might be possible to remove some of the 17 "drop structures" installed in the river as flood control devices. The drop structures look like tiny dams. Migrating fish use a lot of energy getting past them, and it's though they might be too much for tired salmon near the end of long spawning runs.

Part of the restoration project calls for native plants to be reintroduced in the riparian zone. When the Okanagan River was straightened, much of the vegetation along the banks was cut down. That's not good for fish in any environment, but in a desert it probably had devastating effects.

The Okanagan River runs through a remarkably beautiful valley. It should support a great trout fishery, and it should have big runs of sockeye and chinook spawning in it.

The project that's just beginning has that as its ultimate goal.

"It's going to take a lot of work. It's a huge project," said Mr. McGregor.

"A lot of damage has been done over the past century. But there is a lot of energy in the Okanagan Valley right now. A lot of people are pulling together to make this happen."