Raising the River by Razing the Trees

Still struggling with drought on the Colorado River despite a winter of bountiful storms in the Southwest, water managers are dusting off provocative ideas for filling the river -- among them, logging mountainsides to wring more runoff out of national forests and seeding clouds to pull more snow out of the sky.

“A lot of things that are controversial will be looked at,” said Central Arizona Project general manager Sid Wilson. “We can’t do things the way we’ve always done them. We have to find ways that are creative to address tomorrow’s problems.”

Officials are also talking of reactivating a much criticized desalting plant near Yuma and building new storage basins along a Southern California canal that draws from the Colorado, one of the West’s main water supplies.

“You just run into a myriad of ideas,” said Wilson, whose agency supplies Colorado River water to Phoenix and would suffer some of the first cuts if a shortage were declared in the lower basin. “There’s been a lot of work done on weather modification, vegetation management ... just pull together all the information and see what we’ve got.”

About 25 million people from Colorado to Southern California depend on the river for at least some of their water, and although a slew of winter storms loosened the grip of a historic drought this year, the basin’s epic dry spell is far from over. Even without a drought, the time is approaching when use along the 1,400-mile river system will exceed the Colorado’s average annual flow.

Environmentalists say the answer to growing demand is more conservation and more efficient allocation of existing supplies, not efforts to squeeze more water out of the ecosystem.

“Those are ludicrous,” said Jennifer Pitt of Environmental Defense’s Colorado office. “We’re going to cut down our national forests so we can water our lawns on the front range? Give me a break. There’s no way people are going to accept that.”

The idea of opening up the forest to generate more runoff in mountain watersheds is not a new one. Experiments date from the early 1900s, and many have been conducted in Colorado, the main source of snowmelt for the Colorado River.

“People have talked about it literally for over 100 years, and the reality is it becomes very hard to implement,” said Lee H. MacDonald, a Colorado State University natural resources professor who co-wrote an extensive 2003 review of experiments to increase forest water yield. “Socially it’s not particularly acceptable.... It’s hard to cut enough trees to really make a substantial difference to the flow in the Colorado River.”

One of the photographs on the cover of his report shows an experimental forest in Wyoming that was logged to boost water production. Riddled with roads and more than 200 small clear cuts, it looks like a moth-eaten rag.

Although many of the experiments documenting increased water yields involve some form of clear-cutting, Wilson shied away from suggesting that. “Reducing the density of trees and increasing the grasses can improve runoff, but I don’t necessarily believe clear-cutting is the answer.”

The principle of getting more water out of a forest is simple: Remove trees and their roots aren’t pulling water out of the ground and transpiring it into the atmosphere. Snowfall isn’t trapped on limbs, where it evaporates. A pattern of small clear cuts, also known as patch cuts, allows snow to pile up, adding to the snowpack and spring snowmelt.

But the technique works only in areas that get at least 18 inches of precipitation a year, largely limiting it in the Colorado basin to higher-elevation watersheds that are primarily national forestland. And while studies have shown logging for water can increase runoff in wet years as snowmelt is peaking, it has little effect in dry years or during the summer, researchers say.

Moreover, to have a measurable impact, at least a quarter of the vegetation must be cleared from an area, said U.S. Forest Service hydrologist Daniel Neary of the Rocky Mountain Research Station. Conducting that magnitude of timber harvest on a widespread basis would exact a toll, said Rocky Mountain Regional Forester Rick Cables.

“In the high-elevation forest, to get any appreciable increase in water we would have to remove one out of four trees or clear one out of four acres and then maintain it in an open condition,” he said.

“The effects on wildlife ... scenery, recreational opportunities, the environment would be substantial with such an approach. The Forest Service does not believe there would be public support nor would it be wise to try to maximize a single resource -- in this case water -- to the potential detriment of other resources.”

Cloud seeding to promote snowfall is potentially less controversial. It is already being done to some extent in the Colorado basin and has been practiced in the Sierra Nevada in California for decades by public and private utilities to boost precipitation and hydropower flows.

Though Bill Cotton, an atmospheric science professor at Colorado State University, said research on its effectiveness has shown mixed results, under certain conditions seeding can increase snow’s water content by 8% to 10%.

“If we’re going to continue with a drought pattern for the next decade or so, I think there will be an increase, if not in [seeding] operations, then at least research,” he said.

Combining cloud seeding with runoff-enhancing logging could add significant flows to the Colorado, said Dennis Underwood, chief executive of the Metropolitan Water District of Southern California.

“We need to go back and look at work done previously and see if it’s worth pursuing.... If there’s no stomach for it, that’s fine, but you need to go back and visit it,” he said.

More immediately, officials are considering restarting a Yuma plant that takes the salt out of irrigation drainage water so it can be pumped into the river.

Criticized at the time as a boondoggle, the plant was run briefly in the early 1990s by the U.S. Bureau of Reclamation but then shut down because of operation problems and because the water wasn’t needed.

The drought has revived interest in the desalter, and the reclamation bureau is starting repairs on the facility, which could return as much as 100,000 acre-feet of treated water to the river a year. An acre-foot is roughly the amount used annually by two Southern California households.

It would take several years of work and about $28 million to get the plant running again, and its operation would then cost $30 million a year, said Robert Johnson, the regional director of reclamation for the lower Colorado.

If the desalter were reactivated, that would stop the flow of agricultural drainage to the Cienega de Santa Clara, a large, ecologically valuable wetland south of the Mexican border that is mostly fed by the salty irrigation water. The ponds and marshes are used by 95 bird species, including some that are endangered. So drying up the wetlands would come at considerable environmental cost.

Wilson would like to see the Yuma plant in operation, but after visiting the wetlands, he said he recognized their ecological importance.

He and other water managers have been meeting with environmental groups, and he said they hoped to issue a report this month outlining ways the plant could run while still sending water to the Cienega.

The seven Colorado basin states are also asking Congress for $30 million to begin construction of several surface storage basins along the All American Canal, which carries Colorado River water to Southern California farms along the Mexican border. All told, the project would cost $80 million, funding that Congress would have to approve.

More storage there would allow managers to capture flows that swell the lower end of the river system during storms and are lost to Mexico because the river’s reservoirs lie to the north.

“It doesn’t get you any more [flow in the river] but makes more effective use of it,” Underwood said.

But capturing the storm flows means they won’t reach the Colorado’s water-starved Mexican delta. “Any wet-year water goes into the main stem of the delta, and that’s what keeps habitat alive and healthy. So if we are building yet more storage in the U.S., we’re depriving the delta,” Pitt said.