Dammed, Diverted, Divvied Up, World’s Great Rivers Drying Up : Environment: Water demand worldwide has tripled since 1950 and the shortages are only going to get worse as the population increases, experts warn.

When Robert Redford set out to film the movie “A River Runs Through It,” he went to the Blackfoot River in Montana where the novel of the trout-fishing family story was set.

But the Blackfoot doesn’t run through it anymore. The trout are gone, their water habitat degraded by logging and misuse.

So Redford moved the set to the Gallatin and Yellowstone rivers near Yellowstone Park, where the trout still run.

It is the latest chapter in an old story.

Some of the world’s mightiest rivers never reach the sea. They’ve been diverted and siphoned off to grow cotton and lettuce, to fill bathtubs and swimming pools, to turn the turbines of power plants, to cool the wheels of industry.

Unfortunately, when planners were divvying up the rivers’ resources, they didn’t count the rivers in for any, with the result that they greatly changed the ecology and habitat for fish and birds and other wildlife. Or simply erased it.

Some 900 years before Christ, the Assyrian Queen Sammu-Ramat, so the story goes, after irrigating what is now northern Iraq, had inscribed on her tomb:

“I constrained the mighty river to flow according to my will and led its water to fertilize lands that had been before barren and without inhabitants.”

Today, even as some rivers in the heartland of America flood and wipe out whole towns, many of the world’s majestic waterways are drying up, great mountain-born torrents reduced to a trickle.

What happened was a burgeoning population and a need to bathe and feed them.

So today, said Sandra Postel, director of the Global Water Policy Project and a frequent contributor to Worldwatch Magazine, “If you look at all the water taken out of rivers and streams and lakes and aquifers, the world’s total water demand, about two-thirds of it is for agriculture . . . “

Another one-quarter goes to industrial use.

The 9% to 10% remaining sprinkles cities and towns.

“The flooding that we’re seeing in much of the West now,” Postel said, “is because of an unusually heavy year of rainfall. I think this will be one of the few years in which the Colorado River actually reaches the sea, which hasn’t been the case for much of the last 25 years.”

The last time the Colorado reached the sea was in 1993.

In an article in Worldwatch Magazine, “Where Have All The Rivers Gone,” Postel ticks off some trouble spots:

* In Arizona, the Salt and Gila rivers used to join west of Phoenix. Today they dry up east of the city as thirsty farms divert their waters.

* In China, the Heaven River near Beijing dried up 20 years ago. The Yellow River, which earned the reputation as China’s Sorrow because of its frequent flooding, is now dry during the dry season.

* In the Middle East, the Jordan River is so overused that the lower stretches are no more than “a salty trickle.”

In an effort to tame and use the rivers’ flow, governments began building large dams, those over 50 feet high, in the 1930s, including super-dams like the Hoover across the Colorado. There were more than 5,000 large dams in 1950. There are 38,000 today.

The world’s dams hold about 15% of the planet’s renewable water supply. In addition, there are thousands of miles of canals siphoning water out of reservoirs and lakes to take it where the demand is.

Beginning with “The Green Revolution” in the 1960s, the areas under irrigation have doubled.

“In the next 30 to 50 years,” said Postel, “we’re going to see a shift toward more water going to cities. We’re becoming a much more urbanized planet and we’re going to see more population growth. . . . That creates another problem because we have to grow food for all these people in the cities . . . If we’re in a situation of water scarcity, obviously drinking water needs and the needs of people in cities have to be met. But how are you going to grow that food?”

All totaled, water demand has tripled in the last 45 years.

Ironically, the Colorado River’s long-term average flow produces only 90% of the water that has already been promised to seven surrounding states and Mexico. Promises fall short.

The calculation of the flow of the river at its southernmost measuring point was discontinued in 1968 “because there was nothing to measure,” Postel said.

The Nile River in Egypt irrigates 7.4 million acres of cropland, besides providing the water needs of 60 million people, a population growing at the rate of 1 million every nine months.

The Aswan High Dam and its Lake Nasser can store two years’ worth of the average annual flow. Before the dam’s construction, the Nile sent 42 billion cubic yards of water home to the sea each year, 38% of the river’s annual flow, the other 62% being diverted for people and crops.

After the dam was built, with its greater capacity for irrigation, the flow to the sea dropped to only about 7.9 billion cubic yards.

“Not surprisingly, the High Dam has greatly altered the river system, although with the Nile, as with the Colorado, cause-and-effect linkages are not altogether clear,” Postel wrote.

“Out of 47 commercial fish species thriving in the Nile prior to the dam’s construction, only 17 were still being harvested a decade after the dam’s completion. And in the eastern Mediterranean [the Nile’s sea], the annual sardine harvest dropped by 83%--a likely side effect of the reduction in nutrient-rich silt entering that part of the sea.”

In Central Asia, the great Aral Sea, what was once the world’s fourth-largest freshwater lake, is dying for the lack of the two rivers that fed it. That has cost 24 species of fish and 60,000 jobs.

Abandoned fishing villages pepper the former coastline. The species of fish still extant has dropped to four. The catch, which totaled 44,000 tons, has dropped to zero. The winds drive up to 150 tons of toxic dust and salt onto adjacent farms.

Drinking water once supplied by the lake and its rivers is now hazardous to health. Typhoid fever is 30 times what it once was. Hepatitis is up sevenfold. At an old fishing port, esophageal cancer is 15 times the Russian average.

Forests have dried up. Wetlands shrank 85%. Nesting bird species have fallen from an estimated 173 to only 38.

Experts attribute all of this to the diversion of the river water from the Amu Dar’ya and Syr Dar’ya rivers for irrigation.

There are some innovative schemes being born around the world to rescue some of its important rivers. One is multiple use.

“One of the good things about water,” Postel said, “is that using it doesn’t necessarily mean you’ve consumed it or used it up. You can use it once and use it over and over again. It takes good management to do that well. You have to keep the quality high enough to meet the demand down the line. But that’s the name of the game, to make the best use of that water as it is flowing from the watershed down through the system and eventually out to sea, if it makes it that far.

“That’s what a lot of these strategies are beginning to look at.”

It means juggling the supply of water for hydroelectric power, protecting fisheries, urban needs, agricultural uses and industrial needs all from the same water system.

“If you look at the Nile basin, for example, that water is used over and over again,” Postel said. “If you look at each individual farmer, even if the use of the water is not efficient in any given field, the water is not consumed, but flows on to the next field and on and on and on.”

The water sort of steps down on its way to the delta.

Where it doesn’t work is in the Ganges in India. Bangladesh is the last station on the line. After India allocates the water supply, in the dry season when it is crop-growing time, Bangladesh loses crops because the river is all used up.

A free enterprise system for the sale of water is budding in the American West, where water rights are treated as property rights.

Let’s say a farmer has a contract for subsidized water from the federal government. He can turn around and sell all or a portion of his water to a city or a conservation organization or another farmer. With his profit he can improve his irrigation system so that he uses less water.

“Why should a farmer continue to waste water when he can invest in some conservation improvement and have a surplus and then sell it?” Postel asked. “He can get more income that way. So it creates an incentive to use the water more productively and efficiently.”

In the past, water was priced so cheaply that when the farmer couldn’t sell it, there was no incentive to stop wasting it.

At the end of 1992, then-President George Bush signed into law what Postel says was “a real landmark for water management in the West in particular.”

One of its provisions was to mandate 800,000 acre-feet of water from the nation’s largest federal irrigation project, the Central Valley Project, for environmental uses.

There are also signs of international cooperation budding in cross-border allocation of waters.