Earth's rovers are running dry - water shortages are becoming a global trend

In 1922, American naturalist Aldo Leopold journeyed by canoe through the great delta of the Colorado River. What he reported seeing there was a verdant waterscape, where for millennia the river had been depositing its rich silt and building up a diverse ecosystem before entering the Sea of Cortez--known north of the border as the Gulf of California. He saw deer, quail, raccoon, bobcat, vast amounts of waterfowl, and even jaguar. The meandering river, slowing as it spread out through countless green lagoons, led Leopold to muse, "For the last word in procrastination, go travel with a river reluctant to lose his freedom in the sea."

Leopold never returned to the delta for fear of finding this wilderness badly altered. His fears were justified; today, the Colorado's freedom has been lost to a degree Leopold scarcely could have imagined. Except in years of unusually high precipitation, the Colorado River no longer reaches the sea at all--it literally disappears into the surrounding desert. Much of the abundant wildlife is gone. Off the coast to the south, the once-productive fisheries in the Sea of Cortez have declined dramatically. In striking contrast to Leopold's experience, author Philip Fradkin more recently characterized what is now a desiccated place of mud-cracked earth, salt flats, and murky pools as "the most inhospitable terrain on the North American continent."

What has happened to the Colorado is but an extreme example of a disturbing worldwide trend. More and more rivers are running dry as dams and diversions siphon water off for burgeoning cities and thirsty farms. In Arizona, the Salt and Gila rivers used to converge west of Phoenix; now, they dry up east of the city because of extensive diversions for irrigated farm's. In California, approximately 22 miles of the San Joaquin River have been dewatered so permanently that thickets of trees have sprung up in the dry riverbed, sand and gravel are mined from it, and developers even have proposed building houses between the banks. In China, about 30 miles south of Beijing, villagers say the Heaven River dried up 20 years ago. In the water-deprived Middle East, where surface streams extensively are overtapped, the lower stretches of the Jordan River have dwindled to a salty trickle.

It is the decline of the world's larger rivers that most graphically conveys the magnitude of the problem. The Nile, Ganges, Amu Darya and Syr Darya, Huang He (or Yellow River), and Colorado are so dammed, diverted, or overtapped that, for parts of the year, little or none of their freshwater reaches the sea. Their collective diminution portends not only worsening water shortages and potential conflicts over scarce supplies, but mounting ecological damage--which, in turn, places the economies and people who depend on them in jeopardy.

Human efforts to control rivers date back thousands of years. It was not until this century, though, that engineering schemes began to alter natural water courses on a massive scale. The construction of dams to store water and diversion canals to transport it to cities and farms has been central to the economic growth of regions, wet and dry alike.

Around the world, the number of dams more than 50 feel high climbed from just over 5,000 in 1950 to about 38,000 by the mid 1980s. More than 85% of them have been built during the last 35 years. World wide, dams collectively store approximately 15% of the Earth's annual renewable water supply. Thousands of miles of diversion canals siphon water out of rivers and reservoirs and deliver it where and when needed to expanding cities and farming regions. Globally, demand has more than tripled since mid-century, and the rising need his been met by building ever more and larger water supply projects. Many rivers now resemble elaborate plumbing works, with the timing and amount of flow completely controlled by planners and engineers so as to maximize their benefits to human activity.

If the intended triumph of such plumbing was to bring rivers as neatly into the service of human convenience in a bathroom faucet, it hasn't worked out that way. Rivers are central to the planet's ecology, and they can not be turned on and off at will without damaging other parts of the system.

The Colorado River ranks among the most heavily plumbed water courses in the world. Controlled by 10 major dams, it irrigates some 2,000,000 acres of farmland, serves the household needs of more than 21,000,000 people, and generates nearly 12,000,000,000 kilowatt hours of energy annually. Its waters fill swimming pools and sprinkle green lawns some 250 miles away in Los Angeles, power neon lights in Las Vegas, and irrigate thirsty crops in the deserts of California, southern Arizona, and northern Mexico.

There are two major problems, though, with the way the Colorado was divided up decades ago. First, a total of 16,500,000 acre-feet (the volume of water that would cover one acre of land to the depth of one foot) was committed to seven U.S. states and Mexico, but the long-term average flow of the Colorado produces only about 90% of that--more water had been promised than the river reliably could deliver. Second, none of the compacts and treaties dividing up the Colorado's water designated any flow for the river environment itself. including the delta and its abundant wildlife. As long as human demands remained welt below the river's flow, this was not a problem. However, except for unusually high flood years, virtually the entire flow of the river now is captured and used--and has been for some time. Flow readings at El Meritimo, the southernmost measuring station on the Colorado, were discontinued in 1968 because there was nothing to measure.

Besides drying up wetlands and causing a severe deterioration in water quality, the reduction in freshwater has cut the flow of nutrients to the sea and reduced critical habitat for nursery grounds. A large number of species that depend on the lower Colorado-upper Gulf ecosystem are threatened or endangered, including the green sea turtle, Yuma clapper rail, desert pupfish, bonytail chub, razorback sucker, and totoaba, a large steel-blue fish that once supported a popular sports and commercial fishery.

The Cucapa, or "people of the river," a 2,000-year-old culture of fishers and flood-recession farmers, are fading with the ecosystem around them. Just 40 to 50 families remain south of the border. There is little work for the younger tribal members, and many have migrated to the cities. As Anita Alvarez de Williams, an expert on the Cucapa, told a National Geographic writer several years ago, these people "have been around for a couple thousand years. But barring a miracle, you're seeing the last of them."

The consequences of excessive river diversions vary from one basin to another, but there are common themes of ecological and economic disruption. The construction of the High Dam at Aswan on the Nile River, for instance, gave Egypt--a desert country of 60,000,000 people growing by 1,000,000 every nine months--virtually complete control over the Nile's waters and a crucial hedge against drought. Yet, out of 47 commercial fish species thriving in the Nile prior to the dam's construction, just 17 still were being harvested a decade after its completion. Because of the trapping of about 110,000,000 tons of silt each year behind the dam, the Nile delta, so essential to the country's economy, no longer gets replenished and slowly is subsiding into the sea.

In South Asia, the Ganges River no longer reaches its natural outlet in the Bay of Bengal during the dry season because of India's heavy diversions. In 1993, the dry season flow into Bangladesh, India's downstream neighbor, was the lowest ever recorded. As river beds dried up and crops withered, one of this poor nation's larger agricultural schemes suffered an estimated $25,000,000 of losses. Moreover, the lack of freshwater flowing out to sea has caused the rapid advance of a saline front across the western portion of the river delta, harming valuable mangrove forests and fish habitat. Unless more water is allowed to run into the delta during the dry season, this damage is likely to continue, along with a spreading disruption of the area's economy.

Some of the most dramatic consequences of river depletion are found where they empty into inland lakes or seas. The Aral Sea in central Asia, once the world's fourth largest freshwater lake, has been shrinking steadily since 1960 because of the diversion of its two major sources of inflow--the Amu Darya and Syr Darya--for irrigation.

Under the direction of Moscow's central planners, irrigation to grow cotton in the desert of the Aral Sea basin expanded by 50% from the 1960s through the 1980s, reaching some 18,500,000 acres. As more and more river water was siphoned off, inflow to the sea dropped dramatically. During the 1980s, it averaged a mere six percent of the rivers' combined annual flow, compared with more than 50% prior to 1960. Much of the time, these rivers now run virtually dry in their lower reaches.

Shrinking seas

This still-unfolding chain of ecological destruction and human suffering ranks the Aral Sea as one of the planet's greatest environmental tragedies. In 1988, the sea actually split in two--into a larger lake in the south and a smaller one in the north. By the mid 1990s, its area had dropped by 50% and volume by 75%. Salinity levels have tripled.

Twenty of the 24 fish species in the Aral have disappeared, and the catch that totaled 44,000 tons and supported around 60,000 jobs in the 1950s has dropped to zero. Abandoned fishing villages dot the sea's former coastline. There is the bizarre sight of ships sitting on bone-dry land--the sea literally having evaporated from under them. Each year, winds pick up anywhere from 40 to 150,000,000 metric tons of toxic dust-salt mixture from the dry seabed and dump them on the surrounding farmland, harming or killing crops. The low river flows have concentrated salts and toxic chemicals, making water supplies hazardous to drink and contributing to rampant disease.

Both deltas have become severely degraded by the reduction in river flows. Damage to trees and shrubs has destroyed vital habitat for the region's animal life. Wetlands have shrunk by 85%. Combined with high levels of agricultural chemical pollution, this greatly has reduced waterfowl populations. In the Syr Darya delta, for example, the number of nesting bird species has fallen from an estimated 173 to 38.

An old Inca proverb says, "The frog does not drink up the pond in which it lives." This simple wisdom presages one of the looming challenges of our time--reconciling the growing water demands of expanding populations and economies with the need to protect water's fundamental ecological support functions.

Meeting the challenge is going to take the deployment of new technologies, policies, and management strategies. It will require unprecedented cooperation both within and between countries. Most fundamentally, it will take a new ethic of sharing water--not only with each other, but with nature as well.

A critical first step is for societies to recognize that there are limits to the amount of water that can be diverted from rivers, and that, where they already are overtapped, some water needs to be shifted from farms and cities back to the environment. The U.S. Congress took steps in this direction in late 1992 by passing legislation dedicating 800,000 acre-feet of water annually from the Central Valley Project in California, one of the largest Federal irrigation programs, to maintaining fish and wildlife habitat and other ecosystem needs. Two years later, in December, 1994, California and Federal officials reached an agreement to limit the amount of freshwater that can be diverted from the San Francisco Bay delta-estuary, a highly productive aquatic environment that is home to more than 120 species of fish. Farmers stand to lose the most water from this reallocation, while cities likely will face cutbacks mainly in dry years. All Californians will gain in the long run, though, as economic activity comes into better balance with the water environment that supports it.

Saving water for nature will be far more difficult in developing countries, where demands for food and drinking water are rising apace with population growth. Nevertheless, in those countries as well, ensuring minimum water flows to satisfy ecological needs is critical to protecting fisheries, delta economies, and--as the tragedy in the Aral Sea basin underscores--the health of local people.

In rich and poor nations alike, meeting irrigation, industrial, and household demands while also protecting the aquatic environment requires much greater incentives to use and allocate water more efficiently. In most developing countries and dry regions of wealthier ones, agriculture accounts for 75-90% of water use. In such areas, reducing irrigation needs by five-10% can free up substantial quantities of water. Switching from sugar cane or rice to less water-intensive crops, investing in drip irrigation lines or low-pressure sprinklers to reduce evaporation losses, and scheduling irrigation to match a crop's water needs more closely are just a few of the ways farmers can save.

If farmers and other users were required to pay prices for water that reflect its true cost, many would make these efficiency improvements. By heavily subsidizing water, governments give out the false message that this resource is abundant and can afford to be wasted--even as rivers are drying up, fisheries are collapsing, and species are going extinct.

Until sharing agreements are reached among all countries within water-scarce river basins, the potential for economic disruption and conflict will persist. Promising steps forward have been taken in the 10-country Nile basin and the five-country Aral Sea basin, and they deserve sustained support.

The tens of thousands of dams and vast lengths of diversion canals built over the last century stand as concrete testaments to impressive engineering skills and human control over nature. In the years ahead, however, success at water management likely will be judged quite differently--by the ability to share water equitably, to do more with less of it, and to restore life and integrity to the Earth's rivers.

Ms. Postel, director of the Global Water Policy Project, Cambridge, Mass., is the author of Last Oasis: Facing Water Scarcity.

COPYRIGHT 1995 Society for the Advancement of Education
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