IELTS Reading Exercise 8

Water's Edge: A Shrinking River Threatens the U.S. Southwest

The desert sun beats down from a cloudless sky as Las Vegas landscaper Mat Baroudi roars across Lake Mead in his motorboat. It's hot. The lake is the perfect place to be on a scorching Nevada morning. Baroudi loves coming out here with his son to fish and swim. But for the last few years, they have watched the lake shrink from under them.

"Every time we come out here, we're shocked by how much water's missing," Baroudi shouted over the roar of the engine.

To get an idea how far the nation's largest reservoir has fallen, consider this: What was once one of Lake Mead's top scuba-diving spots is now halfway up a dry hillside. Baroudi steers the boat past an island with a squat, beige cylinder the width of a basketball court. It looks a bit like a concrete UFO. It was part of the plant that churned out 4,360,000 cubic yards of concrete to build Hoover Dam, a couple miles over the hills to the southeast. The plant disappeared into the murky depths in the 1930s when the dam was completed and the reservoir filled.

"Now look at it," Baroudi said. The structure sits beached on a rocky outcrop looking down on the lake it helped create. Reaching it is no longer a dive. It's a climb.

Hoover Dam was built to store the waters of the fickle Colorado River, taming floods, relieving droughts and pouring life into the desert southwestern United States. Lake Mead anchors the lower half of the river basin, a system that provides water to nearly 40 million people in seven U.S. states. Cities from San Diego to Denver drink from the Colorado. The river irrigates more than 5 million acres of farmland, including California's Imperial Valley and Arizona's Yuma County, two areas that supply the nation with most of its vegetables through the winter season. Both would be barren without its waters. As Lake Mead recedes, it has left a white stripe of mineral deposits 14 stories tall across the brown and red rock walls, as if to underline a question: Have we overreached?

From North Africa to Southeast Asia, many of the world's key river systems are being stretched to their limits. In a 2012 report, U.S. intelligence agencies said fresh water supplies along the Indus, Mekong, Nile, Tigris-Euphrates and other river systems will not keep up with demand in the coming decades. Food security, economic development and regional stability are all at risk, it warned. The same is true for the Colorado. "The river touches nearly every aspect of life in the Southwest," said Pat Mulroy, former head of the Southern Nevada Water Authority and currently a senior fellow at the Brookings Mountain West research institution.

"You have some of the largest Western cities - some of the largest American cities - that are critically dependent on this water supply," Mulroy said. "You have some of the most productive agricultural areas. You have some of the grandest national parks. You have any number of [Native American] tribal nations. You have an enormous hydropower production. And you have an obligation to deliver water to the country of Mexico. I mean, this is a system that can't fail."

Arizona State University researchers calculated that the river supports 16 million jobs, generates $870 billion in income for workers and contributes $1.4 trillion to the region's economy. But after 14 years of drought, the system is closer to failure than ever. This summer, Lake Mead hit a record low. At 1,080 feet above sea level, it was less than 40 percent full and just 5 feet from the point at which water authorities must cut deliveries downstream for the first time ever. Winter rains have raised the lake a few feet. But forecasts are not looking good. A cut is expected as soon as 2016. Farmers in central Arizona would take the first hit.

A 30-foot drop, to 1,050 feet, threatens the equipment that generates enough hydroelectricity to meet the needs of 1.3 million people in Southern California and beyond. At 1,000 feet, the lower water intake for the city of Las Vegas sucks air. The city is building a "third straw" to draw water from the bottom of the lake, at a cost of $817 million. The reservoir hits "deadpool" at 895 feet. Below that point, water no longer flows out of the lake, leaving users in California, Nevada and Arizona dry. The lake sits in a V-shaped basin, narrower at the bottom than the top. That means the lower the water level gets, the faster it drops. The current drought is already the worst in a century of recorded history. But tree-ring records and other proxy climate data going back more than a millennium show it could still get much worse.

"That region has experienced extended droughts, much longer than the current drought," said Debra Knopman, principal researcher at the RAND Corp. "These droughts can persist for decades, in fact."

Even when the drought does end, the region's water troubles will not. They started even before Hoover Dam was built. When a 1922 law divided the waters of the Colorado River among the seven basin states, hydrologists had just a few short decades of data on how much flowed in the river.

"Lo and behold, it turns out that that was a period of high flow," Knopman said. The river has rarely delivered that much water since. As a result, every drop of its water is spoken for, and then some. And cities that drink from the river continue to grow. "All the users on the system live on the razor's edge," said Kathryn Sorensen, water services director for the city of Phoenix. "We use everything that's available to us every year. And what that means is, we're not leaving water behind to prop up levels in Lake Mead to provide for resilience in drought, megadrought or climate change." And that's a problem, she said. Most models show the region getting warmer and drier through this century, and droughts will get longer and more severe. One 2008 study gave 50-50 odds that Lake Mead would hit deadpool by 2021. City managers across the region face a cardinal challenge: find more water.

Source: VOA News