Welcome to “What’s Up With Water,” your need-to-know news of the world’s water from Circle of Blue. I’m Eileen Wray-McCann.
In research news, a study has found that lakes across the Earth’s middle latitudes are being starved of oxygen, threatening aquatic life with suffocation. The study was published in the journal Nature. It showed that oxygen levels in lakes are decreasing, caused by a combination of factors. One is climate change. Heat-trapping gases in the atmosphere are spiking not only global air temperatures, but also water temperatures. Warmer water absorbs less oxygen. A second factor is the increase in algal blooms, which consume oxygen when the algae decompose. Because the microscopic organisms settle to the lake bottom after they die, the study found that deep water environments are especially vulnerable to oxygen loss. Overall, oxygen levels in lakes are declining more rapidly than in the ocean, where the effect is also being observed.
In China, officials at the Ministry of Water Resources advised that major flooding may strike again this summer, especially in the central and southern regions. Reuters reports that at the end of May, 71 rivers exceeded warning levels, and the Yangtze through the city of Wuhan was more than two meters above normal. Last year, heavy rainfall in the Yangtze basin triggered widespread flooding, which is expected to worsen in the region as the planet warms.
In the United States, documents obtained by the news site Undark showed that failure of aging dams across the country could flood major toxic waste sites. The site referenced 81 high-hazard dams, which are located in 24 states. Undark reports that state and local governments are often unprepared for flooding and don’t recognize the risk posed by dams that are near toxic waste sites, leaving communities vulnerable to disaster and environmental contamination. Experts say hazardous waste sites can be designed to withstand flooding, but flooding hazards must first be recognized.
This week, Circle of Blue reports on private water storage accounts in a shrinking Lake Mead.
The iconic Colorado River basin is shared by seven states and Mexico. It provides some 40 million Americans with a portion of their drinking water and irrigates up to 5.5 million acres. The basin is home to endangered species and supports about $1.4 trillion in economic activity, according to a study in 2014.
Because of record-high temperatures and a drying climate, the Colorado River basin is also dangerously parched. Thirsty soils gulp melting snow before it reaches streams. Lake Mead, which is just 36 percent full, is in poor health. So is Lake Powell, located upstream, at only 34 percent full.
The lower basin states – Arizona, California, and Nevada – rely on water from Lake Mead, whose fluctuations have become a barometer for water stress in the American Southwest. As stress increased in the last two decades, water managers have responded. They have been willing to learn more about the changing hydrology and revise their operating rules, with a discipline aimed at achieving the best and avoiding the worst.
Case in point: an approach known as “Intentionally Created Surplus” or ICS. ICS is a complex and arcane water banking program in the lower Colorado River basin. It was designed to incentivize water conservation, prevent waste, and boost storage in a waning Lake Mead, the largest reservoir in the U.S.
In broad terms, it allows participating water districts to create the equivalent of water “savings accounts” in Lake Mead. If the districts invest in conservation that allows them to use less water than their allocation, they can bank what they did not withdraw as a credit. Those credits can be drawn upon later when the need for water is acute.
The program was adopted in 2007 and later amended. It has already proved its worth, lifting Lake Mead dozens of feet higher than it otherwise would have been. It has also nurtured collaboration among states that will need a united effort to surmount daunting challenges of water availability. In the next two years, the program will be tested in another way, becoming a small but important source of water for Arizona and California even as the lake continues to dwindle to levels not seen in generations.
Water managers in the basin view the Intentionally Created Surplus as a flexible tool for adapting to a drying climate. It is a tool that they will soon call upon. Bill Hasencamp is from the Metropolitan Water District of Southern California, a large regional wholesaler. He told Circle of Blue that the district intends to draw between 100 and 150 thousand acre-feet from its savings this year.
Arizona officials, meanwhile, plan to use about 69 thousand acre-feet of ICS credits to reduce the mandatory cutbacks that will be required next year if Lake Mead declines as expected. The state already used this maneuver to deal with a cutback last year, albeit in a smaller amount. Chuck Cullom of the Central Arizona Project said that instead of taking a major cut in one year, the intentionally created surplus program allows Arizona to “smooth the reduction.” The Central Arizona Project delivers the bulk of Arizona’s Colorado River allocation and is the first to feel the pinch when cutbacks are required.
These acre-feet of water are relatively small but they are significant, especially in these times. An acre-foot is nearly 326 thousand gallons,  the amount of water that will flood one acre of land to a depth of one foot. Right now, if you take 85 thousand acre-feet out of Lake Mead, its elevation will drop by a foot. So these withdrawals from “water savings accounts,” at the high end, amount to two and a half feet of elevation in Lake Mead.
At the same time that water users plan to tap their savings, scholars in the basin are calling for more analysis of the ICS program, especially as Lake Mead declines faster. They want to see how the system responds to ICS use under a range of water supply scenarios.
The last time that water supplies in Colorado River reservoirs dipped to critically low levels was in the late 2000s. Since then, the largest water users in Arizona, California, and Nevada have been stashing water in Lake Mead, in preparation for the next emergency — and in hopes of averting a catastrophic collapse of the region’s water storage system.
That emergency is here. The federal government projects that Lake Mead will drop precipitously in the next two years — perhaps to levels not seen since the Great Depression, when the country’s largest reservoir was first filled.
John Entsminger is the general manager of the Southern Nevada Water Authority. He summarized the situation during a House Natural Resources subcommittee hearing on May 25, saying “While Colorado River water users have invested billions of dollars to reduce consumption and increase resiliency, the situation we face today is real and urgent.”
The Intentionally Created Surplus program has, to this date, worked the same way, with the rules being adapted to avoid a run on the bank. But if Lake Mead continues to decline, as projected, there is concern that the credits might become a stranded asset.
And that’s “What’s Up With Water,” from Circle of Blue, where water speaks. More water news and analysis await you at This is Eileen Wray-McCann – thanks for being here.