No Water to Drink
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No Water to Drink

An American Version of the Crisis

Published in the EarthSphere Blog – Cover Image: No Water to Drink by WM House; ArcheanArt

Heat and drought have engulfed large parts of the American West for the past two decades. This particular disaster started slowly creeping forward about the year 2000 and went unnoticed for many years before people awoke to a harsh reality — ‘water is life, and suddenly there isn’t enough to go around.’ California, Arizona, Nevada, and four other western states now face the unwelcome decision of either negotiating a deal to cut their water usage or having the federal government make those hard decisions about who receives the dwindling supply of life-giving water and who doesn’t.

Some articles about this megadrought place the blame on climate change. But this is a half-truth. Climate change certainly plays a significant role in this unfolding crisis, but mother nature’s natural, long-term weather cycles are also part of the equation.

The Colorado River

The key player in this sad saga is the Colorado River, which flows 1,450 miles from its headwaters in the Rocky Mountains to the Gulf of California. In its natural state a century or more ago, this river delivered about 22,500 cubic feet per second of outflow. However, today, water from the Colorado River is lucky to make it to its final destination in the Gulf of California. Total water flow in the Colorado River has declined by 20 percent over the last century. Under current conditions, river discharge could shrink another 25 percent by the middle of this century.

The river provides water for some 40 million people, who siphon it off bit by bit. Also, it provides irrigation for 5.5 million acres of farmland, and 4,200 megawatts of hydroelectric power generation capacity. Water-storage dams along the river, including those for hydroelectric power, can hold up to four years of average annual river flow and serve as a flow stabilization system. But the demands on this river now exceed its annual flow capacity, affecting six major cities: Denver, Salt Lake City, Las Vegas, Phoenix, Los Angeles, and San Diego.

The “Colorado River Basin Water Supply and Demand Study,” produced by the U.S Department of the Interior Bureau of Reclamation, provides complex scenarios for the future use of Colorado River water. However, the bottom line is that future aspirations look unrealistic under current plans. A future water demand of between 18 and 20 million acre-feet (MAF) per year is projected against the long-term average annual supply of 16 MAF, and the megadrought has cut that 16 MAF to as low as 12 MAF in some years.

What Happened?

The story probably begins before the dawn of civilization, but the farthest back we can track the megadroughts of the American West is about 1200 years. Tree rings tell us a story about mother nature’s fickle behavior.

Dry years show up as patterns of thinner, compacted tree rings, so previous megadroughts appear in the natural records of a tree’s growth. If counted backward through time, the rings account for the last 1200 years, taking us back to the 800s when the first recorded megadrought ravaged the western USA. This long period of severe drought was a harbinger of repeated dry spells in the mid-1100s, the 1200s, and the late 1500s. The dry years of the late 1200s tie into the collapse of the North American Anasazi culture.

The fate of the Anasazi is relevant to us today because we are 20 years into the next megadrought. The tree rings tell us that the last megadrought in western America ended before the Pilgrims landed in 1620. So, the rise of modern America and the subsequent development of the American West occurred in a period of ample water. The term “ample” is used in a relative sense because, after all, we are talking about areas that are largely desert. But still, our calculations for water needs have used a higher baseline for available water than occurs in a megadrought.

Lake Mead

Just 24 miles east of the Las Vegas Strip, the Colorado River stops flowing, blocked by the Hoover Dam. The dam was built in 1935, creating Lake Mead, the largest capacity reservoir in the United States. But the lake has remained below capacity since 1983 due to drought and water shortages.

Water levels in Lake Mead are a measuring stick for the megadrought crisis. When the water level at Lake Mead fell below 1075 feet, the federal government was obligated to declare an official water shortage. At 1045 feet, California is obligated to take cuts in its water allocation. The federal government expects water levels in the lake to reach 1039 feet by December.

This situation engenders images of neighborhoods packing up their belongings and moving elsewhere because, without water, there is no life. Of course, we don’t yet know how this crisis will play out. Granted, most people are not overly sophisticated in their understanding of mathematics, but even the simplest of us can understand the basic proposition for the Colorado River. At the beginning of the 21st century, we started using more water each year than precipitation provided to the river’s watershed. Much like a bank account, if you consistently withdraw more money than you put in, the good times will come to an end.

Winners and Losers

Undoubtedly, whether a water rationing arrangement is negotiated by the states or imposed by the federal government, the ultimate determination of winners and losers will be an unholy mix of science and politics.

Many of the provisions and features of the current water allocation system were put into place a century or more ago, and now they don’t reflect the current mix of sprawling urban landscapes and valuable agricultural lands.

Negotiations will be difficult because no one wants to raise their hand first to volunteer for a big water reduction. Also, an archaic system of senior and junior rights heavily burdens the water rights discussion. The choice will be for states and water districts to reach an agreement that all parties equally dislike but can live with, or have the federal government impose a system that all parties must live with.

Climate Change

There are two paths to a drought. A region receiving less precipitation than normal will see drought conditions. However, hotter temperatures or dryer conditions will cause more water loss through evapotranspiration and also bring on a drought. Both of these enablers occur today in the American West.

Historically, natural cycles drove the occurrence of megadroughts in the American West. But human influences are also at work. Anthropocene climate change and global warming are human-induced changes that amplify the severity of our current megadrought. The megadrought decreases precipitation base levels, and warmer temperatures facilitate more evapotranspiration. Less water is coming in, and more water is going out, providing a recipe for disaster.

Global warming has increased the average global temperature by about 0.8 degrees Celsius over the long-term trend. But this number averages out both larger and smaller regional trends. Average annual temperatures in the American West have increased by 1.2 degrees Celsius over the norm. Higher temperatures induce more moisture loss, so global warming works to amplify the severity of the drought. Some researchers attribute up to 50 percent of the severity of the current drought to human activity.

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.