Walter Youngquist: Geodestinies dams and hydropower

Preface. I was fortunate enough to know Walter for 15 years. He became a friend and mentor, helping me learn to become a better science writer, and sending me material I might be interested in, and delightful pictures of him sitting in a lawn chair and feeding wild deer who weren’t afraid of him. I thought his book Geodestinies: The Inevitable Control of Earth Resources over Nations and Individuals, published in 1997, was the best overview of energy and natural resources ever written, and encouraged him to write a second edition. He did try, but he spent so much time taking care of his ill wife, that he died before finishing it. I’ve made eight posts in Experts/Walter Youngquist of just a few topics from the version that was in progress when he died at 96 years old in 2018 (500 pages).

Other Youngquist Geodestinies Posts:

Alice Friedemann  author of “Life After Fossil Fuels: A Reality Check on Alternative Energy“, 2021, Springer; “When Trucks Stop Running: Energy and the Future of Transportation”, 2015, Springer; Barriers to Making Algal Biofuels, and “Crunch! Whole Grain Artisan Chips and Crackers”. Podcasts: Collapse Chronicles, Derrick Jensen, Practical Prepping, KunstlerCast 253, KunstlerCast278, Peak Prosperity , XX2 report

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Dams flood fertile lowlands and impede the migration of anadromous fish-like salmon. (As a result of more than 20 dams on the Columbia River and its tributaries, its legendary salmon runs were decimated and today exist at no more than three percent of historic levels.) In northerly and mountainous areas, river valleys are important winter rangelands for wildlife, particularly big-game animals. When these valleys fill with water, they are no longer winter range for animals. Also, all reservoirs ultimately will fill with sediment. Whether or not hydropower can be regarded as a renewable resource is debatable. Unless an answer can be found to the problem of reservoir destruction by sedimentation, it is not. Some smaller reservoirs have already met this fate. During the early life of big dams we currently enjoy, they do provide many benefits.

In the case of dams, environmental impacts have been very mixed. Originally, dams were thought to be environmentally benign, producing no noxious fumes like fossil fuel power plants do. Used for irrigation, dams would enable arid lands to produce crops. In the United States, more than 85,000 dams block normal stream flow. About 5,500 of them are more than 50 feet high. But dams have proved to produce diverse, and in some instances, quite unexpected effects on the environment.

Of course, dams and reservoirs impact streams and rivers at the site of the dam itself and within the “footprint” of the reservoir. This is where the shallower, moving waters of a watercourse with a current are converted into deeper, cooler, stiller waters with no current and lower dissolved oxygen levels. But the impact of dams and reservoirs is not restricted to the portion of a formerly free-flowing river they have converted into a lake. Rather, the hydrology and geomorphology of the river downstream of the impoundment is altered permanently as well. The water released from the dam is virtually free of suspended sediments, which have been deposited in the still waters of the reservoir. Thus, the released water downstream of a dam is “hungry” and tends to pick up sediments from the bed and banks of the river downstream; this erosion may or may not be problematic, depending on how the river is used and whether or not structures or resources of values line its banks.

Additionally, dams and reservoirs tend to reduce overall downstream flows (lower annual discharge of water) and to blunt or moderate the peaks of higher flows during the rainy season and floods (which is one of their benefits). For species of fish that depend on environmental cues such as higher water, stronger current velocities, or lower temperatures, these changes can disrupt critical phases of their life cycle, such as spawning. Power

In both mountainous areas and in plains regions, dams may flood what were once the most fertile parts of the region, the lowlands adjacent to the rivers. In parts of Kansas the upland areas have little topsoil. The bedrock is close to or at the surface, whereas the adjacent broad river floodplains have rich alluvial soil. These areas are flooded and lost to agriculture when dams are built. In some cases, the government had to expropriate private farmland to put in the dams, and feelings ran high in this regard. Along one highway bordering a flooded river valley in Kansas, local citizens erected a series of billboards which read: “Stop This Big Dam Foolishness.

Another negative effect of dams may be the loss of valuable bottomland wildlife habitat. In some places, the various extended arms of a reservoir may promote growth of emergent marsh plants, bottomland or riparian woodlands, and other vegetation, and in turn, encourage wildlife. Reservoirs can also provide habitat for waterfowl (swans, geese, ducks), shorebirds, and wading birds such as herons and egrets. This is true primarily in relatively flat and fairly arid regions such as the Great Plains. However, in more mountainous regions of high uplands and deep canyons, the flooding of the canyon areas destroys the vital wintering grounds of big game animals.

At the upper end of the Columbia River System in the United States, the rising waters behind the Libby and Hungry Horse dams have flooded more than 90 miles of tributary streams, destroying more than 50,000 acres of wildlife habitat. The related need to relocate railroad tracks also destroyed 2,100 acres of wetland and riverbank habitat.

The life-giving artery of the arid southwestern United States is the Colorado River. Once flowing strongly to the Gulf of Lower California, it reaches the gulf now only as an occasional trickle and sometimes not at all. Today there are more demands on the Colorado River than there is water to meet them. To control the Colorado and to allow for irrigation and city water supplies, a series of dams have been built. The two most famous are Hoover Dam and its reservoir, Lake Mead, the first one below the Grand Canyon, and Glen Canyon Dam and its reservoir, Lake Powell, just above the Grand Canyon. Both dams and their reservoirs are exceedingly important to the Southwest as sources of power, irrigation water, and municipal water supply. They also provide a variety of recreational activities. But these benefits are not without cost.

Raising and lowering reservoir levels at various times of the year has created unstable water conditions for animal and plant life. There have been significant changes in shoreline vegetation. In particular, the growth of an exotic bush, the tamarisk (also called salt cedar) has been encouraged. This plant forms dense thickets, accumulates litter, attracts obnoxious flies, and produces large amounts of hay fever-causing pollen (Potter and Drake, 1989). Also, sediment that the Colorado River once carried through to the sea is now accumulating behind the dams. In several miles of the lower Grand Canyon, large banks and terraces of mud are forming due to low flows of water. Major flood control releases of water from the dams scour out river bottom vegetation vital to fish life, and also remove the natural sandy beaches, but may bury other areas in mud.

To provide the benefits dams in the U.S. produce, they have flooded an area equal to the size of New Hampshire and Vermont. Today, the only major river (defined as 600 miles or longer) still entirely free flowing in the 48-adjacent states, is the Yellowstone River.

Dams and their reservoirs have a lifespan. When one looks at the recently built huge dams with their reservoirs, it is not apparent that they are not the permanent features they appear to be. We do not see this, because the life of huge dams with their reservoirs is longer than the lifespan of one or perhaps several human generations.

However, in the U.S. and abroad, many smaller impoundments are now simply concrete waterfalls, filled to the brim with mud. At least 2,000 irrigation dams in the United States are now useless having been filled with sediment (Jackson, 1971).

A dam built in India with high hopes of supplying long-term electricity and irrigation water saw its reservoir half filled with sediment in 30 years, and its power producing facilities rendered almost useless. In India, in eight large reservoirs, the actual rates of sedimentation were up to 16 times the projected rates. The lives of the reservoirs were reduced accordingly. A study of 132 dams built 30 to 50 years ago in Zimbabwe found that over half are more than 50 percent filled with sediment (Elwell, 1985).

The silting of reservoirs is a major short-term and long-term problem. It is estimated that Lake Mead, the reservoir behind Hoover Dam on the Colorado, will be filled with sediment in about 400 years. Hoover Dam will be a concrete waterfall. A raft trip through the Grand Canyon reveals benches of sediment already built up in the lower end of the canyon.

The impoundment of sediment behind dams not only eventually fills reservoirs, making them useless, but it also stops sediment from going downstream as it normally would to maintain and build out deltas and marshlands, home to myriad forms of wildlife. Instead, the absence of these stream-borne sediments results in deltas being cut back by wave and current action and diminished in size. Marshlands are invaded by the sea and destroyed.

The United States government, and the world as a whole, began building large dams (those over 50 feet high) in the 1930s. There were 5,000 such dams in 1950. Now there are 38,000, and many more are either in the planning stage or already under construction.

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