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Dams: A Perspective on Temporary Prosperity

By Rachel Olivieri
Between 1950 and 1970, three new dam projects were started every single day around the world. Today, primarily in China, Turkey, Brazil, Japan and India, one new dam project begins daily, with an average completion date of four years. Fifteen hundred dams are currently under construction worldwide.

Dams fragment, divert and subjugate the world’s rivers. Beginning on a large scale in 1936 with Hoover Dam, the engineering marvel of the 20th century, civilization has altered the most important function of the Earth: the water cycle. It is only in blindness and ignorance that millions of dams can exist worldwide, strangling the lubricant of life itself. True, dams have created seemingly unlimited oases in arid regions of the world. They have allowed for unimaginable population centers in water-stressed locations; food production on marginal arid lands; and artificial lakes aplenty for fishing, camping and boating. The damming of streams appears to be a benefit, yet what isn’t accounted for is the short-term duration and ecological costs. Short-circuiting the natural system of limitations has created an artificial bonanza, much as the one-time wonder of fossil fuels short-circuited the usual pace of life and drove the industrial revolution. The debts of temporary prosperity are all due and payable in the 21st century.

Earth Recycling
The world’s water budget is a fixed volume and has remained unchanged for roughly 2.2 billion years. About 1% of the world’s total water circulates as fresh water, oceans represent 97% of the world’s stores, and the remaining 2% is tied up in glaciers and polar ice caps. This finite water pie divides ever more thinly as population, agriculture and the industrial economy expand.

Solar energy evaporates surface water to the atmosphere, where it is transferred to land as water or snow. Erosive rainfall or expanding ice in rock crevices tear down mountains as fast as they rise. The Earth’s lumpy land surface is a massive drainage system. From high to low, meandering and networked creeks and rivers drive the rock and mineral cycle. A river system operates on the principle of erosion and deposition. As a river gains water volume and speeds up, it erodes rock and sediment. As it loses volume and slows down, it drops some of its load. Pulses of water flush sediments onto the river’s floodplain, creating fertile soil before arriving at its delta entry to the sea.

River Interrupted
Dams quiet the waters and backfill canyons, forming massive lakes that release vast amounts of methane from rotting vegetation. The energy-deprived river releases its rock and sediment load, filling the reservoir. The question is not if but when will it end, and what will civilization do when it does? What engineering options remain to further alter, manipulate or control the world?

The National Inventory on Dams tells us that the United States has constructed 79,000 dams large enough to require state and federal monitoring. These higher-risk categories are often located near enough to population centers to pose a direct safety risk to human life and property. Worldwide, there are 800,000 similarly sized dams that are regulated and present equal challenges. Inventoried or not, the total number of dams in the U.S. may exceed 2.5 million and perhaps tens of millions worldwide.

A recent study measured the volume capacities of 29,484 large reservoirs throughout the world. It determined their storage capacity to be about 8.7 billion acre-feet (BAF) of freshwater. That’s enough water to make a nine-foot lake out of Alaska, Texas, California, Montana, New Mexico, Arizona, and Nevada combined. This immense artificial above-ground storage is counter-intuitive to nature’s freshwater storage system, which stores only .016% of circulating freshwater in all natural lakes, rivers, streams, creeks and atmosphere combined. Instead 80-90% of the world’s circulating freshwater is stored underground, free from evaporation and sedimentation.

Still more revealing is the loss of artificial reservoir stores through evaporation. Although evaporation rates vary from region to region, a 1998 U.S. Geologic Survey study of California’s reservoirs in all nine major hydrologic regions recorded 2,342,800 AF of evaporation, about .06% of California’s 40 MAF (million acre-feet) of reservoir storage. Applying .06% evaporation rate to the world’s 8.7 BAF (billion acre-feet) of stored water yields 522 MAF of evaporation, which is about 2.5 years of total California rainfall. That’s water that doesn’t infiltrate as groundwater to feed wells or perennial streams, grow food, or provide water for wildlife and the billion humans on the planet who don’t have access to unpolluted water.

The World Commission on Dams estimates that 3.1 BAF of freshwater is withdrawn from lakes, rivers, and aquifers annually. That equals the total discharge of seven Mississippi Rivers. Here again it would cover with three feet of water the already mentioned seven states, totaling one billion surface acres—a lot of water.

Considering current global population additions (80 million per year), with rising water consumption rates that triple with each population doubling, human enterprises will consume and significantly pollute 90% of all available freshwater by 2025. This leaves a scant 10% to support the Earth’s dwindling ecosystem.

Are We Playing Against Ourselves?
When 1964 American Nobel Prize-winning physicist Charles Townes downplayed his break-out laser technology with reporters he demurred, “When I hear that kind of thing [compliments], it reminds me of what the beaver told the rabbit as they stood at the base of Hoover Dam: ‘No, I didn’t build it myself, but it’s based on an idea of mine.’”

In the 1960s, the age without limits, this remark reflects how little was known and understood about the natural world and the cumulative impacts of dams. The function of the beaver isn’t to dam major rivers but to build small organic dams on the various tributaries. These temporary ecosystems produced abundant life. They reduced flooding and erosion, enhanced groundwater penetration, created the valley’s precious topsoil, and fed a radiant food web. Aldo Leopold, the legendary and visionary U.S. Forest Service land manager, said dams provide only a temporary prosperity followed by tremendous vulnerability. This ecological reality is incontrovertible—all dams have an end date.

California leads the list with dams near self-cancellation. Within the next generation, 85% of all U.S. dams will have degenerated to the point of exhausting their operational lifespan of fifty to ninety years, requiring decommission or massive repairs and upgrades. Considering that every canyon that might reasonably hold a dam already has an aging one, what then?

Let’s pause for just a moment and ask some relevant questions. What will it cost to maintain, repair, upgrade, and build new dams and restore dysfunctional watersheds? Dams provide a tempting illusion of prosperity whose short-term gains vandalize the future of civilization and terrestrial and aquatic biodiversity. This reality remains an abstraction to a world breast-fed on cheap energy, cheap water, and unconscious consumption of finite resources. Dr. Carl Sagan wrote, “We go about our daily lives understanding almost nothing of the world. We give little thought to the machinery that generates the sunlight that makes life possible, to the gravity that glues us to an earth that otherwise sends us spinning off into space, or to the atoms of which we are made and on whose stability we fundamentally depend.”
Without some sense of how the Earth works and our relationship to it, one is deprived of knowing the important questions that promote life and prevent massive-scale destruction and degeneration.