Sunset at Lower Lewis River Falls, WA
Photograph by Scottyboipdx Weber, My Shot
The sun sets over Lower Lewis River Falls in Washington State’s Gifford Pinchot National Forest. The falls mark a wild and scenic stretch of the river, but other sections of the Lewis, which drains the state’s mighty Cascade Range, boast large dam and reservoir systems.
Hydroelectric plants produce power, but they’ve changed the river’s natural character—to the special detriment of migratory fish like salmon. Utilities have agreed to begin trucking fish around the dams along the Lewis River, moving them from below these looming barriers to prime habitat upstream, above the dams.
Horseshoe Bend, Colorado River
Photograph by Frans Lanting
The Colorado River flows 1,470 miles (2.366 kilometers) from the Rocky Mountains to the Gulf of California's Sea of Cortez—or did when its waters were more plentiful. Reduced rainfall and the growing water demands of some 30 million thirsty Westerners have sucked some of the life from the Colorado, and these days its delta is often dry.
Some scientists warn that changing climatic patterns and unchecked human use could dry up the river’s reservoirs within a couple decades.
Santa Elena Canyon
Photograph by Jack DykingaThe Rio Grande flows under the 1,500 foot-high (458 meter-high) cliffs of Santa Elena Canyon in the wild realms of Big Bend National Park.
The west Texas waterway travels through some of the Southwest’s most remote wilderness areas. But the Rio Grande isn’t immune to the impacts of humans.
In the past century, dams have stopped flooding that once created wooded banks for wildlife habitat. Reduced water levels have dried up some sections in recent summers and helped concentrate toxins, which enter the river upstream, into levels dangerous for wildlife
New Orleans and the Mississippi River
Photograph by Tyrone TurnerThe mighty Mississippi River cuts a graceful S curve through the city of New Orleans.
The Mississippi rolls on for some 2,350 miles (3,782 kilometers) from Lake Itasca, Minnesota, to its Louisiana delta at the Gulf of Mexico. It is the second longest river in the United States behind only the Missouri River.
Americans have built thousands of dams and levees along its length during the past century to aid navigation and help control deadly flooding.
However, they also stop sediments from flowing downstream, which is causing the delta to erode so rapidly that some scientists fear an area nearly the size of Connecticut could disappear by 2100.
Ganges River, India
Photograph by Mark Downey/Getty ImagesHindus visit the Ganges River to bathe in the "mother river." The faithful believe its waters are cleansing, but science tells a different story.
Industrial pollution from cities like Kanpur, untreated waste from riverside communities, and even islands of floating trash soil the river's sacred waters. Efforts are under way to clean India’s iconic river, but the Ganges has a long way to go.
Icy Tree on Quebec’s Richelieu River
Photograph by Claudine Besse, My ShotA lonely, icy tree stands sentinel in the mists of Quebec’s Richelieu River. The river, which flows north from Vermont’s Lake Champlain to the St. Lawrence, was an important transportation route for Native Americans and, later, French explorers.
In places the Richelieu can seem unchanged by time, but America’s waters are far less rich than they were in times past. Forty percent of the continent’s fish species are at risk of extinction.
Photograph by Michael NicholsThe Colorado River flows freely through this stretch of the American West, but elsewhere human hands have altered her path for their own ends—and the Colorado is not alone.
Today large dams intercept some 35 percent of all the world’s river flows. Shifting river flows to serve human needs has played havoc with the inhabitants of many freshwater ecosystems. Fish and other aquatic species have lost critical habitat, as well as the seasonal cues, like floods, that help sustain their life cycles.
Glen Canyon and Lake Powell
Photograph by Vincent LaforetThe walls of Glen Canyon seem a bit taller when Lake Powell’s water levels are low, as evidenced by a telltale “bathtub ring” rising from the surface.
The enormous lake’s levels fluctuate with rainfall and snowmelt. Droughts during much of the 21st century’s first decade reduced the lake to nearly half capacity. But even at low levels the nation’s second largest reservoir holds a tremendous amount of water—Lake Powell contains a staggering 1.2 trillion cubic feet (33 billion cubic meters).
Rio Negro, Brazil
Photograph by James P. BlairIndigenous peoples paddle the waters of the Rio Negro, in Brazil’s Amazon Basin. The rivers and streams of this enormous basin, larger than Texas, compose an aquatic ecosystem like no other—and hold an amazing 20 percent of the planet’s available freshwater.
Each year the rivers, home to more than 3,000 fish species, flood during the rainy season to create an amazing ecological mix of aquatic and terrestrial habitats known as “flooded forests.”
Colorado River at Lake Powell, AZ
Photograph by Vincent LaforetSince 1966 Glen Canyon Dam has dramatically altered the Colorado River ecosystem by trapping enormous quantities of silt.
A 2008 experiment unleashed "high flow" waters from the dam to mimic natural flooding that once moved silt and built up sandbars and beaches downstream in the Grand Canyon.
The natural floods once created crucial habitat for plants and animals, and the artificial version shows some promise at doing the same—but USGS scientists say the sandbars created in 2008 vanished in just six months
A management regime of simulated floods might rebuild the Colorado's ecosystem, but must be balanced against lost power production from the dam.
Morning River Sunshine
Photograph by Rami Saarikorpi, My Shot
Not all river ecosystems appear as bucolic as this sunrise scene. Today, large dams intercept some 35 percent of all global river flows, primarily for flood control and hydropower, and some riverbeds are short of water.
The United States is particularly thirsty for freshwater. It takes 1,320 gallons (5,000 liters) of water to produce the daily diet of an average American, and many U.S. homes use more than half of their water just to keep their lawns green.
Silhouetted Trees on Mississippi River
Photograph by Phil Schermiester, My ShotThe setting sun silhouettes riverside trees along the banks of the Mississippi in Nauvoo, Illinois.
The Mississippi rolls on for some 2,350 miles (3,782 kilometers) from Lake Itasca, Minnesota to its Louisiana delta at the Gulf of Mexico. The river nourishes America’s great farmlands, with 92 percent of U.S. agricultural exports coming from the Mississippi Basin. It also takes their bounty to market—60 percent of U.S. export grain travels downriver and heads to sea through Louisiana ports. In addition, birds travel the Mississippi as well—60 percent of all North American species use the basin as a migratory flyway.
Photograph by Chris JohnsA 700 foot-long (213 meter-long) cable and pipe footbridge stretches across the mighty Zambezi River near Chinyingi, Zambia.
The bridge, one of the few over the river, was built by a Catholic priest turned amateur engineer after five people lost their lives in a nighttime boating accident in these same waters.
In less developed regions, the Zambezi is still a main mode of transportation where roads are impassible or nonexistent.