Far below the tourist accommodations and shops selling key chains and T-shirts, beyond windswept creeks and brown valleys dotted with agave and sagebrush, the rocks of the Grand Canyon seem far removed from time. The oldest ones date back 1.8 billion years, not just eons before humans saw them, but eons before evolution endowed any organism with eyes.
If you spend enough time in the canyon, you may also start to feel a bit detached from time.
The immense walls form a kind of cocoon that isolates you from the modern world and its cell signal, its light pollution and its disappointments. They take your eyes up, as if it were a cathedral.
You might think you’re looking all the way to the top. But above are more walls, and above them even more, out of sight except for the occasional peek. Because the canyon is not only deep. It’s wide, too: 18 miles, edge to edge, at its widest point. This is not a simple stone cathedral. It’s a realm: sprawling, self-contained, an alternate reality that exists magnificently outside of our own. And yet the Grand Canyon remains linked to the present in one key respect. The Colorado River, whose wild energy has carved a gash in the canyon over millions of years, is in crisis.
As the planet warms, a lack of snow is depriving the river at its headwaters in the Rocky Mountains, and higher temperatures are robbing more through evaporation. The seven states of the American Union that feed from the River are using almost every drop it can provide, and while a wet winter and a recent agreement between states have prevented its collapse for now, its long-term health remains highly doubtful.
More than a century ago, the mass migration of people to the American West was based on the belief that money, engineering, and grit could sustain civilization in a mercilessly dry place. That belief seems increasingly as tenuous as a dream.
The Colorado River flows so far down the rim of the Grand Canyon that many of the 4 million people who visit the national park each year see it only as a distant thread, glowing in the distance. But the fate of the river is very important to the 450 kilometer long canyon and the way future generations will experience it. Man’s subjugation of the Colorado has already set in motion sweeping changes to the canyon’s ecosystems and landscapes.
John Weisheit, who helps lead the Living Rivers conservation group, has more than 40 years of rafting on the Colorado. Seeing how much the canyon has changed, just in his lifetime, makes him “hugely depressed,” he said. “Do you know how you feel when you go to the cemetery? This is how i feel”.
The lands of western North America are well acquainted with nature’s cycles of birth, growth, and destruction. Many ages and ages ago, this place was a tropical sea, with tentacled snail-like creatures stalking prey beneath its waves. Then it was a vast desert of sand. Then it became a sea again. At some point, energy from deep within the Earth began to push the crust up. Over tens of millions of years, the crust was uplifted and ancient rivers descended, eroding the landscape. Over time, a deep chasm opened up. Weather, gravity, and plate tectonics warped and sculpted the exposed layers of stone into fantastic shapes.
The Grand Canyon is a planetary spectacle like no other—one that is also home to a river on which 40 million people depend for water and energy. And the event that crystallized this strange and uncomfortable duality—that changed almost everything for the canyon—feels almost small in comparison to all the geological upheavals that came before it: the pouring, 15 miles upriver, of a concrete wall.
Since 1963, Glen Canyon Dam has served as a dam to the Colorado for almost 200 miles, in the form of the second largest reservoir in the US, Lake Powell. Engineers are constantly evaluating water and electricity needs to decide how much of the river to let through the dam, first to the Grand Canyon, then to Lake Mead and finally to fields and homes in Arizona, California, Nevada and Mexico.
The dam processes the Colorado’s mercurial flows—a trickle one year and a roaring, furious swell the next—into something less intense at both ends. But for the canyon, regulating the river has come with huge environmental costs. And, as water continues to become scarcer, plundered by drought and overuse, these costs could rise.
Just a few months ago, the water level in Lake Powell was so low that it was barely enough to run the dam’s turbines. If it falls below that level in the next few years — and all indications are that it could — power generation would cease and the only way for water to be released from the dam would be through four pipes that lie closer to the bottom. from the lake. If the water fell much lower than that, the pipes would start to suck air, and eventually Powell would be in a “dead pond”: not a drop would pass through the dam until the water reached the pipes again.
The big problem with low water in the canyon, the one that aggravates all the others, is that things stop moving. The Colorado is a kind of circulatory system. Its flows carved the canyon, but also maintain it, making it suitable for plants, wildlife, and boaters. To understand what has happened since the dam began to regulate the river, first consider the smallest things that its water moves or stops moving.
The Colorado picks up vast amounts of sand and silt as it rolls down the Rocky Mountains, but the dam pretty much prevents all of that from continuing into the Grand Canyon. Downstream tributaries add some sediment to the river, but not as much as that trapped in Lake Powell. Also, when river flows are weak, more sediment is deposited on the river bed.
The result is that the canyon’s sandy beaches, where animals live and boaters camp at night, are shrinking. Beaches once as wide as highways now look more like two-lane roads. Others are even smaller. The remaining sandy space is also being covered with vegetation: reeds and dew flower, cachanilla and batamote. Before the dam existed, spring floods from the river regularly washed away this vegetation.
A lusher, less arid canyon might sound nice, but the grasses and shrubs prevent the wind from blowing sand onto the slopes and terraces, where hundreds of cultural sites preserve the history of peoples who lived in and around the canyon. The sand protects these sites, which include stone structures, flagstone-lined barns and crater-shaped barbecue pits, from weather and the elements. With less sand coming up from the riverbank, the sites are more exposed to erosion and footsteps from visitors.
Other than sand, the Colorado fails to move larger objects in the canyon. Stones and rocks periodically roll in from hundreds of tributaries and side canyons, often during flash floods, creating bends and rapids in the river. With fewer strong flows to remove this debris, more accumulates in those curves and rapids. This has made many rapids steeper and has reduced the paths to navigate them.
There is another aspect of the canyon’s future that worries Victor R. Baker, a geologist at the University of Arizona. He has spent 40 years exploring niches, ledges and tributary mouths in the Colorado Basin. He scours them looking for the very particular patterns of sand and silt left behind by giant floods. Geological evidence upstream of the dam points to 44 major floods of varying sizes there, most of them in the last 500 years.
As the atmosphere warms, allowing it to hold more moisture, the risk of another such deluge could increase. If one hits when Lake Powell is already full of melting snow, it could destroy the dam, not to mention do considerable damage to the canyon.
“I think the future is going to be one that moves towards, as they say in war, long periods of boredom punctuated by brief bouts of complete and utter terror,” Baker said.
By: RAYMOND ZHONG
BBC-NEWS-SRC: http://www.nytsyn.com/subscribed/stories/6763214, IMPORTING DATE: 2023-06-15 22:00:06
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