The Grand Canyon, a cathedral to time, is losing its river
As the planet warms, low snow is starving the Colorado River at its headwaters in the Rockies, and higher temperatures are pilfering more of it through evaporation.
By RAYMOND ZHONG
Down beneath the tourist lodges and shops selling keychains and incense, past windswept arroyos and brown valleys speckled with agave, juniper and sagebrush, the rocks of the Grand Canyon seem untethered from time. The oldest ones date back 1.8 billion years, not just eons before humans laid eyes on them, but eons before evolution endowed any organism on this planet with eyes.
Spend long enough in the canyon, and you might start feeling a little unmoored from time yourself. The immense walls form a kind of cocoon, sealing you off from the modern world, with its cell signal and light pollution and disappointments. They draw your eyes relentlessly upward, as in a cathedral.
You might think you are seeing all the way to the top. But up and above are more walls, and above them even more, out of sight except for the occasional glimpse. For the canyon is not just deep. It is broad, too — 18 miles, rim to rim, at its widest. This is no mere cathedral of stone. It is a kingdom: sprawling, self-contained, an alternate reality existing magnificently outside of our own.
And yet, the Grand Canyon remains yoked to the present in one key respect. The Colorado River, whose wild energy incised the canyon over millions of years, is in crisis.
As the planet warms, low snow is starving the river at its headwaters in the Rockies, and higher temperatures are pilfering more of it through evaporation. The seven states that draw on the river are using just about every drop it can provide, and while a wet winter and a recent deal between states have staved off its collapse for now, its long-term health remains in deep doubt.
The Colorado flows so far beneath the Grand Canyon’s rim that many of the 4 million people who visit the national park each year see it only as a faint thread, glinting in the distance. But the river’s fate matters profoundly for the 280-mile-long canyon and the way future generations will experience it. Our subjugation of the Colorado has already set in motion sweeping shifts to the canyon’s ecosystems and landscapes — shifts that a group of scientists and graduate students from the University of California, Davis, recently set out to see by raft: a slow trip through deep time, at a moment when Earth’s clock seems to be speeding up.
John Weisheit, who helps lead the conservation group Living Rivers, has been rafting on the Colorado for over four decades. Seeing how much the canyon has changed, just in his lifetime, makes him “hugely depressed,” he said. “You know how you feel like when you go to the cemetery? That’s how I feel.”
Still, every year or so, he comes. “Because you need to see an old friend.”
Eras and epochs ago, this place was a tropical sea, with tentacled, snaillike creatures stalking prey beneath its waves. Then it was a vast sandy desert. Then a sea once again.
At some point, energy from deep inside the Earth started thrusting a huge section of crust skyward and into the path of ancient rivers that crisscrossed the terrain. For tens of millions of years, the crust pushed up and the rivers rolled down, grinding away at the landscape, up, down, up, down. A chasm was cleaved open, which the meandering water joined over time with other canyons, making one. Weather, gravity and plate tectonics warped and sculpted the exposed layers of surrounding stone into fluid, fantastical forms.
The Grand Canyon is a planetary spectacle like none other — one that also happens to host a river that 40 million people rely on for water and power. And the event that crystallized this odd, uneasy duality — that changed nearly everything for the canyon — feels almost small compared with all the geologic upheavals that took place before it: the pouring, 15 miles upstream, of a wall of concrete.
Since 1963, the Glen Canyon Dam has been backing up the Colorado for nearly 200 miles, in the form of America’s second-largest reservoir, Lake Powell. Engineers constantly evaluate water and electricity needs to decide how much of the river to let through the dam’s works and out the other end, first into the Grand Canyon, then into Lake Mead and, eventually, into fields and homes in Arizona, California, Nevada and Mexico.
The dam processes the Colorado’s mercurial flows — a trickle one year and a roaring, spiteful surge the next — into something less extreme on both ends. But for the canyon, regulating the river has come with big environmental costs. And, as the water keeps dwindling, plundered by drought and overuse, these costs could rise.
As recently as a few months ago, the water in Lake Powell was so low that there almost wasn’t enough to turn the dam’s turbines. If it fell past that level in the coming years — and there is every indication that it could — power generation would cease, and the only way water would be released from the dam is through four pipes that sit closer to the bottom of the lake. As the reservoir declined further, the amount of pressure pushing water through these pipes would diminish, meaning smaller and smaller amounts could be discharged out the other end.
If the water dropped much more beyond that, the pipes would begin sucking air, and in time Powell would be at “dead pool”: Not a drop would pass through the dam until and unless the water reached the pipes again.
With these doubts about the Colorado’s future in mind, the UC Davis scientists rigged up electric-blue inflatable rafts on a cool spring morning. At Mile 0 of the Grand Canyon, the river is running at around 7,000 cubic feet per second, rising toward 9,000 — not the lowest flows on record, but far from the highest.
The big problem with low water in the canyon, the one that compounds all others, is that things stop moving. The Colorado is a sort of circulatory system. Its flows carved the canyon but also sustain it, making it amenable to plants, wildlife and boaters. To understand what’s happened since the dam started regulating the river, first consider the smallest things that its water moves, or fails to move.
The Colorado picks up immense amounts of sand and silt charging down the Rockies, but the dam stops basically all of it from continuing into the Grand Canyon. Downstream tributaries, including the Paria and Little Colorado, add some sediment to the river, but not nearly as much as gets trapped in Lake Powell. Plus, when river flows are weak, more sediment settles on the riverbed.
The result is that the canyon’s sandy beaches, where animals live and boaters camp at night, are shrinking. Beaches that were once as wide as freeways are today more like two-lane roads. Others are even scrawnier.
Besides sand, the Colorado is failing to move larger objects in the canyon. Cobbles and boulders periodically tumble in from hundreds of tributaries and side canyons, often during flash floods, creating bends and rapids in the river. With fewer strong flows to whisk this debris away, more of it is piling up at those bends and rapids. This has made many rapids steeper and narrowed boaters’ paths for navigating them.
It’s the UC Davis scientists’ sixth night on the Colorado, and the graduate students sit in camp chairs chewing over what they’ve seen.
They are preparing for careers as academics and experts and policymakers, people who will shape how we live with the environmental fallout of past choices. Choices like damming rivers.
Yara Pasner, a doctoral student in hydrology, says she feels a duty to make sure the load on future generations is lessened, even if, or perhaps because, our forebears didn’t do us that courtesy. “There’s been a mentality that we will mess this up and the future generation will have more tools to fix this.” Instead, she says, we’ve found that the consequences of many past decisions are harder to cope with than expected.