美国国家公共电台 NPR--A portion of the Colorado River is among the 10 most endangered rivers in the country（在线收听）

A portion of the Colorado River is among the 10 most endangered rivers in the country

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A conservation group says pollution and climate change are among the pressures on rivers. A stretch of the Colorado River that flows through Grand Canyon National Park is the most endangered river.

LEILA FADEL, HOST:

A new report out today from the conservation group American Rivers names the 10 most endangered rivers in the country. Alex Hager from member station KUNC takes us to one of them, a stretch of the Colorado River that runs through the Grand Canyon.

ALEX HAGER, BYLINE: To understand why a part of the drought-stricken Colorado River is in trouble, you have to start further upstream.

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JACK STAUSS: It's easy for folks to forget about these zones as a big river system.

HAGER: Jack Stauss with the Glen Canyon Institute walks through a breathtaking red-rock canyon in southern Utah. He's about shin deep in a crystal-clear stream near the shores of Lake Powell, the nation's second largest reservoir.

STAUSS: But what's really important to remember is this whole system is connected. It's really all one basin. It's all one big river system.

HAGER: That system starts with snow high in the mountains of Colorado, Utah and Wyoming. Left untouched, most of that snowmelt would flow down into Arizona's Grand Canyon, but that is not the case. Glen Canyon Dam forms this reservoir upstream, and the tightly controlled system that keeps it from drying up threatens to keep water out of the Grand Canyon.

SINJIN EBERLE: Both of the major issues that have already caused harm to the canyon are directly related to elevations in Lake Powell and the temperatures of the water.

HAGER: That's Sinjin Eberle with American Rivers. The first of those issues - invasive fish. Dropping water levels allow smallmouth bass to reach places they mostly didn't before. That poses a new threat to native fish in the Grand Canyon.

EBERLE: That is a direct impact from this drought and aridification and climate change and the reduced supply of water in the system.

HAGER: The second issue, Eberle says - the absence of high-flow events. That's when a wet year prompts water managers to send an extra burst of water down from Lake Powell into the Grand Canyon. That helps rebuild the Colorado River's beaches and animal habitats. But a string of dry years means there hasn't been an extra water boost since 2018. Eberle says that all starts to add up.

EBERLE: Yes, we need to do everything we can to stabilize the system, to reduce demand, to address the supply and demand imbalance on the Colorado River. But let's not do it on the back of a place like Grand Canyon.

HAGER: That's been a tough balance to strike when there isn't enough water to go around to the 30 native tribes, 40 million people and multibillion-dollar agricultural industry that depend on the Colorado River. Jen Pelz is water advocacy director for the Grand Canyon Trust.

JEN PELZ: If there was an easy solution, we would have found it by now. And so I think that the solutions going forward are complicated, and they will take sacrifices from all of the different sectors.

HAGER: Those sacrifices are at the heart of policy talks going on right now. The fate of the Colorado River is tied to decisions made by leaders from Wyoming to Mexico. With about 80% of the river's water going to agriculture, those choices will have wide ranging implications.

PELZ: We need to start thinking more sustainably. And how is this river going to exist for my kids and my kids' kids and your kids and your kids' kids?

HAGER: Pelz says now is crunch time to make sure decisions prioritize the long-term health of the river and the Grand Canyon.

PELZ: And if we don't start thinking on that type of scale, long term, then, you know, the river's going to be diminished to a point where we're not going to be able to turn this thing around.

HAGER: The clock is ticking for states to rework how water from the Colorado River is shared before a major deadline in 2026. If they can't, the federal government has threatened to make tough water cuts for them.

For NPR News, I'm Alex Hager.