What will happen to the Grand Canyon as water levels drop?

On August 29, monsoon storms sat over northern Arizona, pelting the north rim of the Grand Canyon. The rain unleashed flash floods that picked up momentum in the burn scar from the 2025 Dragon Bravo Fire. With burned trees, boulders and unanchored sediment in tow, the water pummeled down Bright Angel Creek, finding the fastest way to the Colorado River below. The floodwaters wiped out bridges, buildings and at least two human lives. It eliminated beaches and built new rapids. This summer, and for the foreseeable future, the canyon is changing. In addition to increasingly catastrophic seasonal floods, a warming climate means the Grand Canyon will more often have too little water. The Glen Canyon Dam, which is located just above the canyon, is consistently releasing its lowest water levels in decades, and the Colorado River’s flows are projected to drop even lower. This is already impacting recreation, the river’s ecology and local tribes. The river flowing through the Grand Canyon — arguably the most majestic and most managed in the country — is bookended between two dams that hold back the biggest reservoirs in the United States. Those reservoirs, which provide water for 40 million people in the Southwestern U.S., have been declining for decades thanks to scant snowfall and the rising temperatures tied to climate change. There is so little water today that the combined water stored in both reservoirs has shrunk to a level not seen since the 1950s, when there was only one reservoir, Lake Mead, and it was only half full, according to Jack Schmidt, the director of Utah State University’s Center for Colorado River Studies. July inflows into the system this year were 12% of the historical average. And according to a Bureau of Reclamation study released in June, Lake Powell, the reservoir above the Grand Canyon, is projected to drop too low to create hydropower by January 2027, a situation that also threatens the structural integrity of Glen Canyon Dam. In response, Reclamation has reduced the volume of water it releases from Powell each month: It’s currently releasing 482,000 acre-feet per month and is projected to drop to 401,000 in October. Those shrinking water levels will affect the entire river basin and beyond, but the Grand Canyon itself will feel the changes first. “The Grand Canyon was used to low flows prior to the dam,” said Jen Pelz, water advocacy director for the Grand Canyon Trust. “But we’ve altered the system so much in the last 60 years by using the dam that we’re not going back to what natural conditions might be if we just drop the water.” The formerly high spring flows and low, warm summer ones are unlikely to return. No one sees how much things have changed as clearly as the 11 tribes who have called the canyon home forever. “Tribal relationship is a millennium longer than any scientist has been studying the Grand Canyon,” said Kurt Dongoske, the Zuni tribal historic preservation officer and principal investigator for Zuni Cultural Resource Enterprise. He said the Zuni believe the Grand Canyon is where they emerged into this world, and that there’s a direct spiritual, cultural and geographic connection between the Canyon and the Pueblo of Zuni, where the Zuni River feeds into the Colorado. Dongoske has attended decades of Reclamation meetings and said that historically, the tribe’s perspective about the value of consistent ecosystem management hasn’t been considered. He expects the agency will pay even less attention to the tribe’s views about ecosystem connectivity as water levels drop. YOU CAN SEE THE CHANGES happening at the smallest scale, in tiny grains of sand: Glen Canyon Dam now blocks more than 90% of the sediment that previously flowed through the Grand Canyon. Pelz said that lack of sediment transport is one of the clearest impacts of low flows because sediment provides the canyon’s structural and ecological foundation, creating sandbars for fish habitat and beaches for rafters. Without sediment, vegetation can’t grow, destabilizing the banks and limiting forage and habitat for the wildlife and insects that are crucial to the food web. Sediment also protects cultural resources, including Indigenous masonry dwellings, seasonal campsites and petroglyphs and pictographs. According to a 2023 report by the U.S. Geological Survey, windblown sand dunes prevent water-based erosion around the Grand Canyon’s sensitive archaeological sites. Nearly 400 of those sites are currently at risk as sediment levels drop. Consistently low sediment-deprived flows erode the canyon little by little, pushing sand downstream into Lake Mead instead of keeping it in the canyon’s ecosystem. To counter that, since the late ’90s, Reclamation has typically released a big pulse of water annually in the spring or fall, known as a “high flow experiment,” to carry sediment into the canyon from upstream. Reclamation neglected to do this in 2025, and even though there was enough sediment to require one in 2026, the agency opted not to because it was deemed politically unpopular. “If we lose those high flows, we lose all the sediment in the canyon,” Pelz said. “I see that as one of the most significant impacts to the Grand Canyon.” WHEN THE RESERVOIR LEVEL DROPS and less water comes through the canyon, the water’s temperature changes, too, because it’s being pulled from the sun-warmed top layer of Lake Powell. Temperatures typically range between 45 and 50 degrees Fahrenheit, but as the lake drops, they’re now approaching 60. Schmidt explained that this causes algae blooms in the warm clear water near the dam, something that doesn’t happen when the water is rich with sediment. Those changes also smother the blue-ribbon trout fishery just below the dam, because the fish can’t handle the heat. This alone has big local economic impacts: Recreation in the area is a $1 billion industry that supports thousands of jobs, from guiding to hospitality to public works. That warm top layer carries another threat: smallmouth bass. These non-native fish thrive in warm water and are pulled down into the canyon through the dam’s turbines as water levels drop. This changes the ecosystem, especially for threatened native fish like humpback chub, whose young they eat. Some 85% of the humpback chub in the U.S. live in the Grand Canyon, thanks to a decades-long recovery program that brought them back from endangered status in 2021 and now supports a nursery at the confluence of the Little Colorado River. But that could soon end as smallmouth bass move through the river. “It’s an ecological, biological issue and a cultural one,” Pelz said. “Fish have been there with the tribes for time immemorial. When I think about the Grand Canyon without native fish, it just changes what it is.” At the same time, revenue from power generation at Glen Canyon Dam supports the native fish recovery program. When power generation drops, so does funding for the fish. In past years, when temperatures in the river exceeded 60 degrees for three days in a row, Reclamation would release what it calls “cool mix flows,” pulling colder water from lower in the lake’s water column to discourage the smallmouth bass and algae and balance out the ecosystem. Now, with lower water levels, the agency has less flexibility to change how and when it releases water to reflect the canyon’s natural variability, even when long-term science and agreed-upon policy supports doing so. The Grand Canyon Trust is monitoring a USGS gauge at mile 15 of the Colorado River to track temperature trends. As of September 10, the water there was 69.4 degrees Fahrenheit and had exceeded the temperature threshold at which a dam release with a cool-mix flow would normally be triggered for 87 consecutive days, since the end of June. Dongoske, who has served as a representative to the Glen Canyon Dam Adaptive Management Program since 1991, said there’s another aspect of river management has been too long ignored: The Zuni not only regard the native fish as kin, they believe that all fish are valuable, and that it’s not the non-natives fault that they ended up in the canyon. “All life-forms deserve respect and their lives should be cherished, which is completely antithetical to how Reclamation treats non-natives,” he said. “Historically, they have not given Indigenous epistemologies equal consideration with Western science knowledge.” RECREATION, TOO, IS deeply entangled in the river flows and the ecosystem’s health, said Ben Reeder, a long-time guide for Colorado River and Trail Expeditions. That’s become increasingly clear as the river drops. Each year, approximately 20,000 people take commercial river trips through the canyon, because it’s the only way to truly see the length and the heart of the Grand Canyon. Those trips can range from three-day motorboat trips to 18-day oar-powered raft trips. Reeder, who runs 36-foot-long motorboats through the canyon, said that as river levels drop it becomes harder to get through rocky technical rapids like Hance and Horn Creek. “Running low water, especially in a big boat, is what separates decent boatmen from really good boatmen,” Reeder said. “It’s definitely more nerve-wracking.” He said that guides have had to adjust their routes, timing and scouting, and that some companies have already started running smaller boats to be able to get through the shrinking river channels. So far no one has been hurt, he said, but boats are getting stuck in the rapids. Reeder, for his part, has changed the type of gear he travels with, bringing a slingshot to help get a rope to shore if his boat gets stuck. “It’s not just about river running, but what happens when things go wrong,” he said. “The Grand Canyon is a living, breathing thing. When you spend a lot of time down there, you start to understand it,” said Reeder, who is also the Grand Canyon River Guides representative to the Bureau of Reclamation’s Technical Workgroup. He said that guides are looking out for each other as they try to figure it out, but he’s worried about the impacts on the industry. “The Grand Canyon is a living, breathing thing. When you spend a lot of time down there, you start to understand it.” Trip bookings are reportedly down by about 25%, after a post-COVID high. Reeder is worried about what will happen in the future as the river drops lower, possibly preventing bigger boats from getting through the canyon at all and cutting off the entire motorized sector of the industry. “The history of Grand Canyon boatmen has always been this resiliency,” he said. “I’m confident we’ll have solutions, but I’m not confident that I’m necessarily going to be able to guide and run boats there the way I am now for the long term. We will have to adapt.” RIGHT NOW, releases from Lake Powell are fluctuating between 6,000 and 9,200 cubic feet per second, compared to the typical average summer flows of 13,000 cfs, according to Jennifer M. Erickson from the Department of the Interior Public Affairs. Such low flows make it impossible to do cool mix flows or high-flow experiments; the latter requires releasing between 31,500 and 45,000 cfs for one to four days. Low flows also eliminate options like the steady-state releases called “bug flows,” which the Grand Canyon Trust’s Pelz said aim to keep fluctuations at a minimum to give bugs the chance to hatch, supporting the food web, including bird populations farther downriver. Dongoske said it’s also important to think about the cascade of impacts outside of the river corridor. “Whatever happens in the Grand Canyon will have impacts on the community of Zuni,” he said. “There’s a continuous spiritual connection.” On a grand scale, Pelz said, low water levels create a feeling of scarcity that inhibits creativity and flexibility. The recent flash flood also raises questions. “We really need to rethink how we’re going to manage the river or how the infrastructure is going to work,” she said. This story was produced by High Country News in partnership with The Water Desk, an independent reporting initiative at the University of Colorado Boulder’s Center for Environmental Journalism.