Excellent Article W. Video Re. Climate Impacts On Colorado & Green Rivers -Habitat, Sediment, More
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It’s a huge playground too, attracting hikers, rafters, mountain bikers, and campers, nearly 750,000 visitors in 2018. Low water in Lake Powell downstream in Glen Canyon National Recreation Area has even revealed long drowned rapids. Canyonlands and nearby Arches national parks feed the gateway tourist town of Moab, Utah’s economy. But the entire region is changing before our eyes, locked into an extended drought, and the climate forecast is grim: warmer and drier. With atmospheric carbon dioxide at its highest level (around 407 parts per million) for at least the past 800,000 years, ecosystems are threatened, rainfall is unpredictable and, a hot and dry desert is going to get even hotter.
What can we expect to happen in the next 5, 10 or 50 years? Terry Fisk is the chief of resource stewardship and science for the National Park Service at Canyonlands, and he’s not exactly sure. “The part where climate change plays in, we can’t really depend on the past as a guide to what to expect in the future,” he said as we sat in his Moab office. “The global situation in the Four Corners area, and particularly San Juan and Grand County (Utah), we are already above 2 degrees Celsius (warmer). And, the Four Corners area, on the U.S. Drought monitor is back in a drought. ... We’re in an unexplored environment for CO2 in the atmosphere. We don’t have any experience in that.”
The Colorado River flows are also forecast to diminish, according to Fisk. “We want to prevent long-term reduction in flow that has a negative effect on ecosystem functions,” he said. “I don’t know if we can say that it’s because of the flows or changes we have seen, since 1963 when Flaming Gorge dam gates closed, but that’s been the biggest impact on the river.”
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But there’s a flip side to river rafting, too; lower flows mean rockier rapids, with some at low levels being impassable. Hoops has seen this along the Green River. “In the extended drought, river levels (flows) are generally lower," he said. "Rapids are formed from rockfall or debris washed into the river because of steeper side channels. Over time, normal spring and fall flushes of the main river current make some form of passage for recreational activities like river running. The near closure of boat passage has already occurred on the San Juan River at Government Rapid.”
Holiday River Expedition’s Lauren Wood has seen changes in as well. “Last year (2019), raft companies had to reduce their season and cut back the number of trips on the river because of diminished flows. In Cataract Canyon inside Canyonlands National Park we are seeing the over-use of the Colorado River system equating to a significant draw-down in "Lake" Powell," she said. "This means each year we wait to see what new zombie rapids may come back to life as the Colorado River cuts a new path through the former high-water lake bed sediments.” Mike DeHoff has been a boatman in Cataract Canyon for years. As Lake Powell water receded, he and others had more rapids to run at the bottom of the canyon. “When the lake was full, it would inundate 65 percent of the canyon,” he said. “When you would run the Big Drops, the biggest rapids in the canyon, while scouting you’d see jet skis and house boats. But that all changed around 2000 when the reservoir (Lake Powell) receded 100-150 feet very rapidly. The river was flowing across its own sediments. We thought it would be a short-term thing and the lake would come back up to its level, but that didn’t happen. Over the last 15 years, the river has slowly been carving back more rapids in that area.
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https://www.nationalparkstraveler.org/2020/02/traveler-special-report-how-climate-change-redesigning-canyonlands-national-park