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When state surveyors measured the Sierra snowpack on April 2, they found 106.5 inches of snow, with an equivalent of 51 inches of water — meaning that if the area were hit with some sort of cosmic laser beam and everything turned to liquid in a flash, that’s how much water would be left behind. Compared to average measurements for this time of year, those readings represent 200% of normal levels.

Next to Sierra-at-Tahoe Resort at 6,800 feet of elevation, the Phillips Station, where the measurement was taken, is part of the American River Basin. That means the snows that drew skiers this winter will soon deliver thrills to another group of outdoor enthusiasts: whitewater rafters.

“It’s shaping up to be a really good season,” says Phillip Schoenhoff, president of Whitewater Excitement, which runs trips on the Merced River near Yosemite National Park and the North, Middle and South Forks of the American River. “All those rivers are predicted to be pretty high this spring.”

Across California, the Sierra Nevada snowpack was at 162% of average earlier this month. In the American River Basin, snowpack measured 186%; the Tuolumne and the Merced River basins were at 176% and 153%, respectively, as of April 1, when the snowpack is typically at its peak. As warmer days melt the snow, those numbers will translate to higher water, gnarlier rapids, and free-flowing California rivers that remain navigable well into the summer.

From mid-April to late June, reservoir-fed rivers like the South Fork of the American will see waters rise as reservoirs hit and exceed capacity. During drier years, scheduled dam releases usually allow rafters to paddle the South Fork six days a week.

“This year, there won’t be any question of seven days of [raftable] water [per week]. And it’ll be high water,” says Nate Rangle, president of outfitter Raft California.

High water can be both a boon and a worry for whitewater outfitters. Rapids are measured on a scale from Class I (gently moving water) to Class VI (potentially fatal aquatic fury that’s impossible or close to impossible to navigate). High water levels can push an exhilarating Class IV rapid into expert territory and beyond.

To prepare for a season of high water and roiling rapids, outfitters are stepping up guide training, raising the minimum age on certain trips and adding extra safety boats or kayakers to accompany groups. Adventure outfitter OARS has increased the minimum age from 14 to 16 on a number of itineraries through the end of June, and Whitewater Excitement sometimes subs out smaller boats for more stable rafts and adds frames on the back so guides use a pair of oars to maneuver instead of a single paddle.

The three companies also screen to ensure their clients’ skill and experience levels match the river they’re booking.

On the South Fork of the American — a Class III river where Raft California usually covers 21 miles over two days — Rangle says heavy flows allow a full-mileage run in a single day. It’s still Class III, but “it’s a lot of Class III. The South Fork at high water is the most fun ride, most bang for your buck,” he says.

On the American’s Middle Fork, however, when the water is double its normal flow rate — up from 1,100 cubic feet per second to about 2,200 CFS — Rangle says the rapids become unrunnable.

“It goes from Class IV to class we’re-not-going-to-do-it,” says the veteran rafter, who’s been paddling California rivers for 40 years. “We know the Middle Fork won’t be runnable in May and early June. We probably won’t be on the Middle Fork until late June and early July.”

When the Middle Fork is too high to paddle — thanks to features like the Tunnel Chute, a funnel of whitewater that barrels into a 90-foot tunnel blasted out by gold miners in the 1860s — Schoenhoff steers clients toward the North Fork, a free-flowing river without an upstream reservoir.

“North Fork right now is the river to get on in California,” he says. “It’s really exciting because we don’t get to get out there that much as guides. We love to show people down the North Fork as well.” . The heavy snowpack will mean it’s navigable weeks longer than normal.

After a weak winter last year left the statewide snowpack at 52% of the historical average, Angels Camp-based OARS had a limited season for some trips. The company, which guides on seven California rivers, ran its final trip on the North Fork of the American on May 1 and sent its last group down the Merced on June 18.

For 2019, OARS sales and marketing Vice President Steve Markle says the company is projecting “raftable flows” on both rivers into June and through July.

Schoenhoff recently paddled the South Fork of the American. Flow was up to 5,000 CFS, he said, well beyond the normal 1,500 CFS. “It feels awesome. All the rapids tend to get a bit bigger, but they maintain that fun character. It’s optimal.”