MOUNT WAIALEALE, Kauai — This legendary peak dominates the geography of Kauai, jutting to an altitude of 5,148 feet and constituting possibly the wettest place on Earth.

Or possibly the second-wettest, after Mawsynram, a mountain in India. Or the second-wettest in Hawaii after Maui’s Big Bog, which may have wrested the wettest title from Mount Waialeale from 1998 to 2007.

“Wettest” is a matter of timing, but with the staggering total of the 519 inches that fell on Waialeale in 2018, the mountain may have reclaimed its rainiest place on earth status — at least temporarily —after decades of declining precipitation.

Think of Waialeale as a giant sponge. It absorbs — depending on how much acreage is attributed to the mountain — from billions to hundreds of billions of gallons of water each year as its summit’s microclimate, flora and fauna create an environment ideal for rainfall accumulation and retention.

Captured by the watershed — a complex system of trees and low-growing plants — the rain percolates downward into the island’s aquifers, where it remains in storage for so long that the 519 inches that fell last year probably won’t emerge from island faucets for 20 or 25 years, according to Melissa Fisher, Kauai forest program director for The Nature Conservancy and a longtime observer of Waialeale.

The landmark Weeping Wall is fed by the heavy rainfall on Mount Waialeale. Nathan Eagle/Civil Beat

All seven of Kauai’s rivers originate at the summit of Waialeale. It is a vast water network, said Makaala Kaaumoana, director of the Hanalei Watershed Hui. The network is so mindbogglingly big, she said, that if you look up at waterfalls cascading down above Hanalei — as tourists often do — you’d think they feed the Hanalei River when, in fact, they are gushing into an entirely different ecosystem.

It is not just the amount of rain falling on Waialeale that distinguishes it. With different vegetation and geology, the rain that falls on the mountain might simply run off. But the unique tree and plant species of the watershed in its upper regions are ideally suited to holding onto as much of that water as possible.

At the top of the mountain, Fisher said, what appear to be flat fields covered in vegetation are actually as soggy as quicksand and wandering off established trails can easily lead to sinking into mud.

“You get stunted everything,” she said. “Everything is a lot smaller in stature because it’s so misty and wet. It looks flat and nice with this little layer of water and tufts of grass, but you step in (at the wrong place) and you’ll lose your shoes and it’ll start coming up to your knees.”

All of this is part of Waialeale’s legend. Remote and often nearly inaccessible except by helicopter (even then, cloud conditions can make landing impossible), it is a dominant element in the mystique of Kauai.

The mountain’s rainfall scorekeeper is Kevin Kodama, a senior hydrologist for the National Weather Service in Honolulu.

The gigantic rainfall total for 2018, Kodama noted, is not even close to the highest-recorded in the last half-century. In 1982, 693 inches fell there. In 1990, the total was 535 inches.

The runoff from Mount Waialeale feeds numerous waterways. Nathan Eagle/Civil Beat

More telling, perhaps, is that the years when Waialeale recorded 400 or more inches of rain have declined over the decades. For example, the 400-inch level was reached in six consecutive years starting in 1986, then recurred — at minimum — every three of four years until 1994. After that, though, the big years grew more infrequent. In fact, a total above 400 inches had not been recorded since 2006 until last year. There was another decade-long stretch, from 1994 to 2004, without a 400-inch total.

Over the last 50 years, Waialeale has experienced both torrential rainfall months and months that were almost completely dry. A total of 149 inches fell in April 1982, for example, and 100 inches in November 1990. By comparison, Waialeale got just under an inch — .96 — in February 1983, and 1.67 in December 2006.

Kodama said April 2018 was also noteworthy, and not because of the 64 inches of rain Waialeale got then, during the island’s disastrous mid-month flooding. It was noteworthy because so many previous months yielded such higher totals.

Kodama’s description of the 682 inches that fell in all of 1982 was that it was a “crazy amount” that makes last year look sane by comparison.

Mount Waialeale rises above Wailua Reservoir. Nathan Eagle/Civil Beat/2019

“March 1982 was 149 inches,” Kodama said. “So for context, last April, with all that big flooding, was 64.24.” But that also underscores the truly unprecedented nature of last April when the brunt of the flooding rains did not fall on Waialeale — as they usually do — but in the now fabled rain bomb that dropped on the Hanalei-Haena area, in a rare downslope drenching.

“After the monster year in 1982, Waialeale dropped off to 329 inches in 1983 and 292 in 1984.

Kodama hestitated when asked if climate change is affecting Waialeale’s fluctuating rainfall.

“Climate is always changing, by nature,” he said. “It’s the causation that is always the question. In the current state of things, it’s automatically associated with global warming.”

And he certainly isn’t saying that last year’s high rainfall means Waialeale’s long-term downward trend has been reversed.

“Heck,” he said, “I can’t even predict a few days in advance.”

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