Lake Waiau is the highest lake on the Big Island, the state of Hawai'i, and the entire Pacific Rim. The Big Island's only other lake, Green Lake, is located on private land in the Puna District. This shallow lake's existence is a mystery. Although there are a few theories, scientitsts are not sure how a lake can exist in such an arid, high altitude location on an island with very porous ground. For some unknown reason, water collects in the basin created by the erosion of Pu'u Waiau. The reason why it does not percolate so easily into the lava rock like water does throughout the rest of the island is unknown. Two theories attempt an explanation: either sulfurous steam altered the volcanic ash to low-permeability clay soil; or explosive interactions between rising magma and water (phreatic eruptions) formed exceptionally fine ash that also would reduce the permeability of the lake bed. One colorful explanation holds that permafrost from the last ice age feeds the lake, altough no permafrost has been found in the area around Pu'u Waiau. Permafrost has been found closer to the summit of Mauna Kea in a few areas.

Waiau means "swirling water" in the Hawaiian language, and this phrase is probably meant to evoke the myth that Lake Waiau is the portal to the spirit world or underworld. In ancient times, the ali'i, Hawaiian royalty, would throw the umbilical cord of their first-born son into the lake to ensure their future success as a chief. 

The hikes presented here allow you to just visit Lake Waiau or to hike to the lake and then continue on the Humu'ula Trail to the summit of Mauna Kea. If you're looking for a great adventure on Mauna Kea but don't want make the investment of the Humu'ula Trail, these hikes are a great option. You'll be able to visit the otherworldly arid environment of upper Mauna Kea, Lake Waiau, and the summit of Mauna Kea. 

Trailheads: From either side of the island, take the Saddle Road, Hwy. 200, to the Mauna Kea road near the 28 mile marker. The road is well-marked. From the turn, follow the paved road for six miles to the Ellison Onizuka Mauna Kea Visitor Information Station (MKVIS). The remainder of the Mauna Kea Road is four-wheel drive only. Do not attempt to drive this road in a two-wheel drive vehicle. If you'd like to visit Lake Waiau and see the summit of Mauna Kea with a two-wheel drive vehicle, you'll need to park at the MKVIS and hike the Humu'ula Trail. There are three trailheads that you can use for this hike, but it probably makes most sense to park at Trailhead 1. Refer to the map above for their locations. Find Trailhead 1 just past the 6 mile marker on the east side of the Mauna Kea Road near towering Pu'u Haukea. Trailhead 2 is located just before a 180 degree switchback in the Mauna Kea Road about a mile past Trailhead 1 on the north side of Pu'u Haukea. This trailhead has a few signs about Lake Waiau. Trailhead 3 is simply the summit parking area near the observatories where the Mauna Kea Road ends. 

Read About Acute Mountain Sickness (AMS)

Weather:

• Summit Forecast

• Mauna Kea Visitor Information Station Forecast

• Mauna Kea Weather Center

Gear: You’ll need winter gear, sturdy boots, plenty of water, and extra food.

Hike: This hike begins at Trailhead 1, visits Lake Waiau, and then continues on to the summit of Mauna Kea. If you'd like to use Trailhead 2 or Trailhead 3 to access these locations, find their locations described below. From the parking area, cross the Mauna Kea Summit Road and find the trail to Lake Waiau to the west. Hike 0.6 mile and find the intersection with the Humu'ula Trail. Take this trail to the north for less than a tenth of a mile and find the intersection of the Lake Waiau trail. This short spur trail travels into Pu'u Waiau's eroded cinder cone and Lake Waiau. Enjoy the lake from a distance. Do not drink or swim in the water. This is a sacred place to the Hawaiian people, and if you happen to find religious offerings you should leave them alone. Once you've marveled at this geologic oddity, return back to the Humu'ula Trail. If you're just visiting the lake, return the way you came. If you'd like to continue on to the summit, hike north along the Humu'ula Trail until you reach Trailhead 2 and the Mauna Kea Summit Road. Unfortunately, this part of the trail is along the road. Hike along the broad shoulder and wave at traffic to ensure that they can see you. After a few long switchbacks, leave the road at the summit parking area (Trailhead 3) and hike the remaining 0.3 mile to the summit. Enjoy the biggest view in the Hawaiian islands. Return the way you came. Although it seems like it might be nice to follow the road from Trailhead 2 back to Trailhead 1, I recommend staying on the trail. The road is difficult to drive and drivers are usually distracted by the incredible scenery, creating a dangerous combination, so it's much safer to hike the trail.