Hydrologic and Isotopic Modeling of Alpine Lake Waiau, Mauna Kea, Hawai'i

Abstract

Analysis of hydrologic, meteorologic, and isotopic data collected over 3 yr quantifies and explains the enormous variability and isotopic enrichment (d 18 O ¼ þ16:9, dD ¼ þ50:0) of alpine Lake Waiau, a culturally and ecologically significant perched lake near the summit of Mauna Kea, Hawai'i. Further, a simple one-dimensional hydrologic model was developed that couples standard water budget modeling with modeling of dD and d18 O isotopic composition to provide daily predictions of lake volume and chemistry. Data analysis and modeling show that winter storms are the primary source of water for the lake, adding a distinctively light isotopic signature appropriate for high-altitude precipitation. Evaporation at the windy, dry summit is the primary loss mechanism for most of the year, greatly enriching the lake in heavy isotopes.

Combined U–Th/He and 40Ar/39Ar geochronology of post-shield lavas from the Mauna Kea and Kohala volcanoes, Hawaii

“…The new U-Th/He age of 119±26 ka and 40 Ar/ 39 Ar plateau age of 123±5 ka confirm this hypothesis. The 3 He C age of ~28 ka suggests a slow incision rate that is consistent with the aridity of this region of the Mauna Kea volcano -both the sample collection point and the drainage area for the gully are east of the coastal wet areas on the west coast of the island (EHLMANN et al, 2005). Again, we underscore that for this sample, the 40 Ar/ 39 Ar age and the U-Th/He age agree well.…”

Climate driven changes to rainfall and streamflow patterns in a model tropical island hydrological system

“…. Four watersheds (Honoli'i,Ka'awali'i,Waikaumalo,165 'Uma'uma) had regions above the lower bounds of the inversion layer at 1830 m (6000 ft) in 166 elevation t where PET exceeds rainfall, resulting in a net loss of water, skewing the watershed's 167 the effective MAR (Ehlmann et al, 2005;Erasmus, 1986 (2007) and Buchanan and Somers (1976). Measurements Daily rainfall values were calculated for each rain gage and mean daily rainfall and total 198 annual rainfall were calculated for each water year.…”

Subsurface architecture of two tropical alpine desert cinder cones that hold water

“…For comparison, Lake Waiau's drainage area is more than 10 times larger, 135,000 m 2 [ Ehlmann et al ., ] and the full Waiau lake has about ~7000 m 2 . The ratio of the drainage area to pond area is 19 for Lake Waiau and 10 for Pu‘upōhaku.…”

“…Even up to now, the lake serves as a spiritual place for local Hawaiian people and as an (unsanctioned) tourist attraction of the Mauna Kea Ice Age Natural Area Reserve. The cinder cone containing Lake Waiau, known as Pu‘uwaiau, has been studied for hydrological [ Gregory and Wentworth , ; Woodcock and Groves , ; Ehlmann et al ., ], ecological [ Wentworth and Powers , ], as well as meteorological and bathymetrical aspects [ Woodcock , ; Patrick and Kauahikaua , ]. The reason for the lakes' existence remains uncertain but fine‐grained ash, permafrost, massive lava beds, and clays have been proposed to cause low permeability [ Ugolini , ; Woodcock , ; Wolfe , ].…”