Abstract by Joseph Tolworthy
A Solute flux mass balance model of Waimea River Watershed, Kauai, USA
Waimea Canyon is a large, V-shaped canyon on Kauai. In contrast, most canyons in the Hawaiian Islands are U-shaped, Waimea Canyon is not. A solute flux mass balance model may give an answer to why Waimea Canyon is different. The total mass flux from the Waimea River watershed is 159 t/km2/yr based on the eroded volume of drainages. Solute flux in the Waimea River watershed, by contrast, is only 34 t/km2/yr. The SiO2 in the stream and groundwaters were combined with the water budget to estimate a solute flux of 24 t/km2/yr in groundwater and 10 t/km2/yr in stream water.
Dissolved loads account for only 21% of material removed from the watershed, while 79% is removed through suspended load and bedload. Comparison of the total mass flux to the dissolved load suggests that physical erosion dominates the denudation of the Waimea watershed. Vigorous downcutting, rather than canyon wall sapping by groundwater, controls the V-shape of the canyon.