Abstract by Joseph Tolworthy
A Water Budget of the Waimea River Watershed, Kauai.
Groundwater recharge in the Waimea River watershed is approximately 7.97x107 m3 a year. Understanding the volume of water and its respective pathways through the watershed contributes to creating a solute flux budget that will give insight into why Waimea Canyon has deep V-shape. Groundwater recharge was calculated using the water budget equation Groundwater recharge = Precipitation – Direct Runoff – Actual Evapotranspiration (AET) + change in soil moisture storage (Shade, 1995). The water budget was created using data from the University of Hawaii’s rainfall and evapotranspiration atlases, United States Geological Survey stream gage data and soil data from the United States Department of Agriculture. The change in soil storage was calculated using methods followed in Shade’s, 1995, water budget of Kauai. Rainfall on the watershed is 2.93 x108 m3, direct Runoff is 1.02 x108 m3 a year, AET is 1.12 x108 m3 and groundwater recharge is 7.97 x107 m3. 38% of the rainfall leaves the watershed through evapotranspiration. 35% of it through direct runoff and 27% of rainfall recharges the groundwater. The change in soil storage is 8.7x106 m3 per year.