Hydrologic response of a Hawaiian watershed to future climate change scenarios

Abstract

The impact of potential future climate change scenarios on streamflow and evapotranspiration (ET) in a mountainous Hawaii watershed was studied using the distributed hydrology soil vegetation model (DHSVM). The hydrologic response of the watershed was simulated for 43 years for different levels of atmospheric CO₂ (330, 550, 710 and 970 ppm), temperature (+1.1 and + 6.4 °C) and precipitation (±5%, ±10% and ±20%) on the basis of the Intergovernmental Panel on Climate Change (IPCC) AR4 projections under current, B1, A1B1 and A1F1 emission scenarios. Vegetation leaf conductance and leaf area index were modified to reflect the increase in CO₂ concentration. The relative departure of streamflow and ET from their levels during the reference scenarios was calculated on a monthly and annual basis. Results of this study indicate that the streamflow and ET are less sensitive to changes in temperature compared with changes in precipitation. However, temperature increase coupled with precipitation showed significant effect on ET and streamflow. Changes in leaf conductance and leaf area index with increasing CO₂ concentration under A1F1 scenario had a significant effect on ET and subsequently on streamflow. Evapotranspiration is less sensitive than streamflow for a similar level of change in precipitation. On the basis of a range of climate change scenarios, DHSVM predicted a change in ET by ±10% and streamflow between −51% and 90%. From the six ensemble mean scenarios for AR4 A1B, simulations suggest reduction in streamflow by 6.7% to 17.2%. These reductions would produce severe impact on water availability in the region. Copyright © 2011 John Wiley & Sons, Ltd.