Climate Change Assessment of Water Resources in Sabah and Sarawak, Malaysia, Based on Dynamically-Downscaled GCM Projections Using a Regional Hydroclimate Model

Abstract

Climate change’s impact on the Sabah and Sarawak water resources in the Northern sector of the Borneo Island, Malaysia, was assessed based on the dynamically-downscaled general circulation model projections (GCMPs) by means of a regional hydroclimate model (RegHCM). Four future projections under the special report on emissions scenarios (SRES) A1B emission scenario from two general circulation models (GCMs) were selected for this study. The RegHCM, which is a coupled nonhydrostatic atmospheric and upscaled land surface process model, is capable of downscaling the outputs of these GCMPs (GCM projections) to the watershed scale at a 9-km grid resolution at hourly time intervals for hundreds of years—a simulation for 420 years was performed in this study. This dynamic downscaling by the RegHCM can incorporate the detailed soil and land-cover data. It is shown in this article that utilizing a methodology that incorporates a GCM, a RegHCM, and a hydrological routing model allows assessing climate change on the hydrologic conditions at the watershed scale. It is revealed that the effect of climate change in the states of Sabah and Sarawak can be quite heterogeneous. Furthermore, it is shown that the effect of a projected land-cover change over a geographical region, such as Sabah and Sarawak, can be evaluated in the future using the RegHCM described in this study. Results indicate that the increase in oil palm plantations in Sabah and Sarawak may not significantly affect the local water resources. In order to improve the assessment accuracy of land-use change, further investigation on the model parameters associated with future land-cover information is desirable.