Assessing the impact of climate change on the land hydrology in Taiwan

The gradually increased temperature resulting from the enhanced greenhouse effects has been found to be an important factor of changes to the global climate which in turn might significantly affect the Earth's hydrological cycles. The possible outcomes of warming climate are changes of precipitation, surface runoff, evapotranspiration, and frequency of extreme weather events, such as floods and droughts. However, such changes at the global scale may not reflect the variations on a regional scale, and more so at the local scale. In this study, a physically based water balance model was applied to study the impact of climate change on the land hydrology, focusing on trends of surface runoff, evapotranspiration, and infiltration in Taiwan. Model forcing of composite temperatures and precipitations were generated by a weather generation model in association with nine climate change scenarios, including outputs of equilibrium experiments and special reports on emissions scenarios, from the IPCC. Although discrepancies among different climate change scenarios are significant, the trend of more extreme precipitations and surface runoffs were observed in most scenarios' runs. The increase of evapotranspiration in both wet and dry seasons is persistent among different scenarios throughout the island due to the projected consistently higher temperature. Although the trends of infiltration for wet and dry seasons are opposite in curtain scenarios, a decreased yearly infiltration was found in most cases as the result of increased precipitation intensity and more evapotranspiration. Timely adaption measures for water resources managements and natural hazard mitigations are required to face these changes of land hydrology components under changing climate.