Technical Note: Assessing Climate Change Impact on Hydrological Components of a Small Forest Watershed through SWAT Calibration of Evapotranspiration and Soil Moisture

Abstract

This study evaluates the future impact of climate change on hydrological components in a 8.54 km2 mixed forest watershed located in the northwest of South Korea. Before future assessment, the SWAT (Soil Water Assessment Tool) model was calibrated using two years (2007-2008) and validated by using one year (2009) of daily observed streamflow, evapotranspiration, and soil moisture. Hydrological predicted values matched well with the observed values during calibration and validation (R2 > 0.6 and Nash-Sutcliffe efficiency > 0.5). The MIROC3.2hires GCM (general circulation model) data of the SRES (special report on emissions scenarios) A1B and B1 scenarios of the IPCC (Intergovernmental Panel on Climate Change) were adopted for future assessment and downscaled using the LARS-WG (Long Ashton Research Station - Weather Generator) stochastic weather generator after bias correction with 30 years (1970-2000) of ground measured data. The A1B scenario reflects a future world of very rapid economic growth, low population growth, and rapid introduction of new and more efficient technology. The B1 scenario reflects a very heterogeneous world. The underlying theme is that of strengthening regional cultural identities, with an emphasis on family values and local traditions, high population growth, and less concern for rapid economic development. As a result, the future changes in annual temperature, precipitation, and evapotranspiration showed an upward tendency and streamflow and soil moisture showed a downward tendency in both scenarios.