ASSESSMENT AND IMPROVEMENT OF WATERSHED WATER CYCLE UNDER THE FUTURE CLIMATE CHANGE USING CAT (CATCHMENT HYDROLOGIC CYCLE ASSESSMENT TOOL)

摘要

This study describes the applicability of CAT (Catchment hydrologic cycle Assessment Tool) model for improving stream watershed water cycle, and suggests the proper water cycle improvement methods by the future climate change impacts on watershed hydrology. The CAT model supports the effective design of water cycle improvement facilities. For future assessment, the forest dominant Gyeongan-Cheon watershed (260.1 km2) located in the north-eastern part of South Korea was selected. The watershed lies between 37.6 °N~38.5 °N and 127.7 °E~138.6 °E. For the evaluation of future water cycle improvement, the two GCMs (MIROC3.2hires and HadCM3) data by SRES (Special Report on Emission Scenarios) A1B and B1 scenarios of the IPCC (Intergovernmental Panel on Climate Change) were adopted and downscaled using LARS-WG (Long Ashton Research Station–Weather Generator) stochastic weather generator after bias-correction with 30 years(1970 ~ 2000) ground measured data of 3 stations, and the future daily data of 2021 ~ 2100 (2021 ~ 2060: 2040s; 2061 ~ 2100: 2080s) were generated at each meteorological station. Using the future prepared climate change scenarios, the CAT model was run for future impact assessment of the study watershed hydrology. In summary, the future changes of MIROC3.2hires annual surface runoff, groundwater fl ow and evapotranspiration were up to -3%, -66% and +11% in 2080s A1B scenario respectively. The future changes of HadCM3 annual surface runoff, groundwater fl ow and evapotranspiration were up to -6%, -65% and +13% in 2080s A1B scenario respectively. Under the condition of future climate scenarios, the effect of water cycle improvement methods was evaluated. By the installation of several improvement facilities (infi ltration, rain tank and green roof), each simulation of the effect of infi ltration facility, rain tank, and green roof on improvements in the water cycle was performed with input values refl ecting the current situation of the study area. When the water cycle improvement facilities were not considered, our simulations showed the base fl ow to decrease by 63% and the surface runoff and evapotranspiration to increase by 56% and 47%, respectively; when they were considered, the simulations showed the basefl ow to decrease by 58% and the evapotranspiration and surface runoff to increase by 72% and 18%, respectively.