Climate change will affect water resources and environment all over the world and its impacts assessment and adaptation are pending issues that are significant in terms of science and policies. However, GCMs and selection of scenarios have never been standardized while the results from systemic researches based on the water cycle mechanism covering weather, hydrologic elements, water resources and environment have been insufficient in Korea. Hence, this study explored and applied appropriate techniques for assessment of climate change impacts on water resources and environment according to the country’s needs.

Precise statistic analysis of elasticity for hydrological elements and trends for detecting climate change were conducted to provide substantial results as to changes in temperature and rainfall in Korea coming from climate change both in terms of time and space and various statistical techniques were applied for this purpose, which is significant. Especially, impacts on water temperature and water environment(quality), so far rather neglected in Korea, were analyzed, which will provide an early-stage contribution to the future water environment research and policies.

Based on selection of the most appropriate GCMs in Korea, which is the most fundamental and basic stage for climate change analysis, and application of downscaling techniques for precise materialization of Korea’s meteorological patterns in terms of space and time, the current climate change scenarios and those forecasting the next 90 years were produced and applied. Various statistical verification involving bias, seasonality, variability, and comparison of test results produced reliable results.

For the first time in Korea, the SWAT model, an integrated hydrological model was constructed for the Nakdong River basin and verified. The climate change scenario, thus derived, was applied to the model to comprehensively analyze and assess climate change impacts around the Nakdong basin based on analysis of yearly and seasonal changes in outflow, daily changes in flow duration, and changes in water pollution loads. The scenario-based studies on climate change impacts including GCM, RCM, downscaling, and SWAT are expected to provide technological methodologies for climate change research and become a foundation for more quantitative, more reliable and analytic studies on the country's climate change based on application to other basins.

If water environment impact assessment and analysis of the future water balance including a forecast of water supply and demand take place based on the results of this study, the results will be sufficiently valuable both as researches on national measures to climate change and policy materials.