This project addresses the question: “What effects are climate change and land use pattern change having on the water cycle and water quality in East Asia’s river basins?”. Models showing interactions among climate, hydrology, land use and water quality are constructed for both the temperate climate of Korea and the tropical climate of Southeast Asia. Specifically, the expected impact of climate changes related to extreme events on loadings of nutrients and microorganisms are determined. This entails a hydrologic/water quality model combined with a climate change model. General Circulation Model (GCM) products are downscaled to be applicable to a hydrologic model. A Soil and Water Assessment Tool (SWAT) model simulates hydrologic processes and the water quality resulting. Validation of predicted with actual results is conducted using both our water quality monitoring data and data collected by local water quality agencies. This project furthermore generates knowledge about changing climate and land use pattern impacts on water quantity and quality at a river basin scale in East Asia. Finally, this project provides scientific baseline information that can be translated into practical knowledge, including tools for assessing and managing risks associated with changes in water quality under rapidly changing climate and land use patterns.