LAUSR

Abstract Due to climate change, food security and water use associated with paddy rice cultivation in Korea are facing great challenges, and practical measures are needed to compensate for the negative impacts of climate change. Transplanting date shift (TDS) has been considered as an adaptation strategy to climate change, however, its impact on water use, water quality, and rice production is still unclear. This study was designed to assess not only TDS but also drainage outlet raising (DOR) as a practical adaptation strategy to climate change. We analyzed the impacts of climate change on water use, water quality, and water productivity in 12 combination scenarios of TDS and DOR using a well-proven APEX-Paddy model according to 10 General Circulation Models (GCMs). We found that the future runoff and total nitrogen (T-N) load appeared differently in each decade, and the future runoff and T-N load increased more than the irrigation water and rice yield over the observed period of time due to the effects of the rainfall amount and rainfall intensity rather than the effects of the increased temperature. The future rice yield declined continuously as the temperature increased due to the rising CO2; however, a significantly amount of irrigation water was saved due to the TDS. According to the DOR implementation, the future runoff, T-N load, and irrigation water requirement were significantly reduced, while the rice yield increased slightly. The RM5 scenario, which includes both the DOR and 40-day delayed TDS, was ranked as the most effective best management practices (BMPs) with the highest water productivity in all of the scenarios. The results of this study indicated that an adequate combination of TDS and DOR taking into account the weather conditions would mitigate the negative impacts of climate change.