Analysis of Effects of Meteorological Drought on River Water Temperature Using SPI and EDDI

Drought is a natural phenomenon that can occur in all climates with various severities and spatial coverages. The frequency and severity of drought are increasing in many parts of the world due to rainfall volatility and increasing temperature caused by climate change. Extreme drought seriously impacts freshwater ecosystems, resulting significant social and economic damage. This study analyzes the effects of drought on the water temperature of major river sections across the Korea using the Standardized Precipitation Index (SPI) and Evaporative Demand Rough Index (EDDI), calculated by monthly precipitation and potential evaporation, respectively. SPI and EDDI are computed for the major watershed of South Korea, Han River, Nakdong River, Geum River, and Yeongsan River. EDDI is calculated for various timescales and the optimal timescale is determined for the highest correlation coefficient between EDDI and water temperature. The copular binding theory describing a joint probability distribution between variables is applied to quantify the sensitivity of water temperature to meteorological drought scenarios. The quantified temperature sensitivity values are spatially presented for the major watersheds in South Korea to identify the effects of meteorological drought on water temperature. The results are beneficial to water resources managers for planning eco-environmental strategy of watersheds considering various drought scenarios. Acknowledgment This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. NRF-2019R1A2C1003114).