Spatial and temporal variation of annual and categorized precipitation in the Han River Basin, South Korea

The effects of variations in annual, seasonal, and extreme precipitation in the Han River Basin (HRB) were explored using innovative trend analysis, Spearmen’s rho test, and Mann-Kendall test. Extreme-value precipitation was analyzed using various precipitation categories (light, low, moderate, high, and extreme). Stations in the north and northeast parts of the basin were more sensitive to precipitation inconsistencies. Hydrologically extreme events such as flood and drought were associated with extreme (> 90th percentile) and light (< 10th percentile) precipitation categories. Significant variability was detected in summer precipitation, whereas annual and extreme precipitation trends were more sensitive in the northeastern parts of the basin, signifying possible flooding aggregation. However, a decrease in flooding in the southern HRB indicated a shift in the precipitation regime from south to north. Overall results suggest that the eastern and northwestern regions were more likely to experience extreme floods during the summer and severe droughts during the fall and winter. An increase in precipitation was observed over time from the south to the north. A warming and wetting trend was observed in the north, while a warming-drying trend was evident in the south. Mitigating hydro-meteorological disasters such as flood and drought in the HRB will require more research attention to these trends.