Have significant changes occurred in extreme precipitation since the Three Gorges Reservoir impoundment?

ABSTRACT The impact of the Three Gorges Reservoir impoundment on precipitation has attracted significant attention. Existing studies on its driving mechanism remain insufficient. This study investigated changes in annual and seasonal extreme precipitation during the pre- and post-impoundment periods (i.e., 1983–2002 and 2003–2022) within the Three Gorges Reservoir Area (TGRA) based on innovative trend analysis. Our major findings indicate a slight increase (0.40 mm/year) in annual precipitation after reservoir impoundment, representing a compromise between a significant decrease in summer precipitation and a significant increase in precipitation during the remaining seasons. Short-term precipitation indices for summer exhibited a significant decline, particularly for higher grades. Significant downward trends in consecutive dry days and upward trends in consecutive wet days were observed during winter, while opposite trends were evident for both indices in other seasons. These observations suggest that the TGRA experienced a drier summer and wetter winter after impoundment. Furthermore, changes in extreme precipitation exhibited strong consistency with intra-annual water area changes due to reservoir impoundment. The weakened South Asia Summer Monsoon Index is identified as another important factor contributing to summer precipitation reduction. These results benefit understanding of extreme precipitation variations resulting from the Three Gorges Reservoir impoundment.