Evaluation of flood frequency under non-stationarity resulting from climate indices and reservoir indices in the East River basin, China

- Clarification of performance of nonstationarity-based hydrological modeling.
- Quantifying influences of climate and human activities on flood processes.
- Potential to differentiate influences of water reservoirs on flood processes.

SummaryThe East River, the major tributary of the Pearl River basin, China, is the major source of water supply for megacities within the Pearl River Delta and also for Hong Kong. In this study, stationary and non-stationary models are used to analyze flood characteristics with time, climate indices, and reservoir index. Results indicate that: (1) the variance of annual maximum stream-flow is constant with time and a linear dependence is detected between annual maximum stream-flow and time at the Longchuan, Heyuan and Lingxia stations and a nonlinear dependence at the Boluo station; (2) Xinfengjiang reservoir is relatively closer to Heyuan station and is believed to exercise a significant influence on the flood process at the gauging station. The Pacific Decadal Oscillation Index (PDO) linearly influences the variance of annual maximum stream-flow at the Lingxia and Boluo stations but nonlinearly at the Longchuan and Heyuan stations. The influences of climate indices on flood processes are significantly distorted by hydrological regulations of water reservoirs, as reflected by a sudden decrease of flood discharge after their construction; (3) in comparison with the stationary model, the non-stationary model with climate indices and reservoir index can better picture changing features of the flood process. This study can serve as a reference for regional planning and management of water resources in the East River basin, and possibly for other river basins on the globe under massive influences of human activities and climate changes.