Revealing the spatial–temporal patterns of hydropeaking induced by the Three Gorges Dam, China

Abstract

Hydropeaking, a common consequence of hydropower dam operation, causes frequent, rapid and short term fluctuations in water flow and water levels. As the number of hydropower dams continues to increase, characterizing the highly variable hydropeaking regimes has become an important topic. However, features of hydropeaking are not well studied for many rivers with a hydropower dam, especially those large hydropower dams. Here, we explored the spatial–temporal patterns of hydropeaking induced by the Three Gorges Dam (TGD), the world’s largest hydropower dam to date, based on long term water level data of ∼450 km downstream reaches. To detect and quantify hydropeaking signals, we used an integrated methodology that combined wavelet analysis with the range of variability method. Results showed that the TGD induced hydropeaking occurred at 1-day and 0.5-day cycles, and the maximum amplitude was 3.43 m, 95 % quantile 1.91 m and 90 % quantile 1.52 m at Yichang gauging station. Amplitude of hydropeaking decreased with distance from the TGD but increased from initial to normal stage of dam operation. Hydropeaking varied seasonally as its amplitude and frequency were higher during the wet season (May–November) than those of the dry season. Operation of the TGD strongly reduced the annual cycle of water level in downstream reaches after removing the effects of precipitation. Our results provide new insights into understanding the effects of large hydropower dams as well as environmental flow management in hydropeaking affected rivers.