A historical analysis of eco-environmental changes in hydrologically regulated lakes.

Human have a long history of implementing hydrological regulations in lakes. With the rapid increase in global population since the mid-20s, the anthropogenic pressure on freshwater resources has intensified, which would result in abrupt change in lake ecosystems. A meta-analysis study had been conducted involving 36 lakes of different types and latitudes from 39 study sites around the world. These lakes were subject to different hydrological regulations between 1900 and 2017. Hydrological regulations tended to result in a more stable water level and poorer water quality. In addition, a turning point occurred in 1956 when the response time interval (RTI)-the time between hydrological regulation implementation and significant ecological change in the lake-decreased significantly since, which coincided with a surge in population size, water and fertilizer usage since the mid-20s. The results of principal component analysis (PCA) emphasized the influence of anthropogenic pressure on the resilience of lakes. The rapid increase of anthropogenic pressure after the mid-20s limited the buffering capacity of large lakes. As the global population continues to grow and water stress is exacerbated by climate change, human may be pressured to implement even larger-scale lake hydrological regulation projects that will likely cause rapid and long-lasting deterioration of these aquatic ecosystems. Environmental resilience analysis combined with multi-indicators is necessary for the monitoring and management of eco-environment changes in regulated lakes.