Deciphering Hulun lake level dynamics and periodical response to climate change during 1961-2020

Study Region: Hulun Lake, the fifth largest lake in China.Study Focus: The notable decline in water level (WL) caused by climate change is the primary challenge faced by Hulun Lake. However, the contribution of climate to water loss and its driving mechanisms remain unclear. The impact of climate on WL change was investigated using wavelet analysis and structural equation models.New Hydrological Insights for the Region: In the past 60 years, the increasing potential evapotranspiration (ETp) caused by warming climate was the main reason for the WL decline (r=-0.67). For period I (1961-1997), reduced runoff due to increasing ETp caused an overall decrease in WL (r = 0.41). During the mid-1980s, the increase in rainfall driven by ENSO (r = -0.66) caused a slight increase in WL (r = 0.31). For period II (1998-2020), deforestation, farmland and urban area expansion were the main drivers behind the significant increase of ETp in the watershed (r = -0.22), which leads to reduced runoff and, consequently, a significant decrease in WL. The influence of climate on WL change weakened compared with that in the first period due to land use change (r = -1.08)