Streamflow reconstruction and its long-term variation characteristics in Lhasa River Basin over the past 5 centuries (1473~2017)

Historical streamflow reconstruction based on the pre-instrumental data for rivers in Tibet can provide long-term perspectives on the impact of the climate change in the Third Pole on Earth.  We use the VIC model to reconstruct the yearly, monthly and daily streamflow of Lhasa River during the past 5 centuries (1473~2017). Compared with the recent 60 years, the past 500 years have 11% more average annual runoff. Signals of long-term variations have been detected including a 60 years cycle and decades of continuous wet/dry years. The streamflow shows almost 50% higher annual and daily maximum runoff and highly variable in the 16th and 17th centuries, and decreased and more stable runoff thereafter till the present. These findings conform to the understanding of climate change in this area: the combined effects of Indian Summer monsoon and mid-latitude Westerlies, and confirms the potential of exploring the historical streamflow features using the VIC model and paleo-climate data. They also reveal the limitation of the recent instrumental records for understanding the long-term hydrological behavior of rivers in Tibet.