Multi-century flow reconstruction of the Lhasa River, China

Abstract

Study region: Lhasa River Basin Study focus: Multi-century records are needed to characterize flow variability including the magnitude and frequency of occurrence of extreme events. Such long records are not available without integrating well-calibrated hydrological models and climate proxies. To test whether 50–70 years of observations represent the long-term flow variability for water resources management, daily flows (1472–2000) were reconstructed by integrating the Variable Infiltration Capacity (VIC) model with proxy-based precipitation and temperature data for Lhasa River. New hydrological insights for the region: VIC performed well during calibration and validation for 3 gauging stations with the Nash-Sutcliffe coefficient of efficiency (NSE) exceeding 0.52. Proxy-based precipitation, temperature, and reconstructed flow are broadly stationary over the past 529 years, while recent decades show detectable local trends. The inter-annual/decadal variability is aligned with long-term variations in sea surface temperatures and the intensity of south Asian summer monsoon. Moreover, higher long-term average, greater variabilities, and persistent periods of above/below-average flows are detected. The maximum daily flows with small annual recurrence intervals (ARIs) less than 60 years would be overestimated based on observations, and underestimated for ARIs > 60 years. It is the first time to have reconstructed long-term daily flows using hydrological models coupled with proxy-based climate data, and this approach offers invaluable insights into the pre-instrumental flow responses to changing climate conditions in Lhasa River basin.

Keywords

• Greater natural variability
• Representability of observed flows
• Daily flow reconstruction
• Water management
• Catchment hydrological modelling