Water Isotope framework for lake water balance monitoring and modelling in the Nam Co Basin, Tibetan Plateau

Abstract

Since the establishment of the Nam Co research station, a large number of water isotope measurements in the watershed was accumulated. A water isotope framework for the Nam Co basin, including the Local Meteoric Water Line, limiting isotopic composition of evaporation and two hypothetical evaporation trajectories, is established. We further applied the isotope mass balance model to estimate the overall isotopic composition of input water to the Nam Co, the evaporation over inputs ratios (E/I) for three consecutive years, and the water yields (Wy, depth equivalent runoff) at a basin scale. Our results clearly suggest a positive water budget (i.e., E/I < 1), providing another line of evidence that the subsurface leakage from Nam Co is likely.