Lake Evaporation and Its Effects on Basin Evapotranspiration and Lake Water Storage on the Inner Tibetan Plateau

Abstract Effects of lake evaporation ( E W ) on basin evapotranspiration ( ET B ) and lake water storage change ( LWSC ) at lake‐basin scale have never been reported for most basins on the inner Tibetan Plateau (IB). In this study, E W of 118 large lakes in 95 closed lake‐basins were estimated, and its effects on ET B and LWSC over 2001–2018 were examined using a derivative‐guided framework from the aspects of E W amount, rate, trend slope and inter‐annual variability. We found that E W amount has a high effect (17%) on regional ET B amount compared to the average lake area ratio ( α ) (∼5%), and the effect has increased significantly (2%/10 a). The spatial pattern of the effect is mainly controlled by α , and the increasing trend of α (0.6%/10 a) also dominated the increasing trend in regional ET B rate (0.30 mm/a) though with large spatial heterogeneity. Variance in α and E W rate have a minor effect (∼3%) on ET B variance, especially for the basins with lower α . The combination of quasi lake inflow ( R L , 41%) and lake surface precipitation ( P W , 16%) offset the depletion of E W (−43%), resulting in the surplus of regional lake water ( LWSC > 0). The increase in E W mount, which is mainly from lake area expansion (90%), caused a decreasing trend in LWSC (i.e., slower growth rate) with a contribution of −59%. This suggests a negative feedback between lake area expansion and E W amount in the IB, and the feedback may continue with the predicted area increases.