| Summary: | The Qinghai-Tibetan Plateau (QTP) is generally considered to be the water source region for its surrounding lowlands. However, there have only been a few studies that have focused on quantifying alpine meadow evapotranspiration (<i>ET</i>) and its partitioning, which are important components of water balance. This paper used the Shuttleworth–Wallace (S–W) model to quantify soil evaporation (<i>E</i>) and plant transpiration (<i>T</i>) in a degraded alpine meadow (34°24′ N, 100°24′ E, 3963 m a.s.l) located at the QTP from September 2006 to December 2008. The results showed that the annual <i>ET</i> estimated by the S–W model (<i>ET<sub>SW</sub></i>) was 511.5 mm (2007) and 499.8 mm (2008), while <i>E</i> estimated by the model (<i>E<sub>SW</sub></i>) was 306.0 mm and 281.7 mm for 2007 and 2008, respectively, which was 49% and 29% higher than plant transpiration (<i>T<sub>SW</sub></i>). Model analysis showed that <i>ET</i>, <i>E</i>, and <i>T</i> were mainly dominated by net radiation (<i>R<sub>n</sub></i>), while leaf area index (<i>LAI</i>) and soil water content at a 5 cm depth (<i>SWC<sub>5cm</sub></i>) were the most important factors influencing <i>ET</i> partitioning. The study results suggest that meadow degradation may increase water loss through increasing <i>E</i>, and reduce the water conservation capability of the alpine meadow ecosystem.
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