Changed evapotranspiration and its components induced by greening vegetation in the Three Rivers Source of the Tibetan Plateau

Abstract

The Three Rivers Source (TRS), that is, the source of the Yangtze (SYZ), Yellow (SYE), and Lancang (SLC) Rivers in the Tibetan Plateau, is the water tower of Asia. Harsh climates, complex topography, and limited ground-based observations hinder our understanding of hydrological processes in this region, especially in a changing climate. Over the past two decades, the vegetation in the TRS has undergone significant greening as a result of the implementation of ecological restoration projections, which in turn has changed the hydrological process in this region. However, the impact of vegetation greening on evapotranspiration (ET) and its components is still unclear. Here, we investigate the response of ET and its components to vegetation changes in the TRS based on the maximum entropy production (MEP) model and detrending attribution analysis. The results show that the MEP model can well capture changes in ET at both the site and watershed scales. The multi-year-average ET of the TRS is 411.7 mm/a, of which the relative contributions of soil evaporation (Es), vegetation transpiration (Et), and canopy interception evaporation (Ei) are 68.21 %, 23.57 %, and 8.21 %, respectively. The annual ET has increased significantly, with a trend of 0.23 mm/a2 (p < 0.05). The contributions of vegetation greening to ET and its three components (Es, Et, and Ei) are 1.95 mm/a, −2.41 mm/a, 1.33 mm/a, and 3.03 mm/a, respectively. The findings are expected to provide guidance for the management of water resources and the implementation of ecological restoration in the TRS.