Spatiotemporal variations of actual evapotranspiration over the Lake Selin Co and surrounding small lakes (Tibetan Plateau) during 2003-2012

Actual evapotranspiration (ET (a) ) over the Tibetan Plateau (TP) is an important component of the water cycle, and greatly influences the water budgets of the TP lake basins. Quantitative estimation of ET (a) within lake basins is fundamental to physically understanding ET (a) changes, and thus will improve the understanding of the hydrological processes and energy balance throughout the lake basins. In this study, the spatiotemporal dynamic changes of ET (a) within the Lake Selin Co (the TP's largest lake) and its surrounding small lakes and land area during 2003-2012 are examined at the basin scale. This was carried out using the well-established Water and Energy Budget-based Distributed Hydrological Model (WEB-DHM) for the land area, the Penman method for the water area when unfrozen, and a simple sublimation estimation approach for the water area when frozen. The relationships between ET (a) changes and controlling factors are also discussed. Results indicate that the simulated land ET (a) from the WEB-DHM reasonably agrees with the estimated ET (a) values from the nonlinear complementary relationship model using appropriately calibrated parameter values at a point scale. Land ET (a) displayed a non-significant increase of 7.03 mm year(-1), and largely depends on precipitation. For the water area, the combined effects of reduced wind speed and net radiation offset the effect of rising temperature and vapor pressure deficit, and contributed to a non-significant decrease in evaporation of 4.17 mm year(-1). Sensitivity analysis shows that vapor pressure deficit and wind speed are the most sensitive variables to the changes of evaporation from the water area.