Characteristics of Evapotranspiration and Water Consumption of Different Underlying Surfaces in Qaidam Basin

The Qaidam Basin is an alpine arid inland basin characterized by water resource shortages and fragile ecological environments. Studying the evapotranspiration and water consumption characteristics of the Qaidam Basin is important for regional water-resource management and environmental protection. Based on eddy covariance flux data for four underlying surfaces (Golmud cropland, shrubland, Nomuhong cropland, and alpine meadow) in the Qaidam Basin in 2020, the evapotranspiration variation characteristics for different underlying surfaces at different time scales were analyzed, the influence of different typical meteorological factors on actual evapotranspiration was explored, and water consumption characteristics of the different underlying surfaces were analyzed. The results showed that the evapotranspiration of each underlying surface was mainly concentrated in the growing season. The Golmud cropland and alpine meadow had the highest evapotranspiration in July, at 62.50 mm and 88.92 mm, respectively, while the shrubland and Nomuhong cropland had the highest evapotranspiration in August, at 40.47 mm and 100.02 mm, respectively. The average daily evapotranspiration of Golmud cropland, shrubland, Nomuhong cropland, and alpine meadow was 1.12 mm, 0.78 mm, 1.98 mm, and 1.79 mm, respectively. The half-hour evapotranspiration reached a maximum value from 14:00–15:00. The evapotranspiration of different underlying surfaces was strongly correlated with air temperature, followed by relative humidity, and weakly correlated with wind speed. Daily evapotranspiration was strongly correlated with the soil temperature of Golmud cropland, shrubland, and alpine meadow, and the soil volume water content of shrubland and alpine meadows. The water consumption variation characteristics indicated that each underlying surface was dominated by water consumption, accounting for 96.73%, 96.26%, 96.26%, 74.30% in Golmud cropland, shrubland, Nomuhong cropland, and alpine meadow, respectively. Among them, precipitation was the main factor affecting the water consumption of the different underlying surfaces. The purpose of this study was to explore the actual evapotranspiration characteristics of different underlying surfaces, the results of which can be used as a reference for studies of the water cycle in Qaidam Basin.