Spatial and Temporal Variations of Terrestrial Evapotranspiration in the Upper Taohe River Basin from 2001 to 2018 Based on MOD16 ET Data

Abstract

Evapotranspiration (ET) is an essential component of watershed hydrological cycle. Spatial-temporal variations analyses of evapotranspiration and potential evapotranspiration (PET) have remarkable theoretical and practical significances for understanding the interaction between climate changes and hydrological cycle and optimal allocation of water resources under global warming background. The MODIS-estimated ET agreed well with basin evapotranspiration from water balance principle methods in the study. The spatiotemporal variations results based on MOD16 ET data showed the following: (1) multiyear mean ET and PET were 464.2 mm and 1192.2 mm, and annual ET showed an upward trend at a rate of 3.48 mm/a, while PET decreased significantly at a rate of −8.18 mm/a. The annual ET trend showed a complemental relationship with PET; (2) at the seasonal scale, ET was highest in summer and least in winter, while PET was higher in spring and summer. The change of ET and PET in spring and summer had a great contribution to the annual variations; (3) ET and PET in the northern part were significantly stronger than those in the western and southern parts; (4) ET in cropland increased significantly, while PET decreased obviously in grass and forest; (5) changes of ET and PET were closely related to climatic factors. The rise in temperature caused the increase in ET and the decrease of wind speed contributed more to the decrease in PET. The results can provide a scientific basis for water resources planning and management.

Comprehensive influence of water resources development and utilization on ecological environment in Taohe River basin

“…Taohe River originates in the north of the Xiqing mountains in Qinghai Province [14] , flows from west to east through Minxian County to the north, and reaches Yongjing County to Liujiaxia Reservoir [15] , with a total length of 673 km and a total basin area of 25527 km 2 . Figure . 1 shows the water system map of the Taohe River basin [16][17] .…”

The Runoff in the Upper Taohe River Basin and Its Responses to Climate Change

“…It is susceptible to the influence of the southwest monsoon originating from the Indian Ocean, and receives abundant precipitation of 400~600 mm per year. Therefore, the natural runoff gradually occupies more than 68.8% of the whole basin, which is the main runoff generation area and an important water supply area of the Taohe River Basin [31][32][33][34]. The water systems in the study area are well developed and have many symmetrical tributaries (Figure 1c).…”

Spatiotemporal Variation in Actual Evapotranspiration and the Influencing Factors in Ningxia from 2001 to 2020

“…The Mann-Kendall test was insensitive to missing data, independent of data distribution and required fewer assumptions. This method is recommended by the World Meteorological Organization as a nonparametric statistical test and has been widely used in trend testing [8,27,[30][31][32][33][34][35][36].…”