Attribution analysis of actual and potential evapotranspiration changes based on the complementary relationship theory in the Huai River basin of eastern China

Abstract

Accurate terrestrial evapotranspiration (ET) estimation and understanding the causes of ET variation are essential for water resource management and irrigation planning. In this research, the complementary relationship (CR) between actual evapotranspiration (ET a ) and potential evapotranspiration (ET p ) was evaluated. An Advection-Aridity (AA) model was calibrated and validated using eddy covariance measurements. The spatiotemporal variations of ET a , ET p and associated meteorological variables were examined through Mann-Kendall (MK) testing and Theil-Sen's estimator, using daily weather data from 137 meteorological stations in Huai River basin (HRB) during 1961-2014. Moreover, the influences of meteorological factors on ET a and ET p were quantified by the differential equation method. The results indicate that CR theory is applicable in the HRB and the calibrated AA model can simulate the ET a well. ET a exhibited a significant increasing trend before 1990 and then decreased significantly. However, ET p decreased significantly before 1990 and then declined slightly. During 1961During -1990, except for significant increasing relative humidity (RH), other meteorological variables exhibited decreasing trends. The aerodynamic component dominated ET a and ET p trends in general. The wind speed at 2-m height (u 2 ) dominated ET a trends except for summer and growing season and ET p trends except for summer, when the dominant factor is net radiation (R n ). During 1991-2014, mean temperature (T a ) and RH showed distinct increasing and decreasing trends, respectively, whereas significant decline in u 2 palpably slowed. The absolute value of the radiative component was larger than that of the aerodynamic one. The dominant factor of ET a trends shifted from u 2 to RH in spring and to R n in autumn, winter and annual timescales. Moreover, the dominant factor of ET p trends changed from u 2 to RH in spring, winter and annual timescales and to R n in growing season and autumn. R n always played a pivotal role in both ET a and ET p trends in summer. K E Y W O R D Sactual evapotranspiration, Advection-Aridity model, complementary relationship theory, differential equation method, Huai River basin

Variation in Reference Evapotranspiration over the Tibetan Plateau during 1961–2017: Spatiotemporal Variations, Future Trends and Links to Other Climatic Factors

“…Sonmez and Kale used the Pettitt analysis to determine that the hydrometeorological elements of the Filyos River (Turkey) experienced abrupt changes in approximately 2000 [49]. Chu et al used the MK test and the Theil-Sen estimate to determine that the abrupt change point of ET 0 in the Huaihe River Basin was approximately 1990 [50]. Wang et al used the MK test and the Pettitt test change-point statistics to find that the hydrometeorological elements of the Taihang Mountain area changed abruptly in approximately 1982 [51].…”

Attribution Analysis of Long-Term Trends of Aridity Index in the Huai River Basin, Eastern China

“…In order to understand the variation of AI more concretely in northern China, Zhang et al [63] used 283 standard meteorological stations to analyze the spatiotemporal variations of AI and its influencing factors. It was found that the AI decreased significantly and the dry and wet areas increased and decreased, respectively, on the east and west sides of 100 • E, and the duration of sunshine and Pre were the main dominant factors in the declining AI trend [33]. Unlike in the study of Zhao et al [60], the AI calculated by the ratio of Pre to ET 0 exhibited a downward trend in the Loess Plateau and the boundary of dry land region was expanded there [64], and Pre was the main cause of AI variations.…”

“…During the half past century, waterlogged areas were widespread, accompanied by a prominent conflict between humans and water or land. Against the historical background, both the disordered Huai River water system and the deteriorated environment have aggravated the frequent occurrence of extreme events such as floods and droughts [33,42].…”

“…Furthermore, it also has scientific and practical applications for improving not only the comprehensive management of regional water resources in a basin but also the management of water-related natural disasters at the basin scale [32]. Since the AI is obtained by the precipitation divided by potential evapotranspiration, and potential evapotranspiration is mainly influenced by four main meteorological factors (temperature, relative humidity, wind speed, and solar radiation) [6,8,33,34]. Thus, clarifying the spatial and temporal trends of AI and determining the contributions of the above five meteorological factors to the AI trends are of greater importance for understanding regional scale dryness climate change features.…”

Assessment of gridded precipitation products in the hydrological modeling of a flood-prone mesoscale basin

“…Similarly, temperatures display a gradual increase with an annual average of 11 °C in the north to 16 °C in the south. Alternatively, the mean annual potential evapotranspiration is estimated to be between 950 and 1,150 mm using the Penman method (Chu et al 2019). In comparison, the annual average runoff depth is approximated to be 231 mm, predominantly occurring in the flood season (Song et al 2015).…”