Evapotranspiration Variations of the Minjiang River Basin in Southeastern China from 2000 to 2019

Abstract

Evapotranspiration is one of the critical processes in the terrestrial hydrological cycle, and the assessment of evapotranspiration is essential for understanding the regional hydrological cycle. In this study, the Minjiang River Basin, a typical watershed in the humid subtropical climate zone, is selected as the study region. The Penman-Monteith equation and the dual crop coefficient method are used to calculate the actual evapotranspiration (ETa) at seven meteorological stations within the study basin. Meanwhile, the applicability of the Global Land Data Assimilation System-Noah (GLDAS-Noah) ETa data in the Minjiang River Basin is evaluated based on stations P-M equation results, then to analyze the changes of the ETa in the Minjiang River Basin from 2000 to 2019. The results show that the GLDAS-Noah ETa data are well applicable in the Minjiang River Basin (R2 > 0.9 and NSE > 0.8). The ETa in the basin shows an increasing trend since 2000, and the increasing rate is 3.60 mm·yr−1 (p < 0.01). The seasonal variation results show that ETa tends to increase in winter and spring, with increasing rates of 1.10 mm·yr−1 (p < 0.01) and 2.60 mm·yr−1 (p < 0.01), respectively, while the ETa did not change significantly in summer and autumn. Annual air temperature has the largest effect on annual ETa (59.6%), followed by precipitation at 33.9%. ETa increased in spring was mainly influenced by increasing temperatures (89.4%) in the Minjiang River Basin from 2000 to 2019. The research results are of great benefit to further improve the understanding of ETa variations in the basin under global warming.

The influence of variations in actual evapotranspiration on drought in China's Southeast River basin

“…The region features a subtropical monsoon climate with an average annual temperature of 18.10 °C and an annual precipitation of 1624.06 mm. The Southeast River basin has experienced a temperature increase of approximately 0.03°C/year over the past two decades and has witnessed one of China's most significant upward trends in annual precipitation (5.9 mm/year) 7 , 8 . Although the Southeast River basin has a typical subtropical monsoon climate, it is subject to drought events and is less resilient to drought risk.…”

“…ET a in the southeastern coastal region of China has increased significantly (1.87 mm/year) during the past four decades 6 . This region has experienced a temperature increase of approximately 0.03 °C/year since 2000 7 . Simultaneously, this region experienced one of China’s most significant upward trends in annual precipitation during 1990–2019, with an increase of approximately 5.9 mm/year 8 .…”

“…Rapid land-use changes in the southeastern coastal region of China, ET a , and the evolution of component proportions are important elements of the regional hydrological cycle 16 . Research on the variability of ET a components in this region and their impacts is still in its infancy 7 , 9 .…”

“…Rapid land-use changes in the southeastern coastal region of China, ET a , and the evolution of component proportions are important elements of the regional hydrological cycle 16 . Research on the variability of ET a components in this region and their impacts is still in its infancy 7,9 .Previous studies have indicated that increases in ET a lead to regional drought events by influencing soil moisture deficits 17,18 . For example, a past study showed that an increase in ET a accelerated the formation and expansion of summer droughts in Europe 11,12 .…”

Variations in actual evapotranspiration and their influence on the seasonal drought in China's Southeastern River basin

“…In the context of global warming, the Southeastern River basin has experienced a temperature increase of approximately 0.03°C/yr over the past two decades 20 . Simultaneously, this region has witnessed one of China's most signi cant upward trends in annual precipitation, with an increase of about 2.5 mm/yr 21 .…”