Multi-Temporal Variabilities of Evapotranspiration Rates and Their Associations with Climate Change and Vegetation Greening in the Gan River Basin, China

Abstract

Understanding the spatial-temporal dynamics of evapotranspiration in relation to climate change and human activities is crucial for the sustainability of water resources and ecosystem security, especially in regions strongly influenced by human impact. In this study, a process-based evapotranspiration (ET) model in conjunction with the Global Land Surface Satellite (GLASS) LAI dataset was used to characterize the spatial-temporal pattern of evapotranspiration from 1982 to 2016 over the Gan River basin (GRB), the largest sub-basin of the Poyang Lake catchment, China. The results showed that the actual annual ET (ETa) weakly increased with an annual trend of 0.88 mm year−2 from 1982 to 2016 over the GRB, along with a slight decline in annual potential ET (ETp). On an ecosystem scale; however, only the evergreen broadleaved forest and cropland presented a positive ETa trend, while the rest of the ecosystems demonstrated negative trends of ETa. Both correlation analysis and sensitivity analysis revealed a close relationship between ETa inter-annual variability and energy availability. Attribution analysis illustrated that contributions of climate change and vegetation greening on the ETa trend were −0.48 mm year−2 and 1.36 mm year−2, respectively. Climate change had a negative impact on the ETa trend over the GRB. However, the negative effects have been offset by the positive effects of vegetation greening, which mainly resulted from the large-scale revegetation in forestland and agricultural practices in cropland. It is concluded that large-scale afforestation and agricultural management were the main drivers of the long-term evolution of water consumption over the GRB. This study can improve our understanding of the interactive effects of climate change and human activities on the long-term evolution of water cycles.

Improving the Representation of Long‐Term Storage Variations With Conceptual Hydrological Models in Data‐Scarce Regions

“…It would therefore be interesting to look into alternative, potentially more accurate estimation methods. In addition, long-term fluctuations in the actual evaporation were observed depending on the satellite product due to the different underlying assumptions and input data (Bai et al, 2019;Feng et al, 2019;Goroshi et al, 2017;Wang et al, 2018). As shown in a previous study by and in Figure S24 in the Supplementary Material, the basin-averaged evaporation was modeled well and incorporating this flux in the calibration procedure did not improve the modeled long-term storage variabilities.…”

Analysis of Runoff Trends and Drivers in the Haihe River Basin, China

“…Climate change and human activities are considered to be two major factors driving changes in the hydrological cycle [1,[26][27][28][29][30]. Climate change includes precipitation and potential evapotranspiration changes caused by temperature changes [15]; human activities include direct and indirect human activities, such as land use/cover change (LUCC) affects canopy interception, soil infiltration, land-surface evapotranspiration (ET) [31,32], and other hydrological parameters during rainfall, which in turn affect the hydrological regimes and runoff mechanisms of river basins [33,34]. Bare land, agricultural land, and settlements have lower evapotranspiration, and the greater the presence of vegetation and forest areas, the greater the evapotranspiration [31,34].…”

Using Eight Crops to Show the Correlation between Paucity Irrigation and Yield Reduction of Al-Hussainiyah Irrigation Project in Karbala, Iraq

“…Other studies used the Penman-Monteith method to estimate crop evapotranspiration [38,39]. Although the Penman-Monteith model was used in the last two decades, Bai et al, adopted this model to estimate canopy transpiration (Ec) and soil evaporation (Es) in their new model to estimate evapotranspiration by using satellite data over a river basin in China [40].…”