Spatio-temporal variation of evapotranspiration and its linkage with environmental factors in the largest freshwater lake wetland in China

Study region: Poyang lake wetland Study focus: Evapotranspiration (ET) is a critical parameter in the hydrologic and energy budget, and it is important for understanding spatio-temporal variations in ET in large lake wetlands. Monthly ET in the Poyang Lake wetland during 2008-2017 was estimated by the remote sensing ET retrieval model based on a Nonparametric approach (RS-NP). And the spatio-temporal variation of ET and the influencing factors were analyzed. New hydrological insights for the region: The validation revealed the usefulness of the RS-NP model in a moist region and yielded a relative error of 6 % (12 %) in the wet (dry) season. Temporally, the average yearly ET was 884 mm with ET/P (precipitation) of 55 %-65 %. The monthly ET/P ratio increased significantly from 40 %-50 % from January to May to 90 %-130 % from July to October. ET in June was lower by over 20 % than that in May and July with the lowest ET/P value (33 %). Spatially, relatively larger and lower ET occurred in the northern and southern parts, respectively. The main factors affecting ET variability were downwelling shortwave radiation (similar to 2/3 contribution) and water area (similar to 1/3 contribution) at the monthly scale. Precipitation and surface temperature dominantly controlled the hysteresis effects with a lag of one month and regulated LE monthly variations. This study improves our understanding of complicated water atmosphere interactions and their linkages with environmental factors in large lake systems.

Automated summary

This study estimated the evapotranspiration in the Poyang Lake wetland from 2008 to 2017 using remote sensing and a nonparametric approach. The results showed that downwelling shortwave radiation and water area were the main factors affecting evapotranspiration variability.