Effects of floating macrophytes on open-water evaporation in a Brazilian tropical reservoir

Abstract

This paper aims to estimate the open-water evaporation (from 1990 to 2021) in an urban reservoir in Brazil and assess the relationship between floating macrophyte coverage (MC) and open-water evaporation, as well as their spatial variability. The Surface Energy Balance System for Water (AquaSEBS) provided similar (root mean square error of 0.5 mm/day) results to reference measurements of class A pan (correction coefficient of 0.7). The discharge of sewage into this urban tropical reservoir resulted in a portion of this reservoir being covered by floating macrophytes. During the study period, positive trends of floating MC area were observed. The days with floating macrophytes depicted higher spatial variability over the open-water evaporation. Furthermore, MC was negatively correlated with the open-water evaporation flux (R2 = 0.65) and led on average to a 17 % reduction (varying from 9 % to 35 %) in the estimated evaporation rate in the free water surface. Overall, the results of this study demonstrate the usefulness of remote sensing products to estimate reservoir open-water evaporation and outline the need to better understand the relationship between MC and reservoir open-water evaporation in tropical and semi-arid areas.