Different Methods for Measuring Evaporation in a Tropical Reservoir: The Case of the Gavião Reservoir in the State of Ceará

Abstract

Studies that allow the estimation of evaporation in reservoirs represent an important action for the adequate management of water resources. Thus, this study aimed at estimating evaporation in the tropical reservoir Gavião, located in the municipality of Pacatuba, Ceará, Brazil, and to verify the effect of these estimates on the water availability of the reservoir using the VYELAS model. The results of Penman's methods and the Water Balance were compared with the values obtained from the hydrostatic pressure sensor, the most accurate. It was possible to verify that, in relation to the pressure difference method, all the conventional methods overestimate the evaporation in the reservoir. The method that presented estimates closer to those obtained by the pressure difference sensor was that of Penman, based on data from an onboard station in the lake, with a deviation of only 12%. The method of water balance also presented reliable results for monthly average. The two methods usually accepted in the evaporation calculation (water balance ignoring the infiltration; and Penman's method for meteorological station data on land distant from the lake) presented the most disturbing evaporation values significantly altering the water availability. The results of the VYELAS model showed that evaporated flows, estimated by several methods, exceeded the reference flow by up to 83%. The results demonstrate the great sensitivity of the estimate of water availability in relation to the evaporation rate in the lake.

Análise de dados volumétricos dos açudes Coremas e Mãe D’água da Paraíba

“…Muitos fatores interferem diretamente no volume de água nos açudes tais como evaporação (Feitosa, et al, 2021), assoreamento (Lopes et al, 2015;Araújo, 2003), aspectos climáticos (Francisco & Santos, 2017), bem como a retirada da água para abastecimento da população e para utilização na agricultura (Rodrigues et al, 2009). Por esta razão, o entendimento sobre a variação volumétrica de um reservatório de água é tão complexo.…”