ANALYSIS OF THE TEMPORAL DYNAMICS OF ACTUAL EVAPOTRANSPIRATION IN A SEMIARID RIVER BASIN USING HYDROLOGICAL MODELING AND REMOTE SENSING

Abstract

Evapotranspiration is one of the most relevant components of the hydrological cycle, especially, in semiarid regions, where there are high temperatures and great water demand for crops, and its analysis is essential for the planning and management of water resources. The objective was to calibrate and validate the Soil and Water Assessment Tool (SWAT) model with real evapotranspiration information from remote sensing, and to investigate its temporal dynamics in an experimental river basin of the Semiarid. The study was conducted in the Riacho Jatobá Experimental River Basin (13.5 km²). Evapotranspiration (ET) data were obtained from the product MOD16A2, from the MODIS sensor. The hydrological simulation was carried out with the SWAT hydrological model. Descriptive statistical analysis and trend analysis were performed using the Mann-Kendall test. The R² values found for evapotranspiration were 0.61 and 0.81 for calibration and validation, respectively. The trend analysis test showed that there is a trend of decrease for actual evapotranspiration for the 2006–2018 period. Of the average annual precipitation in the river basin (722.9 mm), 26% corresponds to the effective precipitation and 74% returns to the atmosphere as evapotranspiration (534.7 mm). The use of alternative data for calibrating the SWAT model is highly relevant, especially for semiarid watersheds.