Estimation of evapotranspiration using micrometeorological and water budget methods in headwater catchments of southeastern Brazil

Study Region: Four small headwater catchments within the Mantiqueira Range, southeastern Brazil Study Focus: We investigated the surface energy balance regime in small catchments using micrometeorological methods (eddy covariance-EC and Bowen ratio), energy balance closure corrections, and basin water budgets, incorporating measurements of streamflow, precipitation, and soil moisture. New hydrological insights for the region: 1) Energy balance closure using EC was significantly improved through corrections. Latent heat flux increased from ≃33 % to ≃55 % of the available energy, while sensible heat flux rose from ≃23 % to ≃37 %. 2) Mean annual evapotranspiration (ET) from the water budget across basins ranged from 2.6 to 2.9 mm day–1, aligning more closely with corrected fluxes, of 2.8 mm day–1. 3) Seasonally, ET peaked at 3.5 mm day⁻¹ early in the year and declined to 1.3 mm day⁻¹ in July, primarily driven by solar radiation, while lagged minima in soil moisture and leaf area index likely contributed to the accompanying reduction in evaporative fraction (LE/Rn) from 0.86 to 0.79 between the first and second halves of the year. 4) The mean annual evaporative index (ET/P) across basins was estimated to range from 59 % to 67 %. 5) Our findings show the possibility of using simple correction methods to estimate sensible and latent heat fluxes with EC in complex terrain regions, with significant gains in energy balance closure.

Abstract licence: CC BY-NC

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