Application of SEBAL and Ts/VI Trapezoid Models for Estimating Actual Evapotranspiration in the Algerian Semi-Arid Environment to Improve Agricultural Water Management

Abstract

Accurate spatio-temporal estimation of evapotranspiration (ET) and surface energy fluxes is crucial for many agro-environmental applications, including the determination of water balance, irrigation scheduling, agro-ecological zoning, simulation of global changes in land use and forecasting crop yields. Remote sensing based energy balance models are presently most suitable for estimating ET at both temporal and spatial scales. This study presents an intercomparison of ET maps over the Habra plain in western Algeria obtained with two different models: Ts/VI trapezoid (Surface temperature/Vegetation Index Trapezoid Model) and SEBAL (Surface Energy Balance Algorithm for Land). Ts/VI trapezoid is the most used model, due to its simplicity, ease of use, few data input requirements and relatively high accuracy. It allows estimating ET directly by using the Priestley-Taylor equation. Whereas SEBAL allows estimating ET as the residual term of the energy balance equation, by using a rather complex hot and cold pixel based contextual approach to internally calibrate sensible heat flux through an iterative approach. The data set consists of four Landsat-8 OLI/TIRS images acquired on 2018-2019 and some ground measurements. In conclusion, the results show that SEBAL and Ts/VI trapezoid models provide comparable outputs and suggest that both the two models are suitable approaches for ET mapping over agricultural areas where ground measurements are scarce or difficult to collect.

Journal of Water and Land Development

“…Temperature errors recorded are almost identical to the values reported in previous studies with an RMSE ranging from approximately 2.8 to 4.2 K [CONSOLI, VANELLA et al 2014;FELLAH et al 2021;MADUGUNDU et al 2017;DOS SANTOS et al 2020;TIMMERMANS et al 2007;ZOU et al 2018]. Noting that for our study site, surface temperature Ts and bare soils (dry pixels) are…”

“…It was noted that the two-source models are more accurate for estimating H with RMSE between 30 and 75 W•m -2 for TSEB and between 25 and 60 W•m -2 for SPARSE. Errors in the estimates are almost identical to those in previous studies [DOS SANTOS et al 2020;FELLAH et al 2021;KUSTAS, NORMAN 1999;TANG, LI 2015;TIMMERMANS et al 2007]. These results are explained by the type of formulation used in each model, thus the two-source models are more robust than the single-source models which do not take into account all resistance parameters such as stomatic resistance and which use a single surface temperature, while the two-source models use a temperature for soil T sl and vegetation T c for estimation H c and H s .…”

“…The soils of the Habra plain consist of sedimentary formation with variable texture: alluvial-colluvial, alluvial, or rarely colluvial. These formations are distributed in less regular and homogeneous entities with a salinity of 8-16 mS•cm -1 at a depth greater than 50 cm and with low leaching [FELLAH et al 2021]. The study site is located in a semi-arid area of a Mediterranean climate characterised by a wet and cold period (minimum air temperature (T a ) lies between 6 and 8°C) in late fall and winter, and another dry and warm period (maximum T a about 42°C) in late spring and summer.…”

“…Fig.2. Illustration of the trapezoid method used for identifying wet and dry pixels; source:[FELLAH et al 2021] …”

STEEP: a remotely-sensed energy balance model for evapotranspiration estimation in seasonally dry tropical forests

“…Firstly, the way ET is obtained differs between STEEP and the other products. While STEEP and other SEB single-source models estimate ET as a combined singular process, i.e., there is no distinction between soil evaporation and transpiration (Sahnoun et al, 2021) and interception loss is not taken into account, MOD16 and PMLv2 discriminate the components of soil evaporation, canopy transpiration, and wet canopy evaporation (Mu et al, 2011;Zhang et al, 2019). With this in mind it is remarkable that STEEP performs better than the other, widely used, multiple-source ET products.…”