Review: Estimating evapotranspiration using remote sensing and the Surface Energy Balance System – A South African perspective

Z Su,La Gibson,Fe Eckardt,C Jarmain

doi:10.4314/wsa.v39i4.5

Abstract

Remote sensing-based evapotranspiration (ET) algorithms developed in recent years are well suited for estimating evapotranspiration and its spatial trends over time. In this paper the application of energy balance methods in South Africa is reviewed, showing that the Surface Energy Balance Algorithm for Land (SEBAL) model is the most widely used, but highlighting the potentials of the Surface Energy Balance System (SEBS) model. The SEBS model is then reviewed in the international literature and lessons learned from South African examples are expanded upon. The SEBS model has been extensively used for teaching and training purposes and has been applied in research projects across many different environments. However, there are discrepancies in the reported accuracy of the SEBS model due to known model sensitivities. It is therefore recommended that any further research using the SEBS model in South Africa should be limited to agricultural areas where accurate vegetation parameters can be obtained, where high resolution imagery with low sensor zenith angles is available, and where canopy cover is complete.Keywords: Evapotranspiration, remote sensing SEBS, SEBAL

Highlights

Accurate estimates of temporal and spatial variations in precipitation and evapotranspiration (ET) are critical for improved understanding of the interactions between land surfaces and the atmosphere (Mu et al, 2007)
Remote sensing-based ET algorithms developed in recent years fill an existing gap: they are well suited for estimating crop water use or ET (Allen et al, 2007) and the spatial trends thereof over time
It will be shown that the Surface Energy Balance Algorithm for Land (SEBAL) model is the most widely applied model in South Africa

Summary

INTRODUCTION

Accurate estimates of temporal and spatial variations in precipitation and evapotranspiration (ET) are critical for improved understanding of the interactions between land surfaces and the atmosphere (Mu et al, 2007). In a water-scarce country like South Africa, with a number of large consumers of water, it is important to estimate ET with a high degree of accuracy This is especially important in the semi-arid regions where there is an increasing demand for water and a scarce supply thereof. Remote sensing-based ET algorithms developed in recent years fill an existing gap: they are well suited for estimating crop water use or ET (Allen et al, 2007) and the spatial trends thereof over time. It will be shown that the Surface Energy Balance Algorithm for Land (SEBAL) model is the most widely applied model in South Africa. It is protected by intellectual property law and is not available for unaffiliated researchers to use.

Methodology

E Rn G0

Findings

CONCLUSIONS AND RECOMMENDATIONS