Adaptation of SEBAL for estimating groundnuts evapotranspiration, in Cyprus

Abstract

The imperative need for data on irrigation management in Cyprushas led to a turnoff regarding the method of collecting and analyzing irrigation management primary data. The time and money consuming direct measurements of evapotranspiration (ETc), such as Pan-evaporation methods, lysimeters and others, are substituted from efficient energy and hydrological models which are adapted to satellite data. Remote sensing methods are attractive to estimate ET as they cover large areas and can provide estimates at a very high resolution. Intensive field monitoring is also not required, although some ground-truth measurements can be helpful in interpreting the satellite images. More specific, for the purposes of this paper, modeling and remote sensing techniques were integrated for estimating actual evapotranspiration (ETa) for a local cultivation (groundnut – Arachis hypogaea, L.), that is cultivated only at the specific area of interest. Data for irrigation management exist for the specific cultivation, from the past, based on the Epan method. These data were used as the reference data for this study and compared to the results. Surface Energy Balance Algorithm for Land (SEBAL) methodology was followed for the first time in Cyprus employing the essential adaptations for the local soil and meteorological conditions. Three plots, cultivated with groundnuts, were selected at the area of interest. The plots are located by the seaside or at very low elevation level, where groundnuts are usually cultivated due to the requirement for mild climate conditions and well-drained soils. Landsat 5 and 7 images were used to retrieve the needed spectral data. Maps of ETa were created using SEBAL model for the area of interest, while irrigation scheduling was provided for a more efficient irrigation management. The results have been compared to the results of the Epan method and FAO-56. The comparison has revealed that SEBAL provides accurate results.without any important statistical difference from the direct measurements of Epan results.