Satellite-based energy balance model to estimate seasonal evapotranspiration for irrigated sorghum: a case study from the Gezira scheme, Sudan

Abstract

Abstract. The availability of the actual water use from agricultural crops is considered as the key factor for irrigation water management, water resources planning, and water allocation. Traditionally, evapotranspiration (ET) has been calculated in the Gezira scheme as the point of reference with evapotranspiration (ET o ) and crop coefficients (k c ) being derived from actual measurements of soil-water balance. Recently developed, advanced energy balance models assisted in estimating the ET through the remotely sensed data. In this study Enhanced Thematic Mapper Plus (ETM+) and MODerate Resolution Imaging Spectroradiometer (MODIS) images were used to estimate the spatial distribution of the daily, monthly and seasonal ET for irrigated sorghum in the Gezira scheme, Sudan. The daily ET maps were also used to estimate k c over time and space. Results of the energy balance, based on being remotely sensed, were compared to actual measurements conducted during 2004/05 season. The seasonal actual ET values, obtained from the seven MODIS images for irrigated sorghum, were estimated at 579 mm. The values for remotely sensed k c , derived during the initial mid-season and late-season crop development stages, were 0.62, 0.85, 1.15, and 0.48, respectively. On the other hand, the values for the experimental k c during the pervious mention stages were 0.55, 0.94, 1.21 and 0.65, respectively. The estimated seasonal ET of the sorghum, derived by remotely sensed k c , was 674 mm. The Landsat data and the Free MODIS provided reliable, exhaustive, and consistent information on the water use, relevant for decision support in the Gezira scheme.

Determining water use of sorghum from two-source energy balance and radiometric temperatures

“…Thus, a relative error of 12 % was obtained for daily ET. A similar RMSD value of ±0.9 mm d −1 and underestimation of 6 % was observed when daily ET values were calculated using the standard FAO56 methodology (Allen et al, 1998). These results are in agreement with some recent works.…”

“…1a). Reference evapotranspiration, ET o , was also determined using the FAO56 Penman-Monteith method (Allen et al, 1998).…”

“…Bastiaanssen et al, 1998;Su, 2002;Kustas and Norman, 1996;Pinter et al, 2003;Gavilan and Berengena, 2007). For example, Bashir et al (2008) used the Surface Energy Balance Algorithm for Land (SEBAL) (Bastiaanssen et al, 1998), together with Landsat/ETM+ and MODIS images to estimate ET of a large irrigated sorghum area. Comparison with ET calculated using the water balance approach, for 4 selected days, showed an average absolute error around 0.9 mm d −1 .…”

Evapotranspiration Variability and Its Association with Vegetation Dynamics in the Nile Basin, 2002–2011

“…Previous works on ET in the region include those conducted at field-scales [34,35] or high resolution imagery [16,36,37], or regional/basin-scale [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50], or the continental/global-scale [17,51,52]. Continental-and regional-scale trend analysis conducted at 0.5° to 1.0° resolution indicated a downward trend in ET over the past few decades in substantial parts of the Nile Basin region [17,51,52].…”

Actual daily evapotranspiration estimated from MERIS and AATSR data over the Chinese Loess Plateau

“…These can be put into two groups broadly: (1) to estimate ET by set empirical relation between ET and parameters (vegetation index, temperature, albedo) that could be measured from meteorological satellites (Index, 1994;Boegh, 2002;McCabe et al, 2005); (2) to calculate the sensible heat flux first and then obtain the latent heat flux as the residual of the energy balance equation, SEBAL (Bastiaanssen et al, 1998), SEBS (Su et al, 1999;Su, 2002), NTDI (McVicar and Jupp, 1999). Most models require a complex and high-quality input data to obtain accurate results and each method has limitations (Bashir et al, 2008). Vegetation index-based scaling method relies on foliage density as the main independent variable, they do not adequately account for direct evaporation from soil or leaves following rainfall events.…”