Bahare Bahman abadi; Abbas Kaviani; peyman daneshkar; Rasta Nazari
Abstract
Reference Evapotranspiration is a complex and multivariate phenomenon that depends on several factors and the most accurate way to estimate is lysimeter, though it is costly and time-consuming. Therefore, the main objective of this study was to estimate actual evapotranspiration based on single-source ...
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Reference Evapotranspiration is a complex and multivariate phenomenon that depends on several factors and the most accurate way to estimate is lysimeter, though it is costly and time-consuming. Therefore, the main objective of this study was to estimate actual evapotranspiration based on single-source energy balance, i.e. SEBAL and SSEB, and two-source energy balance algorithm, i.e. TSEB, in three sensors MODIS, ETM+ and OLI & TIRS in three steps. In evapotranspiration estimating by SEBAL, Soil Adjusted Vegetation Index and the correction factor for soil effects (L) are particularly important. For this purpose, this index was used as calibration coefficient that is selected based on percentage of vegetation coverage. According to the results, the actual evapotranspiration with L calibrated (L=0/5) had lower error in each of the three sensors (RMSE=1/76, 0/84, and 1/49 mm/day). For verification of calibration results, 30% of the remaining lysimeter data was used. The results of the statistical indices showed significant difference between the predicted data at the 95% level and also in the predictions. Finally, by comparing the three algorithms in the three sensors i.e. MODIS, ETM +, and OLI & TIRS, SSEB algorithm in ETM + sensor was introduced as the best algorithm in Qazvin plain area, at 95% significance level and RMSE of 0/41 mm/day.
M Dastoorani; S. Poormohammadi; Mohammad Hassan Rahimian
Abstract
Reliable estimation of actual evapotranspiration of the plants plays an important role on planning and optimization of water use especially in dry land environments, where water scarcity is an important problem. In this study, Surface Energy Balance Algorithm for Land (SEBAL) was used for estimation ...
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Reliable estimation of actual evapotranspiration of the plants plays an important role on planning and optimization of water use especially in dry land environments, where water scarcity is an important problem. In this study, Surface Energy Balance Algorithm for Land (SEBAL) was used for estimation of actual evapotranspiration (ETa) in Ardakan pistachio orchards, Yazd province, Iran. For this purpose, a time series of satellite images including 13 cloud free MODIS data were employed to generate actual ET map of pistachio orchards. Results of this study indicated that seasonal ETa for pistachio trees was about 1150 mm, which was significantly less than the applied irrigation depth, Results of this study emphasize the necessity of a proper irrigation scheduling, irrigation interval, and depth in Ardakan pistachio orchards. Consequently, water productivity will improve and considerable amounts of water will be saved as the result of these improvements.
Mohammad Hassan Rahimian; s pourmohamadi
Abstract
Use of Surface Energy Balance Algorithm for Land (SEBAL) and satellite imagery is a relatively new procedure for estimation of actual ET at different scales e.g. farm, catchments and basin levels. This method is based on computation of latent heat flux as the residual of energy budget equation (LE=Rn-G-H) ...
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Use of Surface Energy Balance Algorithm for Land (SEBAL) and satellite imagery is a relatively new procedure for estimation of actual ET at different scales e.g. farm, catchments and basin levels. This method is based on computation of latent heat flux as the residual of energy budget equation (LE=Rn-G-H) and is now used widely around the world, including Iran, for computation of evapotranspiration under standard and non-standard conditions. Azadegan plain is one of the plains that is now faced with waterlogging and salinity problems due to its special topographic, climatic, and hydrologic situations and also due to improper management of its water and soil resources. The main objective of this study was to use the SEBAL to calculate actual ET (ETa) of winter wheat in 2007-2008 cropping season. For this purpose, a seasonal time series of 19 MODIS satellite images and also ancillary climatic data were acquired and used. Finally, time series of daily ETa maps and also a seasonal ETa map were generated and analyzed. Since the crops of the region are under salinity stress, the calculated ETa is an explanatory of crop water requirement under non-standard conditions. The results could help in advising a proper water management plan and also strategies for control and management of salinity and water logging in the region.