Many applications in water resource management require evapotranspiration (ET) information at the daily and field-level scales; however, no satellite system currently operating is able to capture all the resources of ET dynamics in an agricultural field. Thus, the objective of this study was to apply the SEBAL (Surface Energy Balance Algorithm for Land) and ESTARFM (Enhanced Adaptive Reflectance Fusion Model) methodology to estimate the daily ET in an agricultural area in the municipality of Cascavel, Paraná. We applied the ESTARFM algorithm to MODIS and Landsat 8 images to produce 8 synthetic images. The performance of the algorithm was evaluated by comparing predicted surface reflectance values obtained to real Landsat 8 images. SEBAL was applied to obtain daily evapotranspiration values (ET24) for 3 different targets (maize, soybean and stubble crop). The observed results showed that the predictions of ET using ESTARFM had a general determination coefficient of 0.80 in all analyzed images and ranged from 0.4 < R² < 0.81 when compared with real data from the Landsat 8 images, with soybean crop yielding the worst results. Low error values were found between the synthetic time series data of ET and the real data, with mean less than 1 mm day-1, meaning high reliability of synthetic data. ESTARFM tended to overestimate the ET values when compared with the real data, with the performance strongly affected by a change in the soil cover between the analyzed dates. Input data with the same soil cover is recommended for more accurate results.
The main process that opposes the Greenhouse Effect is called “carbon sequestration”, a phenomenon that essentially seeks to establish a dynamic balance between greenhouse gas (GHG) emissions from the immobilization of its elements, especially C and N. This work evaluated the stocks of carbon and nitrogen in soils of the Brazilian semi-arid submitted to irrigation with treated wastewater from domestic sewage. For this purpose, the carbon and nitrogen stocks in the soil of the semi-arid region of Brazil were compared for four different uses: Open Native Caatinga (ONC); Treated Wastewater Effluent Irrigation (TSEI); Surface Water Irrigation (SWI); and Traditional Rainfed Agriculture (TRA). The hypothesis considered in this research was that the application of treated effluents in agriculture, besides being an alternative that can mitigate the problem of water scarcity of the semiarid region, is also capable of influencing the storage capacity of C and N in the soil, due to its organic load. The results indicate that among the different land uses evaluated, soil C and N stocks were highest in ONC, and decreased with the agricultural land use. The greatest accumulation of C and N in Caatinga is due to the presence of forest litter, and the influence of irrigation with treated sewage effluent was not detected in the present study. It can be concluded that the contribution of vegetation residues to the soil surface is the main factor contributing to C and N storage.
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