Evapotranspiration Estimations in the Brazilian Semi-Arid by Using MODIS Reflectance Products and Agrometeorological Stations 

3. Embrapa Environment, Brazil 

Abstract: The semi-arid region of Northeast Brazil has experienced several cases of strong water scarcity together with increasing land-use changes, demanding large-scale evapotranspiration studies to subsidize water policies. Aiming to subsidize the rational water resources management under these scenarios, the use of the reflectance bands from the MODIS MOD13Q1 product together with a net of 14 weather stations was tested to acquire large-scale actual evapotranspiration (ET) along the dry year 2016. The SAFER (Simple Algorithm for Evapotranspiration Retrieving) algorithm was applied for modelling ET in the counties of Petrolina and Juazeiro, respectively Pernambuco and Bahia states, Northeast Brazil. Clearly one could see higher ET values for irrigated crops (IC) than for natural vegetation (NV) in both counties. Even they presenting similar water flux dynamics along the year, in Juazeiro, ET rates represented 78% of those for Petrolina. One reason for the smaller values in Juazeiro could be attributed to the lower crop water consumption from the São Francisco River. It was demonstrated the potential to monitor large-scale ET at the 16-day MOD13Q1 time-scale by combining remote sensing and agrometeorological measurements in mixed agroecosystems of semi-arid environments.