ESTIMATION OF ACTUAL EVAPOTRANSPIRATION USING SURFACE ENERGY BALANCE APPROACH AND LANDSAT-8 IMAGES OF SEMARANG AREA, CENTRAL JAVA

Water is an indispensable requirement for every creature on the earth's surface. Water is closely related to the hydrological cycle, one of the processes that occurs during that cycle is evapotranspiration both actually and potentially. However, information in terms of spatial distribution of actual evapotranspiration is very rare, particularly in Indonesia. Landsat-8 satellite data offers opportunity in coping with this need, since the image dataset is available in both reflective and thermal spectral bands. Those bands can be generated to land-cover and temperature information, which are important to surface energy balance computation including evapotranspiration. The purposes of this study were (1) to understand the capability of Landsat 8 for deriving actual evapotranspiration (ETa) parameters estimation, (2) to know its accuracy according to data obtained from meteorological and climatology stations, and (3) to determine the spatial distribution of ETa based on land cover information. The ETa can be extracted from remotely sensed images using Surface Energy Balance System (SEBS) algorithms. ETa estimation made use of SEBS algorithm comprising several parameters, i.e. net radiation (Rn), which is proportional to the amount of soil surface heat flux (G0), sensible heat flux (H) and latent heat flux (λE). ETa is part of the λE which is calculated based on SEBS algorithms. The parameters required for SEBS include albedo, emissivity, land surface temperature, NDVI, vegetation fraction, LAI, surface roughness momentum transfer (Z0m), canopy height, and elevation represented by digital elevation model (DEM). Each of these parameters serves to establish th