The impact of deforestation and land-use changes on evapotranspiration of mountainous tropical rain forest area in the northern part of the Lore-Lindu National Park (LLNP) in Central Sulawesi (Indonesia) was quantified using a regional process-based SVAT model “SVAT-Regio”. Description of evapotranspiration of a non-uniform land surface in local and regional scales in SVAT-Regio is based on equations of energy and water balances of individual plants, plant canopy and soil layers for each of many grid cells into which the entire study area is divided. The model uses a multi-layered representation of vegetation cover and soil structure that allows to describe the partitioning of energy and H2O-fluxes among different canopy layers and soil, and to quantify more precisely the total ecosystem fluxes. Selective integration of grid cell fluxes on space and time allows estimating the energy and water fluxes for e.g. ecosystems, catchments or entire study area for different time spans from 1 day to several years.
September of 2004 was selected as a test period for modelling experiments. The regional patterns of meteorological parameters were reconstructed using measurements provided by 10 mobile meteorological stations. Ecophysiological parameters for different vegetation types were determined from own measurements as well as from results of previous scientific studies in the area. The present spatial distribution of the different land-use types was described from analysis of LANDSAT ETM+ observations. The spatial pattern of leaf area index (LAI) was derived from analysis of NDVI data (calculated from LANDSAT ETM+ data) and field measurements at key experimental plots.
A deforestation scenario (allowing for mainly anthropogenic impacts) which was applied in this study assumes a relatively strong decrease of the areas covered by tropical rain forests, i.e. about 15%, and an increase of agricultural (coffee plantations, corn and rice fields) and urban areas. Moreover, the scenario assumes a small increase of grassland areas as well. The results of modelling experiments show that 15% deforestation of the study area results in relatively small decrease of monthly evapotranspiration by about 2%, transpiration by about 6% and interception evaporation by about 5%, as well as an increase of soil evaporation by about 21%. The evapotranspiration decrease was highest in days with cloudy and rainy weather conditions, and lowest in sunny and dry days.