UNCERTAINTIES ASSOCIATED TO CLIMATE SCENARIOS OBTAINED BY ETA CPTEC/HADCM3 MODEL: COMPARATIVE EVALUATION BETWEEN SIMULATED AND OBSERVED DATA OF PRECIPITATION, EVAPOTRANSPIRATION AND RIVER FLOW IN IJUÍ RIVER BASIN, BRASIL.

This study aims to evaluate the climate scenarios simulated by the Eta CPTEC/HadCM3 model, conducted by four members of the HadCM3 global climate model (CNTRL, LOW, MID and HIGH), at the Ijuí River Basin, Brazil. The used control period was from 1961 to 1975, looking for the assessment of climate scenarios and river flow during the 1976 and 1990 period. The task was divided into five stages: spatial interpolation of climate data, correction of simulated climatic variables series (bias correction), calculation of reference evapotranspiration, hydrological simulation of monthly river flow, comparison between simulated and observed conditions of precipitation, evapotranspiration and river flow. Although the correction methods used to eliminate the simulated climate series biases have originated very different scenarios, neither methods presented a better performance in all examined criteria. Sometimes, the differences between the simulated values based on the Eta Model and the observed values were higher than 20%, both in both rainfall and river flow resulting from the hydrologic modeling processes. Therefore, one must consider that these uncertainties will propagate to future scenarios, when analyzing the effects of climate change on water availability.

Climate change; water availability; hydrologic modeling.