Simulação de mudanças climáticas futuras nos recursos hídricos de uma bacia hidrográfica andino amazônica, Peru

Abstract

Assessing the impacts of climate change on water available in the Peruvian Andes, the headwater of the Amazon River basin, is essential for water resources management in mitigating possible predicted impacts. This thesis addresses the Chicllarazo River Basin (BHRC), the main water source for the Cachi Hydraulic System, responsible for meeting the multiple uses of water in the Ayacucho region, including irrigation, public supply, and hydroelectric generation. In the BHRC region, observed hydro climatological data are scarce, constituting a limitation for developing hydrological studies. In this context, the objective was the hydrological modeling of the BHRC with the Soil and Water Assessment Tool (SWAT) hydrological model, evaluating the applicability of the IMERG satellite precipitation. Specifically, the objective was to analyze the hydrological impacts associated with the RCP (Representative Concentration Pathways) 4.5 and 8.5 climate change scenarios for the 21st century, simulated by four global climate models, with downscaling by the Eta model (Eta-BESM, Eta -CanESM2, Eta-HadGEM2-ES and Eta-MIROC5). Satisfactory results were obtained in the steps of calibration (2009-2012) and validation (2013-2016) of the SWAT from observational data from a single meteorological station (Choccoro) and fluviometric gauge station (Chicllarazo). The IMERG was then used as input in the calibrated model, and satisfactory results were obtained only after bias correction from the IMERG. The results concluded that expanding the hydrometeorological monitoring network along the Andes of Peru is relevant, intending to improve hydrological studies. For assessing hydrological impacts resulting from climate change, the low availability of observed data was a limitation to bias correction of climate forecasting, imposing the character of a first approximation to this stage of the present study. Divergences in the precipitation projections for the 21st century were observed, with increased precipitation by the Eta-BESM and Eta-CanESM2 models and reduction by the Eta-HadGEM2 and Eta-MIROC5 models. For the temperature, the four models projected warming. For the mean ensemble of the models for the RCPs 4.5 and 8.5 in the XXI century, an increase in maximum temperatures of 2.3 and 3.1°C, respectively, and in minimum temperatures of 1.2 and 1.8°C, respectively, were obtained. The hydrological impacts simulated with the SWAT model for the 21st century for the mean ensemble were a reduction in annual runoff of 12.3 and 20.4% for RCPs 4.5 and 8.5, respectively, and, individually for each model, the runoff projections signal was similar to those of precipitation. However, the projections of reduction in the future water availability in the BHRC obtained for the mean ensemble can impact the Cachi Hydraulic System. However, it is emphasized that the use of the results requires caution due to the uncertainties present in the modeling of future climatic scenarios, being recommended to develop future studies addressing modeling uncertainties and the IPCC climate scenarios.