Energy and hydrology modeling for the Paraná basin

Sammanfattning: Hydropower in Brazil stands for 64.5% of all energy sources in the country. The largest number of hydropower plants are located in the Paraná basin, which together have an installed capacity of approximately 40 GW including the world’s largest producing hydropower plant, Itaipu. The wet season during Brazilian summer (January-March) is the most important for hydropower. Occasionally, extreme, such as El Niño and La Niña, which are connected to variability of the sea surface temperature in the Tropical Pacific Ocean affect climate patterns. These events could lead to drought and result in dramatic consequences for hydropower production. Rain patterns within the basin reflect the flows during different seasons so that the largest flows in the Paraná River basin occur between January and March. The rivers Paranaíba and Grande are the main tributaries of Paraná with the largest energy inflows. The objective of this project includes the adaption of the Scania-HBV model for the Paraná basin and its evaluation. Thomson Reuters Point Carbon provided the model, which uses precipitation and temperature as input data, and through simplified hydrological processes, simulates inflow to the basin in energy units. Limitations were mainly connected to measurements and calculations of input data. Thomson Reuters Point Carbon uses information about energy inflow for prediction of future hydropower production and prices on the energy market. Severe peaks in prices seem to be connected to long-term droughts in the wet season and technical problems in the hydropower system. Natural energy inflow was the target data used for calibration of the model. The Paraná basin was divided into five sub-basins: Paraná, Grande, Paranaíba, Tietê and Paranapanema. Scania-HBV model was adapted for each sub-basin and the calibration period was chosen from 2005 to 2012. Objective functions were used to find the best fit between observed and calculated energy inflow. Evaluation was done by simulating energy inflow for a validation period from 2000 to 2005. Finally the results from the five models were put together to receive information of energy inflow for the whole basin. Model results were generally satisfying. The model captured common characteristic patterns of energy inflow for each sub-basin and peak events. All sub-basins, except one, exhibited high values of the Coefficient of determination (r2); weekly r2 values of approximately 0.8 (monthly 0.9) in calibration and 0.7 (monthly 0.8) in validation. The final result was satisfying validation showed weekly r2 0.87 (monthly 0.92) for the calibration, and 0.75 (monthly 0.82) for the validation and with a relative low Accumulated difference of -2106 GWh. These objective functions, together with the evaluation of input data, give the conclusion that the model is reliable and probably useful for future predictions of hydropower production at the Paraná River basin.