LULC and Climate Influence on the Remaining Flows of the Batalha and SEFAC HPPs in the São Marcos River Basin, Midwest Brazil

Código

I-EBHE0045

Autores

Josias da Silva Cruz, Leonardo Melo de Mendonça, Claudio Jose Cavalcante Blanco, NELIO MOURA DE FIGUEIREDO, Antônio César Pinho Brasil Junior

Tema

WG 1.04: From local to large scale human-water dynamics

Resumo

The hydroelectric plants installed in Brazil had their energy planning based on hydroclimatic modeling, however, after the installation there are changes in the surroundings of the reservoirs. Thus, climate variability and changes in land use and land cover (LULC) compromise energy planning in installed hydroelectric plants that considered only historical climate variability. To analyze the joint effects of LULC and climate changes on the water availability of the São Marcos River basin, the rainfall-flow model of soil moisture accounting (SMA) was used. In this model, the LULC influence was inserted in two ways, in the canopy model and in the SCS concentration time equation, the first represents the storage of water by the vegetation, which is available for evapotranspiration, and the second requires the CN parameter. For the LULC changes, data from the MapBiomas collection 8 project from the years 2015, 2019 and 2022 were used. The HEC-HMS was used to generate the remaining daily flows of the reservoirs of the Batalha and Serra do Facão hydroelectric plants (SEFAC) using the continuous rainfall-flow model SMA. The SMA rainfall-runoff model was calibrated (2015-2017) and validated (2018-2020), upstream and downstream of the reservoirs, using the Climate Hazards Group station infrared precipitation data (CHIRPS) and ECVWF V5 reanalysis temperature (ERAS5). In the period analyzed, from 2015 to 2022, the LULC change that occurred with greater intensity was the transition from temporary crops to soybeans, which in terms of area had an expansion of 14.0%. According to the adjustment metrics for the upstream calibration and validation of the Batalha and SEFAC HPPs, the model performed satisfactorily. For the downstream points of the reservoirs, the model obtained perfect adjustments for both calibration and validation (RMSE = 0 mm; NS = 1; Pbias = 0 %; R² = 1). These downstream results are explained by the uses of the reservoir models inserted in the HEC-HMS, which used quota-storage data provided by ONS. For the simulation period, the results repeated the good performance presented in the calibration and validation. The years 2016, 2017, 2023 were the years that had the flows reduced upstream of the HPPs. Thus, the remaining flows downstream of the Batalha and SEFAC HPPs are basically the turbine flows, indicating a reduction in rainfall in the watershed and an increase in water withdrawal for irrigation due to the expansion of soybean. Therefore, new HPP projects must consider the changes in their surroundings to avoid conflicts over water resources.