Assessment of rainfall patterns and hydrological dynamics of major reservoirs using Google earth engine (GEE): A comparative study of tropical regions in Brazil and Indonesia

Abstract

This study examines the impacts of rainfall variability on the hydrodynamics of major hydropower reservoirs in two tropical countries, Brazil and Indonesia, using Google Earth Engine (GEE) for data analysis. The primary objective was to identify spatiotemporal patterns of rainfall and their correlation with reservoir water extent changes over a decade (2012-2022). The study employed satellite data from Landsat 8 and Sentinel-2, along with CHIRPS rainfall datasets, to analyze water extent dynamics and rainfall trends. Statistical tools such as the Mann-Kendall trend test, Pearson correlation, and Theil-Sen estimator were used to evaluate trends and relationships between rainfall variability and hydrological responses.The results indicated significant differences between the two regions. In Brazil, reservoirs such as Tucuruí and Balbina exhibited declining rainfall trends (p 0.8). In contrast, Indonesia's Jatiluhur and Saguling reservoirs displayed stable rainfall patterns (p>0.05) and minor changes in water extent (-3% and +2%, respectively), with weaker correlations (r ~ 0.4), highlighting the role of effective reservoir management practices. Comparative analysis underscored Brazil's higher vulnerability to climatic changes due to anthropogenic pressures like deforestation, whereas Indonesia demonstrated greater hydrological resilience.The findings emphasize the need for tailored management strategies, including reforestation in Brazil and advanced water management technologies in Indonesia, to mitigate the impacts of climatic variability. This study contributes to understanding tropical hydrology, offering practical recommendations for sustainable reservoir and water resource management in similar regions globally. Future research should explore longer datasets, integrate machine learning approaches, and examine the role of human activities on reservoir dynamics.