Hydrological system time lag responses to meteorological shifts

ABSTRACT Hydrological system’s sensibility and resilience to dry periods are crucial for estimating the potential impacts of droughts. Quantifying response times (RT) of this system’s components relative to droughts allows one to develop a predictive understanding of future impacts. In this context, this study proposes the use of non-parametric statistical methods to estimate RT between meteorological shifts, given by the Standardized Precipitation Index (SPI), and the respective changes in the hydrological system, measured by river discharge (Q) and reservoir storage time series. Change point (CP) analyses were applied to time series of (i) SPI and accumulated storage relative to 32 reservoirs within the Paraná basin; and (ii) SPI, Q and reservoir storage relative to Furnas hydroelectric power plant. Based on the responses from CP analyses, RT in case (i) varied from 0 – 6 months, whereas, in case (ii), results indicate that significant changes in Q occurred in the same month of changes in rainfall. Results also suggest a minor role of anthropogenic factors (dam operation) compared to natural forcing in reservoir depletion during the 2014 drought than that in 2000/2001. This study reinforces the importance of an optimized reservoir management, considering the balance between anthropogenic and natural forcing as a strategy to combat droughts impacts.