Metodología para la propuesta de caudales ecológicos en función de restricciones ambientales y de gestión

Abstract

Many rules of dam operation aims at regulating the river flow on a seasonal and daily scale in order to supply energy in the demands peaks as well as in the dry season. This regulation changes the water characteristics and the aquatic ecosystems, producing alterations in matter and energy cycle, habitat availability, and in the integrity of the ecosystems. This study proposed an environmental flow regime in order to improve the ecological status of the Rio Grande downstream of the Itutinga Hydropower Plant (Minas Gerais, Brasil). The development of the environmental flow regime was based on different techniques; i) time series analysis of mean daily discharge; ii) biological response of fish and macroinvertebrates to several experiments of flow releases downstream of the hydropower plant; iii) analysis of the actual flow regime with Indicators of Hydrological Alteration (IHA). The annual hydrograph of monthly flows, with an interval of variability, for the environmental flow regime was built with an autoregressive model, whose restrictions were obtained by analyses of the main five flow components (magnitude, frequency, duration, seasonality and rate of change) of the period pre-dam (1934- 1954) and post-dam construction (1990-2011). Besides the IHA, the magnitude of monthly flows was proposed considering the biological responses of fish and macroinvertebrates; additionally, the hydropower company reported some operational limits to be considered. The process presented here showed a new approach for environmental flows in Latin America, based on multidisciplinary analyses which integrate hydrological, biological and real data of dam operation.