Interferências de barramentos no regime hidrológico do estuário do rio Catú-Ceará-Nordeste do Brasil

Abstract

The Catú River estuary lies 26 km SW of Fortaleza in Aquiraz municipality. This study aims to evaluate the small and medium barrier impacts in fresh water inputs and effects on the morphological evolution and environmental fragility of the estuary system. The main superficial flow interventions have been chosen and analyzed as well as the margins use and occupation from 1990 to 2004. The impacts focused in the barrier spilling were simulated through semi-empirical equation models, once there was no fluviometry monitoring stations. The over dimension of the Catú river spill wall, in 993, gave rise to flow relentless in rainy seasons for volumes less than 1 m3.s-1 favoring the mouth silting, estuary area shortage and mangrove decreasing. Afterwards, the wall resizing increased flow rate to 7 m3.s-1 due to flash flood in upstream areas at rainy season, allowing channel clearing and water oxygenation. The public dam Catú-Cinzento, in the river backland, decreases in 30% the lake water input and in the estuary. This caused the estuary water volume shortage from 8.507 m3 to 2.045 m3 under the same climatic and tide conditions. The water residence time is 18 days with low depuration capacity. The existing sedimentary processes configure the study environment as lagoon-estuary evolving to lake.