Quantificação do efeito do açude castanhão sobre o fluxo de material particulado em suspensão e nutrientes para o estuário do rio jaguaribe, Ceará - Brasil

Abstract

The coastal zone is composed by highly environmental relevance ecosystems therein biodiversity is based on transitional land and marine features. This area has large biological productivity which is sustained by intricate biogeochemistry cycle of chemical species influenced by both adjacent watershed and coastal processes. Another feature of this area is the highly anthropogenic pressures that drive significant modifications of riverine material fluxes. Among such modifications, we can exemplify the damming of rivers and reservoir flooding usually occurred on the State of Ceará. The semi-arid climate enforce a large scheme of water management based on reservoir flooding which might induce changes on riverine fluxes from watershed to the coast as well as the ecosystem feature modification. Considering the above-mentioned scenario, this work aim to quantify the fluxes and budgets of water, suspended matter, and nutrients for the Castanhão reservoir from which the reservoir retention or export capacity of the riverine fluxes of the Jaguaribe watershed to the coast were estimated. Across the Castanhão reservoir water sampled were collected at three areas to characterize the concentration, fluxes, and budgets of riverine materials. According to proposed budget, there were a reduction of suspended matter, phosphorous, and nitrogen concentration. Additionally, the strong reduction of water outflow compared to inflow into reservoir was measured and it is the main process inducing the modification of riverine material fluxes. The budgets showed that the Castanhão reservoir and the operational dam procedure invert the natural functioning of the portion of Jaguaribe drainage basin. According to these results the reservoir changes the land-sea water, suspended matter and nutrient fluxes reducing and trapping from 88% to 98% of inflow loads into reservoir over hydrological and chemical conditions measured.