Modelagem hidrodinâmica do ecossistema aquático visando à determinação do hidrograma ecológico no rio Formoso - MG

• Autor(a) principal: Guedes, Hugo Alexandre Soares
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/745
• topic: Ecossistema aquático; Hidrograma ecológico; Modelagem hidrodnâmica; Aquatic ecosystem; Ecological hydrograph; Hydrodynamic modelling; CNPQ::ENGENHARIAS::ENGENHARIA SANITARIA::RECURSOS HIDRICOS

This study aimed at modelling hydrodynamically the aquatic ecosystem aiming at determining the environmental flow regime in Formoso River - MG. The studied area was divided in two monitoring sections of 1 km far, distant from each other 14 km approximately. Simulation of available habitats and their relation to flows in Formoso River, as well as the determination of the ecological hydrograph, were done by using the hydrodynamic model River2D, which consists in a bidimensional model used to study the effects of flow changes on aquatic ecosystem. In order to calibrate River2D model and determine the ecological hydrograph it was necessary to quantify in situ, by means of field observations, several hydraulic, hydrologic and biologic variables. Thus, there were four field campaigns, two in dry period (June, 2011 and July, 2012) and two in rainy period (March, 2011 and February, 2012). The characterization of the microhabitat was done in both sections of 1 km far in Formoso River, where were marked three equidistant cross sections of 500 meters, in which were collected data about speed, depth, flow, cover and substrate, besides cataloguing the taxonomic composition of the icthyofauna in the river. Field observations permitted to identify 17 species of fish in Formoso River, being collected 226 individuals in 24 samples. It was verified that the taxonomic composition is characterized mainly by the species Astyanax bimaculatus and Hypostomus affinis, because of the quantity of individuals in the studied sections. The biology of the species, by means of habitat modelling using the habitat suitability index curves, permitted to part the taxonomic composition in three distinct groups (intolerant, medium-tolerant and tolerant species), being the species Hypostomus auroguttatus, Oligosarcus hepsetus and Leporinus mormyrops bio-index of quality of the aquatic ecosystem. The hydrodynamic model River2D proved to be apt to be used in hydraulic and habitat simulations in both sections studied in Formoso River. Environmental flow regime in the first monitored section varied from 2,70 to 4,99 m3 s-1, referring to August and January, respectively. In the second section, values of environmental flow were between 2,85 and 4,13 m3 s-1, referring to December and May, respectively. Monthly environmental flow proposed in both monitoring section in Formoso River were compared to minimum flow reference used in Brazil, considering the permanence of 100% of Q7,10, Q95 and Q90 in the stream, proving that these methodologies do not consider the environmental aspects, putting at risk the permanence of the species and the local biodiversity. These analyses intended to show that the real environmental flow, proposed in this study, has time and spacial variability, and that to fix only one value of constant flow reference along a year can damage the aquatic fauna. Furthermore, environmental effects that happen in the aquatic habitat are associated to the different levels of the environment regime, not only because of a minimum flow, but also because the medium and maximum flows, besides the characteristics of the hydrologic regime, such as the duration and the frequency of extreme events. Thus, environmental hydrograms were proposed to both monitoring sections in Formoso River, which present potential to become important tools in water resources sustainable management.