Author(s): H. A. Santos; C. Chaves; C. G. Leal; P. S. Pompeu
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Abstract: Velhas River is one of the main tributaries of Sao Francisco River and is located in Minas Gerais State, Brazil. Its drainage area is 2,173 Km2and it crosses 51municipalities where 4.2 million people live. The length of the Velhas River is 802Km, and the basin is under the effects of mining, agriculture and urbanization processes. The most impacted area is the metropolitan region of Belo Horizonte, which receives unclean water from the mines and domestic sewage of 3.87 million people. Recently, the Minas Gerais government has implementing actions to reach the2010 goal: to have a swimmable and fishable river in the metropolitan region of Belo Horizonte. These actions have concerned water quality treatment, and have produced a gradual rehabilitation of the aquatic communities. However, international experiences have showed that the improvement of water quality is the first step for river rehabilitation and not enough to recover the ecosystem's functions and processes in a disturbed reach. In order to study the sedimentation effects on aquatic habitats, the PHABSIM method was applied in a reach of Velhas River. The aim of this study was to assess the lost of physical habitat due to sedimentation processes. This reach was compared to a reference site located in a well-preserve tributary, Curimatai River. The length of both studied reaches was 1 Km and they were simulated in River 2D software. The fish species Astyanax taeniatus was chosen to perform habitat suitability analyses. The Usable Area for this species in Velhas River was higher (9% of the entire reach) than the reference one (3%). However, the species density in the Curimatai River (0.81 ind/m2) was much higher than in the Velhas (0.03 ind/m2). Our results indicate that, at least for Astyanax taeniatus, suitable habitats are still found in Velhas, and the water quality is probably the reason for the low abundance of the species.
Year: 2009