Diagnosis of the environmental quality of races in river Pacuí, municipality of the Coração of Jesus, north of Minas Gerais

Abstract

Water is of great importance to all life forms on the planet, being present in various physical, chemical and biological processes. However, human society has been exploiting this natural resource unsustainably, causing serious problems related to the poor quality of water resources and its scarcity. Therefore, this study proposes to diagnose the environmental quality of a river stretch called Pacuí, municipality in Coração de Jesus, North mesorregion of Minas Gerais. Using the BMWP water quality index, together with the Rapid River Assessment Protocol (PAR). Sampling of macroinvertebrates for application of the BMWP index was obtained by performing 1m trawls using ‘D’ net, in current and backwater areas, in a 50 meter transect, at five points along the river. At each point the 22 parameters established in the PAR were evaluated for environmental assessment and the physical characteristics such as width, flow and depth of the river at each point were measured. It was identified 1031 invertebrates from 11 orders and 34 families. Most of the organisms found are immature insects, highlighting the orders Trichoptera, Ephemeroptera and Odonata, which are organisms sensitive to environmental changes and Diptera which was the most representative order in abundance. River characteristics influenced the abundance of macroinvertebrates, decreasing with increasing flow and increasing with increasing river depth and width. The results for the applied biological indices were corresponding. The BMWP Index rated water from points C, E and D as ‘excellent’ and water from points A and B as ‘good’. The PAR classified the river stretch in points C, E and D as ‘natural environment’, and points A and B as ‘altered environment’. These results demonstrate that benthic macroinvertebrates are influenced by river characteristics. However, the quality of the surrounding habitat is the main factor affecting water quality in the Pacuí river basin. The diagnosis of the environmental quality of the Pacuí River, using biological indexes as tools, allowed to conclude that the water of the analyzed stretch varies between good and excellent, presenting better quality in the points upstream of the main road that crosses the river in the region.