Avaliação da influência dos usos e ocupação do solo na qualidade da água do Rio Vermelho no sudeste de Mato Grosso

Abstract

The present study aimed to identify which land use and occupation in the Vermelho River basin are related to water quality and limnological patterns of the Vermelho River. This region (15º30’/17º15’ S and 53º45’/55º00’ W) is located in the southeastern Mato Grosso State. To this end, we used the database of SEMA/ANA (from 2004 to 2013), and five sampling sites were sampled in 2014. Water analyses followed the Standard Methods, and for the land use and occupation, geotechnological methods were used. Among the 22 limnological variables, 4 variables presented mean values higher than the limits set forth by CONAMA Resolution 357/2005for class II rivers. The limnological variables were largely different over the historical series; however, they were grouped into dry and rainy periods. There was higher similarity between the sites 1, 3 and 5 (group B) followed by the site 2 (group A) and 4 (group C), this last being less similar than others. The WQI classified the water quality of the Vermelho River as Medium for all sampling sites. Importantly, the rainy period altered the water quality, which varied between Good and Poor. Among the variables composing the WQI, nitrate and E. coli were those that influenced the definition of the water quality class in the analyzed stretch, suggesting relationships with land use for agriculture and urban area. The Vermelho River basin is predominantly used for grazing, agriculture and forest remnants, respectively. The current land uses in the sub-basins indicated that in the region of the sites 3 and 4 in the urban perimeter of Rondonópolis, there was a clear effect of land uses on the water quality (color, turbidity, total solids, phosphorus, nitrate and E. coli), when compared to the WQI and CONAMA 357/2005.The Permanent Preservation Area of the Vermelho River presented several indicators of human activities, both in the rural (pastures) and urban area. These indications have been shown to be responsible for changes in the limnological variables of the Vermelho River throughout the historical data series.