Diagnóstico dos usos da água e do solo na bacia do Ribeirão Ponte de Pedra (Mato Grosso) e seus efeitos sobre a qualidade da água

Abstract

The change of use and occupation of the river basin, mainly the conversion of natural areas in agricultural and urban-industrial areas has an important influence on water resources. Thereby to make the diagnosis of water use and its effects on the water quality of Ribeirão Ponte de Pedra basin, this study was divided into two chapters, the first of which was to evaluate the quality and water availability in the basin considering the uses of water and the land use consequences. The classification of these uses was made from Landsat-8 images. Hydrological characterization and water availability were obtained from series of precipitation and water flow of the basin. Water quality and Water Quality Index were analyzed from 18 parameters according to CONAMA Resolution 375/2005. The basin has a large area subjected to anthropogenic influence (75.31%), such as temporary crops, pasture and bare soil, and only 0.9% of forest cover. The hydrologic regime has remarkable seasonality, with a grantable flow 8.26 m3

.s-1, of these 31% have already been granted. The water quality was considered poor and fair in 73% of samples, and five of the parameters have been in disagreement with the law. In the second chapter it was considered that the construction of small hydropower plants (SHP) can cause several changes in river ecosystems, especially when designed in cascade. So it had as objective to quantify the effects of two SHP in cascade operation and evaluate its individual and cumulative effects of altering the water quality of the Ribeirão Ponte de Pedra. Were used 15 water quality parameters derived from the environmental monitoring of the undertakings, collected every six months between 2006 and 2013. The Wilcoxon test has shown that SHP Jose Gelazio significantly changed five parameters, leading to a 3% increase in temperature and 28% reduction of color, 22% of dissolved solids, 20% total solids and 12% suspended solids. The SHP Rondonopolis significantly changed only two parameters, reducing the temperature at 3% and increasing pH at 1.5%. Regarding the cumulative effect the reservoirs significantly changed two parameters, causing an increase of 18% in total phosphorus concentrations and reduced by 48% of the total solids. These effects are associated with an increased water exposure to solar radiation and particle retention process due to increased hydraulic retention time in the reservoirs. With this, it is observed that the cumulative effects of the cascade system was 15% greater than the sum of the individual effects, indicating that projects in cascade tends to potentialize effects isolated. The basin water quality is in concern, being necessary control measures to ensure the multiple uses and environmental quality.