Cobertura, uso da terra e qualidade da água na bacia de contribuição da Estação de Tratamento de Água Moreira - RS.

Abstract

The activities performed in the surroundings of watercourses and the lack of banks protection directly influence on the problems of pollution and contamination of watersheds. Thus an assessment of water quality in the catchment area of the Moreira Water Treatment Plant (WTP), located in the city of Capão do Leão-RS-Brazil, was performed. Daily average data of raw water quality, from samples taken from the withdraw point of the WTP were analyzed for the following parameters: total alkalinity, total hardness, iron, dissolved oxygen, pH, color, free CO2, organic matter and turbidity, from January 2012 to January 2014. It was obtained data about manganese, iron and ammonia nitrogen from March 2010 to January 2014 to verify variability and influences on water quality. It was also undertaken a water quality monitoring in the period from April to September of 2013 in four contributors of the Moreira stream (Carneiro, Moinho, Pestanas and Taquara water streams), in order to verify changes in the physicochemical parameters and the influence of these streams on the withdraw point of the WTP. To interpret the results of water quality it was used the Brazilian legislation on water quality (Resolution n° 357/2005 - National Council on the Environment-CONAMA), which provides standards for the quality of water in water bodies and for human consumption. The results of quality parameters of the water in the Moreira WTP watershed, in the most analyses, comply with the limits set by legislation, with the exception of iron, manganese and color that match-up allowable limit. Changes in turbidity, alkalinity, color and nitrogen occurred during periods of rain. Changes in iron and manganese were also observed in periods of occurrence of rainfall, indicating a probable effect of sediment transport in the watershed containing these elements. These changes are possibly associated with sparse native vegetation along the streams, soil type, presence of quarry and crops, indicating a need for a management plan for this watershed.