This study used multivariate techniques for data analysis in order to determine the natural and anthropogenic factors that contribute to the spatial and temporal variations of water quality in urban watersheds of Caxias do Sul, Brazil. Principal Component Analysis (PCA) was used to analyze data collected at 30 points between September 2012 and January 2014. Monitoring was conducted bimonthly in six urban basins, where a total of 21 physical, chemical and biological parameters were analyzed. We found that PCA can explain 71.3% of the total variance in water quality, and that domestic and industrial pollution are the main Qualidade da água superficial por meio de análise … Rev. Ambient. Água vol. 10 n. 4 Taubaté-Oct. / Dec. 2015 contributors to the water quality variation in the region, especially from the galvanic manufacturing sector. Furthermore, we observed a trend of self-attenuation of pollutants in water downstream from urban areas and great anthropogenic influence as the pressure from urbanized areas decreases.

Water quality in lotic and lentic systems is greatly influenced by the land use in the adjacent areas. This study was conducted in order to assess whether different degrees of preservation of riparian forest (from well preserved with 30m wide up to degraded with < 5 m wide) influence potamoplankton community structure. The study was conducted in three streams in the upper region of the Rio dos Sinos basin, at four sampling sites, with different width of the forest. Samplings were gathered for abiotic and biological analysis in winter (August 2010) and summer (January/February 2011). The analysis of environmental and biotic variables indicated that seasonality was the main determinant of biomass patterns, regardless of the width of riparian vegetation. The potamoplankton community of the studied streams responded to environmental conditions, although lack of significant difference among the different degrees of riparian vegetation preservation has been observed. Increasing trends on biomass, richness and diversity of species, and higher concentrations of total phosphorus and nitrogen in the non-preserved areas might indicate that the different gradients of preservation of riparian vegetation are related with the water quality in subtropical streams and consequently with the potamoplankton structure.

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ResumoO estado qualitativo dos recursos hídricos é essencial à gestão de águas. Buscou-se avaliar a qualidade da água do Rio Tega, em 6 pontos no curso principal, sendo os pontos(A1) localizados em região densamente urbanizada e industrializada e os pontos (A2) a jusante desta região. A coleta ocorreu no período de setembro de 2012 a junho de 2013. Analisou-se os parâmetros de OD, condutividade, ST,DQO,DBO, nitrogênio amoniacal, fósforo total, fenol, cobre, cromo, níquel e zinco. Os resultados indicaram que os pontos localizados na zona urbana, apresentaram uma pior qualidade comparada aos dois pontos à jusante. Nestes pontos (A1), foram observados baixos teores de OD e as maiores concentrações dos demais parâmetros. Nos pontos de jusante, observou-se uma redução nas concentrações dos parâmetros analisados e aumento do OD. Os resultados indicam variação na qualidade da água em função do descarte de efluentes domésticos, indicado pelas concentrações de NH3, PT, DQO e DBO, bem como de efluentes industriais, caracterizado pela presença de metais e fenol. Existe uma tendência de melhora na qualidade da água nos pontos mais afastados da área urbana (A2), demonstrado pelo aumento do OD e redução dos demais parâmetros indicando capacidade de autodepuração do recurso hídrico.

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