Correlation between water quality and precipitation variability in the Southern State of Amapá

Abstract

The objective of this investigation was to quantify the variability of physico-chemical and microbiological water quality parameters under the influence of monthly rainfall in the Lower Jari River, Amapá State. This stretch of the river basin is considered to be at high risk of periodic flooding. The methodology consisted of monthly sampling of surface water from November 2009 to November 2010 at four sampling sites located on a 36 km stretch in front of Laranjal do Jari City, Amapá. In total, sixteen parameters of water quality were analyzed in each sample. We compared the results with the quality standards of CONAMA Resolution N. 357/2005 for Class 2 rivers using the Spearman Correlation Analysis to quantify the degree of association between water quality parameters and monthly precipitation. The parameters Color, Turbidity, Al+3, Mn+2 and E. coli were significantly correlated with the average monthly rainfall. Furthermore, high concentrations of BOD and Total Coliform (TC) indicated greater vulnerability or environmental risk of potential waterborne diseases is associated with wetter periods. The parameters color, Fe, CT and E. coli were in non compliance with the CONAMA (357/2005) Resolution. We concluded that water quality tends to deteriorate during wetter periods or extreme rainfall events, resulting in increased vulnerability or risk to public health.