Abstract

CHAVEZ-ALCANTAR, A. et al. Hydrochemistry of surface water in the cienega of Chapala and water quality index. Terra Latinoam [online]. 2011, vol.29, n.1, pp.83-94. ISSN 2395-8030.

The serious deterioration of water quality caused by pollution is an important factor in the loss of water sources in Michoacán. The “Cienega de Chapala” is an especially vulnerable zone in terms of processes of water pollution. The objective of this study was to evaluate the chemical composition of surface water, the causes of pollution, and the degree of contamination that exist in rivers and water bodies of the area. In order to analyze the chemical and bacteriological composition of water, sixteen sampling sites at three different dates were established for testing on rivers, dams, channels network and Lake Chapala. Multivariate statistical analysis was used, and a water quality index (WQI) was calculated for each site and sampling date. The results revealed that the concentration of contaminants of the surface water increased downstream as the sampling sites of rivers, water bodies and channels network neared Lake Chapala; the highest values found were for electrical conductivity (EC), fecal coliforms (FC), and total P. The change in Na/Ca and Cl/SO4 ionic relationships indicates an increasing trend in Na-SO4 composition. According to the WQI calculated values of sites studied, 44 and 53% presented good or moderately good water quality, respectively. The best water quality was in the rivers and dams where the influence of anthropogenic activities is less, while the lowest quality was found in water of Lake Chapala. The chemical and bacteriological parameters that were significantly associated with the WQI were EC, Pb, Cd, B, P and FC; EC was identified as the principal parameter correlated with the deterioration of water quality. In order of importance, agricultural drainage and residual waters are the main sources of pollution in the zone.

Keywords : Tarecuato river; Jiquilpan river; water pollution; wastewater; multivariate analysis.

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