Influence of Dry and Rainy Seasons on Physicochemical Parameters and Water Quality Index, Zahuapan River, Mexico

Abstract

Rivers pollution is an environmental problem in Mexico. Zahuapan River shows an important level of contamination due to raw wastewater discharges and runoff. The goal of this study was to evaluate the influence of dry and rainy seasons on physicochemical parameters and water quality index in the Zahuapan River. The physicochemical parameters were registered in situ using a portable multiparametric device. The data analysis was taking into account the dry and rainy seasons. Physicochemical parameters among seasons were compared by the Mann-Whitney and t tests. The analysis of physicochemical, temperature and rainfall relationships were carried out through the multiple regression and correlation matrix. Zahuapan River water quality index was estimated by CCME WQI method. Mann-Whitney and t tests evidenced that the physicochemical parameters were significantly different (p<0.05) in dry and rainy seasons. Coefficients of determination indicated that the multiple regression model was a good descriptor of variables. The pH was the best response variable in the rainy season and the EC was the best response variable in dry season.  More correlated pair variables were present in the rainy season than in the dry season. Water quality index got slightly better in the rainy season but due to the given condition of the river, it remained ranked in poorly quality category. The results revealed that the contamination has affected the Zahuapan River sensitivity, that no longer it responds to seasonal changes. The methodology used in this study may be useful in the evaluation of Zahuapan River restoration, and others rivers as well.

Keywords: River pollution, river sensitivity, lineal multiple regression, correlation