Water quality in part of the Submiddle San Francisco region due to seasonality and land use and occupation

Abstract

ABSTRACT Due to the intensification of urbanization and the growth of agricultural areas in most of the river basins, the concern about the sustainable use and maintenance of the water quality of this environmental resource has become growing. This work proposes to evaluate the water quality of the San Francisco River, in the region of Submiddle, verifying the impact of the use and occupation of the soil and the seasonality on this hydric body, besides the attendance to the limits of the standard recommended by CONAMA 357/2005 for Class 2. Samples were collected at sixteen points during the dry and rainy season, and the nine parameters for determining the Water Quality Index (WQI) and the Trophic State Index (TSI) were analyzed. First, the descriptive statistics of the parameters were calculated. Friedman’s non-parametric statistical tests were then applied to analyze water quality as a function of land use and seasonality, followed by the test of multiple comparisons, at a 5% significance level, against the asymmetric behaviour of the data. The analysis of seasonality pointed out significant differences in variables, turbidity, total solids, total phosphorus, TC/E.coli, total nitrogen, temperature, and the TSI of water. Regarding compliance with the legislation and the framework, it was identified that TP (0.03–0.55 mg.L−1), TC/E.Coli (292.39–1600 NMP.100 mL−1), and BOD (1.20–14.00 mgO2.L−1) were in dissonance with what is recommended by the resolution CONAMA 357/2005. Analyzing the effect of land occupation on water quality, significant differences were found according to rural, urban, and domestic sewerage areas. It is expected that this work will help in understanding the characteristics of this water resource, generating data that can be a tool for its management.