Spatial and seasonal variability of the water quality characteristics of a river in Northeast Brazil

This study is aimed to evaluate the influence of land use/land cover as well as the seasonality on the variability of water quality in the Siriri River basin, in the State of Sergipe, Brazil. The following parameters were monitored: temperature (Temp), pH, electrical conductivity (EC), dissolved oxygen (DO), total nitrogen (TN), nitrate as N (NO3--N), total phosphorus (TP), chlorophyll-a (Chl-a), total dissolved solids (TDS), turbidity (Turb), thermotolerant coliforms (TCol), water level (WL), total agricultural area (AGR), total pasture area (PAS), total precipitation in 1 day (Pr1d), 10 days (Pr10d), and 30 days (Pr30d) prior to water sampling date. Analysis of variance (ANOVA) and principal component analysis (PCA)/factor analysis (FA) were utilized to evaluate the data. The results indicate the predominance of organic and biological pollutants in the Siriri River basin, which are related to agricultural activities and urban sewage, mainly in the wet periods. The ANOVA indicates significant influence of locality on pH, EC, TDS, DO, TCol, Chl-a, Turb, TN, TP, and WL. Seasonality factor has a significant influence on Temp, NO3--N, Chl-a, Turb, TN, TP, Pr1d, Pr10d, and Pr30d. The PCA highlights the influence of agricultural activities in component 1 (PC1), explaining 26% of the variance of the river water quality in the watershed.