Surface water quality of the Middle San Francisco river basin after the implementation of irrigated perimeters of Gorutuba/Lagoa Grande and Jaíba

ABSTRACT The irrigation perimeters of Jaíba and Gorutuba/Lagoa Grande are located in the Minas Gerais portion of the Middle São Francisco river basin, Brazil, occupying an area of approximately 31,493 ha. This region has the potential to contaminate water resources as a result of urbanization, deforestation and the application of fertilizers and pesticides in agricultural activities. The aim of this research was to investigate the impact of irrigation on surface water quality in the region, using secondary monitoring. Nine monitoring stations were selected in the region, which represent the diferente uses and occupation of land. The cluster analysis and the nonparametric Kruskal-Wallis test, followed by multiple comparisons, were used to comparatively evaluate the sampling stations and to identify which parameters showed different behavior among these stations. Although it was not possible to observe a pattern of contamination due to the location of the stations, it was found that the stations located along the São Francisco river showed no significant differences, although the use and occupation of land were different. The temporal trend of the constituents was verified by applying the test of the hypothesis of stationarity Spearmant, which found that most of the data analyzed were not stationary, with a tendency of increase or decrease over the analysis period. After the application of these statistical tests, it was concluded that, in general, the implementation of irrigated perimeters caused low impact in water quality in the region, in the period studied, considering the parameters analyzed in this study.