The present study aimed to assess the environmental status and water quality of the Apeú River in relation to the types of land use and occupation, seasonal variation in rainfall and the degree of environmental vulnerability in the hydrographic sub-basin of the Apeú River. Thus, in order to achieve the objective, the performance analysis of the CHIRPS product precipitation estimate for the Apeú sub-basin was carried out, as well as the determination of the environmental diagnosis of the hydrographic sub-basin through geoenvironmental and climatic factors, as well as the spatial characterization. and temporal water quality of the Apeú River and the comparison of the results of the physical-chemical analyzes according to the quality standards established in specific legislation. In view of this, the performance of the precipitation data estimated by the product CHIRPS was evaluated for the sub-basin in relation to the observational data from the INMET and ANA meteorological stations. To validate the data estimated by CHIRPS, the Correlation Coefficient (r), Average Percent Error (PBIAS), Root Mean Square Error (RMSE) and the Agreement Index (d) were calculated. After validation, maps were built to show the spatialization of precipitation estimated by CHIRPS by interpolating the grid points belonging to the sub-basin. In general, product data tended to overestimate the rainfall measured in the region of interest, especially in the rainy season, although there is a better adjustment to that observed in the less rainy period. In addition, soil use and occupation, morphometry, precipitation and environmental vulnerability were analyzed, through geotechnologies. Through morphometry, it was observed that the SBHRA has a rectangular and elongated shape, giving the sub-basin low susceptibility to the occurrence of floods. While the result of use and occupation showed that 55.25% of the SBHRA is composed of dense and secondary vegetation, followed by 27.04% represented by pasture and crops and 16.93% of exposed soil. The integrated analysis of the geoenvironmental variables analyzed, allowed the elaboration of the SBHRA environmental vulnerability map. Allowing to observe that, the SBHRA has higher degrees of low and very low vulnerabilities (65.27%). However, it is clear through the cartographic representation of the vulnerability, an accentuated distribution of the fragments of medium vulnerability (22.47%), mainly correlated to the classes of undergrowth, distributed almost always close to the vegetation areas, followed by the distribution of the high vulnerability (11.26%), correlated with the anthropic areas. As for the surface water quality of the Apeú River, the physical-chemical parameters pH, dissolved oxygen (OD), electrical conductivity (EC), water temperature (Temp), turbidity (Turb), alkalinity (ALC), chloride (Cl-) and total hardness (DT), in a seasonal period of four campaigns (rainy and less rainy) and the
special and temporal quality of the river waters was evaluated, with the aid of descriptive and multivariate statistics at 8 sample points.. According to the results obtained through physical-chemical analysis, as well as the application of descriptive and multivariate statistics, it was possible to observe that in relation to the standards established by CONAMA Resolution 357/2005, the parameters are within the reference values. Through the results, derived from the scientific products produced, it was found that the sub-basin of the Apeú River presents changes in land use and occupation, mainly reflected in the quality of surface water, with alterations caused by pastures in the spring areas, urbanization in the basin area, demonstrating the non-compliance with environmental policies as proposed by Federal Law No. 12,651 / 2012 (Brazilian Forest Code), as well as the presence of areas with medium and high vulnerability advancing towards the forest remnants, mainly in northern region of the sub-basin where the spring points are located, which are on the banks of the Apeú River, configuring a situation of environmental degradation of natural resources at the limits of the hydrographic sub-basin of the Apeú River.
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