Table 03 – Descriptive statistics for WQI data

The analysis of the descriptive statistics for the Water Quality Index (WQI) at sampling points P01 and P02 reveals that the Brejo Alegre Stream predominantly falls into the Poor quality category. For a total of 10 samples at each point, the arithmetic mean WQI was 29.9 at P01 and 29.3 at P02, with the median slightly lower, at 27.5 and 27.0, respectively. These mean and median values consistently indicate that the water body has severe limitations for use, falling within the WQI classification range that requires immediate attention. Although the standard deviation is relatively low (approximately 8.0 at both points), the Coefficient of Variation (CV) of 27% suggests a moderate variability in water quality over the study period. The extreme values also reinforce this poor condition, with the minimum WQI reaching 23.0 (P01) and 22.0 (P02) — indicative of a VERY BAD quality status—and the maximum values only reaching 49.0 and 48.0, which, despite being the highest recorded, still remain in the Poor quality range, never attaining the "Medium" status (WQI >=51).