Tikatuwq: an R package for reproducible freshwater quality monitoring with integrated regulatory compliance assessment

Water quality monitoring programmes generate large volumes of observations, but converting these records into reproducible environmental assessments and regulatory evaluations remains challenging. Here, we present tikatuwq, an open-source R package for discrete freshwater monitoring data. Its modular workflow integrates data import, unit harmonization, validation, computation of the Water Quality Index (WQI/IQA) and Trophic State Index (TSI/IET), parameter-level analysis, visualization, and automated reporting. Regulatory assessment is implemented as a separate component based on Brazil’s CONAMA Resolution 357/2005, enabling environmental indicators and applicable legal thresholds to be examined within a reproducible workflow. We demonstrate the package using 976 parameter-level observations from 52 site–campaign records collected at four stations along the Buranhém River (Bahia, Brazil) between 2020 and 2024. After removing two duplicate records and excluding two brackish-water campaigns, 48 distinct freshwater site–campaign records were retained for the primary analysis. Mean WQI values were classified as Good at all four stations. The river-specific Lamparelli TSI indicated oligotrophic conditions at two stations and mesotrophic conditions at the other two. WQI and TSI showed a moderate negative correlation (Pearson r = −0.46; n = 48). Of 466 parameter–campaign assessments against applicable Class 2 freshwater thresholds, 433 (92.9%) met the selected screening criteria; thermotolerant coliforms accounted for most exceedances. By bringing environmental indices and parameter-level regulatory screening together, tikatuwq supports transparent, reproducible assessments of freshwater monitoring data while retaining a modular structure for future adaptation to other regulatory frameworks.