Seasonal and spatial effects of land use and land cover on stream water quality in a South American rice producing region

Environmental research underscores that land use and land cover (LULC) influence key ecological components, such as water quality (WQ). This study examines how seasonal LULC affects WQ in the Cebollatí and Olimar Grande rivers in the Merín Lagoon Watershed, Uruguay. This region encompasses diverse natural and anthropogenic LULC. It is a key rice-producing area in South America, making it a relevant case study for the Global South, which is often underrepresented in similar research. The analysis focuses on buffers of 1500, 2500, and 5000 m, as well as the catchment defined by WQ sampling sites (SAS). The primary materials and methods comprise summer and winter seasonal LULC maps for 2024, WQ variables (WQVs), and statistical analyses. WQVs comprise total phosphorus (TP), total nitrogen (TN), nitrate (NO₃⁻), dissolved oxygen (DO), and conductivity (EC). The statistical approaches include the paired t-test, the coefficient of determination (R²), and partial least squares regression (PLSR). Most agricultural land is concentrated in buffers. Statistically significant seasonal differences were identified for TP, DO, and EC. The R² scores and PLSR indicate that seasonal and spatial differences exist in how different scales explain WQVs. The multiscale approach demonstrated how buffers and catchments influence the seasonally dissimilar effects of LULC on WQ. Maps were valuable for analysis, but relying solely on them overlooks complexities in the study area’s biophysical and socioeconomic conditions. Future research should develop local case studies across various areas of the CLM to provide a more comprehensive analysis.