Assessment of Hydrochemical Variability in the Svete River and Its Tributaries Under Anthropogenic Pressure

The research was carried out to examine the influence of tributary inflows on the hydrochemical properties of the Svete River, which traverses intensive agricultural regions. Sixteen monitoring sites were selected along the main channel and at major tributary junctions. Water samples were collected monthly from surface layers (0 5 cm) over a one-year period, and concentrations of total nitrogen, total phosphorus, and selected metals were evaluated. A multi-parameter probe and an inductively coupled plasma optical emission spectrometry method were utilized to determine spatiotemporal variations of water quality. Elevated total nitrogen concentrations were observed during the winter and early spring months, reaching up to 14.0 mg L, while concentrations declined to approximately 1.0 mg L in the summer. The total phosphorus concentrations showed more irregular distributions, with peaks of up to 43.0 mg L in June near the river s confluence with Lielupe River. Such fluctuations may be associated with surface runoff, localized anthropogenic inputs, and varied hydrological conditions. Although overall water quality remained acceptable for most sites, the considerable nitrogen and phosphorus loads indicate potential eutrophication risks. It is recommended that the role of agricultural runoff be addressed by adopting advanced nutrient management strategies and promoting wastewater infrastructure improvements in rural settlements. Future efforts should expand the monitoring framework to include emerging contaminants such as microplastics, antibiotics, and pesticide residues.