Nitrate and Phosphorus Transport in a Galician River (NW Iberian Peninsula): Insights From Fourteen Years of Monitoring

The long-term development of water quality metrics is critical to estimate the status of water resources and successful catchment management. This study looks at the temporal evolution of nitrate and phosphorus loads and concentrations in a stream draining rural catchment in Galicia (NW Iberian Peninsula) during 14 hydrological years. The concentrations of both nutrients are relatively low because of the rural nature of the research catchment and low-intensity agriculture. However, catchment nutrient reference levels were widely exceeded. The hydrology controls nutrient fluxes as flow is the main driver of nutrient transfer. For both nutrients there were no consistent trends in nutrient fluxes. The analysed nutrients, however, have been seen to behave differently. As a result, N seems to be decreasing, mainly due to decreased transit in the autumn and spring. Phosphorus, which is primarily transported as particulate matter, exhibits an increase in winter linked to a greater flow and sediment transfer.

Automated summary

This study examines the temporal evolution of nitrate and phosphorus loads and concentrations in a rural catchment in Galicia over 14 hydrological years. While nutrient concentrations are relatively low due to the rural nature of the catchment and low-intensity agriculture, they consistently exceed catchment nutrient reference levels. Water flow is the main driver of nutrient transfer, but there are no consistent trends in nutrient fluxes. Nitrate appears to be decreasing, mainly in autumn and spring, while phosphorus shows an increase in winter due to higher flow and sediment transfer.