Relationships between Phosphorus and Suspended Sediment Concentrations in a Stream Draining a Rural Area in NW Spain

Abstract

This study assesses the possible use of suspended sediment as an indirect measurement of phosphorus (P) concentrations in a rural headwater catchment located in NW Spain. Particulate P accounted for about 70 percent of the P export, indicating that P transport is linked to sediment in this catchment. The relationship between P and suspended sediment concentrations showed that particulate P was strongly dependent on suspended sediment, although the relationship is not consistent throughout seasons. The particulate P–suspended sediment relationship behaved differently at low flow and runoff events; the relationship was only significant during runoff events. This is because low flow is dominated by dissolved P and by pathways that do not mobilize or transport sediment. The particulate P–suspended sediment ratio was lower during runoff events than during low flow, which is consistent with enrichment ratio effects.