AbstractCallahan Reservoir, located in an agricultural area near Columbia, Missouri, was studied for 3 years to determine the inflow and outflow suspended sediment phosphorus (P) and the solution P relationships. During the study, the mean inflow solution ortho‐P concentration was 0.085 mg/liter as compared with 0.041 mg/liter for the outflow. Concentrations of ortho‐P were highest in both the inflow and outflow during the fall and winter. As yearly suspended sediment concentrations decreased in both the inflow and outflow, due to lower runoff and sediment yields, solution ortho‐P (mg/liter), as well as sediment total, inorganic, organic, and exchangeable P concentrations (µg/g), increased. Similarly, as a result of coarse sediment deposition within the reservoir during individual storm events, outflow sediments were enriched in clay and had higher concentrations (µg/g) of total, inorganic, organic, and exchangeable P than inflow sediments. However, because of sediment deposition within the reservoir, outflow volume concentrations (mg/liter) of sediment total P decreased fourfold as compared with inflow sediments.