Nutrients and runoff in a small catchment during spring 2010

Abstract: Eutrophication is an increasing problem in the Baltic Sea and is caused by an excess of nutrients in the water which are primarily transported with the runoff from cultivated land. The peninsula Vikbolandet in Östergötland is dominated by arable land and has stream outflows to the bays of Bråviken and Slätbaken. In this study five streams of Vikbolandet have been sampled during the spring flood period with the aim of connecting concentrations of nutrients in the streams with turbidity and runoff in the catchment. This analysis has then been related to the land use in the small catchment of Vadsbäcken in order to investigate the impact of land uses with areal losses of phosphorus. The results indicate that there are increasing concentrations of phosphorus downstream in the sites of Vadsbäcken and that the transported amounts of phosphorus increases with the spring flood and at a rainstorm event. It is shown that the distribution of agricultural blocks in the catchment of Vadsbäcken has a major impact on the nutrient leakage. There is a co-variation between turbidity and runoff during a rainstorm event and between particulate-bound phosphorus and runoff over time. A further aim has been to investigate possibilities for use of an easily managed, cost-effective environmental monitoring method for nutrient measurements in watercourses. Within four out of five streams at Vikbolandet there is a significant co-variation between turbidity and total phosphorus. Using field measurements of turbidity for environmental monitoring could provide a viable alternative for environmental monitoring of watercourses but will need further investigations of co-variation before being brought into use. Further, this study shows that the transport of phosphorus is underestimated in environmental monitoring