Sediment and phosphorus delivery from field to river via land drains in England and Wales. A risk assessment using field and national databases

Agricultural land drains can facilitate the transfer of sediment and attached phosphorus (P) from land to surface waters. A national risk map is being developed that will identify areas of England and Wales that are most susceptible to such P losses. The map is based on data from various sources, including field studies, laboratory rainfall simulations, and secondary sources. The factors most strongly related to sediment P loss were identified as soil class, rainfall, soil moisture deficit, land use, and type and condition of land drains. These factors were weighted to provide an estimate of risk, and the combined total risk was used to map national risk estimates at a 25 square km resolution. The resulting map indicates that large areas of England and Wales may be at risk of subsurface sediment and P transfer from agricultural land to rivers. Further work is needed to understand these findings at the farm level.