Modelling and managing critical source areas of diffuse pollution from agricultural land using flow connectivity simulation

A combined critical source area and flow accumulation model is described that predicts the spatial distribution in the risk of diffuse nutrient losses from agricultural fields reaching surface waters. The model is applied to a number of agricultural fields under a range of different land management scenarios. The model output highlights the importance of land management features such as tramlines, tracks and field drains in concentrating flow towards receiving waters and in increasing the risk of the delivery of pollutants derived from diffuse agricultural sources to watercourses. The model allows scenario analysis of the likely impact of flow path mitigation on diffuse nutrient loads.