Effects of eutrophication in drainage ditches

Eutrophication of drainage ditches by over-fertilization with nitrogen and phosphorus causes a shift from a mainly submerged aquatic vegetation to a dominance of duckweed. This causes anoxic conditions, loss of biodiversity and hampering of the agricultural functions of the ditches. Simulations with the model PCDitch, previously calibrated on experimental ditches, indicate that this switch may occur as soon as a certain threshold nutrient loading level is exceeded. This level tends to increase with the water depth. It is recommended to validate the model predictions in field situations.