Nutrient removal from rural drainage systems using wetlands: investigating improvement to irrigation drainage systems

This fact sheet briefly describes a National Program for Sustainable Irrigation (NPSI) project in the Goulburn-Broken catchment, Vic, to investigate the potential of reducing nutrients in irrigation drainage systems using in-line wetland technology and batter stabilisation. Two aspects of reducing nutrients were investigated: the use of aquatic plants to remove nutrients, and stabilising the drain cross-section to minimise the drain contribution to nutrient runoff. The results showed that, on average, aquatic plants reduced total phosphorus concentrations in the drain by 23% and average turbidity by 31%. Minor reductions in other nutrients were observed but were not significant. The results indicate that off-line wetland systems could offer significant benefits for nutrient reduction. However, in-line wetlands have limitations in reducing nutrients in irrigation drainage water and would be of greater value in reducing turbidity and suspended solids.