The role of small wetlands in catchment management: their effect on diffuse agricultural pollutants

Murray-Darling Freshwater Research Centre

MDFRC item.

Despite extensive interest in natural wetlands and their use in waste-water technology, little is known about how effective they are for the control of diffuse agricultural pollution. The impact of a small upland wetland located along a drainage line on different storm generated discharge events and resultant downstream nutrient loads over a two year period was assessed. Results for individual events indicated that the relationship between this wetland and its catchment was variable. An annual nutrient budget was determined for this wetland for the period March 1994 to February 1995. The wetland retained 9.7 kg yr-1 (20.5 kg yr-1) of nitrogen and 1.5 kg yrl (±0.1 kg yr-1) of phosphorus which represented 23% of the nitrogen and 38% of the phosphorus that flowed from this catchment. It is concluded that this form of wetland has a role in strategic catchment management for the interception of nutrients flowing from diffuse agricultural sources.