Nitrogen management is a major challenge facing water quality managers in many parts of Australia. Recent research highlights the importance of nitrogen as the nutrient limiting primary production in some coastal waters and riverine systems. In these situations, an increased delivery of nitrogen is likely to boost algal growth to the detriment of ecosystem health. Increased stream loadings of nitrogen are now recognised as a significant impact of upstream land use in catchments. There is currently a recognised lack of reliable information available to managers to support their decision-making on nitrogen management issues. This is compromising the effectiveness of the very considerable investments now being made in riverine restoration to improve water quality. Riparian buffer zones, particularly those on low order streams, offer the potential for reducing nitrogen entry to waterways, from both surface runoff and shallow groundwater flows. While much of the nitrogen entering streams is attached to sediment in runoff, a significant proportion is often transported in a dissolved form as nitrate. Fluxes of nitrate through the riparian zone are intrinsically linked to water movement (both over and through the soil) and are also strongly influenced by biological processes occurring in that zone. The process of denitrification (microbial conversion of nitrate to nitrogen gas) is particularly important because it effectively removes nitrogen from the riparian zone to the atmosphere. Riparian zone denitrification can have an important impact on downstream water quality when significant amounts of nitrate-enriched groundwater are transported at shallow depths through carbon-rich, anoxic riparian soils, at flow rates that allow enough time for the denitrification process to occur. Outcomes: 1) A simple model for describing denitrification and associated processes in riparian zones; and 2) A methodology for identifying the locations within catchments where these processes may be important. This will enhance the utility of the CRC CH’s Toolkit by adding a new capability to catchment water quality models (such as LEMSS) that describes subsurface fluxes of nitrogen in riparian zones and predicts responses to management change. The research is also very relevant to urban stormwater management and will contribute to the better understanding and prediction of bioretention and subsurface wetland systems.
- Get involved
- Contact us