Science Questions – How much Phosphorus and Nitrogen is Moved Through the Landscape into the Streams?

There is a delicate balance between the application of phosphorus and nitrogen as a fertiliser to agricultural land and their harmful effects on surface and subsurface waters. Cost-effective mitigation measures need to target the sources and flow paths that conduct the bulk of the load.

Multiple flow paths (e.g. overland flow, macropore flow, matrix flow, tile drainage) of these substances are studied in the HOAL. A water quality monitoring network was installed. While the high sediment concentrations in the HOAL facilitate the sediment process analyses, they complicate the monitoring of water quality parameters, as they tend to clog sensors.  A new device was developed, termed Water Monitoring Enclosure, that allows in-situ monitoring of water quality parameters for highly dynamic, sediment laden streams. This paper describes the design of the Water Monitoring Enclosure.

Autosampling and grab sampling is performed at regular intervals, and analysed for a range of parameters including stable isotopes. Mixing analyses, assisted by tracer tests, have identified the main sources and flow paths in the landscape.