Modelling catchment management impact on in-stream phosphorus loads in northern Victoria

Area of Science:

• Environmental Science
• Hydrology
• Agricultural Science

Background:

• Phosphorus pollution is a major threat to global river water quality.
• Conceptual models aid in assessing management impacts on phosphorus loads, especially in data-limited regions.

Purpose of the Study:

• To develop and evaluate a coupled point-scale (HowLeaky2008) and catchment-scale (CatchMODS) model.
• To enhance the modeling of farm management impacts on in-stream phosphorus loads.

Main Methods:

• Coupled HowLeaky2008 and CatchMODS models tested in two Australian catchments.
• Model calibration using in-stream attenuation parameters and gauging station data.
• Simulation of phosphorus loads under current and modified farm management practices.

Main Results:

• The coupled model accurately simulated annual phosphorus loads (Nash-Sutcliffe efficiency 0.52-0.83).
• Field exports dominated total phosphorus loads (estimated at 7 t y(-1)).
• Perennial pastures and zero-tillage practices reduced phosphorus loads by 19-31%.

Conclusions:

• The coupled model offers a significant advancement in conceptual modeling for water quality assessment.
• Explicit simulation of soil and climatic impacts on field exports improves landscape process context.
• This approach provides valuable insights for managing phosphorus pollution through improved farm management strategies.