Monitoring phosphorus in rivers

Phosphorus is an essential nutrient for the growth and development of plants and animals. It occurs naturally as phosphate bound to rocks and soil, and during weathering processes it is dissolved and released into water in a plant-available form (dissolved reactive phosphorus). While total phosphorus (TP) and dissolved reactive phosphorus (DRP) occur naturally in rivers, lakes and groundwater, higher than natural concentrations occur due to land use impacts and discharges.

Deforestation and erosion lead to sediment entering waterways, with phosphate bound to the sediment. Phosphorus is a key component of fertiliser, so can enter rivers and streams through leaching processes. Domestic wastewater and animal waste also contains phosphorus, so wastewater discharges can contribute to elevated instream phosphorus concentrations.

High phosphorus concentrations in waterways can cause eutrophication (excess nutrients). Eutrophication can lead to extensive growth of aquatic plants and algae, which can impact the ecological health, recreational, cultural and foodgathering values of the river.