Phosphorus is an element with the symbol P and is naturally present in water in low concentrations. When phosphorus levels increase to very high levels, the waterway is likely to experience rapid weed growth or an algal bloom. Increased phosphorus levels often come from runoff from pastures, crops and lawns that have been fertilised. Phosphorus is measured in mg/L as either ‘total phosphorus’ (TP), or ‘dissolved reactive phosphorus’ (DRP).

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