Water Quality Measurement  | Chemical Parameter

Lake Pend Oreille | Pend Oreille River

Phosphorus occurs mostly as phosphates, the most common form being orthophosphate – also known as a reactive phosphate. Orthophosphates are commonly used in fertilizers for agricultural and residential purposes and are often carried into waterbodies through run-off. Orthophosphate is the form of phosphorus most readily utilized by aquatic organisms, such as plants and bacteria. 

How to use the graph: View data for only one month by clicking on that month in the legend. Supplemental information is provided by hovering over a data point. 

For a link to IDEQ’s Water Quality Standards, click here.

For an explanation on Box Plots, click here.

*NOTE – The data for this graph has been log-transformed for visual aid purposes!!!

Although phosphate is not harmful to humans, anthropogenic inputs of phosphorus are known to have a significant impact on ecosystems and damage the health of rivers and lakes. In high concentrations, orthophosphate, an ingredient in fertilizers, can cause rapid algae growth in surface waters, which can deplete sunlight and oxygen levels and harm fish populations (Gooddy et al. 2015). 

Some sources of excess phosphorus

  • Stormwater runoff and snow melt
  • Erosion and sedimentation
  • Atmospheric deposition
  • Direct input by animals/wildlife
  • Agricultural runoff
  • Detergents and cleaning fluids
  • Failing septic systems
  • Lake mixing (internal loading of phosphorus from sediment/water interface)
  • Wastewater treatment plants and permitted industrial discharge
  • Fertilizer

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