Where does Phosphorus come from and how does it effect the Cahaba?

A naturally occurring substance, phosphorus is essential for life. In fact, it is a critical component of our own DNA, a building block for our cell membranes and an essential nutrient for plant life.

But too much phosphorus in a waterway can spell trouble for the plants and animals that inhabit it.

Most of the phosphorus found in streams and rivers comes from chemical fertilizers that act as a replacement for the phosphorus that plants remove from the soil as they grow. Runoff from lawns, farms, golf courses and other cultivated areas flows into the streams and rivers and becomes concentrated there.

When too many phosphorus compounds are found in a waterway, it can lead to the uncontrolled growth of algae, dissolved oxygen deficiencies, and declines in wildlife and habitat. If allowed to go unaddressed, the higher phosphorus content in the river could also degrade fishing and boating activities and can even impact tourism and property values.


One way to help minimize phosphate runoff is simply never to apply chemical fertilizer in the first place. By completing a soil test before applying fertilizer, you may determine your soil doesn’t need to be fertilized. If your soil does require additional nutrients, consider using compost or other alternatives instead.

If you choose to fertilize your lawn, consider using “slow-release” organic fertilizers, which are broken down by microbes in the soil, and follow all label directions carefully.


  • Avoid herbicides and pesticides wherever possible, as they contain phosphorus.
  • Don’t dump grass clippings in streams, ditches or the river.
  • Collect stormwater runoff from your roof and store it in rain barrels or an underground rainwater recovery system. This water can be used for watering gardens and outdoor plants.
  • Even simple steps like picking up after your dog and properly disposing of pet waste can cut down on the amount of phosphorus entering the Cahaba.