What are phosphates?
Phosphates are chemical compounds made from the elements phosphorous
and oxygen. Phosphorous is usually present in water in the form of phosphate
What factors influence the amount of phosphate in your watershed?
1. Phosphates are usually present in the environment in low concentrations,
which limits plant growth. High phosphate levels can come from man-made
sources such as septic systems, fertilizer runoff and improperly treated
waste-water. The phosphates enter the water as the result of surface
run-off and bank erosion.
2. Many detergents contained phosphates before manufacturers developed
3. An increase in nitrate levels may cause an increase in phosphate
What is the optimal amount of phosphate concentration in a watershed?
1. In a stream draining into a lake, the phosphate level should not
exceed 0.05 mg/L.
2. In a lake or in a steam not draining into a lake, the phosphate level
should not exceed 0.025 mg/L.
3. A river should not exceed 0.1 mg/L phosphates. Phosphates exceeding
these levels can be very harmful.
4. A reading of 1.0 mg/L is considered excellent.
5. A reading between 1.1-4.0 mg/L is good.
6. A reading between 4.1-9.9 mg/L is fair.
7. A reading greater than 10.0 mg/L is very poor.
8. Total phosphorous levels higher than 0.03 mg/L contribute to increased
9. Total phosphorous levels above 0.1 mg/L may stimulate plant growth
sufficiently to surpass natural eutrophication rates.
What factors are affected by the amount of phosphate in a watershed?
1. As phosphates increase, there will be an excess of plant growth (eutrophication)
and decomposition. Consequently, aerobic bacteria will thrive and consume
oxygen as dissolved oxygen levels will decrease and negatively affect
the quality of aquatic animal life.
2. Eutrophication can be detected by a "rotten egg" smell.
3. Algal bloom caused by high phosphate levels can choke out other plants
and completely take over the water. It will also absorb the sunlight
and cause an increase in the waters temperature, but it will also
block sunlight to plants that live on the bottom causing them to die.
4. Animals use phosphorous to conduct metabolic reactions and to produce
5. Plants use phosphorous in order to grow.