During a heavy rain, any excess products on our lawn are washed into a nearby storm drain, or washed directly into a stream. Either way, the products are not treated prior to reaching the stream. This means they are altering the ecosystem of the stream, removing food sources and reducing oxygen levels, thereby killing aquatic life. But chemicals from our lawns aren't the only problem in streams. In fact, the biggest source of water pollution is sediment.
Sediment includes clay, silt, and other components of soil.
It is delivered to the stream the same way as the chemicals described above, by surface water run-off. When excessive sediment is delivered to a stream, it clouds the water, suffocating aquatic life. Yet another source of water pollution from household runoff is yard trimmings. Yard trimmings decomposing in a stream can use up the oxygen that aquatic animals need to survive. Again, this situation can kill aquatic life.