Point source pollution is pollution that comes from one source, such as a factory pipe outlet. Nonpoint source pollution is pollution that comes from many different sources, such as overfertilized lawns, trampled streambanks, or eroding pastures. Test your nonpoint knowledge:
| Pollutant |
| Bacteria | High Temperature, Low Dissolved Oxygen, Salinity | Phosphorus, Nitrogen | Sediment | |
| Nonpoint |
| Septic tanks poorly sited or maintained. | Livestock and pet waste. | | | |
| Straightened streams. | Dikes and dams. | Upland practices, e.g. stream shade removed, poor grazing practices, drained wetlands. | Plant litter, e.g., leaves and lawn trimmings dumped into ditches. | Irrigation leaching. |
| Crop fertilizers, livestock manure. | Landscape, lawn, and garden fertilizers. | Pet excrement. | Septic tanks poorly sited or maintained. | |
| Erosion from poor grazing practices, tilling ground, logging roads. | Sheet, rill, and gully erosion. | Dredging, streambank erosion. | Bed scour from straightened streams. | Construction, land clearing. Natural erosion. |
| Source Impact |
| Bacteria contaminate drinking water and swimming areas. | People eating contaminated fish/ shellfish can contract hepatitis, stomach and intestinal problems, etc. | | | |
| High temperature reduces oxygen. | Plant decay process uses up oxygen. | Low oxygen and high salinity stunt reproduction, increase diseases, and kill fish. | | |
| Nutrients cause algae blooms that die and lower oxygen levels. | Noxious algae blooms and discolored water limit recreation. | Nitrates in groundwater kill livestock and sicken infants. | | |
Sediment fills wetlands, destroys habitat, and smothers feeding and spawning areas. Sediment carries nutrients. Ports are dredged more often. Cities have increased costs to filter drinking water.
