1. Runoff is water from rain or melted snow which is not absorbed and held by the soil, but runs over the ground and through loose soil. Agricultural runoff is water leaving farm fields because of rain, melted snow, or irrigation.
2. As runoff moves, it picks up and carries pollution, which it can deposit into ponds, lakes, coastal waters, and underground sources of drinking water.
3. Agricultural runoff can include pollution from soil erosion, feeding operations, grazing, plowing, animal waste, application of pesticides, irrigation water, and fertilizer. Pollutants from farming include soil particles, pesticides, herbicides, heavy metals, salts, and nutrients such as nitrogen and phosphorus.
4. High levels of nitrates from fertilizers in runoff can contaminate drinking water and cause potentially fatal “blue baby” syndrome in very young infants by disrupting oxygen flow in the blood.
5. Agricultural wastewater generated from a variety of farm activities including animal feeding operations and the processing of agricultural products, can pollute surface and ground water if not properly managed. Examples of agricultural wastewater include but are not limited to manure, milking center wash water, barnyard and feedlot runoff, egg washing and processing, slaughterhouse wastewaters, horse washing waters and runoff associated with composting.
6. Additionally, runoff from croplands can contribute sediment, fertilizers and pesticides into surface waters.
7. Polluted agricultural runoff is the leading source of water pollution in rivers and lakes, according to a federal report. It can also trigger algae blooms in coastal waters, and produce “dead zones” in the ocean where there is no oxygen and few fish or wildlife can survive. In cities and suburbs, urban and industrial runoff is also a major source of water pollution.
8. Agricultural runoff can create a bad taste and odor in drinking water and contaminate drinking water, well water, and food sources. The pesticides in runoff can accumulate in fish, which can expose people who eat the fish to high levels of these chemicals.
9. Runoff occurs when there is more water than land can absorb. The excess liquid flows across the surface of the land and into nearby creeks, streams, or ponds. Runoff can come from both natural processes and human activity.
10. The most familiar type of natural runoff is snowmelt. Mountains that cannot absorb water from heavy snowfalls produce runoff that turns into streams, rivers, and lakes. Glaciers, snow, and rain all contribute to this natural runoff.
11. Runoff also occurs naturally as soil is eroded and carried to various bodies of water. Even toxic chemicals enter waterways through natural processes, such as volcanic eruptions. Toxic gases released by volcanoes eventually return to the water or soil as precipitation.
12. Irrigation practices that transformed California’s scorched desert into one of the nation’s most productive farming regions are the chief cause of pollution ruining the Salton Sea.
13. Growers who put food on the table dump waste water into the sea on a scale that would make big industries blush. Since the first drop of Colorado River water was diverted to make the desert bloom nearly a century ago, irrigated crop land spanning 600,000 acres in the Imperial and Coachella valleys has flushed a steady stream of salts, pesticides, fertilizers and selenium into the sea.