5.2.3: Water Quality Impacts

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Runoff from agricultural areas is often not captured in a pipe and discharged into a waterway; rather it reaches streams in a dispersed manner, often via sub-surface pathways, and is referred to as non-point source pollution. In other words, the pollutants do not discharge into a stream or river from a distinct point, such as from a pipe. Agricultural runoff may pick up chemicals or manure that were applied to the crop, carry away exposed soil and the associated organic matter, and leach materials from the soil, such as salts, nutrients or heavy metals like selenium. The application of irrigation water can make some agricultural pollution problems worse. In addition, runoff from animal feeding operations can also contribute to pollution from agricultural activities.

The critical water quality issues linked to agricultural activities include:

Fertilizers – nutrients (nitrogen and phosphorus)
- Eutrophication – dead zones
Pesticides
Soil erosion
Animal Feeding Operations
- Organic matter
- Nutrients
Irrigation and return flows
- Salinity
- Selenium

Check Your Understanding

Review the following fact sheet on agricultural impacts on water quality:

Protecting Water Quality from Agricultural Runoff, 2005, EPA Fact Sheet on Agricultural Runoff

Knowledge Check (flashcards)

Please take a few minutes to think about what you just learned from the Fact Sheet, then consider how you would answer the questions on the cards below. Click "Turn" to see the correct answer on the reverse side of each card.

Card 1:

Front: What is nonpoint source pollution?

Back: Nonpoint source pollution derives from diffuse sources, such as agricultural chemicals and fertilizers. The pollutants are picked up by the water as it runs off over the surface or travels through soils and as groundwater, and carried to rivers and lakes.

Card 2:

Front: What agricultural activities contribute to nonpoint source pollution?

Back: Poorly located or managed animal feeding operation, overgrazing, plowing too often or at the wrong time and improper, excessive, or poorly timed application of pesticides, irrigation water and fertilizers.

Card 3:

Front: What are the major water pollutants contributed by agricultural activities?

Back: sediments, nutrients, pathogens, pesticides, metals, and salts