Polluted agricultural runoff is a major source of water pollution globally. Agricultural runoff is primarily caused by melted snow or rainfall. It is, in essence, water that does not stay in the soil but instead flows on the surface and carries a variety of polluting elements.
Why does agricultural runoff happen?
Agricultural runoff happens when agricultural activities are not well-managed. Poorly managed animal feeding operations, overgrazing, excessive plowing and other ways of overworking the land, as well as poorly managed water irrigation and inefficient application of pesticides and fertilizers are all recorded causes .
Other sources include soil erosion and animal waste .
Agriculture contaminates our drinking water
Agricultural runoff represents a major threat to rivers and lakes. Dangerous chemicals, waste, and soil create algal blooms, disrupt aquatic ecosystems and lead to the emergence of “dead zones” for animals and plants. It leads to eutrophication (unnatural enrichment of water bodies with organic and inorganic nutrients, leading to the unbalancing of the local marine ecosystem), turbification (reduced water clarity), pesticide contamination, and biological contamination .
In the US, it remains the main source of pollution of drinking water reservoirs . In a 2013 study, three dozen environmental scientists undertook an ambitious task of identifying the harmful effects of agricultural runoff across the U.S. in order to understand and help manage it better .
Contaminated water, through rivers and streams, ends up in water reservoirs that provide drinking water to millions of people and water treatment plans spend vast amount of money on removing potentially harmful chemicals.
Examples of water pollution from agriculture around the world
In Europe, around half of lakes and rivers are still polluted, according to a recent study published in Nature. The worst situation with freshwater quality is in Germany and the Netherlands, where more than 90 per cent of fresh water has failed to reach good quality status.
Pollution from agriculture is the main cause of this contamination, along with urbanization. While agricultural runoff has declined by 20 per cent of average between 1992 and 2012, more than 40 per cent of European rivers still face the issue of algae blooms.
This has direct implications for biodiversity: some 60 per cent of species and 77 per cent of habitats in Europe have assessed between 2007 and 2012 and continued to decline .
In China, world’s largest grain producer with a rapidly growing pig farming industry, huge harvests are irrigated with industrial and agricultural runoff .
In India, agricultural runoff is responsible for large-scale pollution of the nation’s big and small rivers, including the venerated Ganga River .
A number one cause of dead zones
Unfortunately, negative effects of agricultural runoff are not limited to inland waters. Polluted waters also affect the oceans. According to the U.S. National Ocean Service, 80 per cent of pollution of the marine environment come from the land, and nonpoint source pollution from agricultural runoff is the major contributor .
In another study published in Nature journal, Stanford University scientists have provided compelling evidence that agricultural pollution carried into the ocean with runoff waters causes sudden explosions of marine algae capable of disrupting ocean ecosystems and, like in the case of inland waters, create “dead zones” .
What can be done to prevent agricultural runoff?
A connection between agricultural runoff and water pollution, as well as the need to address the negative effects of this process have been discussed for decades at national [10,11] and international levels .
There is a number of solutions and prevention methods that received attention:
- To avoid soil erosion, it is necessary to maintain agricultural soil with a simple method of crop rotation.
- Another method is no-till agriculture, not common in industrial farming and yet an effective measure to reduce soil erosion. Tilling has been proved to increase soil erosion , thus, no-tilling agriculture could help farmers keep the soil in place.
- Nutrient and fertilizer managements are also crucial to reducing the negative impacts of agricultural runoff .
- Management measures aimed at livestock agricultural runoff mitigation are also important. There is a need to minimize erosion of the land for grazing, while maintaining vegetation on it .
- Most importantly, there is a need for wider awareness raising and education to help shift agricultural practices towards sustainable rails.