Agriculture's Water Pollution: Causes And Impacts

Agriculture is the leading cause of water quality impairment in rivers and lakes, with 72% of assessed river length and 56% of assessed lakes impacted by agricultural activities. The intensification of farming practices, increased soil erosion, salinity, sediment loads, and the excessive or improper use of agricultural inputs such as pesticides, fertilizers, and antibiotics have led to water pollution. Additionally, livestock production, which accounts for 70% of agricultural land, contributes to water pollution through manure, antibiotic use, and fish excreta. The unsafe use of non-conventional water sources, such as wastewater, can also lead to the accumulation of pollutants in crops and livestock products, impacting human health.

Agricultural runoff

Agriculture is the leading cause of water quality degradation in rivers and streams, the third-largest cause for lakes, and the second-largest cause of wetland impairments. The National Water Quality Assessment has found that about half a million tons of pesticides, 12 million tons of nitrogen, and 4 million tons of phosphorus fertilizer are applied annually to crops in the continental United States.

The effects of agricultural runoff vary depending on the type of operation, landscape conditions, soils, climate, and farm management practices. Increased levels of nitrogen and phosphorus from fertilizer and manure can stimulate algal blooms in lakes and rivers, leading to hypoxic conditions that are harmful to aquatic life. Algae can also affect the recreational uses of local streams, downstream reservoirs, and estuaries. Excessive sedimentation from erosion can overwhelm aquatic ecosystems, smother breeding areas, and degrade coastal and marine ecosystems, including coral reefs.

Bacteria and nutrients from livestock and poultry manure can cause beach and shellfish bed closures and affect drinking water supplies. Pesticide runoff to streams poses risks to aquatic life, fish-eating wildlife, and drinking water supplies. Pollutants from agricultural operations can also enter groundwater and degrade sources of drinking water.

To mitigate the impacts of agricultural runoff, simple off-farm techniques such as riparian buffer strips or constructed wetlands can be used to cost-effectively reduce pollutant loads entering surface water bodies. Buffer strips are vegetated filter strips at the margins of farms and along rivers that effectively decrease pollutant concentrations entering waterways.

Intense cultivation

The high demand for food has driven the intensification of agriculture, with farmers employing various methods to increase productivity. However, this has resulted in the excessive use of fertilizers, pesticides, and other chemicals, which can find their way into water bodies through runoff, infiltration, and irrigation return flows. For example, the National Water Quality Assessment in the United States has identified agricultural runoff as the leading cause of water quality degradation in rivers and streams.

Soil erosion, a consequence of intense cultivation, exacerbates the problem by increasing sediment loads in water bodies. This excessive sedimentation can overwhelm aquatic ecosystems, smother breeding areas, and degrade coastal and marine environments, including coral reefs. Additionally, the increased use of pesticides contributes to the pollution of surface waters, posing risks to aquatic life, wildlife, and drinking water sources.

Another aspect of intense cultivation is the improper management of livestock waste. Livestock production accounts for a significant proportion of agricultural land use, and the mismanagement of manure can lead to water pollution. Manure contains high levels of nutrients, particularly nitrogen, which can stimulate algal blooms in lakes and rivers. These blooms can deplete oxygen levels, creating hypoxic conditions that are harmful to aquatic organisms.

Furthermore, the widespread use of antibiotics and other veterinary medicines in livestock production has led to the emergence of a new class of agricultural pollutants. These drugs can enter water ecosystems and drinking water sources, contributing to the growing public health crisis of antibiotic resistance.

To mitigate the impacts of intense cultivation on water pollution, various techniques and practices can be employed. Implementing buffer strips, such as vegetated filter strips along farms and rivers, can effectively reduce the concentration of pollutants entering waterways. Integrated farming systems, where crops, livestock, and other resources are managed collectively, can also help optimize resource use and reduce pollution. Additionally, encouraging sustainable diets and reducing food waste can moderate the demand for food, thereby lessening the pressure on intense cultivation practices.

Industrial farming

Secondly, industrial farming often involves large-scale livestock operations, and manure management is a significant issue. Livestock manure contains bacteria and nutrients that can contaminate water sources, affecting drinking water supplies and causing beach closures. Manure also emits ammonia, which combines with other air pollutants, creating harmful solid particles that can be inhaled and cause heart and lung diseases. The widespread use of antibiotics in meat production further contributes to the issue of antimicrobial resistance.

Thirdly, the demand for meat and the intensification of farming practices have led to increased soil erosion, salinity, and sediment loads in water. Sedimentation from erosion can overwhelm aquatic ecosystems, smother breeding areas, and degrade coastal and marine ecosystems, including coral reefs.

Lastly, industrial farming often requires irrigation, and the unsafe use of non-conventional water sources, such as wastewater, can lead to the accumulation of microbiological and chemical pollutants in crops, livestock, and water resources. While wastewater can be a valuable source of water and nutrients if properly treated, its unsafe use can have severe health impacts on consumers and farm workers.

Livestock waste

Additionally, livestock manure contains bacteria that can contaminate water sources and pose risks to human health. The unsafe use of non-conventional water sources, such as wastewater, in livestock farming can further contribute to the accumulation of microbiological and chemical pollutants in the environment and ultimately severe health impacts among exposed food consumers and farm workers. The widespread use of antibiotics in meat production, even in animals that are not sick, is contributing to the public health crisis of antibiotic resistance.

Furthermore, the enteric fermentation process in ruminant animals like cows, sheep, and goats produces methane, a potent greenhouse gas with 28 to 34 times the planet-warming power of carbon. This contributes to climate change and has indirect effects on water resources and quality.

To mitigate the impact of livestock waste on water pollution, various techniques can be employed. These include implementing buffer strips of vegetation along the margins of farms and rivers to reduce pollutant concentrations entering waterways and adopting integrated farming systems where waste from one enterprise becomes inputs for another, optimizing resource use and reducing pollution.

Irrigation

The use of protection zones and buffer strips is another effective way to reduce pollution migration. Establishing vegetated filter strips along the margins of farms and rivers can act as a natural barrier, reducing the concentration of pollutants entering nearby waterways.

Additionally, the timing of irrigation and the application of fertilizers and pesticides can be optimized to avoid runoff events like storms and snowmelt, further reducing the risk of pollution. By maximizing uptake, farmers can minimize the amount of excess nutrients that find their way into water sources.

Furthermore, integrated systems that collectively manage crops, vegetables, livestock, trees, and fish can improve resource use efficiency and environmental sustainability, reducing the environmental footprint of agriculture.

By adopting these improved irrigation practices and techniques, farmers can play a crucial role in mitigating water pollution, protecting aquatic ecosystems, and ensuring sustainable food production.

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