How do agricultural practices affect the quality of freshwater sources?

Agricultural practices can significantly affect the quality of freshwater sources through pollution and over-extraction of water.

Agriculture is a major user of both ground and surface water in many parts of the world, accounting for approximately 70% of global freshwater withdrawals. Over-extraction of water for irrigation can lead to the depletion of water in rivers and lakes, reducing the availability of freshwater for other uses. This can also lead to the lowering of the water table, causing wells to run dry and reducing the amount of water available for domestic and industrial use.

Moreover, agriculture contributes to water pollution through the use of fertilisers, pesticides, and other agrochemicals. These substances can leach into groundwater or run off into rivers and lakes, contaminating freshwater sources. Nutrient pollution from fertilisers can cause eutrophication, a process where water bodies become overly enriched with nutrients, leading to excessive growth of algae and other aquatic plants. This can deplete oxygen levels in the water, harming fish and other aquatic life. Pesticides can also harm non-target species and accumulate in the food chain, posing risks to wildlife and humans.

Livestock farming can also impact water quality. Manure and other animal waste can contaminate water with harmful bacteria and viruses. In addition, the overgrazing of livestock can lead to soil erosion, which can increase the amount of sediment in rivers and lakes, reducing water clarity and harming aquatic life.

Agricultural practices can also affect the quality of freshwater through changes in land use. Deforestation for agriculture can reduce the ability of ecosystems to filter water, leading to increased sediment and pollutant loads in water bodies. Moreover, the conversion of wetlands to agricultural land can reduce the capacity of these ecosystems to absorb and store water, exacerbating flooding and reducing the availability of freshwater.

In conclusion, agricultural practices can have significant impacts on the quality of freshwater sources. These impacts can be mitigated through sustainable farming practices, such as the use of organic fertilisers, integrated pest management, and conservation agriculture.