Agriculture & Water Quality (SL IB Geography)

• Agriculture can impact on water quality in a number of ways
• Wastewater from silage and slurry
• Fertilizers, herbicides and pesticides
• Soil erosion
• One of the main impacts of agriculture is eutrophication

Eutrophication 

• Eutrophication is caused by an increase in the amount of nitrogen and phosphorus that is carried into streams and rivers from slurry and fertilizers
• This leads to nutrient enrichment

The process of eutrophication

• Algae blooms increase because of higher nutrient levels caused by eutrophication, which causes a positive feedback loop
• Increased algae blooms lead to increased decomposition as light cannot reach aquatic plants
• Which decreases oxygen levels 
• This reduces consumers and further increases algae growth
• Anoxia can occur in the autumn season
• Dead zones occur near boundary points between river mouths and coastal zones
• There are three main reasons why eutrophication is a problem:
• Nitrogen can cause excessive growth of algae
• It can affect human health
• A loss of fertiliser is an economic loss for agricultural production
• There are several ways of resolving eutrophication:
• Use different types of fertilisers and detergents, which may alter human effects of pollution
• Pump mud from eutrophic water
• Remove nitrates and phosphates from water

• Reducing nitrate loss in the Northern Hemisphere:
  • Barley straw uses nitrogen in the process of decay
  • When soils are wet, avoid using nitrogen fertilisers
  • Avoid applying nitrogen fertilisers to fields next to streams or lakes
  • Avoid ploughing grass as it releases nitrogen
  • Avoid applying fertiliser if rain is forecast
    • Use barley straw to prevent the growth of algae

Irrigation

• Irrigation has been taking place since ancient times
• Water for irrigation can be taken from surface stores
• There are various types of irrigation including:
• Total flooding, such as in rice fields
• Sprinklers
• Drip systems

Salinisation

• Salinisation may occur due to an increase of salt in the soil left as the water evaporates
• Groundwater levels can be close to the surface
• Capillary forces can bring water to the surface and then evaporation occurs
• When evaporation occurs, soluble salts will be left behind
• These salts make the land toxic to many crops, so the land can no longer be used
• Salinization in San Joaquin Valley, California, was projected to cost the state $1–1.5 billion

Impacts of irrigation

• In addition to salinization, there are various impacts of irrigation:
  • Loss of aquifer capacity 
    • This is caused by diesel-run machinery, which abstracts water faster than the aquifer is recharged
  • In the state of Texas, irrigation has reduced the water table by 50 metres
  • Irrigation has reduced the world’s albedo by 10% because dark green surfaces replace sandy surfaces
  • Evapotranspiration rates increase in the summer when surfaces have been irrigated 
  • Hailstorms and tornadoes can increase over irrigated areas due to an increase in the moisture in the soil, which results in more evapotranspiration

Stakeholders

• There are a number of stakeholders who may be affected by changes in water scarcity and quality, including:
• Governments trying to achieve food security
• Water companies that need to supply clean water to consumers
• Farmers 
• Domestic consumers who rely on clean water supplies
• HEP companies 
• Environmental groups
• Industry 

Water scarcity and quality in France

• The OECD reported in 2020 that agriculture is responsible for 11% of total freshwater abstractions in France
  • In summer, this percentage increases significantly
• Agricultural pollutants are putting pressure on surface waters
• France is part of the European Union (EU) and so has to follow EU laws, which include
  • Three main directives which have frameworks and standards to try and reduce agricultural pollution
  • The 2006 Water and Aquatic Environment Act 
• Agriculture in France is now subject to three fees
  • A fee for the potential spread of agricultural pollution 
  • A charge to distributors of fertilisers and pesticides 
    • The higher the charge, the more toxic the product is
  • A fee for water pollution caused by livestock breeding
  • EU law also states that farmers in France must obtain water permits to abstract water for farming
  • The EU has banned some types of fertilisers which affect aquatic life
• Farmers in France suffer water shortages, which has affected agricultural production
  • In some areas, yields fell by as much as 50%
• In 2022, France’s reservoirs were 80% below normal levels
• French authorities argued that giant irrigation reservoirs are necessary to support French farmers
• French farmers have been using precision farming, which is when farmers observe and manage their farms through the use of Geographic Information Systems (GIS)
  • Through precision farming, the farmers can reduce their water consumption and fertiliser and pesticide use on the farms
  • Precision farming also enables the farmer to help prevent the leaching of fertilisers and pesticides into the soil, which could ‘run-off’ into rivers
• Farmers have been using drip irrigation systems to administer the specific amount of water that is needed for good crop production