Enjeux - Are agriculture and water management incompatible?

Are agriculture and water management incompatible?

Farming activities are often considered to consume too much water and create pollution, with critics pointing to irrigation and the use of natural reserves, and a deterioration of the quality of watercourse and ground water as well as the development of green algae.
All farming activity requires water. Agriculture and water management have always been intimately linked. Agriculture today is the only activity in our country that is asked to output drinkable water.
Does French agriculture use too much water? Does it cause pollution through fertilisers and crop protection products? Is the situation getting better or worse? These are just some of the questions we will address here.

THE CONCEPT

The water cycle

Water is found in great abundance on Earth but 97% of the total is salt water and 2% is set in ice. “Liquid” fresh water accounts for just 1% of the planet’s water resources.
The water cycle includes liquid, solid and vapour states, in oceans, lakes, watercourses, water tables, glaciers and the atmosphere. Solar energy is the driving force behind this cycle and by causing evaporation brings about all the other transformations. The water cycle can be very long, lasting up to tens of thousands of years, if the water is stored in aquifers or in the form of glaciers. The fresh water used by man comes from rain, surface water (rivers, streams and lakes) and water tables.

Water resources in France

The average yearly rainfall in France is 867 millimetres, or 867 litres/m2. For a territory of 551,500 square kilometres, this corresponds to some 477 billion cubic metres of rain every year in our country! Out of this, some 301 billion cubic metres return to the atmosphere through evaporation and 176 billion join watercourses that empty into the sea or seep into the ground. All activities combined (including energy, industry, farming, consumer use), we use 32 billion cubic metres of the total every year for our consumption, with the rest flowing into the ocean or absorbed by the natural environment. These 32 billion cubic litres represent 6% of the precipitation in France. And out of this total, some 25.85 billion cubic metres are sent back into the environment after use. Just 5.75 billion are consumed by industry, agriculture or as drinking water.

Water is essential to all farming activity

No water, no farming. Plants and animals are living beings that need water to grow and develop. Farming activity takes up 33 million of France’s 55 million hectares and 94% of agricultural land is not irrigated. And so our food supply depends to a significant extent on rain, for crops (grain, oil and protein crops, sugar beet, vegetables, and so on) and for pastures (for the grass eaten by animals). Irrigated crops occupy two million hectares, or 6% of useful agricultural land. Irrigation is the farming practice that consumes the most water, ranging from 2.5 billion to 3.9 billion cubic metres depending on the source and the year. According to a recent study made as part of the Casdar research programme, excluding irrigation French agriculture consumes 400 million cubic metres of water, 80% of which is drinking water for animals.

Potable water defined

In France we are fortunate to have sources of potable water practically country-wide. If the question of water has become such an issue, in our country and in Europe as a whole, then it is because we want to protect the volume of water available and, above all, its extremely high quality.
Water is considered as “potable” if we can drink it with no risks to our health. To provide a precise description of potable water, standards have been set on maximum amounts of certain substances. Water must contain no pathogens (such as bacteria or viruses) or parasites. It may contain only the slightest quantities of certain chemicals, including nitrates, hydrocarbons and heavy metals (lead, mercury, etc.). The maximum authorised level of nitrates is 50 mg/l and that of crop protection products 0.1 µg/l per active substance and 0.5 µg/l for all crop protection products. Potable water also has to be clear and have a pleasant taste.

1 2 3 4 / Tout afficher

Imprimer