Water is life

Fast facts: water

• Only 3% of the global water (1.38 billion km3) is fresh water and only 0.0009% is usable for human needs including agriculture (12,000 km3).
• Crops growth needs most of the water for capillary nutrient transport (transpiration): between 300 (cabbage) and 2500 mm (sugar cane) per growing season (seeding/planting to harvesting).
• Agriculture and the food chain needs between 30% and 90% of the available and usable water, due to the agroecological conditions, agriculture intensity and other water utilizations (e.g. cooling water for power plants).
• Between 1961 and 2015 the irrigated farmland increased by 100% towards 340 million hectares.
• The global annual water footprint per capita is about 1,240 m3, with a high variability.

Water is a simple inorganic molecule H2O. It is transparent, tasteless, odorless, and nearly col-orless (pure H2O). A view from space shows that a good two-thirds of our Earth is covered with water ("blue planet"). There are around 1.38 billion km3 of the water on the earth: in the oceans, lakes, rivers, in the air, and underground. Not all global water is suitable for drinking. 97 percent of water is too salty and is undrinkable. This water is mainly found in the oceans. Only three percent (35 million km3) of the global water is fresh water. However, most of it is in the ice masses and in the air as water vapor and is not available or suitable for drinking. Acces-sible and drinkable water is only 0.0009% of all water on earth (12,000 km3).

This scarce drinking water is not even evenly distributed across the earth. There are deserts with almost no water (respectively too deep to be usable without boreholes) and rainforests with lots of water. Water is always an issue, particularly for agriculture: always “too much” or “not enough”. People are made from water (about 70% of the body mass) and need to drink three liters a day (between 1-10 liters a day, due to the condition, size and the activities of the person, and the temperature). This need applies not only to drinking, but also to eating. Drinking water is also needed for other purposes: bathing, cleaning, toilets, recreation, sports, cooling, irrigation and other purposes. However, many people do not have access to sufficient or good quality water as Sustainable Development Goal 6: “Clean Water and Sanitation’ does target (UN water).

Photo 1: Drinking water from a hafir (open water basin) in the Sahel contaminated with camel shit, washing powder, sand and other sediments: 10 liter a day per person needed, no way out.

Water is used in the whole value chain of food production. The ‘water footprint’ is a measure in the sustainability assessment. The average water need per person is 1,240 m3 per year and capita  (Figure below). Every product has an own water footprint from production towards consump-tion. Green water is used for production, blue water in processing and grey water as wastewater. In total the products we consume have significant differences of used water per ton (Mekonnen and Hoekstra 2011).

Water pollution due to agriculture is significant and risk for drinkable ground and open fresh water and sea water as well. Irrigation and drainage have often been associated with a loss of water quality caused by salt, pesticide and fertilizer runoff, and leaching (Mateo-Sagasta et al. 2018).

Table: Global average water footprint of plant and animal food products

Source: Mekonnen and Hoekstra (2010, livestock), (2011, crops)