Water is getting scarce – but what does this actually mean? After all, the planet never loses a single drop of H2O. Although water is a finite resource, it will not be used up as long as we do not render it permanently unusable. However, it is important to integrate human water usage into the natural hydrological cycle and to use the locally available water in an adequate, effective, sustainable and fair way."First, already more than a billion people live in river basins characterized by physical water scarcity. In these areas water availability is a major constraint to agriculture. (...) More areas will face seasonal or permanent shortages. Second, competition for water between sectors will intensify. (...) In most countries water for cities receives priority over water for agriculture by law or de facto, leaving less water for agriculture, particularly near large cities in water-short areas, such as Middle East and North Africa, Central Asia, India, Pakistan, Mexico, and northern China. Water for energy, i.e., hydropower and crop production for biofuels, will further add to the pressure on water resources. Third, signs of severe environmental degradation because of water scarcity, overabstraction and water pollution are apparent in a growing number of places with often severe consequences for the poor who depend heavily on ecosystems for their livelihoods." (Global, p. 341)Despite significant progress in this area, there are still millions of people who do not have access to safe drinking water. Everyday, millions of women and children have to walk long, and often dangerous, distances in order to collect water and carry it home. As is the case for food and land, access to clean drinking water and water for agricultural usage is unequally distributed.
Green and blue water
When it comes to freshwater most people think of water in rivers and lakes, groundwater and glaciers, the so-called “blue water”. Only part of the rainfall feeds this freshwater supply. The majority of rainfall comes down on the Earth’s surface and either evaporates directly as “non-beneficial evaporation” or, after being used by plants, as “productive transpiration”. This second type of rainwater is termed “green water”. The green water proportion of the total available freshwater supply varies between 55% and 80%, depending on the region of the world, as well as local wood density. The biggest opportunity and challenge for future water management is to store more green water in soil and plants, as well as storing it as blue water."In many water scarce areas current per capita water consumption is unsustainable. Globally, water is sufficient to produce food for a growing and wealthier population, but continuance with today's water management practices will lead to many acute water crises in many parts of the world." (Global, p. 279)
Facts & Figures
Between 1990 and 2015, over 2.6 billion people gained access to improved water sources and 2.1 billion to improved sanitation facilities. However, by the end of 2015, over 663 million people - 87% living in sub-Saharan Africa and Asia - were still without access to improved sources of drinking water, 79% of them in rural areas. 2.4 billion people still use unimproved sanitation facilities.
Contaminated water can transmit diseases such diarrhoea, cholera, dysentery, typhoid and polio. Contaminated drinking water is estimated to cause more than 502,000 diarrhoeal deaths each year.
A combination of rising global population, economic growth and climate change means that by 2050 five billion (52%) of the world’s projected 9.7 billion people will live in areas where fresh water supply is under pressure. Researchers expect about 1 billion more people to be living in areas where water demand exceeds surface-water supply.
69% of the world’s freshwater withdrawals are committed to agriculture. The industrial sector accounts for 19% while only 12% of water withdrawals are destined for households and municipal use.
Future global agricultural water consumption (including both rainfed and irrigated agriculture) is estimated to increase by about 19% to 8,515 km3 per year by 2050.
Every day for more than 20 years, an average of 2,000 hectares of irrigated land in arid and semi-arid areas across 75 countries have been degraded by salt. Today about 62 million hectares are affected - 20% of the world's irrigated lands. This is up from 45 million hectares in the early 1990s.
Anthropogenic inputs of excess nutrients into the coastal environment, from agricultural activities and wastewater, have dramatically increased the occurrence of coastal eutrophication and hypoxia. Worldwide there are now more than 500 “dead zones” covering 250,000 km2, with the number doubling every ten years since the 1960s.
Agriculture is a significant water user in Europe, accounting for around 33% of total water use. This share varies markedly, however, and can reach up to 80% in parts of southern Europe, where irrigation of crops accounts for virtually all agricultural water use.
According to the OECD Environmental Outlook to 2050, global water demand will increase by 55% due to growing demand from manufacturing (+400%), thermal power plants (+140%) and domestic use (+130%). These competing demands will put water use by farmers at risk. 2.3 billion more people than today - 40% of the global population - will be living in river basins under severe water stress.
Irrigation provides approximately 40% of the world’s food, from an estimated 20% of agricultural land, or about 300 million hectares globally. Almost half of the total area being irrigated worldwide is located in Pakistan, China and India, and covers 80%, 35% and 34% of the cultivated area respectively.