Water

The intensification of food production and the huge increase in output in the last two centuries have been partially achieved by a massive increase in the amount of irrigated land. In 1800 there were about 8 million hectares under irrigation across the world. In the 19^th century this area quintupled to about 40 million hectares. In the 20^th century there was another 7-fold increase to about 275 million hectares. Overall the growth was just over 34-fold. In total slightly over 15% of the world’s arable land is now irrigated, with the highest proportion in Asia. Irrigation allows crops to be grown where otherwise it would not be possible and it does (as the earliest farmers 7,000 years ago discovered) increase yields dramatically – is south Asia only a third of the rice-growing area is irrigated yet it produces almost two-thirds of the total crop.

However, irrigation can badly degrade the land and lead to waterlogging and salinisation as the early societies in Sumer discovered over 4,000 years ago. These effects are now found in half of the irrigated land in Syria and Iraq, a quarter of the irrigated land in the United States and four-fifths of the irrigated area in the Punjab. In the last 30 years of its existence the Soviet Union lost more previously cultivated land to waterlogging and salinisation than the cultivated area of Ireland and Belgium combined. The main growth in the irrigated area came in the middle of the 20^th century when it increased at about 3% a year. After 1978 this slowed to about 1% a year. However, in the last quarter of the 20^th century the loss of irrigated land was at about 1% a year so that there was little net increase in the area under irrigation.

The expansion of the irrigated area has, alongside a rising population, the demands of industry and increasing consumption per head, placed severe pressure on the world’s water resources.
The world depends on a very limited amount of fresh water – 97% of the world’s water is salt water in the oceans and two-thirds of the fresh water is frozen, mainly in Antarctica.
Most of the rest is in underground aquifers that are too deep to access.
Only a quarter of 1% of the world’s fresh water is in lakes and rivers and a quarter of that is in Lake Baikal in Siberia.
The world’s annual water consumption has risen from roughly 110 cubic kilometres in 1700 to about 5,200 cubic kilometres now – a 47-fold increase but with most of that increase concentrated in the last 50 years.
Throughout history most human use of water has been for irrigation – well over three-quarters of total usage. Nearly all the rest is used by industry.
In India and China about two-thirds of irrigation water is lost through evaporation and seepage out of irrigation canals and in the United States half the water is lost.
Most of the increase in world water use was a ‘free ride’ – using up the water resources of underground aquifers far faster than the rate at which they are replenished.
Fossil aquifers such as the Ogallala under the Great Plains of the United States, that of the North China Plain and the one under Saudi Arabia cannot be replaced at all in any useful timescale.
The Ogallala aquifer is an underground river stretching from Texas to South Dakota that has been accumulated over about 25,000 years.
In the 30 years after 1950 water was being withdrawn at 10 times the rate of replenishment. As wells went deeper to reach the remaining water costs rose until they became uneconomic.
Even the most optimistic estimates suggest that the remaining water will run out in the period 2010-2020, earlier if there is a drought. The effects on agriculture of the collapse of water supplies will be catastrophic.
In India the number of wells rose from 800,000 in 1975 to 22 million in 2002. In many areas the water table is falling at one metre a year.
In Pakistan the water table in the area around Quetta is falling at about 3½ metres a year and the area will run out of water in the next decade.
In Yemen the water table is falling at 2 metres a year and the capital city of Sana’a is expected to have no water within the next few years.
Mexico City is built on a lake and its water use grew 35-fold in the 20^th century, causing the city to sink 5 metres into the lake.
In the 40 years after 1920 Tokyo sank 5 metres because of water extraction but the introduction of strict controls managed to stabilise the situation.

In Saudi Arabia the government decided to use its oil wealth to become self-sufficient in wheat. This involved subsidising domestic production at 5 times the world price and extracting huge amounts of water from the underground aquifer. Half the reserves of water available when extraction started in 1984 have now been used and some wells need to be a kilometre deep in order to find water. The policy is economically and environmentally unsustainable. The situation in China is equally grim. Over-extraction of water from the 4,000-kilometre-long Yellow River caused it to run dry in 1972 and since 1985 for part of every year it fails to reach the sea. The water level in the aquifer under the North China Plain dropped 3 metres in just one year (2000) and around Beijing wells need to be a kilometre deep to reach fresh water. The cities face a water crisis and farm output is falling because of a shortage of water. The wheat harvest in the area fell by 30% between 1997 and 2003. This is one of the major grain-producing areas in China and as a result the Chinese grain harvest fell by almost 14% in the period – an amount equal to the total Canadian grain harvest. The World Bank has warned of ‘catastrophic consequences for future generations.’

The increasing shortage of water has led to a growing number of disputes over this key resource. As water shortages grow more severe over the next few decades the number of conflicts is likely to rise.
In a drive to provide irrigation water (and hydroelectric power for industry) numerous huge dams have been built across the world – in the last half of the 20^th century the number rose from 5,000 to 40,000.
Many of these projects have been highly damaging both environmentally and socially.
Evaporation rates in tropical areas are very high so that much of the water is lost and deforestation of the surrounding slopes produces very high run-off and siltation rates.
The Laoying dam project had to be abandoned before it was completed because of siltation.
A clear illustration of the problems caused by large dams can be found in the Nile. The dam has not solved Egypt’s water problems – at the beginning of the 21^st century Egypt was facing one of the most acute water shortages in the world.

The Aral Sea

The greatest single water and irrigation disaster in world history took place in the last third of the 20^th century in what was then the Soviet Union.

Modern agriculture has, like its predecessors, produced a mixture of achievements, problems, and environmental disasters. What has changed is the scale of the problems. Although more people have been fed than ever before this has been done on a highly unequal basis. Most of the population of the industrialised world has a rich (in many cases over-rich) and varied diet while a large part of the world’s population suffers from a poor diet, malnutrition and the diseases associated with these conditions. The need to bring more land into production and the intensification of that production has produced numerous environmental problems – deforestation, soil erosion, desertification, salinisation and the over-loading of the land and water with fertilisers, pesticides and herbicides. The problem that has affected agricultural societies throughout history – ensuring an adequate supply of food for all – has still not been solved on a global scale.

Chapter 12: The Second Great Transition

The second great transition in human history involved the exploitation of the earth’s vast (but limited) stocks of fossil fuels.

A Green History of the World Part 15

Water

Chapter 12: The Second Great Transition

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