Agriculture – Part 5: Water

Agriculture and freshwater are inextricably linked. Water is essential to agricultural production and food security. Freshwater is an increasingly scarce resource yet indispensable for the existence of all life on the planet. There is no substitute for it.

In the 20th century our world population grew from 1.6 billion in 1900 to over 6 billion by 2000. In that same period our freshwater usage increased by a factor of 6. It is estimated by 2025 that 1/3 of our human population will reside in freshwater scarce countries. As we approach 9 billion or more by 2050 freshwater will become even more scarce.

As freshwater demands increase the volume of water which is finite will lead to a decline in the amount per human inhabitant. Based on a recent UNESCO report, the availability of freshwater will decline from an average of  7,300 cubic meters in 1995 to 4,800 in 2025 per person.

Conservation techniques can help us manage freshwater resources better. Applying technology to create water from air, or to desalinate it from the ocean can increase availability at an increased cost. An equivalent to a cap-and-trade system on freshwater usage can stimulate improved handling of freshwater resources, change agricultural practices and land usage patterns,  and stimulate innovation. Through necessity, the 21st century will have to address freshwater with the same energy it puts into implementing energy conservation, renewable energy, and mitigation of climate change.

Freshwater Usage in Agriculture Today

The World Bank keeps data records on agricultural usage of  freshwater by country. The statistics are revealing. Many of the poorest countries in the world are using water for agriculture at unsustainable rates. The following partial list groups countries by categories of my choosing:

Areas with ongoing wars, and civil unrest:

Afghanistan 99%

Egypt 86%

Eritrea 95%

Iran 92%

Iraq 79%

Israel 58%

Libya 83%

Pakistan 94%

Somalia 99%

Sudan 97%

Syria 88%

Areas stressed by over population

Bangladesh 88%

China 65%

India 90%

Indonesia 82%

Although the lack of freshwater may not be the primary creator of stress for the countries mentioned above  there appears to be a correlation between war and over population, and the scarcity of freshwater.

On the other hand there are countries that have industrialized farming and are net food exporters. Their agricultural freshwater usage patterns are different. Here is a representative sample:

Argentina 66%.

Australia 74%

Canada 12%

United States 40%

Having lived in Canada all my life, a country that has never faced a freshwater shortage  it is difficult to appreciate the challenge that so many countries face when because of freshwater scarcity. Increasingly even net food exporters like Australia and Argentina are experiencing drier conditions and are drawing on freshwater resources in much higher amounts than in the past. So scarcity is a growing problem everywhere.

Climate Change and Freshwater

In our last blog we talked about the impact of climate change on agriculture. Where climate change will have its greatest impact is in the distribution of  freshwater. This will affect aquifers, snow packs, mountain glaciers, lake levels, river flow and volume, and the quantity and intensity of storms.

Atmospheric warming will shift growing zones. Sub-tropical vegetation will migrate further north. Arid regions will get drier leading to increased desertification. Wet areas are expected to get far wetter. Seasonal variation in precipitation will become more extreme. As glaciers and snow packs shrink the rivers that rely on them as water sources will experience greater fluctuations in volume. As sea levels rise coastal aquifers will be invaded by seawater and coastal land under tillage will be lost either through increased salinization or inundation.

Human Land Use,  Migration  and Freshwater

For more than 50 years in the United States human migration has steadily increased the population of southwestern states while depleting Great Lakes and northeastern states. The population shift is away from where freshwater exists in abundance to where it is scarce.

Increasingly humanity resides in cities. Most of our urban population lives along coasts whether by lakes and rivers or by seas and oceans.

Increasingly humanity puts forest land under cultivation removing trees and affecting groundwater tables and soil stability.

Canada which has more freshwater resources than any other country on the planet is thinly populated and even it  is experiencing freshwater challenges in the Prairies as urban centres and agriculture compete for finite surface and subsurface water resources. Add to that the use of water in mining, oil sands extraction, and industry and you have a growing freshwater challenge.

Global Distribution of Freshwater Sources

Earth has water in abundance yet we face a freshwater crisis. That’s because most of the water we have isn’t fresh. And the freshwater that we do have is not distributed evenly or in locations where our largest human populations live.

The surface of the planet features oceans of saltwater, in fact 97.14% of the water on the planet. The preponderance of the remaining water, around 2% is locked up in polar and mountain ice and snow packs. Lakes, streams and rivers represent just 0.014% of the total. The rest is groundwater at 0.592%.

When you view Earth’s northern hemisphere from space you see the dominant features on the planet’s surface, water and ice.

A northern view of our planet displays two of its main features - abundant water and ice.

Other than the large lakes and river systems visible on the lower left  in North America most of the freshwater in this picture is in sea ice or glaciers. At the South Pole Antarctica is locked in ice surrounded by an endless ocean.

Antarctica has been icebound for 35 million years and contains 61% of the freshwater on the planet.

Where the Farms Are Today is not Necessarily Where Freshwater is Abundant

The Case of the United States

The American Mississippi-Missouri-Ohio River basin, California and Florida represent prime agricultural areas in  the United States. These areas are increasingly feeling the demand for freshwater from urban centres, and for industrial use in addition to agriculture.

Freshwater usage as a percentage of precipitation amounts to about 30% in much of the American Great Plains. In some areas experiencing prolonged droughts such as Texas and parts of Oklahoma, Arkansas and Louisiana, that usage exceeds 100%.

California produces 400 different agricultural products including almost 50% of the fresh fruit, vegetables and nuts consumed in the United States. Much of what California farms produce goes to export representing 15% of the United States total exports. California farms rely for freshwater on the river and groundwater of the San Joaquin-Sacramento River system fed by glacier and snow pack melt from the Sierra Nevada Mountains.

Much of the land under tillage in California would not be producing crops if it weren’t for major irrigation projects started in the 1930s moving water from Northern California to farms in the southern part of the Central Valley. Increasing urban growth and industrial freshwater demands have led to additional water projects to move freshwater from locations outside the state. As a result Southern California receives 60%  of its freshwater from the Colorado River.

For such an important agricultural centre of production the growing challenges of declining freshwater sources is leading to major efforts to conserve water through a variety of changes in agricultural practices. This is leading to new irrigation techniques to deliver water more directly to targeted crops, recycling and treatment of  grey water for use in irrigation, and fallowing of land.

For Florida the threat to citrus crops comes not just from cyclical drought but also from increased salinity in the aquifer from which much of the freshwater is derived. Urban demands in Southern Florida compete directly with agricultural requirements. In recent years Lake Okeechobee has experienced declining water levels. Because so much of Florida is at or near sea level, any decline in water levels in the lake means gravity cannot assist in moving the water and imposes  an extra cost in getting it to cities and farms.

Florida agriculture suffers further from its near sea level elevation. In some coastal areas, because of excessive drawing of groundwater, salt water from the ocean is making its way into the aquifer leading to high salinity levels.

The Case of Australia

Australia is at the forefront of the consequences of climate change. The country has experienced every extreme weather event over the last few years including flooding from precipitation in excess of the norm tp prolonged heat waves and drought conditions leading to firestorms.

The cities of Australia are already feeling the scarcity of freshwater with acute shortages predicted by 2030.  Since 2008 Australia has been closely monitoring water usage for agriculture and urban centres. By imposing severe limits on water use, increasing household water charges, developing reverse osmosis desalinization plants, investing in new farm irrigation technology and pipelines to eliminate leaks, $10 billion have led to a 40% reduction in urban freshwater consumption.

Already the driest continent and country in the world, Australia has more to lose than most as climate change alters rainfall and temperature patterns.

The Future of Agricultural Water Management

Climate change is one of a number of drivers that is altering farming practices and leading to dramatic proposals to shift freshwater from where it falls and collects today to where farming and urban centres are and will be located in the future.

Among the solutions are the following:

  1. Changing  the types of crops grown to reflect changing climate and precipitation patterns.
  2. Genetically altering crops to better grow in drier conditions with elevated CO2 and other greenhouse gases.
  3. Improved dry farming techniques with less irrigation in areas prone to drought.
  4. Abandoning agricultural land that is no longer viable because of prolonged drought.
  5. Rethinking urban settlement and encouraging people to move away from drought prone areas.
  6. Recycling water to create closed farming systems.
  7. Reducing CO2, CH4 and N2O emissions to mitigate the consequences of global warming.
  8. Building reverse-osmosis and other types of desalinization plants near urban coastal areas to reduce city demand on other freshwater resources.
  9. Creating and enforcing water usage and trade systems that reward conservation and punish polluters and excessive users.
  10. Building water pipelines to bring water from other water sources to areas where the water is needed for growing crops. This is probably among the most controversial of solutions because of its potential ecological implications.

An Update to this posting:

In this blog I talked about methods for extracting water from the air. One of these ideas has recently received the James Dyson Award.

The technology is called Airdrop, developed by an Australian industrial designer Edward Linacre. Inspired by studying the way the Namibian Beetle survives in that desert by collecting water from early morning dew using its hydrophilic skin, Linacre designed a low-tech solution that extracts water molecules form the air by lowering its temperature so that condensation occurs.

The technology is inexpensive to implement and can be scaled for domestic or large-scale agricultural use.  Using a turbine driven by wind, solar power or another external power source, warm air is driven underground. When the air reaches a depth of 2 metres (6.5 feet) the surrounding soil’s cooler temperatures (5C or 9 F degrees) causes the water in the air to condense.

Airdrop Irrigation is a low-tech solution that can be used in drought-prone areas for agriculture and domestic purposes.

Airdrop uses copper coils as the condensation medium. The water is collected in an underground storage tank and is then pumped underground to plants using subsurface drip irrigation. The Airdrop requires very little power to operate.

Len Rosen lives in Toronto, Ontario, Canada. He is a researcher and writer who has a fascination with science and technology. He is married with a daughter who works in radio, and a miniature red poodle who is his daily companion on walks of discovery. More...