Urban Landscapes in the 21st Century – Part 5: The Evolution of Cities

In urban environments water plays many roles. It is used for drinking, cooking, washing, gardening, parks, recreation, sanitation, and manufacturing. On coastlines and where rivers cut through cities it serves as a transportation artery.

The Drinking Water Dilemma

In a 1996 published paper the author provided statistics showing that freshwater consumption was 40 times greater than consumption in 1700 and that half of that increase had taken place since 1950. With human population continuing to grow this may mean cities in the Developed and Developing World may find themselves without enough freshwater to sustain their populations.For the cities of the Developing World, growing faster and with less freshwater infrastructure the crisis will be unlike anything we have seen before.

In a 2010 published article in 24/7 Wall Street, the authors listed 10 of the largest American cities most likely to run out of freshwater. In order of most likely to least likely they are:

1. Los Angeles
2. Houston
3. Phoenix
4. San Antonio
5. San Francisco-Oakland-San Jose
6. Fort Worth
7. Las Vegas
8. Tucson
9. Atlanta
10. Orlando

Note that these cities occupy the southern areas of the U.S. and many are in the Southwest where migration over the last half century has resulted in increasing water demands for growing populations. Los Angeles long ago ran out of local freshwater and relies heavily on water from the Colorado River basin. Los Angeles receives less than 380 millimeters (15 inches) of rain annually. But its population continues to grow attracting low-income migrants from Mexico and Central America.

Houston, the second city on the list, receives a lot more rain than Los Angeles, 1,400 millimeters (53 inches) annually. This sounds like more than enough to meet population demands. But that’s not the case. Houston is growing rapidly and the withdrawal of water from the local aquifer under the city is causing the land to subside leading to rising sea levels and salinization of freshwater sources.This is a problem for coastal cities in Florida as well.

Many cities on this list are in semi-desert and desert climate zones already water deficient. As these cities continue to grow because of their favourable climate they are depleting all the freshwater sources close by as well as those far away. Like Los Angeles, the cities of Phoenix, Tucson and Las Vegas rely on water from the Colorado River. At their current rates of growth the Colorado River may run dry by the mid-century.

Some recent studies estimate that reservoirs in the Colorado River basin will run dry by 2057. Water demands on the river from urban growth in the U.S. southwest are increasingly unsustainable. Source: PlanetSave

Drought in the Southern U.S. has put other cities at risk. Atlanta, Fort Worth and Orlando have depleted freshwater reservoirs and aquifers through droughts that seem to be longer in duration. Proposed solutions include piping water from wetter areas of the United States and even Canada. This type of solution has led to pushback from local populations at the source who fear that their freshwater resources will be depleted by this growing demand.

For coastal cities like Los Angeles, San Francisco and Houston, desalinization of seawater represents a technological solution that comes at a pretty steep price. Like their Australian urban cousins, most which hug the coastline of that country, desalinization is in their present or near future.

The Freshwater Crisis in the Developing World

In a 1995 study, 31 countries representing almost 500 million population were classified as freshwater stressed or scarce. What is the definition of “stressed” and “scarce?” Hydrologists use the following benchmarks to measure freshwater availability.

1. Adequate = greater than 1,700 cubic meters of water per person per year
2. Stressed = 1,000 and 1,700 cubic meters
3. Scarce = less than 1,000 cubic meters

Most countries of the Northern Hemisphere are classified as Category 1. The exceptions are countries in Central Asia (former republics in the Soviet Union) and regions within very large countries like Russia and the United States (see discussion above on U.S. cities running out of water).

Countries in the Southern Hemisphere more often fit Category 2 and 3. For these countries scarce is becoming more common, and particularly reaching dangerous levels in countries defined as part of the Developing World where migration to cities is continuing to accelerate along with water consumption.

Category 3 has many implications. Freshwater scarcity puts agriculture, the environment, population health and economic growth in jeopardy.

What is even more disturbing is what is forecasted for the Developing World between now and mid-century. By 2025 based on current consumption trends, the number of Category 2 and 3 countries will grow to 50 affecting 3.3 billion people. And by 2050, Category 2 and 3 countries will number 54 and 4 billion people. Almost all affected countries will be in Africa and the Middle East.

In our next blog on the urban landscape we will look at how new urban models, water usage patterns and technology can help avert the growing scarcity of freshwater supply.

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.