Use of water in food and agriculture

Food and agriculture are the largest consumers of water, requiring one hundred times more than we use for personal needs. Up to 70 % of the water we take from rivers and groundwater goes into irrigation, about 10% is used in domestic applications and 20% in industry. Currently, about 3600 km3 of freshwater are withdrawn for human use. Of these, roughly half is really consumed as a result of evaporation, incorporation into crops and transpiration from crops. The other half recharges groundwater or surface flows or is lost in unproductive evaporation. Up to 90% of the water withdrawn for domestic use is returned to rivers and aquifers as wastewater and industries typically consume only about 5% of the water they withdraw. This wastewater from domestic sewage systems and industries should be treated before being dismissed.

Since the 1960s the global nutrition has considerably improved, providing more food per capita at progressively lower prices. This performance was possible through high-yielding seeds, irrigation and plant nutrition. As population keeps increasing more food and livestock feed need to be produced in the future and more water applied to this purpose. Irrigate agriculture will have to claim large quantities of water to produce the food required to feed the world. The main source of food for the population of the world is agriculture: this term also includes livestock husbandry, manages fisheries and forestry.

The composition of meals changes gradually as lifestyles change. What agriculture produces is driven by consumer demand, and changes in consumer preferences have an influence on the water needed for food production.
Cereals are by far the most important source of total food consumption: in developing countries the consumption of cereals 30 years ago represented 61% of total calories. It decreased to 56% nowadays and this reflects diet diversification, proving that more countries achieve higher levels of nutrition. It is expected that cereals will continue to supply more than 50% of the food consumed in the foreseeable future. A large proportion of cereals is produced for animal feed.
Food production from the livestock sector includes meat (beef, pork, poultry, etc.), dairy production and eggs.

For vegetative growth and development plants require water in adequate quantity and at the right time. Crops have very specific water requirements, and these vary depending on local climate conditions. The production of meat requires between six and twenty time more water than for cereals.

The following tables give an overview of the water consumption in food and agriculture.
Specific values for the water equivalent of a selection of food products are given in the first table. The second table shows the amount of water needed necessary for a few products per unit of consumption. A glass of wine acquires for example 120 liters of water, a hamburger 2.400 liters, a cotton shirt 4.000 liters and a couple of shoes made out of cows leather 8.000 liters.
The third table gives an overview of the amount of virtual water used in the different kind of agricultural products. The big difference between the countries is due to the climate, applied technology and the amount of production related to it.

Product

Unit

Equivalent water in m3 per unit

Cattle

head

4000

Sheep and goats

head

500

Fresh beef

kg

15

Fresh lamb

kg

10

Fresh poultry

kg

6

Cereals

kg

1.5

Citrus fruits

kg

1

Palm oil

kg

2

Pulses, roots and tubers

kg

1

Product

Quantity

Equivalent water in liters

glass of beer

250 ml

75

glass of wine

125 ml

120

glass of milk

200 ml

200

glass of apple juice

200 ml

190

cup of coffee

125 ml

140

glass of orange juice

200 ml

170

cup of tea

250 ml

35

chips bag

200 g

185

slice of bread

30 g

40

egg

40 g

135

slice of bread with cheese

30 g + 10 g

90

hamburger

150 g

2400

potato

100 g

25

tomato

70 g

13

apple

100 g

70

orange

100 g

50

cotton T-shirt

500 g

4100

pair of shoes

1

8000

sheet A4 paper

80g/m2

10

microchip

2 g

32

Amount of virtual water per food per country in m3/ton

U.S.

China

India

Russia

Indo
nesia

Austra
lia

Brazil

Japan

Mexico

Italy

Nether
lands

World Average

Rice

1903

1972

4254

3584

3209

1525

4600

1822

3257

2506

-

3419

Wheat

849

690

1654

2375

-

1588

1616

734

1066

2421

619

1334

Corn

489

801

1937

1397

1285

744

118o

1493

1744

530

408

909

Soya beans

1869

2617

4124

3933

2030

2106

1076

2326

3177

1506

-

1789

Sugarcane

103

117

159

-

164

141

155

120

171

-

-

175

Cottonseed

2535

1419

8264

-

4453

1887

2777

-

2127

-

-

3644

Carton plaxel

5733

3210

18694

-

10072

4268

6281

-

4812

-

-

8242

Coconut

749

2255

-

2071

-

1590

-

1954

-

-

2545

Roast coffee

5790

7488

14500

-

21030

-

16633

-

33475

-

-

20682

Tea leaves

11110

7002

3002

9474

-

6592

4940

-

-

-

9205

Beef

13193

12560

16482

21028

14818

17112

16961

11019

37762

21167

11681

15497

Pork

3946

2211

4397

6947

3938

5909

4818

4962

6559

6377

3790

4856

Goat's meat

3082

3994

5i87

5290

4543

3839

4175

2560

10252

4180

2791

4043

Mutton

5977

5202

6692

7621

5956

6947

6267

3571

16878

7572

5298

6143

Chicken

2389

3652

7736

5763

5549

2914

3913

2977

5013

2198

2222

3918

Eggs

1510

3550

7531

4919

5400

1844

3337

1884

4277

1389

1404

3340

Milk

695

1000

1369

1345

1143

915

1001

812

2382

861

641

990

Milk powder

3234

4648

6368

6253

5317

4255

4654

3774

11077

4005

2982

4602

Cheese

3457

4963

6793

6671

5675

4544

4969

4032

11805

4278

3190

4914

Cow leather

14190

13513

17710

22575

15929

18384

18222

11864

40482

22724

12572

16656

The amount of water involved in agriculture is significant and most of it is provided directly by rainfall. A rough calculation of global water needs for food production can be based on the specific water requirements to produce food for one person. The present average food ingest 2800 kcal/person/day may require 1000 m3 per year to be produced. The world population is about 6 billion, so water needed to produce the necessary food, excluding water losses due to the irrigation system, is 6000 km3. Most of it is provided by rainfall stored in the soil profile and only 15% is provided through irrigation. Irrigation therefore needs 900 km3 of water per year for food crops. On average just about 40% of water withdrawn from rivers, lakes and aquifers for agriculture effectively contribute to crop production (the rest is lost through evaporation and deep infiltration). Consequently the current global water withdrawals for irrigation are estimated to be about 2000 to 2500 km3 per year.

The irrigation level varies from area to area, mostly depending on climate conditions and on the development of irrigation infrastrure. The following figure shows the area equipped for irrigation as percentage of cultivated land by country.

Irrigation-water management has a log way to adapt to the increasing production requirements, however water-saving technologies are already available and can significantly reduce the waste of water. If incentives are in place, as increasing the price of irrigation water, farmers will adopt water-saving irrigation technologies. The main technologies likely to be used in developing countries, where labour is normally abundant but capital scarce, are underground and drip irrigation. Both technologies depend on the frequent application of small amounts of water as directly as possible to the roots of crops. Reducing the pollution loads of water used by farms, industries and urban areas would enable much more of it to be re-used in irrigation. There are enormous potential benefits to be had from the use of wastewater for irrigation.

Agriculture will remain the dominant user of water at the global level. In many countries, in particular those situated in the arid and semi-arid regions of the world, this dependency can be expected to intensify. The contribution of irrigated agriculture to food production is substantial but in future the rate of growth will be lower than in the past. Both irrigated and non-irrigated agriculture still have scope for increasing productivity, including water productivity. Arguably, the expansion of irrigated agriculture protected people on the nutritional fringe from premature death, and preserved tracts of land under forest and wetlands from encroachment by hard-pressed farmers.

However, pressures to encroach on such lands persist.

Sources:

  • Agriculture, food and water – a contribution to the World Water Development Report, FAO 2003

  • Crop and drops – FAO 2002

  • H2O Tijdschrift voor watervoorziening en waterbeheer – N 4, February 2005



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