The main uses of water, that is, liquid freshwater, is in agriculture. This is clear based on the statistics from the United Nations, notably UN-Water and the Food and Agriculture Organization (FAO).
UN-Water, through its web site unwater.org (2011c), summarized how water is used worldwide:
This means that crop and livestock production absorbed the bulk of the uses of water. This usage largely consists of irrigation. About 70% of this agricultural use of water comes from aquifers, streams, and lakes.
However, only a minimal portion (20%) of cultivated lands worldwide benefit from irrigation. Nevertheless, there has been an increase in the area of irrigated lands. In 2006, some 301 million hectares (ha) were irrigated, up 116% from 139 million ha in 1961 (FAO 2011). In 2011, statistics supplied by FAOSTAT of FAO (2013) reveal that about 318.3 million ha of land have been equipped for irrigation.
The positive impact of the use of water in irrigating crops may have been thought minuscule, but no. The total area of cultivated lands, including both rainfed (80%) and irrigated (20%), increased by only about 7% to 1.5 billion ha in 2006 from 1.4 billion ha in 1961. However, irrigation typically doubled farm yields. In some crops, yields even quadrupled (unwater 2011a). The number of crops grown in one year also increased from 1 to 2. In developing countries, mean cereal yield was 3.3 tons under irrigated culture compared to only 1.5 tons per hectare in rainfed lands. Irrigation contributed 40% to the world supply of food although only 20% of cultivated lands were irrigated (FAO 2011).
There are reasons why it is important to formulate strategies to further improve efficient use of water or its conservation. As revealed by unwater.org (2011a), one person only needs 2-4 liters (li) of water per day but some 2,000 to 5,000 li of water are needed to produce the same person’s food for one day. Additionally, about 1,000 to 3,000 li are used to produce 1 kg of rice but 13,000 to 15,000 liters are needed to produce 1 kg of beef from animals fed on grains.
Ironically, according to Bruinsma (2003), there appeared to occur a change in diet preference towards meat and animal-based products. The amount of meat consumption in developing countries increased by about 124% from 11.4 kg during the mid-1970s to 25.5 kg per capita in 1997/99 (mean of 3 years is considered). This is with the inclusion of China and Brazil which are highly populous. Without them the percentage increase is only about 41% (from 11 kg to 15.5 kg), but the increase is still considerable.
The land area of the world is about 13 billion hectares. However, only around 12% thereof (1.5 billion ha) are cultivated while 27% is utilized as pastureland for the production of livestock (Turral et al. 2011). Livestock production accounts for the largest use of the world’s land area and contributes about 40% to the gross value of agricultural production. Between the period 1997/99 to 2030, the number of animals under domestication throughout the world will increase from (in millions) 1,497 to 1,858 for cattle and buffalos (24.1% increase), 1,749 to 2,309 for sheep and goats (32%), 873 to 1,062 for pigs (21.6%), and 15,067 to 24,804 or 64.6% increase for poultry (Bruinsma 2003).
Approximately 40% of water used for irrigation in the world originate from ice and snowmelt in the Himalayas and other mountain ranges. However, it is expected that the amount of snow and ice in Himalaya will go down by about 20% by 2030 due to climate change (Turral et al. 2011; UN-Water 2011a).
Increasing the area of irrigated lands is a logical strategy to increase food
production through agriculture in view of the projected increase in human
population (about 2.4 billion more from 2010 to 2050). As already stated,
statistics show that irrigation increases farm yields annually and per unit
area of land.
The supply of water is not unlimited. According to unwater.org (2011b), the quantity of freshwater for ecosystem and human use is limited to 200,000 km3, equivalent to 52,834.4 trillion gallons or 200,000 trillion liters.
But in 2050, human population is projected to increase to about 9.3 billion (9,306,128,000). Multiplying by the given maximum uses of water per day (4 li for drinking and 5,000 li for food), the overall use of water will amount to about 37.2 billion li for drinking and 46.53 trillion li for food or a total of about 46.57 trillion li every day.
Assuming that these are the only uses of water, it will take 4,295 days, or about 12 years for the available supply of water (200,000 km3) to be exhausted if there is no replenishment through the hydrologic cycle. But the assumption is wrong.
Man has other more uses of water such as for bathing, washing and cooking. Agriculture uses 70% of world water and engages in activities other than food production. Also, 22% of water is used as coolant and for
other industrial purposes. Moreover, its availability differs from country to
country and according to season. Population density likewise differs by country
and so it is expected that the pressure of scarce water will be more felt in
those which are thickly populated per unit area of land.
according to unwater.org (2011c), there will be 1.8 billion people in countries
and regions with serious water supply problems. It is also predicted that there
will be 50% increase in the rate of water withdrawal in 2025 in developing
countries and 18% in developed countries. In Europe, the rate of withdrawal of
groundwater has already exceeded the rate of recharge in 60% of cities having
population in excess of 100,000 people. Turral et al. (2011) cited that
overall use of water in crop production, attributed to evapotranspiration, can increase from 7,130 km3 in year 2000 to as
much as 13,500 km3 in 2050, an increase of up to 89.3 percent.
(Note: This is an
introductory review of the uses of water. For further details, the listed
references are suggested reading. )
BRUINSMA J. 2003. World agriculture: towards 2015/2030: an FAO
perspective. London: Earthscan Publications Ltd. Retrieved March 30,
2013 from ftp://ftp.fao.org/docrep/fao/005/y4252e/y4252e.pdf.
[FAO] Food and Agriculture Organization of the United Nations. 2011. Fast facts: The state of world’s land and water resources. Retrieved Mar. 28, 2013 from http://www.fao.org/fileadmin/user_upload/newsroom/docs/en-solaw-facts_1.pdf.
[FAO] Food and Agriculture Organization of the United Nations. 2013. FAOSTAT. Retrieved Mar. 29, 2013 from http://faostat3.fao.org/home/index.html#DOWNLOAD.
TURRAL H, Burke J, Faurès J. 2011. Climate change, water and food security. Rome, Italy: Food and Agriculture Organization of the United Nations. Retrieved Mar. 29, 2013 from http://www.fao.org/docrep/014/i2096e/i2096e.pdf.
UNWATER.ORG. 2011a. Water, agriculture and food security. Retrieved Mar. 24, 2013 from http://www.unwater.org/statistics_sec.html.
UNWATER.ORG. 2011b . Water resources. Retrieved Mar. 24, 2013 from http://www.unwater.org/statistics_res.html.
UNWATER.ORG. 2011c. Water use. Retrieved Mar. 24, 2013 from http://www.unwater.org/statistics_use.html.
(Ben G. Bareja March 2013)