Agriculture is regarded the most water consuming activity on Earth. More than 2,000 litres of water is used in order to produce enough food for one person for one day.
Less than 3% of the world's water is fresh - the rest is seawater and undrinkable.
Of this 3% over 2.5% is frozen, locked up in Antarctica, the Arctic and glaciers, and not available to man and 0.5% Fresh water available.
Thus humanity must rely on this 0.5% for all of man's and ecosystem's fresh water needs
10,000,000 km3 stored in underground aquifers. Since 1950 there has been a rapid expansion of groundwater exploitation providing: 50% of all drinking water;
40% of industrial water; and 20% of irrigation water. 119,000 km3 net of rainfall falling on land after accounting for evaporation.
91,000 km3 in natural lakes.
Over 5,000 km3 in man made storage facilities reservoirs. There has been a 7 fold increase in global storage capacity since 1950.
2,120 km3 in rivers - constantly replaced from rainfall and melting snow and ice.
As farmers, industry and people take too much water there is nothing left for nature. The concept of water stress is relatively simple: it applies to situations where there is not enough water for all uses, whether agricultural, industrial or domestic. Defining thresholds for stress in terms of available water per capita is more complex, however, entailing assumptions about water use and its efficiency. Nevertheless, it has been proposed that when annual per capita renewable freshwater availability is less than 1,700 cubic meters, countries begin to experience periodic or regular water stress. Below 1,000 cubic meters, water scarcity begins to hamper economic development and human health and well-being.
How much Water is available to us?
There is only 2.590% of water fresh for consumption.
And the remaining 97.410% is found in oceans.
Within the above 2.590% of fresh water, 1.984% is found in Ice Caps & Glaciers, 0.592% is ground water and only 0.014% is the accessible ground water.
Out of 0.014% of accessible fresh water, 0.007% is found in Lakes, 0.0001% in Rivers, 0.0001% in Biota and the last 0.001 in the Atmosphere.
Predicted water shortage by 2025
One third of the world population live in water scarce countries and this is set to rise to two thirds within 25 years. These countries include Africa and Asia. And the main cause of the problem is primarily due to increasing population.
How many litres of water are expected to produce a kilogram of food?
Global water use has tripled since 1950 and has been increasing faster than the world population. In that case much of the water extracted ends up wasted.
Agriculture is the world biggest water guzzler as it takes at least 2,000 litres to produce enough food for one person for one day.
· Potatoes 1,000 litres
· Maize 1,400 litres
· Wheat 1,450 litres
· Rice 3,450 litres
· Chicken 4,600 litres
· Beef 42,500 litres
There are some populations that are using a smallest amount amount of water each day per person.
· Gambia 4.5
· Mali 8.0
· Somalia 8.9
· Mozambique 9.3
· Uganda 9.3
· Cambodia 9.5
· Tanzania 10.1
What is our current position in South Africa?
The World’s average annual rainfall is approximately 860mm. South Africa is approximately 502mm. 65% of South Africa gets less than 500mm p.a. Annual runoff of all rivers is estimated at about 53 500mi. cubic meters. Only 62 percent runoff plus about 5400mi. cubic metres of ground water is possibly economically useable. This makes 2,347 litres per person per day, potentially available for our present population of 45 million. 461 litres per day required for people with low lifestyle. Weighted average for the present population is 638 litres/dap/d.