Unfortunately, of this volume 97.5% is salt water, 99% of it being in the seas and oceans, and only the remaining 2.5% is fresh. Of the 2.5% fresh water, 68.7% is frozen in the poles and glaciers, 30.1% is underground and 1.2% is on the Earth’s surface. Only 21.4% of surface water is in lakes and rivers, the remainder is either in the form of ice, in the atmosphere or in other forms making it difficult to use.
In summary, the main sources of water for human development use are ground waters, rivers and lakes, which in total represents less than 0.76% of the water on our planet, that is about 10,500,000 cubic kilometers. If this water could be distributed equitably to each inhabitant on our planet, it would correspond to about 1,440,000 cubic meters2. This figure ensures that, globally, there is enough water in our world for future generations, although 90% are not renewable resources and their location does not correspond exactly to the areas of higher demographic development, of greater demand for water. This is the main cause of water stress in large world regions, either due to lack of natural resources or due to lack of economic resources to manage it.
According to the F.A.O. and the UN, global water use was 4,000 cubic kilometers per year in 2010, in global average 69% used for agriculture, 19% for industry and 12% for municipal use, including drinking water. The ratios (% agriculture, industry and municipal) differ markedly between world regions and the degree of economic development, ranging respectively from 94% – 1% – 5% for the African Sahel to 9% – 68% – 23% for Central Europe.
The water stress degree determines consumption and economic development in a very remarkable way. In addition, the water leaks in the networks and non-revenue water represent more than 30% worldwide, something that should be reduced in order to optimize and rationalize the consumption.
Los Glaciales National Park
Santa Cruz Province - Argentina 2017
Yamanouch - Japan 2018
Jaipur - India 2017
75% of the water in the industrial sector is used in the production of electricity, a consumption that should be reduced in the future with the more progressive use of renewable energy, but the rest of the industry will need to triple the consumption by 2050 to maintain the levels of progress, especially in developing countries. The “Water-Food” nexus is very important, and with the growth of the world population, the consumption of water for agricultural use will continue to increase, as will the demand for high quality drinking water for municipal use. How long can the growth of water consumption be prolonged when the world population reaches 9.7 billion in 2050? Each person needs to drink only around 2 liters per day; however, if the consumption distribution in municipal uses were uniform among the current 7.3 billion inhabitants of the planet, it would mean that the average consumption would be about 180 liters per inhabitant per day. These average figures don’t represent the reality; which ranges from the less than 10 liters in some rural African areas, or arid areas in South America, to more than 600 liters in some North American states. This consumption of water, distributed as potable, is used in all domestic areas and public services in addition to those 2 liters necessary for the human physical subsistence. One of the most important recent milestones in July 2010 was the recognition by the United Nations General Assembly of the human right to water and sanitation. The Assembly recognised the right of all humans to a sufficient amount of water for domestic and personal use (between 50 and 100 liters of water per person per day) that should be safe, accessible and affordable (the cost of water should not exceed 3% of household income). Despite this fact, 2.1 billion people still do not have access to safe managed drinking water.
Water treatment began in the early twentieth century and dramatically reduced mortality among the population, especially children. But to our great dismay, more than one hundred years later, non-potable water and poor sanitation are the main cause of the death of 1.5 million children every year, most of them under five, in developing countries.
Currently around 4,500 million people still lack safe managed sanitation services, 2,300 million of which do not have basic sanitation facilities, such as toilets or latrines. That’s more than 30% of the world’s population! And to complete these figures, it is important to highlight that 80% of wastewater returns to the ecosystem without being treated or reused.
Despite the great technical progresses of the twentieth and twenty-first centuries, a large part of the world’s population still does not have access to them.
Over the past 4 decades, these technical advances have led to great developments in desalination of brackish and sea waters. This technology allows to generate new water resources from resources that could not formerly be used due to the high content of dissolved salts, such as in seawater. Nowadays desalination is a mature and well experienced technology with over 50 years of experience. To date, more than 20,000 desalination plants have been built in over 150 countries around the world, with a total production capacity of more than 105,000,000 cubic meters per day. Desalination technology by reverse osmosis membranes has seen huge progress, minimizing its energy consumption, being very environmentally friendly and able to produce drinking water at a very low cost, between 0.5 and 1.0 U.S. dollars per cubic meter (only 0.0005 or 0.001 dollars per liter).
São Paulo - Brazil 2014
Cremation at Manikarnika Ghat
Varanasi - India 2017
Miguel Angel SANZ President of the International Desalination Association
1 1 cubic kilometer (km3) is equal to 1,000,000,000 cubic meters
2 1 cubic meter (m3) is equal to 1,000 liters