Water covers approximately 75% of the earth’s surface; It is fundamental for both environmental and social processes and indispensable for the emergence and development of life. Currently we are altering aquatic systems at an accelerated pace and we face very serious problems related to the use and maintenance of this valuable resource.
Water forms a large layer, which we call the hydrosphere, on the Earth’s surface and its distribution area is estimated to cover 510 million km2. The total volume of water on the planet is approximately 1,390 million km3. These are the Earth’s water reserves and of them only 0.26% is directly usable by the human species. Seawater, which covers a large part of the planet, contains 33 parts per thousand of dissolved salts, so it would need to undergo prior treatment so that we could give it the uses of fresh water. Water is essential for life, and what is found in our body must have certain characteristics, such as having a certain content and quantity of salts and being free of organisms that harm health. In order for us to consume and use it in our homes, in the production of foods of plant or animal origin and in industry, water must be fresh and of a certain quality.
The water cycle
We can say that water, like energy, is neither created nor destroyed, it is only transformed. It is in continuous circulation and movement, changing from one state to another, but its quantity on the planet remains constant. And the water that rains, is stored or evaporates in streams, rivers, lakes, lagoons and coastal areas finally reaches the oceans, it is part of what is called the hydrological cycle, which consists of three main phases: precipitation, evaporation and flow, both surface and underground. Each of these phases involves transportation, temporary storage and change of state of the water (solid, liquid and gaseous), depending on several factors, such as the temperature at which the water is, the latitude of the geographical area and the time. of the year.
Water is stored in different aquatic systems, such as seas and oceans, lakes, dams, rivers, aquifers, swamps and polar caps, and in each one it is maintained for different periods of time. But of all these systems, only freshwater systems depend largely on the functioning of living beings that are not marine: the plants and animals that need freshwater to live and that are the basis for the development and maintenance of humanity on the earth.
Fresh water reserves are being used by the human species at an extremely fast rate, much faster than it takes to recover, so this resource, considered renewable, is beginning to become non-renewable.
Quantity and quality
The amount of water we have on Earth does not increase or decrease, but the human population has grown drastically, and therefore our need for this resource has also grown. Furthermore, while the amount of water is constant, the way it is distributed over time is not: it is irregular throughout the year and also varies in different years depending on global climatic conditions. Likewise, different ecosystems, such as humid forests, pine forests, scrublands, grasslands or deserts, influence the form and amount of water that penetrates the aquifer systems, its conservation in the soil or its passage into the atmosphere, which causes the availability of this resource to be variable in each region of the planet.
More than 2.2 million people die each year from diseases related to the use of contaminated water.
In addition to geographical and temporal distribution, water quality is another factor to consider, since an important part of the total fresh water we have is unusable because we have modified it by contaminating aquatic systems with a great diversity of substances such as: metals, fats, oils, fuel derivatives, industrial solvents, as well as thousands of types of microorganisms.
It is important to consider that even if you have the necessary amount of water, it may not meet certain conditions that allow adequate use. Water for human use and consumption is different from that which will be used for irrigation, or for the cultivation of aquatic organisms, generation of electrical energy or for industrial use. The problem in some areas is that the same water is applied to any use, without taking into account its quality, which causes serious problems. Those related to health aspects are of utmost importance, but so are those that are causing changes, mostly irreversible, in the planet’s ecosystems.
When referring to water quality, it is necessary to specify what type of substance it contains, whether suspended or dissolved (salts, metals, hydrocarbons, pesticides, etc.), or from what organism (viruses, bacteria, parasites, etc.). ) is treated and in what concentration or quantity it is found, to understand the alteration of the water or the aquatic system and how serious, reversible or irreversible it is.
In urban areas there are various polluting sources that alter the quality of water in surface bodies such as lakes and rivers, which carry substances and organisms to lagoons and coastal areas. But, even when we don’t see them, we are also contaminating groundwater systems with a wide variety of compounds and organisms that are released to the surface and migrate or move downward to reach the aquifers.
Compounds or pollutants can be incorporated into bodies of water punctually, that is, in a single place, or diffusely, covering an entire region. Generally, in a single water storage system, such as a lake for example, several types of pollution occur.
Rural agricultural areas in which fertilizers and pesticides are used are examples of non-point or diffuse pollution, which produces problems in large irrigation areas, where water containing these compounds is discarded. The same thing happens in livestock activity, where a series of alterations are generated by microorganisms that are dragged into bodies of water, contaminating them.
The greatest demand for water occurs in large cities or megalopolises, in which the problem of its supply is linked to the health and well-being of thousands or millions of people who live there and who depend on the existence of water resources to live. enough in the region.
FRESHWATER RESOURCES
Region
Average annual cubic meters per capita
Oceania
53 711
South America
36 988
Central Africa
20 889
North America
16 801
Eastern Europe
14 818
Western Europe
1 771
Central and South Asia
1 465
Central Africa
1 289
North Africa
495
Source: United Nations Environment Program 2002
Crisis of the new century
The water usable by humans has been greatly reduced, which in the 21st century has led us to face a major global water crisis. For now, conflicts over water occur only between regions, for example those that exist on the northern border of Mexico with the United States along the Rio Grande and the Colorado River, but it is very possible that the need for this resource partly triggers the wars of the future.
Around two million tons of waste are dumped daily into the different water storage systems, including industrial, fertilizer and pesticide waste.
And what can we do to use water properly and cooperate so that this crisis does not continue and reach irreversible dimensions?
The different authors of this issue of the magazine As you see? We try to introduce the reader to the topic of water from different perspectives. We hope with this issue to convince you of the importance of water as a non-renewable resource and the need for each of us to do our “grain of sand” to use it in the most appropriate way and help its conservation.
Marisa Mazari Hiriart works at the Institute of Ecology as a senior researcher. For the last 10 years she has studied water problems in the Metropolitan Zone of Mexico City.