The panorama of water in Mexico, in terms of availability, quality, contamination, and access are not entirely encouraging, neither today nor in the immediate future. Although its situation has been mainly determined by natural issues, in recent years various human activities, such as agriculture and industrial processes, have made it more acute.

Water is the greatest evidence of life. Therefore, when studying a planet, one of the first things to be investigated is the presence of that resource as an indicator of the probability of life.

Water is also an essential element for living beings. We are composed of water, as are plants, animals, food, and clothing. The body of an adult is composed, on average, of 60 percent water and that of a baby of 83 percent.

Moreover, sea jellyfish is composed of 95 percent water, fish are composed of 65 to 80 percent, insects are composed of 40 percent, tree trunks are composed of 50 percent, melons and grapes are composed of 98 percent, and potatoes are composed of 80 percent.

Also, living organisms require water to perform their vital functions, such as feeding, waste disposal, and regulation of body temperature (through sweating). Without water, plants, for example, would not be able to carry out the fundamental process of photosynthesis.

In our case, we need it for the maintenance and proper functioning of the brain. Water is also indispensable for personal hygiene and household cleaning, for the production of goods and services, and even for entertainment and transportation (water parks, museums, fuel generation, steel, etc.). Everything around us, besides containing water, was made with a certain amount of it.

In short, water is the most important natural resource for our existence. But it is not infinite, even if you think the opposite because it is abundant on Earth.

It has been called Planet Water because of the enormous blue layer that covers its surface: approximately 1,400 million km3 of water. 97.5 percent of that water is salty and found in the seas and 2.5 percent is fresh.

However, not all of this freshwater is available for consumption: 68.9 percent is frozen in glaciers and ice caps in places like Greenland and Antarctica; 30.8 percent is a subway in deep, hard-to-reach subway deposits (aquifers); and only 0.3 percent is located in places considered accessible, such as rivers and lakes.

Within this framework, to have water of sufficient quality and quantity to satisfy our needs, without compromising those of future generations, resource management actions are required that involve governments, private initiatives, civil society, educational institutions, and all users as a whole.

For this reason, this article aims to provide information of general interest on the subject of water in Mexico, to raise awareness among the public about the importance of their participation in improving water use practices daily.

Water quantity, availability, and extraction

Annually, Mexico receives an enormous amount of water in the form of precipitation: about 1,489 km3 (one thousand four hundred and eighty-nine cubic kilometers). With it, you could make a pool the size of Mexico City, 1 kilometer deep.

Of that water, it is estimated that 73.1 percent evaporates and returns to the atmosphere, 22.1 percent runs off in rivers or streams and 4.8 percent infiltrates into the subsoil naturally and recharges the aquifers. With all this amount and considering the exports and imports of water to neighboring countries (Rio Bravo and Grijalva), each year the country has 460 billion cubic meters of fresh water or about a quarter of the aforementioned pool.

Even though this amount of water is available every year, there are differences in the availability per person and region because most of the national territory is arid and semi-arid and therefore receives very little water. Only in the southern and central areas, where the climate is temperate and tropical, about 75 percent of the total water is received.

Another important factor in determining the availability of water per person is the number of inhabitants. The outlook is not encouraging, since from 1950 to 2010 the country's population quadrupled and went from being mostly rural to predominantly urban.

This has mainly translated into:

Low availability of water per inhabitant. In 1910 it was 30 thousand cubic liters per year and now it is 3 thousand 982.

Greater pressure on the water in urban areas. The concentration of population and, consequently, the accelerated growth of cities have implied strong pressures on the environment, derived from the increase in the demand for food, products, services, and greater use and contamination of water.

In Mexico, the availability of water per inhabitant, on average, is low compared to other countries, due to overpopulation.

The World Health Organization (WHO) establishes that less than 5 thousand cubic meters of water per inhabitant per year represents a low availability. It also highlights that a person requires between 20 and 100 liters of water per day to perform all their daily activities, however, in Mexico, each inhabitant occupies 200 liters per day on average.

Despite the average amount of water available per inhabitant in Mexico, the figures vary considerably in each region, which is why Conagua divides the country into 13 Hydrological Administrative Regions (HAR) to manage national waters.

The Hydrological Administrative Regions where the country's largest cities are located (for example HAR Rio Bravo in Monterrey; HAR Aguas del Valle de Mexico in the Federal District; HAR Lerma-Santiago in Guadalajara) have the lowest water availability, mainly due to the strong demand (or degree of pressure) on the resource. If we add to this the issue of inadequate use of the vital liquid, we are talking about a present and future that is worrying for our survival.

Hand in hand with population growth has increased the demand for water, which in turn has increased the amount of water that is extracted from surface and subway sources. In the last 50 years, the amount of water extraction in Mexico has increased sixfold, placing us in the top 10 countries in the world in this area.

Uses of water

According to its uses, water is classified as follows:

Consumptive. When there is water consumption, understood as the difference between the volume supplied and the volume discharged. That is the water that is consumed and, therefore, spent.

Non-consumptive. When water is used but not consumed, as in the generation of electrical energy, the volume stored in the dams is used.

The consumptive use is divided into:

Domestic-public. Used in homes, industries, and services connected to drinking water networks, for example for cleaning (public roads), recreation (fountains), and even protection (firemen). The main source of supply is the subway (62 percent). The municipalities are responsible for providing this service, as well as drainage, sewage, and treatment.

Self-supplying industry. Includes those that take water directly from the country's rivers, streams, lakes, or aquifers (with a permit called a Title of Concession, granted by Conagua), such as those in the mining, water, and gas supply, construction, and manufacturing sectors.

Agriculture. It is mainly used for farming, but also includes aquaculture, the livestock sector, and forestry.

Electrical energy. Used for the generation of electric energy, which does imply an expense of water for its production, such as dual steam, carb electric, turbo gas, and internal combustion plants. The highest percentage of use is in the Petacalco coal-fired plant, located on the coast of Guerrero near the mouth of the Balsas River.

In the world, the main use of water resources is also in the agricultural sector, with 72 percent of total extraction.

In the case of non-consumptive use, its use in hydroelectric plants stands out, where about 20 percent of the country's electrical energy is generated annually. Because the rivers with the greatest flow in Mexico are the Balsas and the Grijalva, the country's largest hydroelectric plants are located there: the Adolfo López Mateos and Chicoasén, respectively.

Water quality

The determination of the water quality is mainly based on the materials and substances that are dissolved or in suspension and the organisms that are found there.

When we speak of water quality, we are referring to the properties or characteristics it must have for specific uses. For example, treated water used for irrigation or in fountains is not suitable for human consumption, or water used for washing clothes is not suitable for watering plants but is suitable for household cleaning.

There are three sources of water contamination:

Biological. Produced by microorganisms, such as bacteria, viruses, and protozoa from living organic matter, generally fecal or food waste.

Physical. Generated from solid waste (garbage) thrown into water bodies.

Chemistry. Originated in general by industrial processes and factories, for example when dyeing leather for shoes or clothing.

There has always been contaminated water, however, since 1900 this condition has intensified due to industrialization processes.

The quality of water is evaluated with the following indicators:

Biochemical Oxygen Demand at five days

Chemical Oxygen Demand.

Total Suspended Solids.

The first two are used to determine the amount of organic matter present in water bodies, which generally come from municipal and non-municipal wastewater discharges.

The five-day Biochemical Oxygen Demand indicator determines the amount of biodegradable organic matter, while the Chemical Oxygen Demand indicator measures the total amount of organic matter. When the concentration of these two parameters increases, the amount of dissolved oxygen in water bodies decreases, affecting aquatic ecosystems.

The Total Suspended Solids indicator has its origin in wastewater and soil erosion. When Total Suspended Solids levels increase, the water body loses the ability to support the diversity of aquatic life.

To constantly monitor water bodies (rivers, lakes, coastal lagoons, and aquifers) the National Monitoring Network has 1,815 stations located in key points throughout the country.

The problem of water pollution can be addressed in the following ways:

Reducing the amount of wastewater and its concentration of pollutants. Wastewater comes from discharges from any public or private use, they have a varied composition (that is, they can contain different types of materials or contaminants) and are classified into municipal and industrial: the former correspond to those that are conducted in the urban and rural municipal sewage systems and the latter are those that are directly discharged by industries called self-supplied because they have their drainage systems.

It is possible to reduce the amount of wastewater and the concentration of pollutants, for example, by replacing traditional toilet boxes with smaller ones and reducing the number of toilet flushes, as well as by not dumping heavy materials such as oils or detergents, since they are very difficult to treat.

Reducing the pollutants carried by the water before being discharged into rivers, lakes, and seas with a treatment that retains or eliminates them. Currently, 31.7 percent of wastewater is treated nationwide.

Through wastewater treatment, which is a process of cleaning and restoring water. Depending on the contaminants it contains will be the type of treatment you receive, for example, if it was used for household cleaning will be treated differently if it was used in mining processes.

The treatment of wastewater consists of three stages:

Physical (primary). Solid matter not dissolved in the water, such as plastics, aluminum, Unicel, and some oils and soaps are filtered out.

Biological (secondary). With the help of bacteria, organic matter is removed, forming a sludge that separates the contaminants from the water.

Disinfection (tertiary). Using chlorine or ultraviolet light, pathogenic microorganisms and unwanted color and odor are eliminated from the water.

There are 2,029 treatment plants in operation in the country, which in 2009 treated only 31.7 percent of the wastewater. However, the problem lies mainly in the large amount of wastewater we generate. Once treated, the water can be used in agriculture and industry, as in the case of the Villa de Reyes thermoelectric plant in San Luis Potosí.

The water path

The water that reaches our homes is not generated in the hydraulic systems (canals, dams, ducts). It comes, first, from the possibility of storage in rivers, lakes, and lagoons and in its infiltration through the soil so that in some cases it can percolate to greater depths, forming phreatic mantles.

The possibility of having water in sufficient quantity, quality, and regulated over time depends on the conditions of the territory, in terms of soil conservation, vegetation, and biodiversity. Therefore, the management of the territory and the management of water resources are closely linked. So, to have drinking water suitable for human consumption, it must go through a rather complex process.

Pumping the water into the houses is not a simple task, besides it represents an important cost and significant consumption of electricity. For example, in the Valley of Mexico, the Cutzamala System provides 18 percent of the water needed for that region, in which 1,844 million pesos are invested annually in electricity.

Depending on the physical, geographical and meteorological characteristics, as well as the place or population where the water is taken, the source of supply is determined without harming or compromising the environmental balance. The sources of water supply are divided into:

Subway. They are found under the ground between cracks and spaces in the earth, accumulated in aquifers.

Superficial. They are above ground, circulating, or at rest. Rivers, streams, lakes, and lagoons are some examples.

Once the source from which the water will be obtained is identified, it goes through a process that generally involves extraction, purification, conduction, and supply:

Caption-extraction. The water is obtained from a river, lake, or aquifer and is then taken to a water treatment plant. If the source is a subway, very deep excavations are made and if the source is superficial, dams are built.

Drinking water treatment. The water is treated to improve its quality and make it suitable for human use and consumption.

Conduction. The water is pumped to a high area and then allowed to flow with the help of gravity through pipes (aqueducts) from where it is made drinkable to a delivery point near the city.

Supply. Water is delivered to the community through a pipeline known as the distribution network.

Virtual water and water footprint

The percentage of water we use daily for drinking, washing, cleaning the house and clothes, or preparing food is only 4 percent of the total. The remaining 96 percent corresponds to our indirect use of water resources.

We all use water indirectly every time we consume food or product, or every time we use a service, since the water was used in the elaboration process.

The sum of the water that each person, country, or region uses in their different activities and the water needed to produce the goods and services they consume is called the water footprint. To make this calculation, the amount of virtual water used in each product and service must be known, that is, the amount used in its elaboration, from the extraction of the raw material to its processing and distribution.

The water footprint comprises the amount of green, blue, and greywater used and generated during the production of a product or for the provision of a service:

Green water. It is the rainwater stored in the soil as humidity.

Bluewater. It is the water obtained from a surface source (river, lake, stream) or subway (aquifer).

Greywater. The one that is contaminated during the production processes.

Four main factors determine the water footprint of a country:

The type of consumption. What is consumed?

The level of consumption. High, low, and regular, and intensity or frequency with which the products are consumed.

The climate.

The efficiency with which the water is used. Processes, technologies, and methods used during production.

Conclusions

The challenges are great and complex. We have to add wills, capacities, and resources. We must also change our traditional way of relating to water; we cannot continue to use it as if it were an inexhaustible resource, but as a scarce and costly good, which must be managed responsibly for our benefit and that of future generations.

It is up to each one of us to do something:

Governments:

Implement policies for the sustainable management of water resources.

Coordinate actions that allow the participation of all sectors and water users.

Businesses:

Adopt production processes that are compatible with the environment.

Provide services that respect ecosystems.

Social sector:

Participate in environmental education processes.

Participate in influencing public policies.

Change consumption patterns.

Adopt technologies that allow for the reduction of water consumption.

Academy:

Develop research that provides sustainable technological solutions to water issues.

Disseminate the results of its research promptly to facilitate technology transfer.

Schools:

Adopt educational schemes that encourage the modification of water consumption habits and goods in general.

To adopt tools that facilitate the understanding of the functioning of water, from a basin perspective.

You and all of us:

Modify our consumption habits.

Adopting technologies to reduce water consumption.

Participate informally in collective decisions.

The panorama of water in Mexico, in terms of availability, quality, contamination, and access are not entirely encouraging, neither today nor in the immediate future. Although its situation has been mainly determined by natural issues, in recent years various human activities, such as agriculture and industrial processes, have made it more acute.

Therefore, participation and social commitment, as well as effective coordination among the different actors are of utmost importance to achieve efficient water resources management. Undoubtedly, you can contribute at the individual and collective level: get informed, commit yourself, and act.

Source: National Water Commission CONAGUA