Problems of Water Supply in Mexico

Why are there water supply problems in Mexico? If we look at the context of our country, we will find a clue. Mexico has an extension of almost 2 million square kilometers and a population of more than 126 million, according to the National Population Council (CONAPO). This means that it has an approximate density of 65 inhabitants per square kilometer. This can be seen in Figure 1.   

Similarly, it has been determined that water scarcity is related to the fact that in 49 percent of the territory, it rains less than 600mm per year. The country also is classified into semi-desert and desert areas, where it can be seen that water is scarce on the surface and the water option falls to groundwater (Figure 2).

As can be seen in Figure 1, the largest number of inhabitants in the country is concentrated in the central and eastern regions, where there is less scarcity of surface water. However, as can be seen in Figure 2, in central and northern Mexico, with the exception of the Sierra Madre Occidental and Sierra Madre Oriental, the rest are wide areas with very low rainfall, which has resulted in intensive use of groundwater. 

These natural conditions have led to a large number of aquifers being in a state of overexploitation. But what does this term mean? Overexploitation is an exploitation regime that causes undesirable effects in an aquifer. However, this term tends to be totally subjective, since in the case of an aquifer it can represent the extraction up to a volume where it can affect the environment, shallow wells, wells hand drilled, as well as the quality of groundwater.

In all the brown areas of Figure 2, groundwater is practically the only available water resource. Likewise, since the '60s, the volume of water that has been extracted from the subsoil exceeds the water that enters naturally to the aquifers, according to Chávez and Morales.

Other reasons for which large volumes have been extracted from the aquifers are linked to the demographic explosion, population concentration (Figure 1) and intensive extraction for agricultural purposes. All of these reasons are related to human activities.

Thus, the consequences of the current situation of water scarcity are linked to natural situations and others have been induced by man. Altogether has caused the overexploitation of  aquifers and deepening water levels in the wells, which has consequently increased the extraction costs. Also added is the long list of factors such as the reduction of the stored groundwater reserve, the reduction of the flow that is extracted from the wells, the deterioration of the quality due to the extraction of deeper water, intrusion of seawater, entry of contaminated water through cracks formed by the overexploitation of aquifers, drying of wetlands, lakes and springs, loss of native vegetation, differential settlement and cracking of the land with serious impact on infrastructure, among others.

According to National Water Commission (CONAGUA) figures, 653 aquifers have been identified in Mexico, of which 115 are overexploited. Although this represents a reduced percentage of 18 percent, it is not a minor problem because these are located, as can be seen in Figures 3 and 4, in urban areas where almost 30 percent of the country's total population is concentrated, according to information from the National Institute of Statistics and Geography (INEGI). 

This problem has not been resolved and to date there are no concrete plans by the authority that lead to actions, through which the daily volume of water that is extracted from the subsoil is reduced. 

To solve this, the questions are: where can you get water in regions where it rains very little and there are no permanent rivers or streams? Where can you supply large and small populations, as well as productive human activities? 

In this regard, the proposal is to carry out the following important actions:

• Efficient use of water in major cities, for example, by finding leaks in drinking water and sewage delivery networks, to fix them and stop waste from continuing.
• Increase prices based on usage of water and the amounts used in each of these applications, including water supplied to the population, to minimize waste.
• Greatly increasing the use of treated wastewater. This so far has been an almost totally wasted water resource, which represents a very important volume. For example, in 2013 there were 2,287 wastewater treatment plants in operation, with a combined installed capacity of 152,171.88 liters per second (lps) and a treated flow of 105,934.85 lps, equivalent to 9.15 million cubic meters per day, according to the National Inventory of Water Treatment and Treatment Plants. However, in a study carried out by the Mexican Institute of Water Technology in treatment plants with design flow rates greater than 400 lps, the volume of treated wastewater that was reused was only between 3 and 12 percent. 
• Given the above, it is inadmissible that in a country with water shortage problems, less than 15 percent of the treated wastewater is used and the rest is thrown away. Especially when we are experiencing a climate change in which there will be great periods of extreme drought. For this reason, investments should be made in treatment plants at the tertiary level and pipelines to move the treated wastewater. Incentives should be provided to operating agencies to invest more in their treatment plants and to promote the exchange of water between users. The end result is that farmers and industrialists, who do not necessarily require first-use water, can make exchanges with the operating agencies in their water rights. 

It is necessary to accelerate the process of education and a change of mentality among society, officials, researchers, politicians and professionals dedicated to surface and groundwater. So that everyone participates in ending this waste of treated wastewater that goes against logic. There is a water shortage in Mexico, but we resist using treated wastewater efficiently.

What is exposed here is the result of the experience obtained in the development of research carried out throughout the country. It allows us to provide a general idea for future communications to demonstrate the problems and solutions in projects related to water resources in Mexico.