Water resources in Mexico
Water resources in many parts of Mexico are under stress, especially in the arid northwest and central regions where most of the population lives and most of the economic activities are located. The country has put in place a system of water resources management that includes both central (federal) and decentralized (basin and local) institutions.
Despite many achievements, the water resources sector in Mexico still faces some challenges, including: (i) increasing water scarcity, (ii) over-exploitation of freshwater resources, especially groundwater, (ii) deteriorating water quality, (iii) lack of financial sustainability of the water sector, (iv) modernizing water supply and sanitation services, (v) improving competitiveness and efficiency of irrigation, (vi) strengthening water institutions, (vii) adapting to climate change impacts, especially droughts and floods.
History and recent developments
Mexico has a long and well-established tradition on water resources management (WRM) which started in the 1930s when the country began investing heavily in water storage facilities and groundwater development to expand irrigation and supply water to the rapidly expanding population.
The 1934 Código Agrario, promulgated during the Cárdenas administration (1934-1940), granted the federal government sweeping powers to define the "public interest" to which water could be harnessed. By virtue of such legislation, between the 1930s and 1970s, the ejido sector and rural communities were subject to direct federal control over water. Private landowners, on the other hand, enjoyed the benefits of federally subsidized irrigation infrastructure and guaranteed market prices. Over time, large landowners became highly capitalized, while small farmers, by the 1970s, were suffering from the effects of water monopolies.
In the 1970s, the Mexican government entered into a tripartite agreement with the World Bank, and the United Nations Development Program to prepare the 1975 National Water Plan (NWP) which identified the need to enact a National Water Law (NWL) and a National Water Authority as well as decentralize responsibilities and promote water user participation in operational and maintenance (O&M).
The NWP spurred a significant institutional development and infrastructural achievements. In 1983 the federal government transferred the responsibility for water supply and sanitation to municipalities and states. The Mexican Institute of Water Technology (IMTA) was established in 1986, and the National Water Commission (CONAGUA, sometimes also called CNA in 1989). Also in 1989 the first Basin Council in Lerma–Chapala was created, incorporating water users from multiple sectors.
During the 1990s, Mexico's groundwater boom took place with rapid development and pumping of aquifers for combined agricultural, urban, and industrial demand. Also the federal government (CNA) decentralized responsibility for large irrigation infrastructure to autonomous agencies (irrigation districts).
In 1992, Mexico adopted a National Water Law, which contained specific provisions for the role of the CNA, the structure and functioning of river basin councils, public participation in water management, etc.
In 1993, the Cutzamala system was completed, becoming one of the largest pumping schemes in the world, pumping 19 cubic meters of water per second into the Mexico City Metropolitan area, over a difference of altitude of 940m and a distance of 162 km.
In 1997 the first technical groundwater committee was created to manage an overexploited aquifer in the state of Guanajuato.
With the 2004 Revision of the National Water Law, the thirteen decentralized CNA regions would become basin organizations serving as the technical arm of more broad-based basin councils that incorporate civil society interests including the private sector and citizens’ groups.
The largest river on the Pacific coast is the Balsas River (24 BCM/year) and the largest river on the Atlantic Coast is the Grijalva–Usumacinta flowing from Guatemala to Mexico (115 BCM.year). The longest river (2018 km) and also the river with the largest basin (226,000 km²) is the Rio Bravo, called Rio Grande in the United States.
Water is abundant in the relatively sparsely populated South and scarce in the more densely populated Center and North of the country. The Center and the North of the country where 77% of Mexico's population lives and 85% of its GDP is generated dispose of only 32% of the country's renewable water resources.
Total water withdrawals for consumptive use are 78 BCM/year. The largest consumptive water user is agriculture (78%), followed by domestic use (17%) and industry (5%).
There are no estimates on the Minimum Environmental Flow Requirements in Mexico. Environmental demand thus is de facto absent from the official water balances in Mexico.
There are seven major lakes in Mexico. By far the largest and most important is the Chapala Lake in Central Mexico with an area of 1,116 km² and a storage capacity of more than 8 BCM. Actual storage volume varies between 1 and 10 BCM since measurements began in 1935. The lake is only 4 to 6 m deep.
There are 667 large dams with a storage capacity of 150 BCM and an actual storage of 70 BCM in 2005. The largest dam by storage volume is the La Angostura Dam on the Grijalva River in the state of Chiapas with a storage volume of more than 10 BCM.
Overall, only 18% of water resources in Mexico are withdrawn for consumptive use. However, there is water stress in several regions of the country. The highest pressure on water resources is encountered around Mexico City (120% of resources), in Baja California (86% of resources) and in Sonora in the Northeast (79% of resources).
CNA has defined 653 "aquifers" out of which 104 were categorized as overexploited in 2005. Total groundwater use was 27.5 BCM/year, while recharge is estimated at 77BCM/year. Out of the country's 13 administrative hydrological regions, in 4 regions abstraction exceeds recharge: Baja California, Northeast, North-Center and the Valley of Mexico.
Water balance and climate change
In the context of the US National Assessment of the Potential Consequences of Climate Variability and Change (National Assessment on Climate Change) published in 2000, which was part of the US Global Change Research Program (Global Change Research Act), the National Ecology Institute of the National University of Mexico (UNAM) carried out a study on Impacts of Climate Change and Climate Variability in Mexico for the Mexican Ministry of Environment and Natural Resources. According to the study Mexico will experience less or normal summer precipitation and increased precipitation during winter. The report also details predicted impact by regions. For example, in the Lerma-Chapala basin the predicted increase in temperature coupled with a decrease in rainfall could result in severe water supply shortages, exacerbated by growth in population and industries. In northern areas and regions with large populations, especially in Central Mexico erosion and drought severity will increase with higher temperatures and rainfall variations in these arid and semi arid regions. Agricultural practices may also have to change, with a severe drought in Chihuahua in 2012, which some scientists attribute to climate change, leading to 350,000 head of cattle starving to death due to a shortage of pasture caused by a lack of rain.
Water quality and pollution
Information on the water quality of Mexico's rivers published by the National Water Commission is limited to only two parameters, Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). No other water quality indicators are used to classify water bodies and no water quality data using other pollutants as parameters are readily available.
Surface water bodies in Mexico are classified in five different ambient water quality classes, using BOD and COD as indicators. In 2005 surface water quality was measured in 509 sites using these parameters.
Using BOD as an indicator, in 2005 5% of water bodies were classified as highly contaminated (BOC > 120 mg/l) and 10% as contaminated.(BOD > 30 mg/l). If COD is used as an indicator, the respective shares increase to 12% for highly contaminated (COD > 200) and 26% for contaminated (COD > 40) waterbodies.
Legal and institutional framework
The main law governing water resources management in Mexico is the National Water Law of 1992, revised on April 29, 2004. According to the Law, key functions in the sector are the responsibility of the federal government, through the National Water Commission (CNA or Conagua). CNA's mission is to "manage and preserve national water resources, with the participation of the society, to reach a sustainable use of the resource." CNA has a staff of 16,000 and an annual budget of 18.6bn Pesos in 2005 (more than US$1.5bn) and is considered to be one of the most powerful federal agencies in Mexico. CNA administrates major federal programs to support investments in water supply and sanitation as well as in irrigation. It also directly manages certain key hydraulic facilities such as the Cutzamala Pipeline that supplies a large share of the water used in the Metropolitan Area of Mexico City. CNA also owns and operates most dams in Mexico and operates the country's water monitoring network.
Through the 2004 revision of the National Water Law two new entities were formally created: Basin Councils (Consejos de Cuenca) and Basin Agencies (Organismos de Cuenca). The basin councils consist of representatives of the federal government, state and municipal governments, as well as at least 50% representatives of water users and NGOs. The basin councils are not decision-making bodies, but are consultative bodies. There are 26 basin councils. The basin agencies, on the other hand, are the regional administrative branches of the CNA, which retains the ultimate decision-making power.
Obviously other entities such as the Ministry of Finance, the Federal Congress, State Governments and State Congresses, as well as the Ministry of Environment and Natural Resources are important decision-makers in the sector.
Three groups of institutions have been assigned with the main responsibilities for WRM: (i) the National Water Commission (Comision Nacional del Agua –CONAGUA), at the federal level; (ii) Water Commissions (Comisiones Estatales del Agua – CEAs), at the State level; and (iii) basin authorities and basin councils.
CONAGUA is the highest institution for water resource management in Mexico, including water policy, water rights, planning, irrigation and drainage development, water supply and sanitation, and emergency and disaster management (with an emphasis on flooding). CONAGUA is formally under the authority of the Ministry of Environment and Natural Resources (Secretaria del Medio Ambiente y Recursos Naturales – SEMARNAT) but it enjoys considerable de facto autonomy. It employs 17,000 professionals and has 13 regional offices and 32 state offices.
The CEAs are autonomous entities that usually are under the authority of the State Ministry of Public Works. Their attributions are different among states and can include water resources management, irrigation and the provision of water supply and sanitation services.
The recently created Basin Authorities (BAs) will develop from the 13 existing Regional Offices of CONAGUA and are expected to be responsible for formulating regional policy, designing programs to implement such policies, conducting studies to estimate the value of the financial resources generated within their boundaries (water user fees and service fees), recommending specific rates for water user fees and collecting them.
Basin Councils (BCs) are expected to guide, together with CONAGUA, BAs work. There are a total of 25 BCs that have been established with the same basin boundaries as the BAs, but in some cases with two or more BCs within the area of one BA. Some states are located entirely within the area of one BC. In other cases, one state is divided between two or more BCs. In the latter case, the state participates in all of the BCs within its territory.
The 2004 amended National Water Law (NWL) aims to restructure CONAGUA key functions through the transfer of responsibilities from the central level to subnational entities: the basin agencies (Organismos de Cuenca – BA) and Basin Councils (Consejos de Cuenca – BC). BA and BCs are expected to play an increasing role in the sector limiting CONAGUA's role to the administration of the NWL, the conduct of national water policy, and planning, supervision, support and regulatory activities.
The NWL also introduced a Water Financing System (Sistema Finaciero del Agua – SFA). CONAGUA will create together with the Ministry of Finance appropriate instruments to determine funding sources, spending guidelines, cost recovery, settling of accounts and management indicators.
Instruments: Permits and pricing
Two key instruments of water resources management at the disposal of the CNA are permits and abstraction charges. However, the effectiveness of permits is reduced by the fact that the total volume of water for which permits have been granted exceeds total water availability in some regions. A total of 344,473 permits were registered in 2005 in the public register of water rights established in 1992. The total volume of water for which permits were granted is 76 BCM/year, excluding permits for hydropower, which is a non-consumptive use of water.
Water resource pricing through abstraction charges is carried out on the basis of the Federal Rights Law, which classifies the country in nine water scarcity zones. In zones with the highest water scarcity, generally in the North, abstraction charges are highest. However agriculture as the major water user is exempt from the abstraction charge and the charge only paid by industry and municipal users. This considerably limits the effectiveness of the charge as a tool for water demand management, although it has been very effective at mobilizing financial resources. Total revenues from abstraction charges were 6.5bn Pesos in 2005, accounting for 80% of CNA revenues.
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