Mexico, a classified arid and semi-arid country, has a total land area of 2 million square kilometres, 23% of which is equipped for irrigated agriculture. The agricultural sector plays an important role in the economic development of the country accounting for 8.4 of agricultural gross domestic product (GDP) and employing 23% of the economically active population. Irrigated agriculture contributes about 50% of the total value of agricultural production and accounts for about 70% of agriculture exports. Mexico's government initiated a number of structural reforms in the water sector aimed to introduce modern water management and irrigation.

Development

Infrastructure Of the 62,000 square kilometres with irrigation facilities in Mexico, about 42,000 km2; (67%) are irrigated with surface water, and the remaining, some 20,000 km2; (33%) are served by groundwater pumping. Approximately 33,000 km2; correspond to 80 bigger systems, namely irrigation districts (Distritos de Riego – DR). The remaining 29,000 km2; are distributed among more than 30 thousand small size communal and irrigation units (Unidades de Riego – UR).

The average plot size is relatively small, less than 1 ha is common, particularly in the irrigation units. At the same time, many landowners have farms larger than 50 ha and family farms, combining individual land holdings, may surpass 500ha.

Irrigation infrastructure and irrigated area

Water origin DR (%) Area (%) UR (%) Area (%) System (%) Area (%) Dam 56 46 4 14 4 41 Derivation 17 11 7 20 8 16 Spring 1 1 4 6 2 3 Pumping 1 2 8 10 10 6 Well 10 10 74 47 73 27 Surface + Groundwater 15 12 3 4 3 7 TOTAL 84 DR 33,000 km2 39,490 UR 29,560.32 km2 39,574 systems 62,560.32 km2 Source: FAO

The most important irrigation projects in Mexico are: Culiacán-Humaya-San Lorenzo Project, Yaqui River Project, Fuerte River Project, Colorado River Project, Lower Bravo River Project, Higher Lerma River Project, Lagunera Region Project, Guasave Project, Mayo River Project, Lázaro Cárdenas Project, and Delicas Project. These projects range from some 2,500 km2 to around 800 km2 of irrigated area each one.

Linkages with water resources

The mean annual rainfall of 777 mm results in a mean annual runoff of 410 km2, slightly more than 62 km3 of yearly renewable groundwater (including an estimate of 15 km2 of induced replenishment in the irrigation areas), and the remaining, some 1,060 km2, evaporates. Most of the country experience in rainy season, from June to mid-October and significantly less rain during the remainder of the year. February and July generally are the driest and the wettest months, respectively. Less than a third of the runoff from precipitation occurs within 75% of the national territory, where most of the irrigated land is located.

In 1995, 61 km3 were used for irrigation, 67% of which was supplied by superficial water, 33% from groundwater. Only 40 km3 were actually used, due to inefficiencies related with water canals and evapotranspiration.

There are three main watersheds in Mexico: the Western or Pacific Watershed, the Eastern or Atlantic Watershed (Gulf of Mexico and Caribbean) and the Inland Watershed, where rivers do not empty out into the sea. Two thirds of the country's 146 rivers drain into the Pacific Ocean.

There are approximately 100 rivers in the Western or Pacific Watershed, the most important in terms of water flow being the Balsas, Colorado, Culliacan, Fuerte, Lerma-Santiago, Verde, and Yaqui rivers.

The Eastern Watershed is made up of 46 main rivers, the most important being the Bravo, Coatzacoalcos, Grijalva, Pánuco, Papaloapan and Usumacinta Rivers.

The Inland Watershed is made up of large closed basins. The Nazas-Aguanaval river system is the largest.

Environmental impact

More than 22 km3 of waste water are discharged into Mexico's water bodies. Agricultural use accounts for 50% of this volume, mainly in the form of nonpoint discharges with high levels or residues for pesticides, fertilizers, and other chemicals.

Vast expanses of southern and southeastern tropical forest have been denuded for cattle rising and agriculture. Deforestation has contributed to serious soil erosion nationwide. In 1985, the government classified almost 17% of all land as totally eroded, 31% in an accelerated state of erosion, and 38% showing signs of incipient erosion.

Soil destruction is particularly pronounced in the north and northwest, with more than 60% of land considered in a total or accelerated state of erosion. Fragmented because of its semiarid and arid character, the soil in this region has become increasingly damaged through excessive irrigation with waters high in salt. As a result, desertification is spreading throughout the region.

Ineffective irrigation has generated salinization and drainage problems in 384,163 ha in a total drained area of 5,203,346 ha.

History

Irrigation development in Mexico was a governmental concern during the PorfiriatoC.B. Kroeber, Man, Land, and Water: Mexico's Farmlands Irrigation Policies, 1885-1911. Berkeley and Los Angeles: University of California Press 1983. and was affected by the Mexican Revolution and the agrarian reform. At the beginning of the Revolution (1910), there were about 1.2 million ha of irrigated land. Much if this land had been developed by land companies, mainly American, to grow plantation crops such as sugar cane and cotton. After the creation of the National Irrigation Commission in 1926, the irrigated area quickly expanded, and the agricultural census reported a total of 4.3 million ha of irrigated land by 1960. By the late 1980s, Mexico had about 6 million ha under irrigation.

During the 1980s and 1990s, irrigation development slowed down due to the economic crisis. The irrigation sector focused then on optimizing the use of existing infrastructure. In 1997, the total irrigated area accounted for 6.2 million ha, 5.4 million ha were actually irrigated. The northern states of Sinaloa and Sonora, account for 15% and 11% respectively of the total irrigated land.

Institutional development Food production requirements and the need to settle vast unpopulated areas in the northern region bordering the United States triggered the creation of the National Irrigation Commission and the enactment of the Irrigation Act of 1926. Water use was then low, even regionally and locally, so planning was undertaken project by project. Land reform, a stepping stone of post-Revolutionary governments, was closely related to irrigation projects.

In 1946, The Ministry of Water Resources took place of the National Irrigation Commission and, for the first time, responsibility for water development was concentrated within the realm of a single ministry. Water use increased substantially as a result of the economic development policies, especially for the industrial sector.

During the 1940s and 1950s, River Basin Commissions were created to launch regional development programs sustained by water-related projects. In 1975, the first National Water Plan provided a framework for improving water resources management consistent with national and regional objectives. In 1976, the National Water Plan Commission was created to implement the plan and update it systematically. Also in 1976, the Ministries of Water Resources and Agriculture become the Ministry of Agriculture and Water Resources, mainly to unify governmental actions directed at solving the growing problems of the agricultural sectors. This institutional change, however, caused a disintegration of water planning and management.

The economic crisis of the 1980s led to drastic changes in Mexico's irrigation policy. The National Development Plan (1989–1994) called for an increase in irrigation efficiency and the use of existent infrastructure. Under the National Program for Decentralization of Irrigation Districts, derived from the National Development Plan, Mexican government initiated the management transfer of irrigation districts to Water User Organizations (WUOs). The National Program, implemented by CONAGUA, originally planned the transfer of operation and maintenance of 21 irrigation districts, comprising 1.98million ha. To date, actual targets far exceed the target of 1.98 million ha of area during the 1990–1994 period.

Legal and institutional framework

Legal framework In 1992, the Mexican government issued the renewed federal National Water Law (NWL), and the corresponding Regulations issued in 1994. These legal instruments, together with the Mexican Constitution, are the main judicial basis for water and irrigation management in the country, and entitle the nation with the original property of practically all waters.

The NWL explicitly declares sustainable development as its primary objective. Furthermore, the last is consistent with Mexico's initial efforts related to decentralization, water-user participation, efficient use of water, expanded participation of the private sector, and fiscal policies related to the collection water levies for both water use and water pollution control.

Institutional framework The National Water Commission (Comisión Nacional de Agua – CONAGUA) was created in 1989, as the National Water Authority an autonomous agency under the Ministry of Environment and Natural Resources. CONAGUA should coordinate investments in the water sector, setting priorities reflecting each river basin's actual situation.

The Instituto Mexicano de Technología del Agua (IMTA) was created in 1986 to foster the technological effort needed for a policy implementation, especially in relation to efficient use of water and conservation of water quality in every sector of water use.

Officers from both Government agencies have close contact and relationships with the people managing the Irrigation Districts.

Concerning irrigation, there are three main groups of institutions: the irrigation districts, the irrigation units, and small private irrigation schemes.

The irrigation districts, covering 3.4 million ha (or 53% of the irrigated area), are large-scale irrigation schemes supplied mainly with surface water and some with groundwater. The responsibility for their operation and maintenance (O&M) has been transferred to water users associations (Asociaciones Civiles de Ususarios – WUAs) in the 1990s except for 5% of the area that is still operated by CONAGUA as well as some of the upstream infrastructure such as dams and large canals.

The irrigation units, covering about 2 million ha (or 32% of the irrigated area), are smaller public irrigation schemes, supplied from both surface and groundwater and operated and maintained from their inception by agricultural producers.

Small private irrigation schemes, covering about 0.9 million ha (15% of the irrigation area) are supplied primarily from groundwater. Agricultural producers carry out O&M.

The National Federation of Users of Irrigation Water (Asociación Nacional de Usuarios de Riego), established in 1994, represents the interests of WUAs in negotiations with the Government.

On-farm water management Agricultural producers who are interested in organizing a common irrigation systems form Water User Associations (WUA). The 1992 National Water Law (Ley de Aguas Nacionales), and the implementing regulation of the 1004, Law on National Waters (Reglamento de la Ley de Aguas Nacionales) recognize WUAs as civil non-profit associations responsible for irrigation infrastructure management as well as management of Irrigation Districts and Irrigation Units. Despite the increasing role of agricultural producers, CONAGUA remains the sector's dominant player in terms of policies, subsidies, programs and norms.

WUA consist of water users and its functions are the delivery of irrigation water and operation and maintenance of canals and dispute settlement. WUAs can also construct their own infrastructure or participate in government-financed construction projects.