Irrigation

Irrigation, the artificial watering of crops. Much of Latin America receives insufficient precipitation for farming. To expand and improve arable land, pre-Hispanic horticulturalists had developed water management systems by the first millennium bce in both Mesoamerica and the Andes. The simplest method, pot irrigation, is familiar to all gardeners and leaves few, if any, archaeological traces. Water is carried by hand and applied to individual plants. Very effective use is made of limited amounts of water, but labor demands are high, so early farmers began to devise other methods of redirecting water's natural flow.

In central Mexico, rubble or earthen storage dams may have been built across natural channels to collect ephemeral surface runoff at the site of Teopantecuanitlán, in northern Guerrero State between 1200 and 1000 b.c., and in the Tehuacán Valley, between 750 and 600 b.c. However, the earliest undisputed remains of a Mexican irrigation system are at Santa Clara Coatitlán, now within metropolitan Mexico City. Here unlined canals branched off a channelized gully and took water to fields from about 900 b.c. Near the present city of Puebla, canal networks carried water from ephemeral stream channels by the middle of the first millennium b.c. In Tlaxcala State, there is evidence that terraced fields were watered by a dam, reservoir, and canal system around the same time.

A canal fed from a dammed reservoir is found just below the archaeological site of Monte Albán, Oaxaca. Part of this canal is cut into bedrock, demonstrating that its builders had the theoretical knowledge to plan water flow without trial and error. The Monte Albán canal carried water from about 550 to 250 b.c. By a.d. 200, mortared masonry storage dams and aqueducts were functioning near Monte Albán.

By 1519, when Hernán Cortés arrived in the Valley of Mexico, hydraulic works had reached monumental proportions. Tenochtitlán, the Mexica (Aztec) capital, occupied an island in Lake Tetz-coco. The Mexica redirected rivers and constructed aqueducts, dams, dikes, and open canals. Mortared aqueducts carried sweet water from springs at Chapultepec (later a park in Mexico City) and Coyoacán across the lake to Tenochtitlán, where it was used for drinking, bathing, and watering gardens.

The Peruvian and north Chilean coasts receive little or no precipitation, so agriculture is dependent upon irrigation. Dozens of small rivers and streams, many seasonally dry, flow down the western slopes of the Andes, through the coastal deserts, and into the Pacific. Pre-Hispanic farmers drew water directly off these rivers; directed water in long-distance canals from higher, moister elevations; diverted spring flow; and dug wells and trenches down to the water table. The early prehistory of Andean irrigation is unclear, but simple canals were probably built as early as the second millennium b.c. to extend floodwater farming of coastal valleys.

On Peru's north and central coasts, attempts were made in the mid-first millennium a.d. to build open canal irrigation networks supplied by two or more rivers. However, some of the long-distance linkages, including a 71-mile canal joining the Chi-cama and Moche drainages, may never have functioned. In the Chilca Valley, and elsewhere on Peru's central coast, ancient farmers dug a few meters to the water table, creating moist sunken fields called mahames or hoyas. This practice extended agriculture into areas without surface water.

The Andean Central Highlands receive unreliable precipitation during a wet season from November to April. To extend the growing time, or to produce two crops per year, agriculturalists made extensive use of open canals combined with terraces. These techniques were well established by the mid-first millennium a.d., the apogee of the Wari state. By 1500 the Incas had brought basic irrigation to near perfection. Water was so important to the lords of Cuzco that they conceptualized their whole social structure in terms of its natural and artificial flow.

In parts of Latin America, waterlogged or flooded fields are a major problem for farmers. Both in lowland Mesoamerica and the Lake Titicaca basin, indigenous cultivators built extensive systems of ridges and furrows for planting and water containment. Some Maya cities and the early Andean state of Tiwanaku depended heavily upon such raised fields. However, construction of some Andean raised fields predated the rise of the Tiwanaku state by more than one thousand years. Remnants of chinampas, or "floating gardens," can still be observed in the Valley of Mexico. These are artificial planting platforms constructed and maintained in shallow lakes.

The aridity of Spain and Portugal stimulated the development of Iberian irrigation and made the conquistadores appreciative of the sophisticated indigenous hydraulic systems they encountered in the New World. Native waterworks and concomitant social structure were often retained. However, the requirements of sugarcane, water mills, and horses meant that Iberians needed more water than the pre-Conquest Indians. The most remote branches of canals were often abandoned to provide greater volume and flow elsewhere. This has preserved remnants of ancient systems, especially in the valleys of Peru's north coast. The Spanish introduced many Old World hydraulic devices, including the arched aqueducts that were a hallmark of ancient Roman technology. Examples can still be seen in Mexico near Zempoala and Hidalgo and at the city of Querétaro; in Peru at Cuzco; and in Brazil at Rio de Janeiro.

Another Iberian introduction may have been filtration galleries, also called minas, ganats, foggaras, or puquois. Such galleries are lines of vertical wells linked at their bottoms by slightly sloping tunnels with the main water outlet at the tunnel's mouth. The largest and best-studied Spanish water mina is in Madrid. It was begun in the early thirteenth century under Christian control. Spanish engineers built several filtration gallery systems in Mexico, including those at Tehuacán and Puebla. Dozens of others were constructed in the Andes during the viceregal period, but many scholars believe that the systems in the Nasca drainage were built in the first millennium a.d. by people of the indigenous Nasca culture.

Latin American agriculture remains dependent upon irrigation. Ambitious, high-tech projects have become almost impossible to finance in the wake of the 1980s debt crisis. However, in remote areas farmers continue to employ the agricultural technology of their pre-Columbian and Spanish ancestors.

A major change since the late 1980s has been the privatization of water resource management. The World Bank and other critics have accused Latin American governments of mismanaging water resources. Yet, many groups in Ecuador, Peru, and Bolivia have successfully protested water privatization schemes, as exacerbating social and economic inequality. A vigorous debate in the early twenty-first century continues over whether water and irrigation projects should be public or private or if a third, moderate, approach can be achieved.

See alsoAgriculture; Potato.

BIBLIOGRAPHY

For an excellent survey of ancient Mexican hydraulic technology see William E. Doolittle, Canal Irrigation in Prehistoric Mexico (1990). A study of the important prehistoric, colonial, and modern Tehuacán system can be found in Kjell I. Enge and Scott Whiteford, The Keepers of Water and Earth: Mexican Rural Social Organization and Irrigation (1989). A good general work on the central Andes is Michael E. Moseley, The Incas and Their Ancestors: The Archaeology of Peru (1992). A beautifully illustrated pioneering study of ancient Andean waterworks is Paul Kosok, Life, Land, and Water in Ancient Peru (1965). An influential article on the social organization governing canals is Patricia J. Netherly, "The Management of Late Andean Irrigation Systems on the North Coast of Peru," in American Antiquity 49, no. 2 (1984): 227-254. Sunken fields have been described in Ana María Soldi, Chacras excavadas en el desierto (1979). A general discussion of raised fields can be found in Clark L. Erickson, "Prehistoric Landscape Management in the Andean Highlands: Raised Field Agriculture and Its Environmental Impact," in Population and Environment 13, no. 4 (1992): 285-300. For a controversial study of Andean filtration galleries see Monica Barnes and David Fleming, "Filtration-Gallery Irrigation in the Spanish New World," in Latin American Antiquity 2, no. 1 (1991): 48-68; an opposing point of view is Ronald I. Dorn et al., "New Approach to the Radiocarbon Dating of Rock Varnish, with Examples from Drylands," in Annals of the Association of American Geographers 82 (1992): 136-151. A solid book on highland irrigation, with emphasis on present practice, is William P. Mitchell and David Guillet, Irrigation at High Altitudes: The Social Organization of Water Control Systems in the Andes (1994).

Additional Bibliography

Aboites, Luis. El agua de la nación: Una historia política de México (1888–1946). Mexico City: Centro de Investigaciones y Estudios Superiores en Antropología Social, 1998.

Bennett, Vivienne, Sonia Dávila-Poblete, and Nieves Rico. Opposing Currents: The Politics of Water and Gender in Latin America. Pittsburgh, PA: University of Pittsburgh Press, 2005.

Eakin, Hallie Catherine. Weathering Risk in Rural Mexico: Climatic, Institutional, and Economic Change. Tucson: University of Arizona Press, 2006.

Gelles, Paul H. Water and Power in Highland Peru: The Cultural Politics of Irrigation and Development. New Brunswick, NJ: Rutgers University Press, 2000.

                                    Monica Barnes