| Oriental Basin | |
|---|---|
 Valley of Libres | |
  Oriental Basin | |
| Floor elevation | 2,360 m (7,740 ft) |
| Geography | |
| Coordinates | 19°25′00″N 97°24′00″W / 19.41667°N 97.40000°W |
| Rivers | Río Salado |
The Oriental Basin, also known as the Libres-Oriental Basin, Oriental-Serdán Basin or San Juan Plains (in Spanish, Llanos de San Juan or Cuenca de Libres-Oriental), is an endorheic basin in east-central Mexico. It covers an area of 4,958.60 square kilometers, lying in the states of Puebla, Tlaxcala, and Veracruz.
The climate is temperate and subtropical, semi-arid to subhumid, with summer rains. Average annual temperature 12-16 °C, and annual total precipitation is 400–800 mm. The Trans-Mexican Volcanic Belt pine-oak forests ecoregion covers the mountains surrounding the basin to the west, north, and east.[1] The mountains to the north and west, including the Cofre de Perote volcano, leave the valley in a rain shadow, and the xeric shrublands of the Tehuacán Valley matorral ecoregion occupies the center of the basin, and extend south into the Tehuacán and Cuicatlán valleys.[2] Vegetation includes pine-oak forests and pine-fir forests at higher elevations, with dry scrub pine forests, oak forests, juniper scrub, yucca scrub, halophytic vegetation, and grassland. It includes the Llanos de San Juan and Llanos de San Andres.[3]
The basin contains several shallow, mostly alkaline lakes. Two ephemeral playa lakes, Totolcinco (El Carmen or Totolcingo) and Tepeyahualco (El Salado), lie in the lowest part of the basin (2300 meters elevation), and remain dry for most of the year. The basin includes six maar lakes, locally called axalpazcos, lying in shallow volcanic craters and sustained by underground water. A northern group of lakes – Alchichica, Quechulac, Atexcac, and La Preciosa – lie southeast of Lake Tepeyahualco, and the southern lakes, Aljojuca and San Miguel Tecuitlapa, lie southeast of Lake Totolcinco. The basin also has five dry maars, called xalapazcos.[4]
Chief towns in the basin include El Carmen Tequexquitla, Tlaxcala; Perote, Veracruz; and Oriental, Puebla.
Groundwater levels in the basin have been dropping in recent years because of over-exploitation for irrigation and destruction of natural recharging areas. In addition, the government is considering pumping freshwater from the Oriental basin to Mexico City to the west and Puebla to the south.[5]
- ^ "Cuenca Oriental", Comisión Nacional para el Conocimiento y Uso de la Biodiversidad. Accessed October 17, 2009. [1]
- ^ "Tehuacán Valley matorral". Terrestrial Ecoregions. World Wildlife Fund. Retrieved October 18, 2009.
- ^ "Cuenca Oriental", Comisión Nacional para el Conocimiento y Uso de la Biodiversidad. Accessed October 17, 2009. [2]
- ^ Caballero, Margarita; Gloria Vilcara, Alejandro Rodríguez, Diana Juarez. "Short-term climatic change in lake sediments from lake Alchchica, Oriental, Mexico". Geofísica Internacional (2003), Vol. 42, Num. 3, pp. 529-537. [ ]
- ^ Alcocer, Javier (2003). "The future of salt lakes: the case of Mexico". Abstract, "Environmental Future of Aquatic Ecosystems," 5th International Conference on Environmental Future, 23–27 March 2003, Zurich. [3]