Geography and climate
Guanajuato is located in the center of Mexico, northwest of Mexico City, bordering the states of Zacatecas, San Luis Potosí, Michoacán, Querétaro, and Jalisco. It covers an area of 30,589 km² and is ranked 20th out of 31 states. It has an average altitude of 2,015 meters (6,611 ft) above sea level, with its territory divided among three of Mexico's physical regions, the Sierra Madre Oriental, the Mexican Plateau and the Trans-Mexican Volcanic Belt. The Sierra Madre Oriental in Guanajuato consists of the Sierra Gorda and the Sierra del Azafrán in the northeast. The Mexican Plateau extends through the center of the state. Within, it subdivides into various regions parted by low-lying mountain chains such as the Sierra de la Cuatralba and the Sierra de Cubo. The Trans Mexican Volcanic Belt crosses the state in the south and includes the Bajío area, the Altos de Jalisco and the valleys area in the far south. The state is crossed by several mountain ranges which have mountains between 2,300 and 3,000 meters high. Mountain ranges average 2,305 meters and flat areas lie at around 1,725 meters above mean sea level. The other important mountain ranges include the Sierra Gorda to the north, the Sierra de Guanjuato in the southeast, the Comanja in the northwest and the Codorniz in the east.
The state is divided into five regions, taking into consideration geography and climate. These are called Altos de Guanajuato, La Sierra Central, Bajío, La Sierra Gorda, and Los Valles del Sur. The Altos de Guanajuato, located in the north of the state, are a chain of forested mountains interspersed with pastures, small fields and areas with cacti and other desert plants. They begin near the border with San Luis Potosí, and extend south to Dolores Hidalgo and then to San Miguel de Allende, then to the Querétaro border. The altitude of this area varies from 1,800 to peaks over 2,900 meters such as the La Giganta and La Sierra del Cubo mountains. The climate is mostly semiarid with a rainy season in the summer, with average temperatures between 15 and 20 °C. However, lows in the winter frequently reach 0 °C or lower with frosts. Wildlife is found mostly in the most rugged and inaccessible areas and includes deer, coyotes, eagles and rattlesnakes.
Cerro Culiacán from Jaral del Progresso
La Sierra Gorda is shared between Guanajuato and Querétaro and is considered to be an important biosphere. This area is the most rugged in the state where most of the natural areas and small villages are remain intact due to their inaccessibility. The Sierra Gorda is part of the Sierra Madre Occidental, with extreme variations in its geography and climate. The rugged terrain means that there are a wide number and variety of micro-climates, although average temperatures vary only between 16 and 19 °C. It lowest point is a canyon called Paso de Hormigas in Xichú at 650 meters above sea level with a very warm climate suitable for tropical fruit. The highest point is Pinal de Zamorano at 3,300 meters, followed by El Picacho de Pueblo Nuevo, El Zorillo and El Cuervo all above 2,700 meters. The largest changes are seen in arid versus wetter zones, which can often be relatively nearby, with foliage changing from rainforest to pine forest to desert landscapes. In 1997, the Sierra Gorda region in Querétaro was declared a Biosphere Reserve by the federal government, with the Guanajuato portion added in 2007. On the Guanajuato side, it covers 236,882 hectares over the municipalities of Xichú, San Luis de la Paz, Atarjea, Victoria and Santa Catarina. Culturally, the Sierra Gorda region is the far western part of La Huasteca, which extends over parts of the states of Querétaro, San Luis Potosí, Hidalgo and Veracruz.
The Sierra Central is a series of low, gentle mountains in the center of the state which are part of the Sierra Madre Occidental. They cover twelve municipalities: Ocampo, San Felipe, León, Silao, Guanajuato, Dolores Hidalgo, San Miguel de Allende, Irapuato, Salamanca, Santa Cruz de Juventino Rosas, Comonfort and Apaseo el Grande. Wild vegetation runs from tropical rainforest to arid grasslands with cactus, with cypress trees along rivers and other surface water. Wildlife includes raccoons, quail, rabbits, skunks and migratory birds. The land is productive, especially for fruit orchards producing guavas, tejocote, apples, limes, quince and more. Desert fruits such as cactus pears (tuna), garambullos and xoconostle are also produced commercially.
The best-known geographical region of the state is called the Bajío, which is a relatively low, relatively flat area of between 1,700 and 1,800 meters, that surrounds the Lerma River and its tributaries. Centered in Guanajuato, parts also extend into the neighboring states of Querétaro and Jalisco. This low area is the source of its name, coming from the Spanish word "bajo" or low. The Bajío is filled with rolling hills and interrupted by the occasional chain of low mountains such as the Gavia and the Culiacán. Before the arrival of the Spanish, this area was covered in dense forests of holm oak and mesquite trees; however, mining's need for wood fuel eventually cleared those forests. Today, the area is the center of most of the state's agriculture and industry since the terrain allows for the building of highways and large farms, which produce grains, vegetables and fruit. This farmland is considered some of the most productive in Mexico.
Los Valles del Sur, also called the Valles Abajeños, are valleys located in the southwest part of the state, bordering the state of Michoacán. This area is distinguished by the large number of Purépecha place names and covers the municipalities of Valle de Santiago, Yuriria, Tarimoro, Apaseo el Alto, Moroleón, Uriangato, Santiago Maravatío, Acámbaro, Jerécuaro, Coroneo and Tarandacuao. The area is part of the Trans-Mexican Volcanic Belt with elevations ranging between 1,700 and 2,000 meters. The soil is fertile due to its volcanic base, producing crops such as sorghum, wheat, corn and vegetables. The land also produces building materials such as tezontle and black sandstone. In the higher elevations, there are forests of pine and holm oak but these have been much reduced because of deforestation. In the more arid areas, mesquite, nopal and other desert plants can be found. There are several small lakes, the best known being the
Yuriria Lake as well as canyons and cave systems, some of which were used for ceremonial purposes by pre-Hispanic peoples. It is also the home the
Siete Luminarias de Valle de Santiago, a set of seven inactive volcanic craters located in the northwest and southwest of the Santiago Valley. The volcano cones rise abruptly out of the ground with craters that measure up to one kilometer across. Locals call the formations "holes" (hoyos) and they are named La Alberca, La Cíntora, Estrada, Blanca, Alvarez, Solís and Rincón de Parangueo. La Cíntora and Rincón de Parangueo contain cave paintings and evidence that people once lived in the craters. La Alberca (The Pool) is a crater lake with is open to the public for swimming, rowing or boating. The name of "Siete Luminarias" (Seven Lanterns) comes from an imagined time when the seven were active at once in prehistory.
The state has about 1,500 bodies of surface water, along with underground aquifers in most parts of the state. The principal lakes in the state are the Cuitzeo, which is on the border with Michoacán and the Yuriria. Several of the Siete Luminarias craters have also developed crater lakes, especially in the ones called "La Joya", "Parangueo" and "Olla de Zìntora". The most important river in Guanjuato and one of the most important in the country is the Lerma River, along with its tributaries Guanajuato River, La Laja, and Turbio. The Lerma River basin covers 81% of the state (center and south) with the Pánuco River basin (north of the state) and Cuitzeo Lake covering the remaining. The Lerma River is regulated through various dams in part to control the fact that it ran very high in the rainy season and very low in the dry season. These dams include the Ignacio Allende, la Purísima, Solís, La Gavia, Conejo II and Santa Ifigenia.
Climates in the state are grouped by precipitation and average temperatures into three major groups. The semi-arid climate is characterized by the fact that evaporation often exceeds precipitation. Most of the vegetation in these areas is arid grassland with desert plants such as nopal. These climates cover about forty percent of the state, mostly in the north. Semi-arid temperate regions are found in the municipalities of San Felipe, San Diego de la Unión, San Luis de la Paz, part of Dolores Hidalgo and
San José de Iturbide, where precipitation varies between 400 and 500 mm and the average temperature is between 16 and 18 °C. Semi-arid semi hot climates can be found north of Dolores Hidalgo, around León and in areas near Celaya. In these municipalities, rainfall averages between 600 and 700 mm and the average annual temperature is between 18 and 20 °C. Temperate climates are judged by the presence of holm oak and pine forest, pine forests and/or pine forests with meadows. Humidity varies in these forest regions. Temperate semi-moist areas are mostly found in the southeast municipalities of Apaseo, Coroneo and Jerécuaro and in the center of the state. Precipitation varies from 600 to 700 mm and the average temperature is between 16 and 18 °C. Temperate and somewhat humid climates have rainfall averages of between 700 and 800 mm, with temperatures between 16 and 18 °C. These can be found in Pénjamo, Coroneo, Jerécuaro and parts of Guanajuato (municipality) and Dolores Hidalgo. Temperate climates with the most humidity are found in the Santa Rosa and municipality of Guanajuato. These have rainfall averages of over 800 mm and average temperatures of under 16 °C. Hot and moist climates in the state have temperatures ranging from 18 to 22 °C and are associated with tropical rainforest, with some grassland. These climates are subdivided into two types, one that receives less rainfall with a significant dry season and the other which is wetter. The drier type is found in Abasolo, Irapuato, Salamanca and Romita. In total, these hot and relatively moist climates can be found in about 40% of the state.
From the beginning of the colonial period, much of the state's environment suffered greatly due to the mining techniques and intensive agriculture introduced by the Spanish. The process has been ongoing since then to modern times. Before the conquest, the state was covered in forests, but mining requires large amounts of fuel to process minerals, so those forests were cut down for fuel as well as numerous construction projects. Agriculture leached nutrients from the soil and caused erosion, and introduced plants, animals and diseases have had large impact. Today, the state contains twenty one protected areas which extend over 63,611 hectares in twenty six municipalities. These natural reserves include Sierra de Lobos, Siete Luminarias, the Silva Dam, Megaparque de Dolores Hidalgo, Cuenca de la Esperanza, Las Fuentes, Peña Alta, Pinal de Zamorano, Parque Metropolitano, La Joya Crater, Yuriria Lake, Las Musas, Culiacán and La Gavia Mountains, Sierra de los Agustinos, Cerro de Cubilete, Cerro de Amoles, La Purisima Dam, Arandas Mountain, La Soledad Dam, and the upper basin of the Temascatío River. Another protected area is the federal Biosphere Reserve of La Sierra Gorda. In Guanajuato, it extends over 236,882 hectares and contains 182 bird species, 42 mammal species and 84 plant species, including two recently discovered ones called
Beaucamea compacta and Calibanus glassianus. The park contains a number of species which are in danger of extinction including the black bear and the puma. The climate is semi-arid with variations in temperature due to altitude changes, but most of the area is covered in tropical forest in which many plants lose leaves during the dry season from November to May.