Why was Valle de Chalco Solidaridad created? It emerged from the old Lake Chalco bed. This land was substantially drained in the 19th century.
Valle de Chalco Solidaridad is a municipality in Mexico. It sits on Mexico City’s eastern outskirts. Once part of Chalco, it became separate in 1994. President Salinas de Gortari created it. His National Solidarity Program supported this change.
Xico is technically the municipal seat. It is named after a high point. This land was once an island. Now, it is a small hill in an urban area.
“Chalco” comes from the Chalca tribe. They lived around the lake before the Spanish conquest. By 2006, Valle de Chalco included part of the world’s largest mega-slum. This included Ciudad Nezahualcoyotl and Ixtapaluca.
Archaeologists say people lived around Lake Chalco around 2400 B.C. Major settlements began around 1240 B.C. The Chalca tribe migrated here then. Other diverse tribes followed. They added “Chalca” to their names.
By 1410, Chalca lands formed a loose group. It divided into four domains. In the 14th century, the Mexica Aztecs settled nearby. They built Tenochtitlan. It is now Mexico City. The Chalcas and Mexicas fought ritual wars called Flower Wars. During the Spanish conquest, the Chalca joined Hernán Cortés.
Under President Porfirio Díaz, the drained lake bed became part of the Hacienda de Xico. After the Mexican Revolution, land went to the ejido system. This meant communal ownership. People mainly used it for dairy farming.
Near the 1970s, things changed. People from Mexico City came to the region. They illegally bought land from ejidatarios. The new settlement grew without basic services. There was little water, no sewers, and limited electricity. The government started providing services in 1988. The Programa Nacional de Solidaridad helped. It regularized 77000 homesteads.
Valle de Chalco’s population grew fast in the 1980s and 1990s. By 1995, it had 287073 residents. Growth has slowed since then. Undeveloped land is scarce. In 2005, there were 332279 residents. The 2010 census counted 357645 people.
The most common local hazards in Valle de Chalco Solidaridad are subsidence and flooding. Volcanoes like Popocatepetl and Iztaccihuatl also surround the basin. During the rainy season, water must be pumped from lagoons. This prevents floods. Runoff water from highlands often overflows the La Compañía and Acapol rivers.
La Compañía Canal is important. The Acapol River is outside the study area. La Compañía River starts in the Iztaccihuatl foothills. It flows northeast into the Canal General in the former Lake Texcoco. The river is 30 km long. It includes the San Rafael, Santo Domingo, and San Francisco tributaries. It crosses the plains of the former Lake Chalco. It also goes by the Mexico-Puebla highway. La Compañía Canal used to be an open sewage canal. It collected wastewater from Valle de Chalco Solidaridad and Chalco. Today, it is a piped sewage canal.
The land in Valle de Chalco has minimal slope. The soil is silty loam, clayey loam, and sandy loam. These soils compress easily. Clays absorb lots of water. This increases their volume. When water evaporates, the volume decreases. This causes cracks in the ground. It also damages buildings.
Over the past 20 years, the environment has changed. Overexploitation of aquifers has caused subsidence. In the plain’s center, subsidence reaches 40 cm each year. This happens where lacustrine sediments are thick. This soil compaction damages La Compañía Canal. It reduces pressure on canal walls. About 90% of urban land faces seismic hazards.
Flooding is a serious issue here. In 2000, wastewater flooded 80 hectares. This was due to a rupture in La Compañía Canal. Over 6700 households suffered. People had gastrointestinal, skin, and waterborne diseases. Power, water, and food were unavailable. In 2010, cracks in La Compañía Canal walls damaged El Triunfo, San Isidro, and Avándaro. Floods affected 447592 m2. About 11250 people were impacted. The economic impact was 2.7 to 3.0 million USD.