Lerma River  The Lerma River () is Mexico's second longest river. It is a river in west-central Mexico that begins in Mexican Plateau at an altitude over above sea level, and ends where it empties into Lake Chapala, Mexico's largest lake, near Guadalajara, Jalisco. Lake Chapala is the starting point of Río Grande de Santiago, which some treat as a continuation of the Lerma River. In combination, the two are often called the Lerma Santiago River (). The Lerma River is notorious for its pollution, but the water quality has demonstrated considerable improvement in recent years due mostly to government environmental programs and through massive upgrading projects of sanitation works. The Lerma River originates from the Lerma lagoons near Almoloya del Río, on a plateau more than above sea level, and southeast of Toluca. The lagoons receive their water from springs rising from basaltic volcanics that flow down from Monte de Las Cruces. These are located between the Valley of Toluca and the Basin of Mexico. The river forms the short border between the states of Querétaro and Michoacán then flows west-northwest through the state of Guanajuato. After turning southward, the river separates Guanajuato and Michoacán, and Michoacán and Jalisco before flowing, after a course of about , into Lake Chapala, west-southwest of La Barca. It has a length of . When it empties into Lake Chapala, the system stands at above sea level. Some people consider the long Río Grande de Santiago, which continues from Lake Chapala northwest towards the Pacific Ocean, to be a continuation of the Lerma River. During the 17th and 18th centuries, large haciendas were established along this river, including the Atenco ranch, which was founded with bulls that belonged to Hernán Cortés. The bulls from this area are considered some of the finest stock for bullfighting. The river is dotted with cities such as Lerma and San Mateo Atenco to small picturesque villages with cultural significance such as Malinalco. The Lerma River–Lake Chapala basin is considered to be the most important watershed in the country by the federal government. With its major tributaries, the Laja, Apaseo, and Turbio the Lerma constitutes Mexico's largest river system. The Lerma River is not navigable by water craft, but it is critical to regional agricultural irrigation.