How the country drains
Mexico has roughly 630,000 km of watercourses in 757 basins, which CONAGUA groups into 37 hydrological regions. The continental divide follows the Sierra Madre Occidental and then the volcanic belt across the middle of the country: rivers on the Pacific side are short and steep, falling from 2,000 m to the sea in under 300 km, while those on the Atlantic side cross wide coastal plains to the Gulf of Mexico. The real imbalance, though, runs north to south. The south-east — Chiapas, Tabasco and southern Veracruz — holds under a tenth of the population and produces about two-thirds of the national runoff. The dry north, from Sonora to Tamaulipas, contains most of the irrigated farmland and depends on dams and groundwater; the Río Bravo below the last diversions and the Colorado in its Mexican delta reach the sea only in wet years.
The ten longest rivers
Lengths below are for the whole system, including tributaries that carry the name upstream and the sections outside Mexico. The Bravo and the Usumacinta are shared rivers; the Lerma–Santiago, the Balsas and the Nazas lie entirely within the country.
| River | Length (km) | Source | Mouth and states crossed |
|---|---|---|---|
| Bravo (Rio Grande) | 3,034 | San Juan Mountains, Colorado (US) | Gulf of Mexico at Matamoros; Chihuahua, Coahuila, Nuevo León, Tamaulipas |
| Grijalva–Usumacinta | 1,521 | Guatemalan highlands | Gulf of Mexico in Tabasco; Chiapas, Tabasco, Campeche |
| Lerma–Santiago | 1,281 | Almoloya, State of Mexico, 2,600 m | Pacific in Nayarit via Lake Chapala; five states |
| Nazas–Aguanaval | 1,081 | Sierra Madre Occidental, Durango | Closed basin at Torreón; Durango, Coahuila, Zacatecas |
| Conchos | 900 | Sierra Madre Occidental, Chihuahua | Joins the Bravo at Ojinaga; Chihuahua |
| Balsas | 771 | Puebla–Tlaxcala highlands | Pacific at Lázaro Cárdenas; Puebla, Morelos, Guerrero, Michoacán |
| Fuerte | 540 | Sierra Tarahumara, Chihuahua | Gulf of California near Los Mochis; Sinaloa |
| Pánuco (Moctezuma) | 510 | Hidalgo, near the Valley of Mexico | Gulf of Mexico at Tampico; Hidalgo, San Luis Potosí, Veracruz, Tamaulipas |
| Yaqui | 410 | Sierra Madre Occidental, Sonora | Gulf of California near Guaymas; Sonora |
| Papaloapan | 354 | Sierra de Oaxaca | Alvarado lagoon, Gulf of Mexico; Oaxaca, Veracruz |
Rivers of the dry north
Everything north of the Tropic of Cancer is worked hard. The Conchos rises in the Sierra Madre Occidental in Chihuahua, waters the Delicias irrigation district and joins the Bravo at Ojinaga; under the 1944 water treaty Mexico delivers an average of about 432 million m³ a year to the United States from the Conchos and five smaller tributaries, and the payments fall due in five-year cycles that drought regularly disrupts. The Nazas and the Aguanaval never reach any sea: they drain into the closed Bolsón de Mapimí, and since the Lázaro Cárdenas and Francisco Zarco dams were built their water goes to the cotton and dairy fields of the Comarca Lagunera around Torreón. The Yaqui, the Mayo and the Fuerte support the irrigated valleys of Sonora and northern Sinaloa, which grow much of Mexico's wheat and winter vegetables. The Colorado enters Baja California already almost fully allocated upstream, and its delta is now mostly dry salt flat.
Rivers of the south-east
The Grijalva and the Usumacinta drain the wettest corner of Mexico and meet in a shared delta in Tabasco before entering the Gulf of Mexico. The Usumacinta forms about 200 km of the border with Guatemala, passing below the Maya city of Yaxchilán, and is the largest Mexican river by volume. The Grijalva runs through the 1,000 m walls of the Sumidero Canyon outside Tuxtla Gutiérrez and is then held back by four dams in a chain — La Angostura, Chicoasén, Malpaso and Peñitas — with a combined capacity near 4,800 MW, roughly two-fifths of Mexico's hydroelectric power. Chicoasén, at 261 m, is the tallest dam in the country. Neither river has been dammed on the Usumacinta itself, and repeated proposals to do so have been shelved. Farther north the Papaloapan and the Coatzacoalcos drain the Veracruz plain, where annual rainfall exceeds 3,000 mm in places.
Lakes and reservoirs
Mexico's natural lakes are few and shallow. Lake Chapala, about 1,100 km² and nowhere much deeper than 10 m, supplies a large share of Guadalajara's drinking water and rises and falls sharply with the Lerma's flow. Cuitzeo in Michoacán is the second largest but dries back in bad years; Pátzcuaro, about 97 km², is the third. On the coast the Laguna de Términos in Campeche covers roughly 1,500 km², the largest coastal lagoon in the country, and the Laguna de Bacalar in Quintana Roo runs 42 km along a limestone fault. Storage is otherwise artificial: some 5,000 dams exist, of which about 180 large ones hold four-fifths of the stored water. Mexico's renewable water works out at roughly 450,000 million m³ a year, but three-quarters of it falls where a quarter of the people live.
Questions about Mexican rivers
What is the longest river in Mexico?
The Río Bravo del Norte, called the Rio Grande in the United States, at about 3,034 km — but it rises in Colorado and only its lower half is Mexican. The longest system entirely inside the country is the Lerma–Santiago, about 1,281 km from the State of Mexico to the Pacific in Nayarit.
Which river forms the US–Mexico border?
The Río Bravo, from Ciudad Juárez to the Gulf of Mexico at Matamoros — about 2,000 km of the 3,152 km boundary. West of El Paso the border is a surveyed land line across the desert. See the US–Mexico border map.
Which Mexican river carries the most water?
The Usumacinta, which discharges roughly 1,700 m³ per second into the Gulf of Mexico through Tabasco. The Grijalva–Usumacinta basin produces close to 30% of Mexico's surface runoff.
Are Mexico's rivers navigable?
Only in short stretches. Shallow-draft boats work the lower Usumacinta, Grijalva, Papaloapan, Coatzacoalcos and Pánuco. No Mexican river carries scheduled long-distance freight; cargo moves by road and rail.
Where is Lake Chapala?
In Jalisco and Michoacán, about 45 km south-east of Guadalajara. At roughly 1,100 km² it is Mexico's largest natural lake: the Lerma flows in at the east end, the Santiago flows out at the north-west corner.