Kristin Jacobs, age 10, of Galveston, Tex., for her question:
HOW LONG IS THE RIO GRANDE?
The fifth longest river in North America, the Rio Grande flows for 1,885 miles through the Southwestern United States and forms the boundary between the U.S. and Mexico for about 1,240 miles, almost two thirds of the countries' common border.
Early Spanish explorers gave the river its name, which means large river. Many Mexicans call it the Rio Bravo bold or wild river. Others call it Rio Bravo del Norte, or bold river of the north.
In the southern Rocky Mountains in southwestern Colorado, on the Continental Divide, the Rio Grande rises. It flows southeast through the vast San Luis Valley, turning south at the small city of Alamosa.
From there, the Rio Grande crosses into New Mexico and flows south through the center of the state. In northern New Mexico, the river is fed by other mountain streams and passes through a series of basins separated by narrow valleys.
Above Albuquerque the valley widens and the river flows onto a dry plateau. To the south, the Elephant Butte Dam holds back the river for about 40 miles. A bit downstream is the Caballo Reservoir.
The American Dam controls the waters of the Rio Grande north of E1 Paso at the Texas, New Mexico and Mexico borders.
From E1 Paso to the Gulf of Mexico the river forms the international boundary. It flows southeast from E1 Paso to Presidio, where it turns north to pass around the mountainous Big Bend country. Then it flows eastward until the Pecos River joins it. The river makes a final turn southeast for the rest of its course.
Amistad Dam spans the river about 12 miles northwest of Del Rio, Texas, forming a reservoir that extends upstream for 86 miles.
Near the Rio Grande's lower course, the river may be dry in late summer because of little rainfall and diversions for irrigation.
About 50 miles below Laredo, the Salado River, a major tributary with headwaters in Mexico, joins the Rio Grande. Falcon Dam, about 20 miles below the mouth of the Salado River, forms Falcon Reservoir, which extends upstream more than 35 miles.
At Rio Grande City is the Los Olmos Reservoir on another tributary, the Rio Los Olmos. Lake E1 Azucar lies across the Rio Grande at Camargo in Mexico.
Farther downstream is Mission Reservoir, which was built jointly by the U.S. and Mexico to hold back floodwaters for the lower valley's irrigation projects.
Between Rio Grande City and Brownsville, farmers grow citrus trees, vegetables and cotton in the irrigated valley.
In 1936, a 17 mile canal was built from Brownsville to Laguna Madre, with jetties through the barrier beach to the Gulf of Mexico.