RIO GRANDE, a North American river, which rises in the San Juan mountains of southern Colorado, flows south-east and south in Colorado, south by west and south-east through New Mexico and south-east between Texas and Mexico to the Gulf of Mexico. Its length is approximately 2,200m. and for about 1,3oom. it forms the international boundary between the United States and Mexico. It presents many features of a complex physio graphic type, being first a river of the Rocky Mountains, then of the interior deserts and then of the gulf coastal plain. The Mexi cans call it the Rio del Norte in its upper course, the Rio Bravo in the middle section and the Rio Grande only in its course through the coastal plain. From its headwaters, r2,000ft. above the sea, it rushes rapidly down a mountain canyon to San Luis valley, in Colorado. It flows with moderate speed through this broad valley, enters a long canyon with a maximum depth of 400f t., about 4m. above the boundary between Colorado and New Mexico, and is hemmed in between canyon walls or the sides of narrow mountain valleys throughout its course in New Mexico. It passes through a series of picturesque canyons, some of them 1,750ft. in depth, in the "Big Bend," and becomes a silt-laden stream with a shifting channel in its passage through the coastal plain. In its course through the plain its channel is so much ob
structed by sand bars that it is of no importance for navigation. As the increasing diversion of the water of the upper Rio Grande for irrigation in Colorado and New Mexico resulted in a scarcity of water for this purpose in Mexico, that country complained, and to remedy the evil the Reclamation Service of the United States proposed the construction by the United States of a storage dam across the river, near Engle, New Mexico. Mexico agreed to this proposal and a treaty covering the matter was proclaimed in Jan. 1907. Mexico receives 6o,000 ac.ft. of water annually from the Elephant Butte reservoir in New Mexico. Since 1910 the delta of the Rio Grande, known as the Lower Rio Grande valley, has been developed by water diverted from the river. The irrigated dis tricts, over 20o,000ac. in area, extend from the town Rio Grande to the gulf, a distance of about loo miles. The semi-tropical cli mate of the region makes it ideal for citrus fruit and vegetables for the winter market. The principal cities on the river are : Brownsville, Texas; Matamoras, Mexico; Laredo, Texas; Del Rio, Texas; El Paso, Texas; Ciudad Juarez, Mexico and Albuquer que, N.M.