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~4 ...~ ~-;''' CONDITIONS ON IRRIGATED SECTIONS IN THE MIDDLE RIO GRANDE IN NEW MEXICO ~~ :.', by JOHN C. THOMPSON i~" ~fl Project Engineer, Middle Rio Grande Project, Bureau of Reclamation, U. S. Department of the Interior, Albuquerque, New Mexico ~~.1 ,." ~.~ -:,., The Middle Rio Grande area is located along the Rio Grande between Cochiti and San Marcial, New Mexico, extending from 40 miles north to 100 miles south of Albuquerque. Its history of irrigation ex- tends back pfObably as far as any area in the United States. The irdgated lands lie in a narrow ship, from I to 5 miles wide, on both sides of the Rio Grande. They are located within the Middle Rio Grande Con- servancy Dishict, and compdse the pfOject lands of the Bureau of Reclamation's Middle Rio Grande Project. The elevation of the lands vades ffOm 4,450feet above sea level at San Marcial to 5,250 feet at Cochiti. There are approximately 122,000 acres of water fight land in the pfOject, of which 80,000 acres, including some 9,000 acres of Indian lands, are being irdgated. The lands generally are smooth and very gently sloping. The soils have developed from recent alluvium, and range in color and texture ffOm light brown sand and sandy loams to dark reddish-brown clays. They ate, in general, fertile and well adapted to irrigation. A detailed land classification by the B utesu of Reclamation shows that there are 81,600 acres of inigable land in the project. This land is considered by the Bu- reau to be suited to sustained economic use for ir- dgation agdculture. While there may be some shifts of water use to the better quality lands, no increase in the acreage irrigated is expected. The climate of this area is arid and irrigation is necessary fm pwfitable farming. The annual pre- cipitation at Albuquerque has averaged only slightly over 8 inches, individual years varying from about 3 inches to 16 inches. Parts of the Middle Valley have been irrigated for many centuries. They were irrigating here when COfOnado came in 1540, the first recmded history. The first irrigators were Indians J who were followed by Spanish colonists, and then by Anglo-Amedcans who began settling in the area in the latter half of the nineteenth century. Maximum development was reached in 1880 when, it is reported, 124,800 acres were developed between Cochiti and the site of Elephant Butte Reservoif. For the next 40 years the general trend was downward. The unstable river, :1 ;""1 \.l:; ;~ ., ".~ <' ^;. 'I < ~ ; ~! floods, and watedogging of lands caused ifdgated acreage to go out of production. According to re.. ports, only about 40,000 acres were under develop- ment in 1925. The continued detedoration of the valley lands finally caused community action that resulted in the formation of the Middle Rio Grande Conservancy District in 1925. The works con~tructed by the distfict were completed in 1935, and include El Vado Reservoir, four major diversion dams, two canal headings, and over 1,500 miles of canals and lat- erals, drains, and levees. These works were a val.. uable aid to irdgation in the distdct, but the if. dgators have continued to be plagued with pfOblems of water shortages, floods, a high water table, and sediment deposits in canals and laterals. Present Water supply shortages in the Middle Rio Grande Valley are the resu~t of several factors, including below normal runoff, high nonbeneficial consumptive use by pmeatophytes along the fiver and in bosque areas, and increased Basin depletions by pumping for municipal <<nd ifdgation use and by soil and moisture conservation measures on the watershed. The runoff of the Rio Grande at Otowi was only 530,000 acre-feet in 1953 and 435,000 acre-feet in 1954, which is less than 50% of nOfmal. The average for the last ten years was only 766,700 acre-feet. Studies made in 1947 by the Bureau of Reclamation show that the average annual depletion in the valley between Cochiti and San Marcial was approximately 536,000 acre-feet fm the calendar years 1936 thru 1945. A large percentage of that amount, appfOxi- mately 238,700 acre..feet, was consumed non bene- ficially by bosque areas (areas grown up in brush, trees and native vegetation). The area and density of the phreatophytes have increased considerably since that time. Except for works now under way by the Bureau of Reclamation, the area would doubt- less be experiencing an even greater percentage ofnonheneficial consumptive use. The Rio Grande thru the Middle Valley is generally an aggrading stream. This aggravates the flood danger, increases water losses, and hinders the drainage of iuigated lands. Dudng the period 1936 .'.' r. .' ,..:" 27 V~I(.,...,",U