OCR Text |
Show trols would be located and designed to stop head cutting of gullies in alluvial fills and to increase storage of ground waters. Major flood control works such as large dams and floodways and extensive levee systems must be built on the main streams and larger tributaries to provide justifiable protection for high value areas such as Albuquerque, Roswell, Carlsbad, and Brownsville, and the Rio Grande Valley between Cochiti and Elephant Butte. Only such structures will be able to control floods from snow melt within designed floodways. Large dams can detain oc- casional extreme floods that now cause spectacular damage, and floodwaters can be released in amounts that can be conveyed in improved stream channels and floodways without overflow and excessive bank cutting. Watershed treatment and major works on the main streams in the Rio Grande Basin complement each other. Each requires different methods of control and each is an essential component of a complete flood control program. Irrigation The Present Situation Irrigation along the Rio Grande goes back a thousand or more years when it was used by Pueblo Indians or their ancestors. Spanish colonization during the seventeenth and eighteenth centuries brought about an expansion of irrigated farming in alluvial valleys. Irrigation begun by Anglo- American settlers about 1880 spread during the next two decades. It resulted in many of the large canal systems and other irrigation works found there at the present time. According to the Interdepartmental Committee's report,1 the Middle Rio Grande in 1800 had about 100,000 acres in irrigated cultivation; in 1880,125,- 000 acres- and in 1924, 40,000. This striking re- duction in acreage was due to sedimentation and waterlogging. After various drainage and flood control works were carried out, irrigated land was increased to about 93,000 acres. Subsequently, lands have gone out of cultivation again. The present works were originally built as pri- 1 The Secretary of Agriculture and the Secretary of the Interior created the Interdepartmental Committee on the Rio Grande in 1939. It was disbanded early in World War II. vate undertakings, constructed by individuals, by communities, and by irrigation districts or water companies. In general, they are local develop- ments, independent of each other. Irrigation is accomplished by direct diversion of unregulated stream flow, storage in reservoirs, and by use of ground water. The Middle Rio Grande Conservancy District is a feature of special interest. This was formed in 1923 by special act of the New Mexico Legislature to cope with the irrigation and flood situation of the valley lands along the river from Cochiti to San Marcial. Its purpose was to provide some 69,000 acres with efficient irrigation, drainage, and flood control and assure an adequate water supply. Omitted were some 93,000 acres in tributary valleys adjacent to the main stem. An "official plan" was adopted. Construction was begun in 1930 and completed in 1934. About $9,316,000 was spent on the works, of which the Federal Government contributed $1,321,000 on behalf of the Pueblo In- dians. Bonds were sold. Agricultural lands were to carry 45 percent of the cost on a basis of ap- praised benefits. The balance was to be met from public utilities and urban property. Most of the agricultural taxes were immediately in default. The Reconstruction Finance Corpora- tion bought most of the bonds in 1934 and resold them to the district in 1946. New bonds have now been issued at 2.7 percent interest instead of 4 percent. Of these, 4.6 million dollars now become due in 1977, and 2.4 million dollars in 1978 with $750,000 additional callable at any time. In 1948 about 84 percent of the tax levy of $942,000 for maintenance and operation was collected. The conservancy district encountered difficulties primarily because insufficient consideration was given the sediment problem, floods were greater than anticipated, farm incomes were declining, and many small owners were failing to live up to their obligations. The proposed plans for flood control works in the valley will aid in meeting the flood and sediment problem. Developed surface water and ground water sup- plies in the basin are fully appropriated, and over- expansion of irrigation has taken place in some areas. More land is under irrigation than can be supplied with water in years of low water. Present total area of irrigated land is approxi- mately 2 million acres. Additional water must come from importation from other basins and salvage of avoidable waste. 305 |