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00 ':'") .-t ..-4 ~::p' the wide variation in daily meteorological conditions recommendations for frequency of irrigation are left to the Bureau of Reclamation's Irrigation Management Services program as the recommended scientific approach, or to the experience and judgement of the individual farm operator. Three management practices share equal importance in reducing runoff, erosion, and sedimentation from the grazed non-irrigated uplands. These are the number of grazing animals, the season of grazing, and the duration of grazing. (:' Four types of improvements have been identified as needed for existing on-farm irrigation systems. Ditch 1 ining or pipel ines with necessary measuring devices and control structures will reduce ditch seepage and improve on-farm water management. Land leveling adapts the field to the use of lined ditches or gated pipes and enhances uniform application of irrigation water. Subsurface drains for existing open drains can improve field shapes and the layout of irrigation systems. Changing where appl icable to drip or sprinkler methods of irrigation will increase irrigation efficiency and reduce the potential for salt load pickup. The need for three types of physical improvements for the grazed non- irrigated areas has been determined. Seeding with brush control and fencing will improve vegetative cover. Stockwater development and distribution systems will enhance site control for grazing, and erosion control dams; gully plugs and grazingland mechanical treatment are positive means of reducing erosion by holding storm water on the ground. The Grand Valley study area reaches into Mesa and Garfield Counties in western Colorado, and consists of 839,000 acres of grazed non-irrigated uplands and 126,000 acres in the valley. Of the grazed uplands, 17~,000 acres (21 percent) are in private ownership and 664,000 acres (79 percent) are publicly owned. Although the Grand Valley covers 126,000 acres, only 66,000 acres make up the irrigated farmland and about 6,000 acres are not cultivated in anyone year. Soils in the valley are typical of desert soils -- they are low in organic matter, high in weatherable minerals and associated salts, and are chemically similar to the geologic materials from which they were derived. One-third of the area is affected by accumulations of salts or alkali, and sodium is the most prevalent soluble salt. In 1975 the population of Grand Valley was about 62,000, up 13.8 percent from 1970, and is projected to be 90,000 by the year 1990. Percapita income for Mesa Coun~y was $3,409 in 1972 compared with $4,006 for the state. Farm population for Mesa County totaled 3,898 in 1970 down 42.7 percent from 1960. In 1974 352 farms had sales between $2,500 and $9,999; 145 had sales between $10,000 and $19,999 and 269 had sales over $20,000. Grand Valley contains about 65 percent of the irrigated crop land in Mesa County but the value of farm product sales amounts to about 75 percent of the total for the county. 2