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Show exist in most areas. These ground-water reserves can continue to serve future generations if they are properly managed and integrated with other sources of water made available to the Region. Long range water resource planning concepts should be established that would conserve and regulate this diminishing resource at a socially optimum level, particu- larly in growing metropolitan areas where heavy water demands will be sustained over long periods of time. The following maps show depths to ground water in 1965 a^cl the I960 to 1965 changes in depth to water. Increased Water Yield Increases in water yield can be obtained from forest land by reducing the water used by onsite vegetation. This increase can be realized by specific timber harvesting practices and by conversion of chaparral and deep-rooted riparian trees and shrubs to shallow-rooted grasses and forbs. The Water Yield Augmentation Map, following page 62, shows the extent of the areas suitable for this type of management. The maximum average annual potential increase in water yield within the Region through vegetation management is estimated at 1.1 million acre-feet from 5.1 million suitable acres. The amounts actually realized would be much less than this potential because of such considerations as esthetics, outdoor recreation, and wildlife habitat requirements and other land management objectives. LANDS In 19655 there were approximately 36.2 million acres of land suitable for irrigated cropland in the Region. Of this acreage, about 1.6 million acres were also suitable for nonirrigated crop production. The avail- ability of suitable lands will greatly exceed projected requirements Tor irrigated croplands and would also be far in excess of that which couLd be irrigated with projected water supply developments. In 1965, there were approximately 85 million acres of land suitable for livestock grazing in the Region, of which about 76 million acres were available. This included 25 million acres of forest types (conifer, woodland, chaparral, and riparian), 51 million acres of range types (southern and northern desert shrub and grassland), all croplands, and portions of undeveloped lands within urban areas. Of the 30 million acres of forest land in the Lower Colorado Regi-on, 6 million acres are suitable for the production of commercial timber products. About one-half million acres of this land are included wittiin the boundaries of national parks and other areas where commercial timber harvesting is modified or precluded. 59 |
