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Show storage during the growing season may be equiv- alent to a substantial part of the year's average rainfall. In the arid areas, however, essentially no sus- pended water may be available naturally for growth of plants, at any time. Under such con- ditions, crops can be grown only under irriga- tion. For the Nation as a whole, natural sus- pended water storage is inadequate for the fullest production of food, forage, fiber, and timber. This makes of utmost importance the proper management of all other opportunities for stor- age, including the best of both ground and surface water reservoir possibilities to provide the con- servation storage which serves many of the needs of man. Joint Management of Land and Water The proper management of land and water is an inseparable problem. There are vari- ous ways in which land and water management prevents excessive runoff and conserves soil. What is done in the management of land is im- portant not only in terms of conserving soil and assuring increased yields of food, forage, fiber, and timber products, but also to minimize the filling up of stream channels and reservoirs with silt. The effects of such a program on the recharg- ing of ground water supplies, and even upon stream flow, may be either to augment or to decrease supplies, depending upon the nature of the subsoil and the characteristics of the vegeta- tion. Thus forests and other vegetal covers extract and dissipate water whenever available during the growing season. It has been demonstrated in Colorado, California, and North Carolina that removal of cover commonly increases runoff or ground water storage, or both, rather than de- creases them. To quote the Geological Survey: * 1 Water Facts in Relation to a National Water Resources Policy.-A Statement to the President's Water Resources Policy Commission, United States Department of the In- terior, Geological Survey, April 1950, p. 17. To be judicious and effective over the Nation, land management practices must be adapted to a very wide range of environments, involving com- plex interplay between factors of climate, topog- raphy, bedrock, and surficial geology, hydrology, and vegetation. Much fundamental research, with close collaboration between hydrologist and agrono- mist, remains undone. It is ventured that ultimate land management standards will be predicated on minimal effort that will sustain an optimum yield of land products-food, forage, fiber, and timber- and will limit movement of sediment reasonably; in other words, that good management can increase land productivity largely to the extent that it in- creases soil water storage (for larger extraction by the growing product), but over extensive areas any such increase in soil water must be at the expense of" recharge to ground water bodies having other uses. Another closely related factor is the prevalence in certain of the more arid areas of nonbeneficial vegetation which extracts large quantities of water that would otherwise contribute to ground water supplies. For example, the Geological Survey estimates that natural waste of this sort is roughly 1.5 million acre-feet a year, both in Ne- vada and Arizona, and that about 400,000 and 700,000 acre-feet a year, respectively, could be salvaged in these States by careful removal of such water consumers. In the 17 Western States, it is estimated that nonbeneficial plants waste from 20 to 25 million acre-feet of water a year. If half of this could be salvaged, it would provide annually the equiva- lent of water to a depth of 3 feet for some 1,700,- 000 acres. These facts indicate the extent to which land management and water resources planning are interrelated and point to the importance of in- cluding both ground water and surface reservoir storage in the total program. This will involve particularly the gathering of data on all phases of the country's ground water resources. Then through artificial recharge we may make the max- imum use of these reservoirs, which are proof against evaporation, provided ground water is below the root zones of plants. The possibilities of artificial recharge of ground water reserves from temporary excesses of sur- face waters reveal the importance of including 911609-5( -10 111 |