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Show 4. RESTRICT THE ACCUMULATION OF WATER IN OPEN LAKES 5. PREVENT OR REDUCE THE COSUMPTION OF WATER BY LOW VALUE OR USELESS PLANTS 6. COLLECT FOR MANAGED APPLICATION ALL THAT PORTION OF THE RECOVERABLE WATER CROP FOR WHICH EFFECTIVE CONTROL FACILITIES ARE AVAILABLE 4. Restrict the accumulation of water in open lakes, swamps, and other mechanisms of excessive evapotranspiration. The rate of evaporation from lakes and swamps is approximately double the requirements for support of useful vegetation for similar areas. Generally, water reaching these super- evapotranspiration mechanisms is returned to the atmosphere, yielding little or no valuable results in the process. Not only is the water wasted, but land surfaces are generally covered by plants of little or no economic significance. These are the areas of water abundance where surplus waters are available because the mechanism for its collection and channeling are efficient. Water accumulates, however, in excessive amounts and the opportunity for its effective use in plant growth is limited or non- existent. 5. Prevent or reduce the consumption of water by low value or useless plants. The pattern of distribution of precipitation by nature rarely provides water in harmony with the requirements for effective photosynthesis. Almost everywhere the harvestable results are only a fraction of the potentials that would be attainable with an appropriate water supply. Plants growing on watersheds seldom attain more than a small fraction of the values which can be secured from plants grown under effective water management. To the full extent that effective facilities are available, all manageable water should be shifted from low order to high order uses. 6. Collect for managed application all that portion of the recoverable water crop for which effective control facilities are available. Effective water control facilities must include units that can receive and impound water regardless of its pattern of requirements for each use. For each area, surface and subsurface storage facilities will generally determine the amounts that can be controlled and many of the conditions governing the results that can be obtained from water in its high order uses. For some areas, available water will be in excess of the capacities of storage facilities, but for most areas there will be un- utilized capacities when all water that can be recovered has been channeled to storage. Capacities of reservoirs are largely dependent upon rates of withdrawals for application. This is especially so for many underground reservoirs, which can become essentially enlarged, expandible channels for the flow of water near the last stage of its cycle. Since the highest results from the use of water can be attained only when applications are in harmony with the requirements for use, the storage facilities must permit the withdrawal of water whenever needed. Subsurface water reservoirs often permit such withdrawal in complete harmony with all such requirements and are especially effective when located underneath or near the point of use. Stored waters are shielded from dissipation through evaporation and through losses from seepage. 38 |