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Show In general, those areas that have the most potential for water salvage from phreatophyte control would be areas with the most potential for waterfowl and wildlife refuge and management areas. In most cases water obtained from phreatophyte control would be of such low quality that it couldn't be used directly for municipal and industrial purposes. To satisfy these uses would require an upstream exchange of water, either by groundwater development or reservoir development. Water from salvage would then be released to meet downstream rights. Various plans ha, ve been proposed to develop additional groundwater by lowering the water table and eliminating existing areas of phreatophytes. These plans have been based on the assumption that artesian pressures can be lowered by additional groundwater pumping, thereby reducing the amount of water available to the phreatophytes; however, this is not always the case. The same confining materials that create artesian conditions help create favorable conditions for phreatophyte growth. These confining layers help accumulate and convey the seepage from irrigation and precipitation to lowlands. There a sufficient water table condition is created to support phreatophyte growth. Artesian pressures do cause movement from the artesian aquifer to the shallow water table; however, the confined aquifer contributes only a small portion of the water consumed by phreatophytes. The only major reduction of pressure- induced discharge occurs in flowing wells and springs. This takes water away from the streamflows for downstream users, and the phreatophytes also continue to consume water. The most effective method of reducing phreatophyte areas is to uproot the plant, disc the area, and burn the slash and the seeds contained in it. However, well established salt cedar is deep- rooted and difficult to remove by this method. Following this eradication, the area must be sprayed at intervals to kill new growth, since phreatophytes reestablish themselves rather quickly. Considerable initial expense is involved, as well as spraying expenses at intervals. Although some sprays have been banned because of their detrimental effects on the environment, several, materials are available that can be used for this purpose. ( b) Control of Evaporation from Impoundments The reduction of evaporation loss from lakes and reservoirs is a potential source of water. This loss can be decreased by diking off shallow areas to reduce the surface area and/ or by using a chemical ( hexadecanol) to form a monomolecular film on the water and thereby 529 |