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In general, the amount and type of vegetational ground cover, the areal extent of the watershed, and the slope of the terrain are directly related to the percentage of water that will enter the drainage system as surface flow or as percolated water. In riparian areas of the lower Colorado River, efforts are being made to clear extensive stands of the exotic salt cedar (Tamarix chinensis) to reduce evapotranspirative losses and increase streambed capacity to carry floodwater (Anderson and Ohmart 1984). Revegetating cleared areas with native shrubs and trees results in a decrease in total foliage density, while enhancing riparian bird habitat.

Improvement of riparian ecosystems also may increase groundwater storage (Skinner et al. 1985). Storage of water in the semiarid West during periods of high flow has been a major justification for constructing dams and reservoirs. Lack of adequate sites for dams, present economic constraints, and concerns for existing environments now limit construction of new water storage facilities. Consequently, water planners should examine alternative methods to store water such as improving riparian zones of floodplains and adjoining aquifers of streams tributary to those dammed. Improved riparian zones could create desired aquatic habitat during decreased flow and still store water. However, it is imperative to understand riparian zone processes to meet flow regimes and to maintain desired aquatic conditions.