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Riparian Ecosystem Creation and Restoration:
A Literature Summary

Functions

Hydrologic Flow


Hydrology is a key element in determining the composition and productivity of plants and corresponding animal associations (Fredrickson and Reid 1986). Plant composition, habitat structure, and productivity are determined by the timing, duration, and extent of flooding. Understanding the effects of shortand long-term fluctuations on the system is one of the greatest challenges facing managers because natural hydrology is continually modified by man's activities Hydrologic regimes vary daily, seasonally, and over long periods, and wetland and riparian productivity is largely determined by these fluxes. Modification of the natural dynamic regime can lead to extended extremes of drought or flooding, with a resultant drastic decline in productivity.

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.


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