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Assessing the Functions and Services of Non-Perennial Waters in Arid Regions

Abstract

There are significant and on-going issues faced by the U.S. Army Corps of Engineers and other federal agencies in regulating and affording protections to arid non-perennial stream resources in western arid regions of the U.S. (i.e., Arid West). The significance of these issues is magnified by the large portion of dryland areas situated within the U.S., as well as worldwide, where non-perennial streams also comprise most of the stream types. It is essential for politicians, decision makers, and those assessing and managing aquatic resources to be aware of the current body of understanding available on these important resources. An in-depth literature and geospatial analysis was conducted on arid non-perennial stream functions as they relate to key climate ecosystem controls, influential environmental parameter controls, and hydrology (e.g., streamflow regime) forcing functions at various landscape scales and settings. Out of the overall stream function categories of Biogeochemical, Habitat, Hydrology, Sediment, Biodiversity, Energy Dissipation, and Connectivity examined within global and U.S. literature, only Biogeochemical, Habitat, Hydrology, Sediment emerged as the primary function categories of study focus. Global and U.S. data followed similar overall trends with generally a higher coverage of Habitat functions above all other function categories, which was unexpected given the higher importance of Hydrology and Sediment within the overall hierarchy of influences among stream function categories. Other similar overall trends within global and U.S. data included higher occurrences within cold steppe subclimes, steppe precipitation areas, and ephemeral streams. Of the three environmental parameters (watershed position, stream planform type, and riverine corridor sampling location type) analyzed, these patterns tended to be more consistent when compared across watershed positions, with generally more deviation when viewed through the lenses of stream planform types and sampling type locations. Arid non-perennial streams provide critical watershed functions in various arid environs, yet further focused research is needed to augment Biodiversity, Energy dissipation, Hydrology, and Connectivity functions across both ephemeral and intermittent arid streams. Future global and U.S. research is also recommended within cold desert subclimes, across a greater diversity of channel forms and small-scale sampling location types, and with intermittent streams for providing information essential to regional stream assessment, management and regulation of arid non-perennial streams.

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