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Southwest Region Threatened, Endangered, and At-Risk Species Workshop: Managing Within Highly Variable Environments Hydrology and Ecology of Intermittent Stream and Dry Wash Ecosystems
Citation:
Levick, L., D. Goodrich, M. Hernandez, D. J. SEMMENS, J. Stromberg, R. LEIDY, M. Apodaca, P. Guertin, M. Tluczek, AND W. G. KEPNER. Southwest Region Threatened, Endangered, and At-Risk Species Workshop: Managing Within Highly Variable Environments Hydrology and Ecology of Intermittent Stream and Dry Wash Ecosystems. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-07/142 (NTIS PB2008-105119), 2007.
Impact/Purpose:
Given their vast extent, ephemeral and intermittent streams are crucial to the overall health of a watershed, providing a wide array of functions including forage, cover, nesting, and movement corridors for wildlife. Because of the relatively higher moisture content in dryland streams, vegetation and wildlife abundance and diversity is higher than in the surrounding uplands. Ephemeral and intermittent streams provide the same hydrologic functions as perennial streams by moving water, nutrients, and sediment through the watershed. When functioning properly, dryland streams provide many of the same services as perennial riparian-wetland areas, such as landscape hydrologic connections; stream energy dissipation during high-water flows that reduces erosion and improves water quality; surface and subsurface water storage and exchange; groundwater recharge and discharge; sediment transport, storage, and deposition aiding in floodplain maintenance and development; nutrient cycling; wildlife habitat and movement/migration; support for vegetation communities that help stabilize stream banks and provide wildlife services; and water supply and waterquality filtering. Ecologically sustainable land and wildlife management requires a landscape or watershed-scale approach to ecosystem protection, and would be meaningless and ineffective if these supporting waterways are significantly degraded.
Description:
Ephemeral (dry washes) and intermittent streams make up approximately 59% of all streams in the U.S. (excluding Alaska), and over 81% in the arid and semi-arid Southwest (Arizona, New Mexico, Nevada, Utah, Colorado and California) according to the National Hydrography Dataset. They are often the headwaters or major tributaries of most perennial streams in the Southwest, and make up 94% of stream miles in Arizona. Given their vast extent, ephemeral and intermittent streams are crucial to the overall health of a watershed, providing a wide array of functions including forage, cover, nesting, and movement corridors for wildlife. Because of the relatively higher moisture content in dryland streams, vegetation and wildlife abundance and diversity is higher than in the surrounding uplands. Ephemeral and intermittent streams provide the same hydrologic functions as perennial streams by moving water, nutrients, and sediment through the watershed. When functioning properly, dryland streams provide many of the same services as perennial riparian-wetland areas, such as landscape hydrologic connections; stream energy dissipation during high-water flows that reduces erosion and improves water quality; surface and subsurface water storage and exchange; groundwater recharge and discharge; sediment transport, storage, and deposition aiding in floodplain maintenance and development; nutrient cycling; wildlife habitat and movement/migration; support for vegetation communities that help stabilize stream banks and provide wildlife services; and water supply and water quality filtering. Ecologically sustainable land and wildlife management requires a landscape or watershed-scale approach to ecosystem protection, and would be meaningless and ineffective if these supporting waterways are significantly degraded.
URLs/Downloads:
HYDROLOGY AND ECOLOGY OF INTERMITTENT STREAM AND DRY WASH ECOSYSTEMS
Lainie%20Levick--Hydrology%20White%20Paper[2].pdf