EXECUTIVE SUMMARY

The term Baseflow Augmentation by Streambank Storage is used in this report to refer to the temporary storage of subsurface water in floodplains, streamsides, streambanks and/or streambottom during the wet season, either by natural or artificial means, for later release during the dry season to increase the magnitude and permanence of low flows.

Baseflow augmentation is intrinsically related to the type of streamflow regime, whether ephemeral, intermittent, or perennial, and to the characteristics of the stream-aquifer system, whether effluent or influent. Sustainable amounts of low flow appear to be possible only in streams that can remain effluent throughout the dry season. In order for the stream to remain effluent, the aquifer feeding the stream should be: (1) replenished seasonally with adequate amounts of moisture, (2) shallow enough to be intersected by the stream bottom, and (3) of sufficient size and suitable drainage characteristics.

Adequate aquifer replenishment leads to shallow groundwater tables, which, in aquifers of sufficient size and suitable drainage characteristics, can cause a stream to flow year-round. While aquifer replenishment is generally subject to management, the hydraulic properties of aquifers are largely determined by nature, with little or no human intervention. Therefore, it should be possible to accomplish baseflow augmentation with a management strategy focused on adequate seasonal replenishment of selected aquifers. The aquifer's size and hydraulic properties can be used to identify those which can be readily managed for baseflow augmentation. the vegetative aspects of baseflow augmentation should also be taken into account. Vegetation aids in aquifer replenishment and in raising stream base levels, thereby helping to create an environment conducive to baseflow augmentation.

Four case studies of baseflow augmentation were reviewed for this report: Camp Creek (Oregon), Sheep Creek (Utah), Alkali Creek (Colorado), and Trout Creek (Colorado). These experiences have shown that it is possible to accomplish baseflow augmentation with a broad range of land and water management strategies. At Camp Creek, baseflow augmentation was primarily the

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result of livestock grazing exclusion. At Sheep Creek, sediment accumulated behind a large barrier dam, and created an artificial aquifer. To this date, this dam and aquifer capture and store water during the high flow season, and release it during the low flow season. The Alkali Creek and Trout Creek watershed rehabilitation projects showed that baseflow augmentation can be counted as the byproduct of structural and nonstructural watershed treatments for the control of gully erosion.

Management strategies for baseflow augmentation fall under one of the following five categories: (1) rangeland management, (2) upland vegetation management, (3) riparian vegetation management, (4) upland runoff detention and retention, and (5) the use of instream structures. When properly designed and implemented, any of these strategies or a combination thereof can lead to baseflow augmentation, given the proper topographic, geologic, hydrogeologic, and climatic setting.

This literature review has shown that the physical mechanisms and related processes governing baseflow augmentation by streambank storage are reasonably well understood. Moreover, the limited field experience reviewed for this report has clearly shown the wide-ranging benefits to be derived from a management strategy focused on baseflow augmentation. However, additional research is needed on how to successfully integrate the concept of baseflow augmentation within comprehensive resource management strategies, given the economic, political, and institutional constraints.
 

Project Manager:  Donna S Lindquist

Research Director: John W. Icanberry

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"When forests are destroyed (as they are everywhere in America by the European planters), the springs dry up entirely or become less abundant. The river beds, remaining dry during part of the year, are converted into torrents whenever great rains fall onto the adjacent mountains. The sward and moss disappearing with the brushwood from the sides of the mountains, the waters collecting from the rain are no longer impeded in their course; and instead of slowly augmenting the levels of the rivers by progressive filtration, they furrow during heavy showers the sides of the hills, bear down the loosened soil, and create those sudden inundations that devastate the country. Hence it results that the destruction of forests, the want of permanent springs, and the occurrence of floods, are three phenomena closely connected together."
— Alexander von Humboldt

Personal Narrative of Travels
to the Equinoctial Regions
of the New Continent
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ACKNOWLEDGMENTS

The author wishes to thank the following individuals, who reviewed this report in its draft form and made substantial contributions to its content, language, and style.
 
 

Leonard F. DeBano USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Tempe, Arizona
Robert L. Beschfca Oregon State University, Corvallis, Oregon
Linton y. Bowie Pacific Gas and Electric Company
Korbin D. Creek Pacific Gas and Electric Company
Wayne Elmore USDI Bureau of Land Management, Prineville, Oregon
Gary Freeman Pacific Gas and Electric Company
Chuck Harnish USDA Forest Service, White River National Forest, Glenwood Spring, Colorado
Larry L. Harrison Pacific Gas and Electric Company
Burchard H. Heede USDA Forest Service Rocky Mountain Forest and Range Experiment Station, Tempe, Arizona
Donna S. Lindquist Pacific Gas and Electric Company
George R. McCalla Pacific Gas and Electric Company
William S. Platts Don Chapman Consultants, Boise, Idaho
Roland J. Risser Pacific Gas and Electric Company
Fred D. Stabler USDI Bureau of Land Management, Rawlins, Wyoming
Bruce Thomas USDA Forest Service, San Isabel National Forest, Salida, Colorado
Ellen H. Yeoman Pacific Gas and Electric Ccmpany

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