Channel and Perennial Flow Initiation in Headwater Streams: Management Implications of Variability in Source-Area Size Kristin L. Jaeger Æ David R. Montgomery Æ Susan M. Bolton Received: 28 September 2005 / Accepted: 23 April 2007 Ó Springer Science+Business Media, LLC 2007 Abstract Despite increasing attention to management of headwater streams as sources of water, sediment, and wood to downstream rivers, the extent of headwater channels and perennial flow remain poorly known and inaccurately depicted on topographic maps and in digital hydrographic data. This study reports field mapping of channel head and perennial flow initiation locations in forested landscapes underlain by sandstone and basalt lithologies in Washing- ton State, USA. Contributing source areas were delineated for each feature using a digital elevation model (DEM) as well as a Global Positioning System device in the field. Systematic source area–slope relationships described in other landscapes were not evident for channel heads in either lithology. In addition, substantial variability in DEM-derived source area sizes relative to field-delineated source areas indicates that in this area, identification of an area–slope relationship, should one even exist, would be difficult. However, channel heads and stream heads, here defined as the start of perennial flow, appear to be co-located within both of the lithologies, which together with lateral expansion and contraction of surface water around channel heads on a seasonal cycle in the basalt lithology, suggest a controlling influence of bedrock springs for that location. While management strategies for determining locations of channel heads and perennial flow initiation in comparable areas could assign standard source area sizes based on limited field data collection within that landscape, field-mapped source areas that support perennial flow are much smaller than recognized by current Wash- ington State regulations. Keywords Headwater streams Á Channel initiation Á Perennial initiation Á Source area sizes Á Seasonal flow characteristics Á Forest hydrology Introduction Headwater streams account for most of the drainage net- work and supply water, sediment, and wood to downstream fish-bearing channels (Gomi and others 2002, May and Gresswell 2003). Headwater streams also serve as critical habitat for aquatic species, some of which do not occupy larger channels (Wilkins and Peterson 2000). Increased pressure on the water and sediment regimes in headwater systems as a result of land use activities such as timber harvest and road building can impact headwater channels as well as the downstream network (Wemple and others 1996, Jones and others 2000, LaMarche and Lettenmaier 2001, Gomi and others 2004). It can therefore prove ben- eficial to restrict land-use activities around headwater streams. However, knowledge of the upstream extent of headwater streams, whether defined by the headward extent of channel systems or the uppermost point of perennial K. L. Jaeger College of Forest Resources, University of Washington, P.O. Box 352100, Seattle, WA 98195-2100, USA Present Address: K. L. Jaeger (&) Department of Geosciences, Colorado State University, 322 Natural Resources Building, Fort Collins, CO 80523, USA e-mail: kljaeger@cnr.colostate.edu D. R. Montgomery Earth & Space Sciences, University of Washington, P.O. Box 351310, Seattle, WA 98195-1310, USA S. M. Bolton College of Forest Resources, University of Washington, P.O. Box 352100, Seattle, WA 98195-2100, USA 123 Environ Manage (2007) 40:775–786 DOI 10.1007/s00267-005-0311-2