Moving Headwater Streams to the Head of the Class

Extract

Everywhere on Earth, streams and rivers occur in hierarchical networks resembling the branching pattern of a tree, with smaller branches joining to form larger branches as water travels from uplands to lakes, estuaries, and seas. The finest branches of these networks, beginning where water flowing overland first coalesces to form a discernible channel, are called head-water streams. Conservative estimates indicate that headwater streams account for more than 70 percent of stream-channel length in the United States (Leopold et al. 1964), yet because of their small size, these streams are often missing from maps that guide the management of natural resources.

Relative to larger streams and rivers that are fed by upstream networks and affected by cumulative upstream stressors, the small drainage areas of head-water streams give these systems high levels of hydrologic independence and ecological autonomy. This independence justifies the use of headwater watersheds as building blocks in the construction of protected-area networks (Saunders et al. 2002) and their prioritization in management and regulatory efforts to protect many of the ecosystem services we value, such as clean water, recreational opportunities, nutrient removal, and biodiversity.