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Attachment 8.4 99 Surface Water Identification Training and Certification Program NC Division of Water Quality, Wetlands /401 Unit Hydrologic and Water Quality Functions of Headwaters Streams and Riparian Zones James D. Gregory Department of Forestry, NC State University January 30, 2002 Introduction The smallest steams in a watershed (headwaters streams) in aggregate are the principal connection between the land (terrestrial ecosystems) and the stream network (lotic ecosystems). Headwaters streams drain excess water and associated inorganic and organic constituents (dissolved and solid) from the watershed land areas and transport that water with associated constituents to the major tributaries and the main stem of a river system. Hydrologic, biological, and chemical processes that occur in the riparian zones and within the stream channels serve to remove many of the dissolved materials and solids that are transported off the land. Headwaters stream corridors in which ecological functions occur at the maximum levels found under natural conditions are, thus critical to maintaining acceptable water quality in the major tributaries, the main stems of rivers, and the large estuaries to which the rivers of the state discharge. The term "headwaters streams" is increasingly being used in the hydrology, geomorphology, and regulatory literature without clearly defining what is meant. Often, writers are referring to the portion of the stream network that is located farthest from the mouth of a watershed. In all cases, "headwaters" refers to the smallest streams in a stream network. However, I prefer to define headwaters steams in the context of the hydrologic role of small steams in a watershed as follows. Headwaters stream — refers to the first order and second order streams of a watershed without regard to location in the watershed or their classification as intermittent or perennial. Thus a headwaters stream can occur in the highest elevation area of a river basin at the farthest location from the mouth of the river or as a first or second order tributary to the main stem of river near the estuary. In terms of the regulatory application of the stream origin and stream corridor functions discussed in this training program, I also offer the concept of the "regulatory stream origin ". Identifying an intermittent or perennial stream origin in the field is an opinion based on best professional judgment. However, the stream definitions outlined below that have been adopted by the NC Environmental Commissions and the procedures for applying those definitions in the field are based on the following policy: The origin of a regulated stream is the most upstream point on a first order stream where the ecological functions of a stream are present and operating at a minimal level. S: \2_Boards \BOCC \2010 BOCC Agendas \6 -1 -10 \Upper Eno Critical Area Amendments\Att 8\Att 8.4 - Stream Order Info.doc