new policy for IP v 2.2

Draft Guidance for the
Determination of the Origin of Perennial Streams
NC Division of Water Quality (DWQ)
12 October, 2004, Version 2.2
Background: A Stream Technical Advisory Committee (TAC) was established by the DWQ in
December 1998 to provide technical, scientific input related to the definitions of streams and
waterbodies in the Neuse River basin. The TAC approved a stream classification methodology that
evaluates the geomorphology, hydrology and biology of stream features to determine the origin of
intermittent streams as well as narrative definitions for these stream types (NCDWQ 1999). DWQ
utilizes a numerical cutoff of 19 points with this evaluation form as an appropriate value to classify a
stream as at least "intermittent". However, DWQ has not utilized a numerical cutoff for the perennial
threshold. Currently, the DWQ relies on a policy to describe the thresholds between intermittent and
perennial channels which suggests that investigators use the presence of biological indicators such as
fish, crayfish, amphibians, mussels (clams) or large (multi-year) tadpoles as perennial stream indicators.
This internal policy has proven to be effective in many instances such as intermittent/perennial
determinations during unusual flow periods (such as extreme drought) and in some ecoregions of North
Carolina (Triassic Basin and coastal plain streams). In addition, DWQ's water supply watershed
protection rules, which are implemented by local governments, and compensatory stream mitigation
requirements are affected by whether a stream is perennial or intermittent. His provides another reason
for DWQ to develop and utilize a more scientifically valid definition for perennial streams.
Recent and on going Investigations: As part of a recent investigation for the City of Greensboro,
personnel with Law Engineering and Environmental Services (now MacTec Environmental Services),
with the support of DWQ personnel, used a modification of the DWQ stream classification method and
recommend a numerical cutoff for a perennial stream origin in the piedmont of 30 points (Lawson, et al.
2002). In addition, DWQ biologists have been looking for the presence of keystone aquatic species as
reliable determinants for perennial channels. These investigations suggest that the presence of a select
group of benthic macroinvertebrates that require water for their entire life cycles (rheophilic taxa) is a
reliable method to determine the origins of perennial channels. A proposed list of these organisms is
included with this policy revision (Tables 1 and 2). The DWQ is currently conducting an investigation
to determine the ecological functions of intermittent stream channels. Results from this federally funded
investigation also has corroborated using a suite of rheophilic aquatic insect taxa to determine perennial
stream origins.
Revised DWQ Policy for the Definition of Perennial Stream Origins: A perennial stream is defined as a
well-defined channel that contains water year round during a year of normal rainfall' with the aquatic
bed located below the water table for most of the year (15A NCAC 213.0100). This definition also notes
that perennial streams exhibit the typical biological, hydrological, and physical characteristics
commonly associated with the continuous conveyance of water.
Therefore, to implement this definition, a perennial stream can be determined as follows:
A stream channel is perennial when any of the following criteria are met:
' Normal Rainfall is defined as the 30 year average, provided by NOAA National Climatic Data Center, computed
at the end of each decade. These data are available as annual and monthly means.
I . Biological indicators such as fish, crayfish, amphibians, mussels (clams) or large (multi-
year) tadpoles are present, OR
2. A numerical value of at least 30 points is determined from the most recent version of the
DWQ stream classification form , OR
3. Benthic macroinvertebrates that require water for entire life cycles are present as 3rd or 4th
instar larvae. A list of the benthic organisms commonly collected by DWQ biologists
during perennial stream determinations are shown inTables 1 and 2.
DWQ staff suggest that a stream be examined using these three criteria in the sequence above -
namely, a field examination should first look for criterion 1 and then criterion 2. If the channel
does not meet either of these two criteria and the field biologist believes the channel to be
perennial, then the third criterion should be utilized - however identification by a well-trained
aquatic entomologist is required for the proper use of this criterion. In most instances, the use of
either of the first two criteria should be sufficient to make a stream determination.
Table 1. Ephemeroptera, Plecoptera and Trichoptera (EPT) perennial stream indicator taxa.
Ephemeroptera
(Mayflies) Plecoptera
(Stoneflies) Trichoptera
(Caddisflies)
Family Baetidae Peltoperlidae Hydropsychidae
Caenidae Perlidae Lepidostomatidae
Ephemerellidae Perlodidae Limnephilidae
Ephemeridae Molannidae
Heptageniidae Odontoceridae
Leptophlebiidae Philopotamidae
Siphlonuridae Polycentropidae
Psychomyiidae
Rhyacophilidae
Table 2. Additional indicators of perennial stream features.
Megaloptera Odonata Diptera Coloptera Mollusca
Family Corydalidae Aeshnidae Ptychopteridae Elmidae Unionidae
Sialidae Calopterygidae Psephenidae Ancylidae
Cordulegastridae Planorbidae
Gomphidae Pleuroceridae
Family Libellulidae Tipulidae Dryopidae
Genus Tipula sp. Helichus sp
List of References
Lawson, J., R. Darling, D. Penrose, and J.D. Gregory. 2002. Stream Identification and Mapping for Water-Supply
Watershed Protection. In Proceedings, Watershed 2002, February 23-27, 2002, Fort Lauderdale, FL.
NCDWQ. (North Carolina Division of Water Quality) 1999. N. C. DWQ Stream Classification Form - Internal
Guidance Manual. North Carolina Division of Water Quality, Wetlands/401 Unit.
'Use of this form requires Division-based or approved training (or appropriate certification in accordance with GS
143-214.25).
2Recognition and/or identification of these organisms will require Division-based or approved training.