SI-2B (10/13/04 version)
Environmental Targets And Priorities, Stream Integrity, Stream/Watershed Components: Primary Headwater Streams


Ohio EPA defines headwater streams as a stream with a watershed less than or equal to 20 square miles. Headwater streams are the very small streams, creeks, and swales that are the origins of larger streams and rivers. Headwater streams comprise about 78% (115, 000 miles) of flowing waters in Ohio and affect the ecological and economic variability of downstream rivers through the regulation of flood waters, the maintenance of safe and high quality drinking water and pollution prevention. Therefore, the task of protecting water quality in larger streams and lakes begins with evaluating and protecting their source - primary headwater streams.

"Primary headwater" streams are those with less than 1 square mile of drainage area and deepest pools less than 40 cm. The natural or expected aquatic conditions in primary headwater streams can range from permanent spring fed environments with year round aquatic life, to seasonally flowing waters with temporary aquatic species, to drainage ways that only flow during and shortly after rainfall events. Primary headwater streams with permanent flow may not be visible, as some water flows through crevices or pores below the stream bed surface. Where flows are permanent, primary headwater streams may harbor a unique native fauna of temperature sensitive fish and/or amphibians, benthic macroinvertebrates, and aquatic plants. Salamanders replace fish as the top vertebrate predator in primary headwater streams.

A large proportion of the impacts to primary headwater streams are due to nonpoint source impacts (PDF 296kb). The cumulative effects of such impacts over a relatively large area and over time can be quite substantial. However, the hydraulic conditions in headwater streams fall outside the benthic macroinvertebrate ICI (PDF 801kb) sampling protocols for placement of artificial substrates, which require flowing water at 30 cm in depth with current velocity of 0.3 fps or greater.

Classifying Primary Headwater Habitat

Ohio does not consider grass waterways or other watercourses without a defined stream bead and bank, primary headwater streams. In addition, streams that have sufficient amounts of water throughout the year to support sufficiently large fish communities are assigned aquatic life uses under current water quality standards regulations for Ohio.

Remaining streams with drainage areas of less than 1 square mile can be categorized into Class I, II or III Primary Headwater Habitat Streams using the Headwater Habitat Evaluation Index (HHEI). The three metrics or indicators used in the HHEI are channel substrate (or bed material), bankfull width, and maximum pool depth. Further details are available by clicking here.

Regulation of Primary Headwater Habitat

Some primary headwater habitat streams are named in the Ohio's Water Quality Standards rules, in which case specific beneficial use designations (e.g., warmwater habitat or coldwater habitat) are assigned to the streams. However, most primary headwater streams are not named in the rules. For these waters no beneficial use designations are currently assigned.

The chemical water quality criteria for the warmwater habitat use designation apply to all surface waters of the State, including primary headwater streams, not specifically named in the Ohio's Water Quality Standards rules. If a primary headwater stream is named in the Ohio Water Quality Standards rules, the water quality criteria associated with the designated beneficial uses apply

Primary headwater streams, even if not specifically named in the Ohio's Water Quality Standards rules, are considered general high quality waters and are subject to all applicable provisions of the antidegradation rule.