“The Experimental Stream facility was put into operation in 1987 by Proctor and Gamble
for risk assessment research on stream ecosystems. Today, the National Risk
Management Research Laboratory of the U.S. Environmental Protection Agency leads
research in the facility, expanding upon its experimental foundation to help the Agency
address multiple research needs related to protecting the health of stream ecosystems
The Experimental Stream Facility is named for it’s eight experimental stream mesocosms,
or half-way worlds between the laboratory and real streams. The artificial streams aren’t
scaled-down replicas of meandering stream channels, and can’t recreate the
geomorphological conditions of real streams. However, they can recreate the microhabitat
properties found in localized riffle–run- pool sections of regional streams.
During experiments they flow continuously with water supplied by real local streams, and they
naturally with biological organisms provided by these sources. They are also subject to the
changes in water quality that occur ‘naturally’ in these local streams. Indeed, they are designed
to provide a balance between controlled laboratory conditions and the natural
variability that is characteristic of stream ecosystems.
The upper section of each experimental stream is characterized with flows that are more
laminar, and is lined with clay tiles. The tiles provide a standard-sized substrate for studying
the attached stream periphyton community, which can be seen as a gelatinous matrix
consisting of algae, microbes, and deposited sediment. Periphyton fuels production in
stream ecosystems. During experiments, tiles are periodically removed for analyses that
determine the structure and function of the periphyton community.
The lower section of each mesocosm contains trays filled with gravel, similar to the best
riffle habitat for aquatic insect communities in real streams. During experiments the gravel
trays are routinely removed and the organisms making-up the biotic communities are
identified and measured. Certain aquatic insect groups are well-established indicators of stream condition.
The gravel trays also give size-specific information on sediment accumulation.
Special samplers are buried in the gravel of each tray to obtain information on the
chemistry of the gravel space. The data collected from all of these analyses
allows for focus on biogeochemistry, energy flow, and food chain dynamics. Finally, the
lower section can be isolated with nets to measure the type and number of organisms
drifting from the gravel, which may occur naturally or when organisms are stressed.
Analyses that are conducted on the gravel trays in the Experimental Stream Facility,
are also done on trays that have been placed in several local streams. Sampling and analysis
protocols used in the mesocosms and real streams are similar. This helps to apply the
results obtained under experimental conditions to real field conditions. Experimental Stream
Facility research is an integral part of a watershed scale case study designed to
characterize, track, and model changes to water quality associated with land use, storm
water control measures and other characteristics of the watershed.
Back at the mesocosms, tail tanks at the end of each gravel section can be considered
similar to pool habitat. In these tail tanks, there are a number of sensors monitoring
water quality parameters like dissolved oxygen, pH, temperature, conductivity, and turbidity.
The tail tanks also house clam monitors that provide continuous data on shell opening and
closing behavior, which can signal changes in water quality. Flow can be supplied from
these tanks to additional small tanks for exposure studies on larger stream biota
such as fish or amphibians. Data from the sensors in the tail tanks is continuously
transmitted to a central computer that provides continuous monitoring of water quality
parameters, as well as control of parameters such as water flow. The primary water source
for experiments is the Lower East Fork of the Little Miami River. A secondary water source is
a nearby headwater stream which is mostly forested. Treated wastewater from the plant
next door can be mixed in, and filtered tap water may also be used. The stream
can be run in parallel or in series, to create, in effect, longer stream sections. Recirculation
loops control water residence time while maintaining turbulent features of the main channel.
Mixing tanks are part of a chemical dosing system that allows for the accurate addition
of single or multiple chemical stressors. Grow lights simulate solar irradiance of about 10% of
full sun. This intensity is similar to a forested stream where leaves shade the channel.
Two mesocosms have additional high intensity lights to simulate streams flowing through an
open field. The lighting systems are controlled by the central computer to simulate daily cycles.
Collectively the experimental capabilities just discussed offer a broad array
of conditions that can be controlled in research studies. In conclusion, research at the
Experimental Stream Facility is important because small streams comprise over 72% of
the river miles in the United States. The role these small subwatershed streams play
in the overall health of larger watersheds is largely unknown. Research at the
Experimental Stream Facility will help environmental managers do a better job
of protecting ecological and human health.”
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