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Experimental Stream Research

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Small stream ecosystems include over 72% of the U.S. river miles. Yet, their role in managing watershed-level water quality remains uncertain. The potential impact of naturally occurring biogeochemical functions within an individual small stream may seem minimal. But the accumulated impact of the many small streams within a watershed may be significant.

Watershed Perspective

Small streams are largely unmapped, unregulated, and overlooked in watershed models. They are generally not considered in the TMDL (Total Maximum Daily Load) process or in land use regulations. They are often ignored in land development plans. They are often replaced with culverts, storm sewers, or lined ditches. This eliminates any role they may play in maintaining water quality.

EPA researchers are studying the importance of small stream ecosystems and the services they provide for effective watershed management. The Experimental Stream Facility sits at the downstream end of Little Miami River (East Fork watershed). Studies allow EPA to collect and analyze data on in-stream process-level biological, chemical, and physical interactions. Each study is designed to provide information on small stream ecosystem structure and functions that can be used for the development and testing of:

  • new indicators of ecological stress;
  • water quality monitoring technologies;
  • watershed monitoring strategies; and
  • water quality management methods and models.

This data is incorporated into a multi-spatial scale watershed research plan designed to characterize, track, and model changes to water quality associated with the National Pollutant Discharge Elimination System (NPDES) and Best Management Practices implementation projects.

Contaminant Perspective

In addition to watershed management research, EPA is characterizing how streams and rivers react to and process in-coming contaminants and stressful mixtures. EPA is conducting mesoscale (of medium size) studies to gain a better understanding of the impact of contaminant stressors on multiple ecosystem hierarchical levels and which level(s) are the most sensitive to stress.

Understanding the impact of and reducing the amount of contaminants on small streams is of concern to environmental stakeholders, including:

  • local and state governments,
  • utilities,
  • developers, and
  • homeowners.

Knowing how contaminants affect water ecosystems will help determine which pollutants may need to be regulated. Adoption of the watershed approach and best management practices to control pollutants is helping to reduce contaminants atthe watershed level. The ESF mesocosms are especially useful for studying the impacts of contaminants, such as:

  • endocrine disruptors,
  • pharmaceuticals, and
  • pesticides.

Contaminants can be added at:

  • environmentally relevant levels;
  • levels observed in natural ecosystems and
  • levels reported in literature.

Exposure at these levels lets researchers observe:

  • more subtle changes (e.g. gene and protein expression) in stream
  • changes in biotic communities and
  • ecosystem structure and function. 

The post-dose recovery period built into each experiment provides additional information on the ability of the ecosystem to recover when the contaminant is removed from the ecosystem. The relative importance of specific changes in stream habitat (e.g. sediment load, flow rates) on contaminant impact can be simulated and are often included as interacting variables. Additional biotic indicators can be studied through the use of

  • emergent traps,
  • fish deployments,
  • in-stream invertebrate exposures, and
  • real time biomonitoring.

References and Products

Contact
Donald Brown, (513) 569-7630
Christopher Nietch, (513) 569-7460

TMDL –– Each State must establish the total maximum daily load for certain pollutants for certain waters.

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