Investigating the Impact of Lowered Stream Flow on Stream Community Structure and Ecosystem Functioning

EPA Grant Number: F6E11094
Title: Investigating the Impact of Lowered Stream Flow on Stream Community Structure and Ecosystem Functioning
Investigators: Walters, Annika
Institution: Yale University
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2006 through September 1, 2009
Project Amount: $111,172
RFA: STAR Graduate Fellowships (2006) RFA Text |  Recipients Lists
Research Category: Aquatic Ecosystems , Fellowship - Aquatic Systems Ecology , Academic Fellowships


The maintenance of sufficient instream flow to maintain downstream ecosystems is a growing concern as the demand for water resources continues to increase. My research explores how changes to the natural flow regime, specifically lowered flow, affect stream communities, species interactions, and ecosystem functioning.

Flow is one of the key drivers in stream ecosystems; it can affect the abundance, distribution, and behavior of stream organisms through its effects on key ecological processes such as dispersal, habitat use, resource acquisition, and competition. The goal of my study is to link the effect of an altered stream hydrological regime with ecological interactions and ecosystem processes by examining stream community structure, species interactions, productivity, and decomposition in experimentally manipulated stream reaches.


I use natural stream reaches in which I alter the hydrologic regime using water diversion stations to create 100m low flow sections. I then sample above and below the diversion stations (control and low flow). I monitor changes in physical habitat characteristics, resource availability and quality, and aquatic insect and fish communities. I also explore effects of lowered flow on species interactions through small-scale experiments investigating grazing and predation, and examine ecosystem level processes including stream metabolism and leaf decomposition. I hope these varied approaches will give a more complete picture of the linkages between hydrology and ecological processes at the stream community and ecosystem level.

Expected Results:

I expect that low flow will affect habitat and resource availability with implications for stream community structure and ecosystem functioning. I hope results will be applicable to policy on instream environmental flows and mitigation strategies for drought events.

Supplemental Keywords:

streams, low flow, environmental flows, water diversion, aquatic insects, community structure, ecosystem function, hydrology, leaf decomposition, species interactions,, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Habitat, Environmental Monitoring, Ecology and Ecosystems, habitat dynamics, brown trout, fish, ecological consequences, breeding site contamination, stream flow, conservation biology, stream ecosystem

Progress and Final Reports:

  • 2007
  • 2008
  • Final