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Environmental Flow Research in the Tennessee River Basin

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Key Findings

 

Streamflow influences fish health and abundance in Tennessee

Analysis of streamflow and fish-community data across the Tennessee River Valley identified three aspects of streamflow essential to habitat suitability and food availability for insectivorous fish communities: constancy (flow stability or temporal invariance), frequency of moderate flooding (frequency of habitat disturbance), and rate of streamflow recession. Watershed management decisions that minimize change in these aspects of streamflow have the potential to increase the health of the fish community. Learn more…

Graph showing fish abundance


Climate and basin factors can be used to predict ecologically-relevant aspects of streamflow


Graphs showing mean annual runoff, frequency of moderate flooding, and timing of annual maximum streamflow

Throughout the US there are many more places were ecological sampling has occurred than where streamflow data is collected. Because of this disconnect, streamflow at places of ecological sampling must be estimated if any correlation between these two factors is to be determined. There are several ways to do this; we used a statistical approach. Streamflow is dictated by climate and basin influences, such as monthly mean precipitation, percent forest, and depth to bedrock. A statistical model was built to relate climate, land use, physical and regional basin factors to 19 ecologically-relevant aspects of streamflow (called streamflow characteristics). There were 231 sites in the Tennessee and Cumberland River basins available for model development. Some aspects of streamflow such as mean annual runoff, were highly predictable using statistical methods, other streamflow characteristics like annual maximum flow were less so. Learn more…


Place is more important than land use for influencing streamflow

Map of Tennessee

When predicting ecological-relevant streamflow characteristics the most influential variables relate to where the site is located (regional physiology) versus what type of land cover (forest, agriculture, or urban) is present.  In our statistical models, regional physiology was the most influential group of variables in predicting streamflow characteristics. This includes the percent of a watershed within either the Interior Plateau or Blue Ridge Level 3 ecoregions (Omernik 1987). Learn more…


Altered streams have a different “hydrologic profile” than other streams

Most streams in the United States have experienced some amount of alteration from natural conditions. Alteration can be a direct or indirect result of such processes as construction of a dam, withdrawing water from the stream or converting forested land to urban land within the watershed. Streamflow characteristics for altered streams have a different “hydrologic profile” when compared to a pristine or minimally-altered stream. For our study we considered the most forested sites within each ecoregion to be minimally-altered and the reference “hydrologic profile” to be the range of calculated values for each streamflow characteristic within this group. Learn more…

Graph showing streamflow characteristics

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