The Harpeth River, one of the most ecologically, culturally, historically, and
recreationally significant rivers in Tennessee, drains nearly 900 square miles
in Middle Tennessee and flows through one of the fastest growing areas in the
country. It is a state designated Scenic River in Davidson County and easily accessible
from downtown Nashville.
In 2010, the Harpeth River Watershed Association (HRWA) secured support from
collaborative funding programs of the U.S. Fish and
Wildlife Service, Southeast Aquatic Resources Partnership, and the National Fish Habitat Partnership (NFHP)
for activities that improve fish habitat and remove blockages to fish
passage. This project removed the only barrier on the Harpeth River, a
lowhead dam, and eliminated a 1.7-mile-long impoundment in order to reconnect
36 miles of river and restore riffle/run aquatic habitat that is presently
submerged. The project was a collaboration between HRWA, the City of Franklin,
and the TN Department of Environment and Conservation (TDEC), with a total cost
of $870,000. With the removal of the lowhead dam, the entire river system is
now a free-flowing river, making the Harpeth one of only three rivers in
Tennessee to achieve this status.
Completed
in 2012, the SARP-nominated Harpeth River and the associated “Lowhead Dam
Removal and Stream Restoration Project” was recognized as a NFHP “Water to
Watch” http://fishhabitat.org/content/harpeth-river-tennessee.
Since that time, the project has continued to provide a variety of outstanding
ecological and community benefits.
I. Fishing/Recreational Opportunities
The project has made a
significant difference in promoting more angling and paddling opportunities to
the public.
Fishing
– While this has historically been a popular fishing spot and location of the
Tennessee Wildlife Resource Agency’s (TWRA) annual trout stocking, use of the
Eastern Flank for fishing has increased.
Link:
TWRA trout stocking location map http://www.arcgis.com/home/webmap/viewer.html?webmap=863204a4d2334a80b223a61e498a97cf&extent=-93.7896,31.6695,-77.5628,38.9228
Habitat/Water Quality Improvements
The project has made a
significant and measurable difference to improving habitat and water quality.
The
Tennessee State Wildlife Action Plan notes a number of aquatic species of
concern in the Harpeth River, including multiple freshwater mussels and
darters. The Harpeth is one of three of
the last remaining rivers in Middle Tennessee with darter species that need
riffle/run habitat. The Harpeth and its
tributaries are known for smallmouth bass, and other sport fish as well.
The City of Franklin withdraws from the Harpeth for its drinking water
plant from the shallow impoundment behind the lowhead dam, constructed in
1963. The structure was removed as part
of modernizing its water withdrawal as a condition in its state 2007 Aquatic
Resource Alteration Permit (ARAP). This project’s design is based on Natural Channel Design methods replaced the 6.2-foot-high
lowhead dam with a low-profile, in-stream, double cross vane boulder structure
to restore the natural fish habitat in this area, and reestablished natural
river flows intended to increase dissolved oxygen levels in the river. The
new double cross vane restores the river’s water surface elevation to nearly
original levels, while maintaining the City of Franklin’s ability to withdrawal
water.
The former lowhead dam created a 1.7-mile-long pool in the river that had inundated
natural riffle/run habitat. During the summer, oxygen levels were measured
significantly below state standards in the water behind the lowhead
dam. With only a trickle of water over the structure during the summer,
fish could not move upstream beyond the lowhead dam. In addition to the
fish passage barrier removal and enhanced connectivity, the restoration also
included stabilizing the eroding streambanks and revegetating the riparian zone
with native vegetation.
Habitat
– The Tennessee Wildlife Resource Agency biologists also did pre and post-project
fish community studies in April 2011 and April 2015. According to the 2015 assessment,
“The physical aspects of the habitat restoration project appear to be very
successful. The new habitat was stable and connectivity for fish greatly
improved.”
Link: Fish Community Assessment of the Harpeth
River Before and After a Habitat Restoration Project in Tennessee
Water
quality – For several years, the HRWA has conducted dissolved oxygen (DO)
sampling. Prior to the lowhead dam removal DO concentrations were 2.0 mg/l in
the stagnant algal pool below the structure during the summer. Contributing
factors to these low DO levels included the lowhead dam and the City’s drinking
water withdrawal operations (prior to the ARAP water withdrawal permit) would
pump the river until the flow didn’t go over the dam during the day. The pumps
were turned off at night and the river’s flow would build up and then flow over
the structure. This was a common pumping
operation until Sept 2007.
More
recent DO studies conducted by the HRWA indicate increased DO and water quality
improvements. It is also possible that
the combination of the project and the ARAP water withdrawal permit that now
manages the City’s water withdrawals to maintain ecological flows has improved
the Harpeth’s summer conditions through Franklin. Benthic data collected by the
City of Franklin just upstream of the sewer plant discharge point every year
has shown an improvement in benthic macroinvertebrate scores.
I.
Socioeconomic Benefits
There have there been
remarkable social benefits to the City of Franklin, Tennessee and the local
community as result of the project.
The Harpeth River, one of the most ecologically, culturally,
historically, and recreationally significant rivers in Tennessee, drains nearly
900 square miles in Middle Tennessee and flows through one of the fastest
growing areas in the country. The City of
Franklin, TN is situated in Williamson County, one of the wealthiest counties
in the nation. While the exact economic benefits of the project have not been
quantified, it was very significant in changing the story on the river to the
city leadership. The City now celebrates the Harpeth River as a major
asset, along with its civil war history. Franklin’s success nationally has
been driven by the huge efforts on historic preservation and marketing.
With the removal of the lowhead dam by this project, the entire river system is
now free-flowing without barriers, making the Harpeth one of the few rivers in
Tennessee to achieve this status.
Link: Franklin’s Former Lowhead Dam Site
Is Now A River Access & Historic Battlefield Park
Since the removal of the lowhead dam and the implementation
of the restoration project, the Harpeth River has received positive state and
national recognition, including the following:
Initiative https://www.doi.gov/pressreleases/Salazar-Highlights-11-River-Projects-in-Southeast-and-Mid-Atlantic-States-under-Americas-Great-Outdoors-Rivers-Initiative
- The Department of Interior’snational recognition of the project as part of the President’s River’s
Environmental Stewardship http://www.harpethriver.org/programs///newwaterquality2/newwaterquality2/dam/the-harpeth-river-restoration-project-recognized-with-2013-governors-environmental-stewardship-award.829819
- TheHarpeth River Restoration Project Recognized with 2013 Governor’s