The Upper Flint River Basin
A number of factors make the upper Flint River Basin an appropriate setting for developing science to address water and ecosystem management issues. The upper Flint River flows unimpeded by major impoundments for about 195 river miles from its Piedmont headwaters onto the Coastal Plain Province and harbors habitats and biologically diverse communities that have been lost from impounded reaches of many other eastern rivers. The upper Flint River Basin also supplies water to a growing population in the Atlanta metropolitan area and is a major recreational resource for the region, providing canoeing, white-water rafting, and sportfishing opportunities.
Long-term streamflow gaging stations have provided flow data for more than 90 years in the upper Flint River Basin. Recently completed investigations of freshwater
mussel distributions and fish-habitat relations in the upper mainstem, and an aquatic Gap Analysis Program (GAP), provide baseline data for the system.
Continued growth in the Atlanta area will increase pressure on the ecological systems of the Flint River Basin because of the potential for increased water withdrawals, reservoir construction for water storage, urban runoff, and additional wastewater loadings. Thus, this setting incorporates problems common to many regions and rivers in the Eastern United States — how to balance water-supply development with protection of diverse aquatic ecosystem — and provides an opportunity for interdisciplinary innovation
in providing science-based solutions.
CHARACTERISTICS OF THE UPPER FLINT RIVER BASIN
The Flint River begins beneath Hartsfield
– Jackson International Airport on the south side of Atlanta and flows southward across the Georgia Piedmont and Coastal Plain to its junction with the Chattahoochee River, later forming the Apalachicola River. The upper Flint River Basin has a drainage area of about 2,630 square miles. Land use in the basin, which includes parts of the upper Coastal Plain, consists of about 57 percent forest, 17 percent agriculture, and 12 percent urban, with most of the urban land
concentrated in the extreme northern
part of the basin (Georgia Land Use Trends, 1998).
Population growth in the six-county Upper Flint Water Supply Management Area (UFWSMA, shown below) has increased more than 200 percent since 1970, from 133,470 to 302,714 during 2000 (CH2MHill, 2003). Predictions are that more than 550,000 persons will live in the six-county UFWSMA by 2030.
Water-Supply and Instream-Flow Issues
Most of the water supply in the upper Flint River Basin comes primarily from the Flint River or its tributaries. Withdrawal
from the 32 permitted municipal and industrial water-supply intakes totals about 108 million gallons per day (Mgal/d) and agricultural interests are permitted to remove an additional 90 Mgal/d from streams in the basin (Victoria P. Trent, Georgia Environmental Protection Division, written commun., 2005). Proposals have been submitted to increase surface-water supply capacity
in the upper Flint River Basin by 12.7 Mgal/d (about 7 percent) by building two additional reservoirs and expanding an existing reservoir (Georgia Department
of Natural Resources, 2003a). Under an interim State policy, required minimum flows below new reservoirs or stream withdrawals must adhere to one of three guidelines. Provide a minimum of:
- the monthly 7Q10 (the 7-day,
consecutive low flow with a
10-year return frequency);
- 30 percent of the mean-annual
flow for unregulated streams; or
- seasonally adjusted percentage of mean-annual flow for regulated streams.
The guidelines also suggest that site-specific studies can be used to determine minimum flows.
Stormwater Runoff
Stormwater runoff increases as impervious
surface increases. This affects stream geomorphology, water quality, temperature, aquatic ecosystems, and stream baseflows. No statewide policy currently exists to manage stormwater runoff except related to construction. Some municipal and county governments have implemented, or are in the process of implementing, stormwater-management
programs.
Federally and State-Listed Aquatic Species
The upper Flint River Basin contains extensive shoal habitat that supports riverweed (Podostemum ceratophyllum), waterwillow (Justicia sp.), and shoal lily (Hymenocalis coronaria). At least five fish species that are endemic to the Apalachicola River Basin occur in the upper Flint River Basin. The upper Flint River Basin historically supported at least 25 species of mussels including 6 federally
listed species. Recent surveys have reported only 20 species of native mussels
remaining in the basin.
Water Quality and Aquatic Biological Integrity
Urban development in the upper Flint
River Basin has resulted in water-quality
problems in the headwaters. Studies in
the early 1970s noted severe water-
quality problems due to high levels of
bacteria and nutrients in many of the
tributaries and the mainstem reaches of
the upper Flint River. During the period between 1972 and 1990, ammonia, dis-
solved nitrate, and phosphorous decreased
in the mainstem reaches due to improve-
ments in the quality of wastewater dis-
charges. A study conducted during 1992
found that nutrient levels in the mainstem
of the Flint River decreased by almost
an order of magnitude from those found
during the mid-1980s (Frick and others, 1996). From 1998 to 2002, 28 stream seg-
ments in the Flint River Basin were listed
as not supporting or only partially sup-
porting their designated water uses. Of the
28 stream segments, 14 are located in the
upper Flint River Basin and were listed as
having poor or very poor fish and inverte-
brate communities (Georgia Department
of Natural Resources, 2003b).
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U.S. Department of the Interior |
U.S. Geological Survey
