In 1991, the Apalachicola-Chattahoochee-Flint (ACF) River basin was selected for investigation in the NAWQA Program. The watershed boundary of the ACF River basin defines an ecosystem in which the quality of the water is a result of the complex interaction of natural and human influences on land and water resources.
The purposes of this report are to describe the environmental setting and the influence of this setting on aquatic ecosystems of the ACF River basin. The environmental setting includes physical, biological, and cultural characteristics of the ACF River basin. The physical setting includes physiographic, soil, climatic, and hydrologic factors. The biological setting summarizes historical and current (1992) information on habitats and aquatic biota within the basin. The cultural setting describes how the human population uses land and water resources within the basin.
Available literature and reports from Federal, State, and local agencies are used to describe the environmental setting of the ACF River basin. Whereas many of these reports deal with topics of limited scope and geographic extent, it is the objective of this report to provide a broad synthesis of topics relevant to understanding determinants of the health of the aquatic ecosystem and water-quality conditions in the ACF River basin.
Although the basinwide scope of NAWQA's ACF River basin study is unprecedented, water-quality assessments of regional scope have been conducted previously in parts of the basin. The USGS conducted two earlier regional water-quality studies, one in the Apalachicola River basin (Elder and others, 1988), and another in the upper Chattahoochee River basin (Cherry and others, 1980).
In 1971, the Georgia Water Quality Control Board (predecessor to the Georgia Department of Natural Resources, Environmental Protection Division) published a water-quality assessment of the Chattahoochee River from its headwaters to Lake Seminole, and an assessment of the Flint River from Fulton County to near Griffin, Ga., (Georgia Water Quality Control Board, 1971a,b). Another water-quality study of regional scope was conducted on West Point Lake by the USGS for the U.S. Army Corps of Engineers (USACOE) (Radtke and others, 1984).
Near West Point Lake, the Chattahoochee River defines the state
boundaries between Alabama and Georgia. The Flint River basin is contained
entirely within Georgia. Except for the upper reaches of the Chipola River in
Alabama, the Apalachicola River basin is contained within the panhandle of
Florida.
The northernmost part of the ACF River basin is within the Blue Ridge Province
where headwaters of the Chattahoochee River arise. Less than one percent of the
basin lies within the Blue Ridge Province. The Blue Ridge Province is dominated
by rugged mountains and ridges that range in altitude from 3,000 to 3,500 feet
(ft). The boundary between the Blue Ridge and the Piedmont is defined by a
sharp change in slope at an altitude of approximately 1,700 ft. The Blue Ridge
and Piedmont Provinces are underlain by mostly Precambrian and older Paleozoic
crystalline rocks that include mica schist, felsic gneiss and schist, and
granite and granite gneiss. Less extensive outcrops of quartzites are also
present.
The part of the ACF River basin within the Piedmont Province in Georgia contains
parts of seven physiographic districts-the Dahlonega Upland, the
Hightower-Jasper Ridges, the Central Uplands, the Gainesville Ridges, Winder
Slope, the Greenville Slope, and the Pine Mountain Districts (Clark and Zisa,
1976). In the Piedmont Province within Alabama, the ACF River basin lies in the
Piedmont Upland District (Copeland, 1968).
The northeast trending linear-ridge structure of the Hightower-Jasper Ridges,
the Central Uplands and Gainesville Ridges Districts strongly control the course
of the upper Chattahoochee River and its tributaries. In particular, highly
fractured faults in the Gainesville Ridges District forces the Chattahoochee
River and its tributaries into a rectangular drainage pattern. Within these
three ridge districts, altitudes range from about 1,500 ft in the northeast and
to about 1,000 ft in the southwest. Relief, the distance between minimum and
maximum altitudes, varies from approximately 500 ft in the northeast to 100-200
ft in the southwest (Clark and Zisa, 1976).
The Greenville Slope District in Georgia and the Piedmont Upland District in
Alabama are both characterized by rolling topography with altitudes ranging from
1,000 ft in the Greenville Slope to 500-800 ft in the Piedmont Upland (Clark and
Zisa, 1976; Copeland, 1968). Streams occupy broad, shallow valleys separated by
broad, rounded divides and have dendritic drainage patterns.
The Pine Mountain District in Georgia rises abruptly from the Greenville Slope
District to altitudes of 1,200-1,300 feet. The Pine Mountain District is
dominated by Pine Oak Mountain, which is capped by quartzite. This district is
notable for the presence of natural, warm-water springs flowing from fractured
quartzite. Watersheds on the southern face of this west-to-east trending
mountain ridge have rectangular drainage patterns (Clark and Zisa, 1976).
The Fall Line is the boundary between the Piedmont and Coastal Plain Provinces.
This boundary approximately follows the contact between crystalline rocks of the
Piedmont Province and the unconsolidated Cretaceous and Tertiary sediments of
the Coastal Plain Province. As implied by the name, streams flowing across the
Fall Line can undergo abrupt changes in gradient which are marked by the
presence of rapids and shoals. Geomorphic characteristics of streams differ
between the Piedmont and Coastal Plain Provinces. In the Coastal Plain, streams
typically lack the riffles and shoals common to streams in the Piedmont, and
exhibit greater floodplain development and increased sinuosity (Wharton,
1978).
The Coastal Plain Province contains three distinct regions-a hilly region
immediately below the Fall Line; a region of karst topography; and a low-lying
coastal region. The Fall Line Hills District in Georgia and Alabama, and the
Chunnennuggee and Southern Red Hills Districts in Alabama are highly dissected
with relief ranging 50-250 ft. Cretaceous sediments lie in a band immediately
below the Fall Line and crop out into younger Eocene-Paleocene sediments of the
low-lying Dougherty Plain District.
The Dougherty Plain and the Mariana Lowlands Districts are characterized by
outcrops of the Ocala and Suwannee Limestones that result in a karst
topography. The Dougherty Plain slopes southwestward with altitudes of 300 ft in
the northeast to less than 100 ft near Lake Seminole. The flat to very gently
rolling topography contains numerous sinkholes and associated marshes and
ponds. Small streams in the Dougherty Plain District are frequently intermittent
during the summer. The eastern boundary of the ACF River basin includes a small
portion of the Tifton Upland District where the boundary with the Dougherty
Plain is defined by the steeply sloping Pelham Escarpment. This solution
escarpment continues to the northeast, forming the surface-water divide between
the Flint River basin and the Ochlockonee River basin to the east.
A detailed description of physiography in the Apalachicola River basin is
contained in Leitman and others (1983). The upper part of the basin lies within
the Tallahassee Hills, Grand Ridge, New Hope Ridge, and Marianna Lowlands
Districts. As it flows through the Tallahassee Hills District, the Apalachicola
River is bordered on the east side by steep bluffs. The Tallahassee Hills
District has altitudes as high as 325 ft, and is bounded on the south by the
Cody Scarp, where elevations drop 15 to 20 ft to the Gulf Coast Lowlands. The
Marianna Lowlands is a karst plain drained by the Chipola River, the largest
tributary within the Apalachicola River basin.
The Gulf Coast Lowlands lie south of the Tallahassee Hills, Grand Ridge and New
Hope Ridge Districts and extend to the Gulf of Mexico. This flat, sandy lowland
was shaped by waves and currents during inundation by Pleistocene seas. This
district is less than 100 ft in elevation. As the Apalachicola River flows
southward through the Gulf Coast Lowlands, its floodplain broadens in width from
3 to 5 miles (mi).
Soils of the ACF River basin are divided into
six major land-resource areas (10K) (formally called soil provinces).
The Southern Piedmont, Georgia Sand
Hills, Southern Coastal Plain, and Eastern Gulf Coast Flatwoods land-resource
areas cover 97 percent of the ACF River basin. The Southern Piedmont
land-resource area is dominated by ultisols. Piedmont ultisol soils are acid,
low in nitrogen and phosphorus, and generally lack the original topsoil. Topsoil
erosion began with intensive cultivation of cotton in the 1800's (Wharton,
1978).
Soils in the Southern Coastal Plain and the Georgia Sand Hills land-resource
areas are derived from marine and fluvial sediments eroded from the Appalachian
and Piedmont Plateaus. Ultisols are found throughout the Southern Coastal Plain,
with the exception of some areas in the Georgia Sand Hills and Dougherty Plain
where entisols locally are present.
The Eastern Gulf Coast Flatwoods land-resource area, which composes much of the
Apalachicola River basin, is dominated by spodosols. Spodosols of the low-lying
Eastern Gulf Coast Flatwoods are poorly-to-very poorly drained.
Basinwide patterns in soil leaching and runoff potential provide information on
areas that may be susceptible to greater contaminant transport through
infiltration or runoff. Soils with high leaching rates are concentrated in thesandy Cretaceous sediments below the Fall Line and in the sandy surficial sediments of the East Gulf Coast Flatwoods.
Runoff ratings are based on the inherent capacity of bare soil to permit
infiltration, and consider slope, frequency of flooding during the growing
season, and permeability (Brown and others, 1991). Soils with high runoff
ratings are distributed throughout the basin, but are concentrated in areas
having low permeability, steep slopes; or where flooding is frequent or the
water table is near the surface, such as in floodplains and other low-lying
areas. In the ACF River basin, soils with the highest runoff rate are present on
steep slopes in the Blue Ridge, several areas in the Piedmont Province, the Fall
Line Hills District, and in the lower Apalachicola River basin where soils
commonly remain saturated.
Because the ACF River basin spans about 5 degrees of latitude, it has a sharp
gradient in growing seasons. Average annual temperature ranges from about 60°F
in the north to 70°F in the south. Average daily temperatures in the basin for
January range from about 40°F to 55°F, and for July from 75°F to 80°F.
In the winter, cold winds from the northwest cause the minimum temperature to
dip below freezing for only short periods. Summer temperatures commonly range
from the 70's to the 90's.
Precipitation is greatest either in the mountains as a result of their
orographic effect or near the Gulf of Mexico as a result of the availability of
moist air. Average annual precipitation in the basin, primarily as
rainfall, is about 55 inches (in.), but ranges from a low of 45 in. in the
east-central part of the basin to a high of 60 in. in the Florida panhandle
(U.S. Geological Survey, 1986).
Evapotranspiration generally increases from north to south and ranges from about
32 to 42 in. per year. In the east-central part of the basin, precipitation and
evapotranspiration are about equal. Average annual runoff ranges from 15 to 40
in. Runoff is greatest in the Blue Ridge Mountains and near the Gulf coast (Gebert and others,
1987).
Thirteen of 16 dams on mainstem locations in the ACF River basin are on the
Chattahoochee River. Dam construction in the basin began in
the early 1800's on the Chattahoochee River above the Fall Line at Columbus,
Ga., to take advantage of natural gradients for power production. Annual flow
has not been appreciably altered by the system of dams, although storage is used
to augment flows during periods of low flow; and daily fluctuations below some
reservoirs can be dramatic. Pronounced decreases in the frequency of high and
low flows have occurred since the start of operation of Buford Dam that forms
Lake Sidney Lanier. Lake Sidney Lanier, West Point Lake, and Lake Walter
F. George provide most water storage available to regulate flows in the
basin. Lake Sidney Lanier alone provides 65 percent of conservation storage,
although it drains only 5 percent of the ACF River basin. In addition, West
Point Lake and Lake Walter F. George provide 18 and 14 percent, respectively, of
the basin's conservation storage (Leitman and others, 1991).
Over most of its length, the flow of the Chattahoochee River is controlled by
hydroelectric plants releasing water for production of hydropower. These
hydroelectric plants use hydropeaking operations to augment power supply during
peak periods of electric demand. At Cornelia, Ga.,
the Chattahoochee River is free flowing; however, throughout the remainder of
its length, the river's hydrograph shows the influence of hydropeaking operation. Hydropeaking operations can result in daily stage fluctuations
of 4 ft or more.
In contrast to the mainstem Chattahoochee River, many tributaries
remain free flowing. Flows of tributaries in forested basins are
represented by Snake Creek that drains 35.5 sq mi above
streamflow-gaging station 02337500. Flows typical of urban basins are
represented by Peachtree Creek. Above streamflow-gaging
station 02336300, Peachtree Creek drains a 86.8 sq mi urban basin in
Metropolitan Atlanta. Similar to most Piedmont streams, both streams
have higher sustained flows during winter months, and show responses
to storm events throughout the year. However, sharper peaks in the
hydrograph of Peachtree Creek reflect the greater influence of
impervious land cover in this urban basin.
Spring Creek, formerly a Flint River tributary that now discharges directly into
Lake Seminole, drains 585 sq mi in a region of karst topography. As implied by its
name, flow in Spring Creek is dominated by ground-water discharge directly into
its limestone bed.
From 1977-92, the discharge of the Flint River based on mean daily flows at
Newton, Ga., was 4,030 cfs. Mean daily discharge ranged from 922 cfs in 1991
to 47,000 cfs in 1990. Two hydropower dams located on the Flint
River impound run-of-the-river reservoirs and do not
appreciably influence the flow of the Flint River. The Flint River has one of
only 42 free-flowing river reaches longer than 125 mi remaining in the
contiguous 48 states (Benke, 1990).
Higher flows during winter months are evident in the annual hydrographs of the
Flint River, Ichawaynochaway Creek, and Spring Creek. During
winter months, Coastal Plain streams, such as Ichawaynochaway and Spring Creeks,
flow for sustained periods through their floodplains.
Because of rainfall-distribution patterns, the average annual runoff from the
Chattahoochee River exceeds that of the Flint River. The Chattahoochee River
makes a greater contribution to peak flows in the Apalachicola River than the
Flint River. However, during extreme dry periods, the greater flow contribution
in the Apalachicola River comes from the Flint River, where baseflow is
sustained by ground-water discharges (Elder and others, 1988).
Leitman and others (1983) studied stage and discharge records from 1929-79 to
determine if significant hydrologic changes occurred in the Apalachicola River
as a result of dam-flow regulation. Dams have had little effect on the magnitude
of high flows or seasonal distribution of discharge over an annual cycle. Dam
regulation did reduce the amount of time that flow was at low extremes. Water
stages in the river within the first 30 mi downstream of Jim Woodruff Lock and
Dam have lowered due to scouring of the river bottom.
Aquifers in the Coastal Plain Province consist of alternating units of sand,
clay, sandstone, dolomite, and limestone that dip gently and thicken to the
southeast. Confining units between these aquifers are mostly silt and clay. From
the Fall Line to the Gulf of Mexico, progressively younger sediments crop out
and overlie older sediments. The complex interbedded clastic rocks and sediments
of Coastal Plain aquifers range in age from Quaternary to Cretaceous. Because of
gradational changes in hydrologic properties, aquifer and stratigraphic
boundaries are not always coincident.
The surficial aquifer system is a shallow, mostly unconfined water-table aquifer
consisting of cross-bedded sand, gravel and clay with undifferentiated alluvium
near rivers. Surficial deposits are associated with all outcrop areas shown on the Generalized Outcrop map. However, only in the southern part of the ACF River basin do these
deposits contain ground water whose use warrants mapping as a single aquifer
(Miller, 1990). Isolated domestic wells withdraw water from the surficial
aquifer system.
The Floridan aquifer system, one of the most productive aquifers
worldwide, underlies about 100,000 sq mi in Florida, southern Alabama,
southern Georgia, and southern South Carolina. The Floridan aquifer
system is comprised of a thick sequence of carbonate rocks that are of
Tertiary age and are hydraulically connected in varying degrees
(Miller, 1986). The Ocala Limestone is one of the thickest and most
productive formations that crops out in the Dougherty Plain and gives
rise to a karst topography riddled with sinkholes. The complex
hydrogeology of the Floridan aquifer system is reflected by highly
variable transmissivities that range from 2,000 to 1,300,000 feet
squared per day (sq ft/d). Range in transmissivities in the Ocala
Limestone is caused by the variable, fractured nature, and the
dissolution of limestone that creates conduits and solution openings
(Miller, 1986).
The Tallahatta Formation of Eocene age is the principal water-bearing formation
of the Claiborne aquifer (McFadden and Perriello, 1983). The Clayton Formation
of Paleocene age is the water-bearing formation of the Clayton
aquifer. Cretaceous units crop out immediately below the Fall Line. The
principal water-bearing formation is the Providence Sand of Late Cretaceous age
(McFadden and Perriello, 1983). Older Cretaceous strata generally are too deep
to be economically developed.
Aquifers in the Piedmont and Blue Ridge Provinces are in crystalline rocks that
crop out in the northern part of the basin and extend to the Fall Line. These crystalline rocks have similar hydraulic characteristics and are
mapped as one aquifer. The metamorphic and igneous crystalline rocks of the
crystalline aquifer are overlain by pockets of regolith (weathered,
unconsolidated rock debris) of varying thicknesses. The greatest thicknesses of
regolith, as much as about 100 ft, are in draws and valleys. Because the
crystalline rocks have few primary pore spaces, ground water is obtained
primarily from the regolith and from fractures in the rock. Reported yields of
wells completed in these rocks range from zero to 471 gallons per minute
(gal/m), but are commonly less than 50 gal/m (Cressler and others, 1983; Chapman
and others, 1993).
The regional direction of ground-water flow is from north to south; however,
local flow directions vary, especially in the vicinity of streams and areas
having large ground-water withdrawals. Rivers and streams in the Coastal Plain
Province commonly are deeply incised into underlying aquifers and receive
substantial amounts of ground-water discharge. Strata associated with the
Floridan aquifer system are exposed along sections of the Apalachicola,
Chattahoochee, and Flint Rivers; and Spring Creek (Maslia and Hayes, 1988). As a
result of the hydraulic connection between the Floridan aquifer system and the
Flint River, ground-water discharge contributes more significantly to baseflow
in the Flint River than in the Chattahoochee River. Aquifer discharge to the
Chattahoochee River is estimated to be one-fifth of the amount that discharges
to the Flint River (Torak and others, 1993).
Text is extracted from Couch and others, 1995
Physical Setting
The physical setting of the ACF River basin includes its location, physiography,
soils, climate, surface- and ground-water hydrology, and its natural water
quality. These physical factors provide the natural template that influences the
basin's biological habitats and diversity, and the way in which humans use the
basin's land and water resources.
Location
The ACF River basin NAWQA study area (12K)is about 20,400 sq mi. This number includes the drainage area at the mouth of the Apalachicola River (19,600 sq mi) (U.S. Army Corps of Engineers, 1985); the New River watershed (about 510 sq mi) (U.S. Geological Survey digital files); and the Apalachicola Bay and surrounding coastal areas and barrier islands (about 270 sq mi) (U.S. Geological Survey digital files). The Chattahoochee and Flint Rivers merge in Lake Seminole to form the Apalachicola River, which flows through the panhandle of Florida into the Apalachicola Bay, and discharges into the Gulf of Mexico.
Physiography
The ACF River basin contains parts of the
Blue Ridge, Piedmont, and Coastal
Plain physiographic provinces (12K) that extend throughout the southeastern United
States. Similar to much of the Southeast, the basin's physiography
reflects a geologic history of mountain building in the Appalachian Mountains,
and long periods of repeated land submergence in the Coastal Plain
Province. Glaciers, which influenced the physiography of much of North America,
never extended to the southeastern United States. Physiography within the major
provinces is not homogeneous and has been subdivided by the States of Alabama,
Florida, and Georgia into the districts shown on the Physiographic Province map. Although similar physiography may extend across state boundaries, districts may be assigned different names by state geologists in each state.
Soils
Three major soil orders-ultisols, entisols, and spodosols, and more than 50 soil
series-are present in the ACF River basin (Hajek and others, 1975; Perkins and
Shaffer, 1977; Caldwell and Johnson, 1982). Ultisols are characterized by sandy
or loamy surface horizons and loamy or clayey subsurface horizons. These deeply
weathered soils are derived from underlying acid crystalline and metamorphic
rock. Entisols are young soils with little or no change from parent material and
with poorly developed subhorizons. These soils are frequently infertile and
droughty because they are deep, sandy, well-drained, and subject to active
erosion. Spodosols are characterized by a thin sandy subhorizon underlaying the
A horizon. This sandy subhorizon is cemented by organic matter and aluminum.
The ACF River basin is similar to much of the southeastern coastal plain in the
dominance of ultisols. Entisols are found at and below the Fall Line and in the
Dougherty Plain; and spodosols are found in the Gulf Coast Lowlands.
Climate
The ACF River basin is characterized by a warm and humid, temperate
climate. Major factors influencing climate variability in the basin are
latitude, altitude, and proximity to the Gulf of Mexico.
Surface-Water Hydrology
The Chattahoochee and Flint River basins in Georgia contain most of the
headwater watersheds for surface waters that flow into or are used by the
Florida and Alabama parts of the basin. This section describes the hydrology of
the Chattahoochee, Flint, and Apalachicola River basins. Throughout the ACF
River basin, low flows usually occur from September to November and peak flows
usually occur from January to April when rainfall is high and evapotranspiration
is low.
Chattahoochee River Basin
The Chattahoochee River-whose name is derived from Creek Indian words meaning
painted rock-drains an area of 8,770 sq mi and is the most heavily used water
resource in Georgia. The Chattahoochee River arises as a cold-water mountain
stream in the Blue Ridge Province at altitudes above 3,000 ft and flows 430 mi
to its confluence with the Flint River. The discharge of the Chattahoochee River
based on median daily flows near Columbia, Ala., during water years
1977-92 was 8,250 cubic feet per second (cfs). Median daily discharge ranged
from a low of 498 cfs in 1989 to a high of 191,000 cfs in 1990.
Flint River Basin
The Flint River is about 350 mi long and drains an area of 8,460 sq mi. Most of
the larger tributaries in the ACF River basin are located in the Coastal Plain
Province part of the Flint River basin. These tributaries-with their Creek
Indian meaning in parentheses-include Ichawaynochaway Creek (buck sleeping
place), Chickasawhatchee Creek (council house creek), Kinchafoonee Creek (mortar
bone or pounding block creek), and Muckalee Creek (pour-upon-me creek) (Utley
and Hemperley, 1975).
Apalachicola River Basin
The Apalachicola River flows unimpeded for 106 mi from Jim Woodruff Lock and Dam
to the Gulf of Mexico. The river drains about 2,600 sq mi and its shallow estuary
covers about 208 sq mi. Tidal influences do not extend beyond 25 mi upstream from
the river's mouth. The Apalachicola River falls 40 ft as it flows through the
Gulf Coast Lowlands. The width of the river ranges from several hundred feet
when confined to its banks to nearly 4-1/2 mi during high flows. The discharge
of the Apalachicola River is 21st in magnitude among the rivers of the
conterminous United States, and is the largest in Florida, accounting for 35
percent of freshwater flow on the western coast of Florida (Livingston,
1992). During 1977-92, the discharge of the Apalachicola River based on mean
daily discharge at Sumatra, Fla., was 19,602 cfs. Mean daily
discharge at Sumatra ranged from 5,800 cfs in 1981 to 178,000 cfs in 1990.
Eighty percent of the Apalachicola River flow is contributed by the
Chattahoochee and Flint Rivers, 11 percent from the Chipola River, and less than
10 percent from ground water and overland flow (Elder and others, 1988). The
Chipola River-Apalachicola River's largest tributary-drains one-half of the
Apalachicola River basin. The Chipola River is classified as a spring-fed river
with baseflow derived principally from aquifers.
Ground-Water Hydrology
Six major aquifers underlie the ACF River basin. These aquifers, listed in
descending order, are the surficial aquifer system, the Floridan aquifer system,
the Claiborne aquifer, the Clayton aquifer, the Providence aquifer, and the
crystalline rock aquifer. Generalized outcrop areas and stratigraphy of aquifers underlying the Coastal Plain Province (11K); generally are separated by confining units.
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Last Modified: Thursday, 17-Jul-2008 11:10:58 EDT
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