'ujseg iuaujssassy vamoidVIODIHDVWdV 3H1 Nl

n^i3a QNV iN3minNCOVER PHOTOGRAPH: The Landsat image on the cover shows the extent ofthe flood plainintheApalachicola River Basin, Florida. Thedark color ofthe flood plain is caused by the low reflectance from flood waters. The 200-m wide river is barely visible in the center ofthe 3.2 to 8.0-kmwide floodplain. TheApalachicola River flows fromLake Seminole (at thetop), 171 km south, toApalachicola Bay (near the bottom of the scene). Thenumerous white squares nearthetopofthe sceneare agricultural fieldsir FloridaandAlabama. Thelargeredareaeastof the river is pine forest (Apalachicola National Forest). The faint brown color on thebirdsfoot delta at the river mouth is marsh. The lightbluecolorsnearthebeachesatthebottomofthesceneareacombination of shallow areas and areas with high suspended sediments caused by ocean currents. Thefalse-colorcompositewasobtainedonFebruary6, 1977,by aLandsat multispectral scanner andincludes bands 4, 5, and 7. The scene ID is 2746-15190, and more information on this and other satellite images is available through the U.S. Geological Survey, EROS Data Center, Sioux Falls, S. Dak., 57198.

### Chapter C 

# NUTRIENT AND DETRITUS TRANSPORT IN THE APALACHICOLA RIVER, FLORIDA
By HAROLD C. MATTRAW, JR., and JOHN F. ELDER

U.S. GEOLOGICAL SURVEY WATER-SUPPLY PAPER 2196-C Apalachicola River QualityAssessment

### UNITED STATES DEPARTMENT OF THE INTERIOR

WILLIAM P. CLARK, Secretary
GEOLOGICAL SURVEY Dallas L. Peck, Director

UNITED STATES GOVERNMENT PRINTING OFFICE: 1984

For sale by Distribution Branch Text Products Section U.S. Geological Survey 604 South Pickett Street Alexandria, Virginia 22304
Library of Congress Cataloging in Publication Data Mattraw, H. C. Nutrient and detritus transport in the Apalachicola River, Florida. (U.S. Geological water-supply paper; 2196-C) Bibliography: p. Supt. of Docs, no.: I 19.13:2196-C 1. Sediment transport Florida-Apalachicola River Watershed. 2. Detritus Florida-Apalachicola River Watershed. 3. I. Elder, John F. II Title. III. Series. GB850.M37 1984 551.48'3'097559 83-600181

# FOREWORD
The ApalachicolaRiver Quality Assessment was designedto evaluate the numerous factors that influence the nutrient and detrital yield of the river to Apalachicola Bay. The excellent hydrologic gaging system on the Apalachicola River permitted subdivision ofthe flood plain into three input-output units. The systematic analysis of nutrient sources, transport, and yields in the flood plain required new study techniques and data collection methods for (1) river and wetland hydrology, (2) tree species abundance and distribution, (3) leaf-litter production and decomposition, and (4) nutrient and detritus transport. These factors are the focus of separate WaterSupply Papers in the series (number 2196) dealing with the Apalachicola River Quality Assessment. Nutrient and detritus transport and ultimate yields are discussed in this paper. Extensive information from the previous papers is cited as necessary to develop a cogent scenario for nutrient and detritus yield. The main purpose of this characterization of nutrient and detritus sources and mechanisms is to provide a quantitative methodology for evaluating densely forested bottom-land hardwood swamps. The Apalachicola flood plain has demonstrable importance to a highly productive Apalachicola estuary. A more accurate appraisal of wetland functions is available through the quantification of the flood-plain treecommunity nutrient and detritus supply to a commercially valuable mariculture. The approach used in the Apalachicola River Quality Assessment is an attempt to better understand the wetland function and to begin to quantify the roles of specific components, such as flood-plain leaf-litter fall.

PhilipCohen ChiefHydrologist U.S. Geological Survey

in

# CONTENTS

Foreword 111 Abstract Cl Introduction Cl Purpose and objectives of the Apalachicola River Quality Assessment Cl Setting C3 Background C7 Conceptual design C8 Approach and methods C8 Subbasin approach C8 Intensive data-collection transect approach C8 Discharge approach C9 Water-quality sampling approach C9 Sample location and frequency C9 Sample handling Cll Bulk precipitation approach and method C14 Ground-water component CIS Detritus methods CIS Suspended detritus CIS Bottom-load detritus C16 Flood-plain detritus C16 Net collection C16 Plastic-sheet collection C17 Data handling C17 Results C21 Seven hydrologic periods C21 Water budget C22 Streamflow C24 Precipitation C24 Ground water C25 Chipola River inflow C26 Evapotranspiration C27 Overall water budget C28 Nutrient concentrations C29 Nutrient concentrations in the river C29 Bulk-precipitation concentrations C29 Ground-water chemistry C30 Chipola River C31 Nutrient transport C31 Nutrient transport residual C33 Transport, 1979-80 C33 Detritus C38 Concentrations C38 Transport C38 Flood-plain transport C38 Deposition on flood-plain floor C38 Error analysis C42 Water budget C42 Nutrient and detritus concentrations C43 Transport C44
ContentsDiscussion C44 Flood-plain role in nutrient transport C44 River basin nutrient yield C47 Sources of nutrients C52 Flood-plain detritus contributions C52 Flood-plain-net estimate of detritus C53 Plastic-sheet estimate of detritus C53 Significance offlood-plain-net and plastic-sheet estimates C54 Nutrient yields for the Apalachicola-Chattahoochee-Flint River system C54 Long-term factors influencing nutrient transport C55 Summary C56 Selected references C57 Supplementary data I Flood-plain detritus data C60 Supplementary data II Deposition on plastic sheets C61 Metric conversion factors C62 FIGURES 1. Maps ofthe drainage basins ofthe Apalachicola, Chattahoochee, and Flint Rivers in Alabama, Florida, and Georgia (left) and the Apalachicola and Chipola Rivers showing the flood plain and gaging station drainage divides (right) C2 2. Photograph ofJim Woodrufflock and dam C4 3. Map ofDead Lake, Chipola Cutoff, andApalachicola RivernearWewahitchka, Florida C5 4. Map ofApalachicola River, Brickyard Cutoff, and Brothers RivernearBrickyard Landing C6 5. Map ofApalachicola River subbasin components and gaging locations CIO 6. Photographshowinglocationsoflitter-fallcollectionplotsandwater-levelobservation sites nearthe Sweetwatertransect C12 7. Photograph showing locations oflitter-fall collectionplots, water-level observation sites, and rainfall gage near the Brickyard transect C13 8. Diagram ofwater-quality sample handling procedures CIS 9. Photograph ofbulk precipitation apparatus used forcollection oftotal carbon, total nitrogen, andtotal phosphorus samples C17 10. Map showing locations ofNational Weather Service and U.S. Geological Survey rain gages and bulk precipitation sample collectors in the Apalachicolabasin, Florida CIS 11. Map ofthe potentiometric surface ofthe Floridan aquifer in May 1976 C19 12. Photograph ofsampling apparatus usedforcollection ofbottom-load particulateorganic material C20 13. Histogram showingresults ofcross-sectional sampling onJuly 2, 1979 C21 14. Photographs offlood-plain detritus netusedto measure transportedforest litter C22 15. Diagram ofmajor steps indatacollection andhandling C23 16. Diagrammatic representation ofApalachicolawaterbudget C24 17. Graphofmean nutrientconcentrationsfortheperiodFebruary 1979 throughJuly 1980 atthefourmainrivercollection stations with standarderrorbars C30 18. Probabilityplotsoftotalcarbon, total nitrogen, andtotal phosphorusconcentrationsinbulkprecipitation samples C30 19. Graphoftotal organic carbon concentrations, mean sample interval discharge, and sevenhydrologicperiods at Sumatra C32 20. Graphofpaniculateorganiccarbonconcentrations C39 21. Graph ofbottompaniculate organic carbonconcentrations C40 22. Graphofannual paniculateorganiccarbontransport C41

VI Contents23. Graphofannual nutrienttransportatfourApalachicola River sites andthe ChipolaRiverOutlet atDeadLake, showing errorranges C45 24. Graphofcumulativecarbontransportinthe ApalachicolaRiver basinfromJune 3, 1979, throughJune 2, 1980 C48 25. Graphofcumulative nitrogentransport inthe ApalachicolaRiver basin fromJune 3, 1979, throughJune 2, 1980 C49 26. Graph ofcumulativephosphorus transportin the ApalachicolaRiver basin fromJune 3, 1979, throughJune 2, 1980 C50 27. Graphofobserved versus constantratetransport offive paniculate organic carbon fractions inthe Apalachicola River basin fromJune 3, 1979, throughJune 2, 1980 C51 TABLES 1. Abundance of 18 tree species in the Apalachicola River flood plain C6 2. Species composition and frequency of five major tree communities in the Apalachicola River flood plain C7 3. Ten dominant species of invertebrates collected by otter trawl in Apalachicola Bay C7 4. Stage-discharge gage stations on the Apalachicola River, Florida C9 5. Data-collection procedures used in determining nutrient and detritus transport Cll 6. Water-quality sample collection dates at the major river-gaging stations CI4 7. Analytical techniques used in the determination of chemical and physical characteristics of water samples C16 8. Flow volumes by gaging sites and the seven periods C24 9. Precipitation in the seven periods and the Apalachicola basins from June 3, 1979, through June 2, 1980 C25 10. Mean discharge per unit watershed area based on low-flow measurements C26 11. Inflow from Chipola River at Dead Lake, June 3, 1979, through June 2, 1980 C27 12. Estimates of annual evapotranspiration (ET) in Apalachicola subbasins, June 3, 1979, through June 2, 1980 C27 13. Water budget in the upper subbasin (Chattahoochee-Blountstown),by periods, June 3, 1979, through June 2, 1980 C28 14. Water budget in the middle subbasin (Blountstown-Wewahitchka), by periods, June 3, 1979, through June 2, 1980 C28 15. Water budget in the lower subbasin (Wewahitchka-Sumatra), by periods, June 3, 1979, through June 2, 1980 C29 16. Water budget in the Apalachicola basin (Chattahoochee-Sumatra), by periods, June 3, 1979, through June 2, 1980 C29 17. Mean nutrient concentrations and chemical characteristics of ground water compared with water ofthe Apalachicola River near Blountstown and the Chipola River near Wewahitchka C31 18. Total carbon transport in the upper subbasin, by periods, June 3, 1979, through June 2, 1980 C34 19. Total carbon transport in the middle subbasin, by periods, June 3, 1979, through June 2, 1980 C34 20. Total carbon transport in the lower subbasin, by periods, June 3, 1979, through June 2, 1980 C34 21. Total carbon transport in the Apalachicola basin between Chattahoochee and Sumatra, by periods, June 3, 1979, through June 2, 1980 C35 22. Total nitrogen transport in the upper subbasin, by periods, June 3, 1979, through June 2, 1980 C35 23. Total nitrogen transport in the middle subbasin, by periods, June 3, 1979, through June 2, 1980 C35
Contents VII24. Total nitrogen transport in the lower subbasin, by periods, June 3, 1979, through June 2, 1980 C36 25. Total nitrogen transport in the Apalachicola basin between Chattahpochee and Sumatra, by periods, June 3, 1979, through June 2, 1980 C36 26. Total phosphorus transport in the upper subbasin, by periods, June 3, 1979, through June 2, 1980 C36 27. Total phosphorus transport in the middle subbasin, by periods, June 3, 1979, through June 2, 1980 C37 28. Total phosphorus transport in the lower subbasin, by periods, June 3, 1979, through June 2, 1980 C37 29. Total phosphorus transport in the Apalachicola basin between Chattahoochee and Sumatra, by periods, June 3, 1979, through June 2, 1980 C37 30. Daily detritus fraction transport at Sumatra, by periods, June 3, 1979, through June 2, 1980 C42 31. Deposition of material during 9 to 11 months on plastic sheets randomly located in intensive plots C43 32. Nutrient yields, on an areal basis, for various drainage areas ofthe ApalachicolaChattahoochee-Flint River system C55

VIII Contents

# Nutrient and Detritus Transport in the Apalachicola River, Florida QyHarold C. Mattraw, Jr., andJohn F. Elder

Abstract TheApalachicola River in northwest Floridaflows 172 kilometers southward from Jim Woodruff Dam near the Florida-Georgia border toApalachicola Bayon the Gulf of Mexico. The basin is composed of two 3,100-squarekilometer subbasins, the Chipola and the Apalachicola. TheApalachicolasubbasin includesa454-square-kilometer bottom-land hardwood flood plain that is relatively undeveloped.Theflood plain contains morethan 1,500treesper hectare that annually produce approximately 800 metric tons of litter fall per square kilometer. Spring floods of March and April 1980 carried 35,000 metrictons of particulateorganiccarbon derivedfrom litterfall intoApalachicola Bay. The estuarine food web is predominantly detrital based and represents an important commercial source of oyster, shrimp, bluecrab,andvariousspeciesoffish. Thewater budget oftheApalachicola basin is heavily dominated by streamflow. For a 1-year period in 1979-80, 28.6 cubic kilometers of water flowed past the Sumatra gage on the lower river. Eighty percent of this volume flowed into the upper river near Chattahoochee, Fla., and 11 percent was contributed by its major tributary, the Chipola River. Contributionsfrom groundwaterand overland runoffwere lessthan10percent. Streamflow increases downstream were accompanied by equivalent increases in nitrogen and phosphorus transport. The nutrients were released to the river bythe flood-plain vegetation, but also were subject to recycling. The increase in the amount of organic carbon transport downstream was greater than streamflow increases. The flood plain is an important source of organic carbon, especiallyin detritalform. Several methods for measurement of detritus in the river and flood plain were developed and tested. The detritus datafrom theflood plain added semiquantitative evidence for transport of detritus from the flood plain to the riverflow, probablyaccountingfor mostofthecoarse particulateorganic materialcarried bythe river. During the 1-year period of investigation, June 3, 1979, through June2,1980, 2.1 x 105 metrictons of organic carbon were transported from the river basin to the bay. Nitrogen and phosphorus transport during the same period amounted to 2.2x 104 and 1.7x 103 metric tons, respectively. On an areal basis, it was calculated that the flood plain contributed 70 grams of organic carbon per square meter per year, 0.4 gram of nitrogen per square meter per year, and 0.5 gram of phosphorus per square meter peryear. The flood plain acts asa source ofdetrital carbon, but for the solutes, nutrient release is approximatelybalanced bynutrient retention.

INTRODUCTION 

### Purpose and Objectives ofthe Apalachicola River Quality Assessment The Apalachicola River Quality Assessment was initiated in 1978 as part of a national river quality assessment program of the U.S. Geological Survey. The purpose ofthe ApalachicolaRiver Quality Assessment wasto evaluate the importance ofthe Apalachicola River and its associated flood plain in supplying nutrients and organic detritustoApalachicolaBay (fig. 1). The specific goals ofthe ApalachicolaRiver Quality Assessment were process oriented rather than problem oriented. Its primary purpose was to investigate river-wetland relations and controlling factors that influence the yield of nutrients and detritus to the bay. Emphasis was on processes that influence nutrient and detritus flow rather than on problems involving environmental disturbance orpollution. Special attention was givento methods developmentbecause ecological studies oflargeriver-wetland systems have been rare and few methods particularly applicable tothis typeofstudy havebeen described. The subtle but profound impact of hydrologic factors on tree-community distribution and on leaf-litter production and decomposition is difficult to document, and thoroughly documented methods ofstudy are lacking. The more direct result of seasonal flooding the erosion of large quantities of nutrients and decaying leaf litter from the flood plain and transport into the river is more evident. However, methods for studying transport of large organic particles in the flood plain also lack documentation. Even the present (1980) techniques used to study
Nutrient and Detritus Transport in the Apalachicola River, Florida C185°I5' 85°00' 84°45' 84°30'

33<

25e 88° 84e

EXPLANATION APALACHICOLA RIVER DRAINAGE SYSTEM

0 100 200 KILOMETERS I______|______| ALABAMA! ~R_ORIDA

EXPLANATION ^f (_ WEWAHITCHKA [ ] Flood plain A Apalochicola River

basin boundary Drainage divide for - gaging stations Gaging station

29°45 -

Figure 1. The drainage basins of the Apalachicola, Chattahoochee, and Flint Rivers in Alabama, Florida, and Georgia (left) and the Apalachicola and Chipola Rivers showing the flood plain and gaging station drainage divides (right).particulate transport within the river lack standardization. To a large extent, the Apalachicola River Quality Assessment was designed to test methods with whichto evaluate the influence of hydrologic factors on tree distribution, leaf-litter production, leaf-litter decomposition, and transport of nutrients and detritus. All of these methods were ultimately directed toward understanding the role of the flood plain in the nutrient and detritus yield to Apalachicola Bay. The specific objectives of the Apalachicola River QualityAssessment were (Mattraw andElder, 1980) 1. To determine the accumulation oftrace elements and organic substances in benthic organisms and finegrained sediments; 2. To describe how tree distribution on the flood plain is related to the pattern of flooding (duration, level, andfrequency); 3. To assess the importance of leaf production and decomposition on the flood plain to detritus and nutrient yields ofthebasin; and 4. To identify major sources ofnutrientstotheriver system and to quantify transport ofnutrients and organic detritusin variousparts ofthe system. The specific purpose ofthis report is to address the fourth objective by presenting the results of nutrient and detritus transport determinations. The results of transport are directly dependent on an analysis of the basin water budget. The water budget and nutrient transport calculations are for the 366-day period from June 3, 1979, through June 2, 1980. The area considered is the 3,100- square-kilometer Apalachicola River basin in northwest Florida. Important aspects discussed include methods of measurement, hydrologic features that affect nutrient flow, changes in nutrient and detritus concentration over space and time, andthe efficiency offlood-plain litter-fall capture by the flood waters. Throughoutthisreport, theterm "nutrients" refersto both suspended particulate and soluble or dissolved nitrogen, phosphorus, and organic carbon. "Detritus" refers to organic particulate matter that contains leachable nutrients as well as numerous other elements associated with biological tissues. A conceptual design, methods, results, and analysis of errors are presented for the nutrient and detritus transportfrom the Apalachicolabasin. 

### Setting The Apalachicola River winds 172 km through the northwest Florida Panhandle and empties into the Gulfof Mexico (fig. 1) through Apalachicola Bay. In 1954, the Jim Woodruff Dam was constructed 1.5 km downstream from the confluence ofthe Chattahoochee andFlint Rivers and became the upstream limit ofthe Apalachicola River. The reservoir behind the dam, 15,200 ha in area, was filled by 1957. The entire Apalachicola-ChattahoocheeFlint River drainage basin is 50,800 km2 in area, encompassing parts ofGeorgia, Alabama, and Florida. The part below the dam, which drainsto the ApalachicolaRiverdirectly, has an areaof6,200km2

. Jim Woodruff Dam (fig. 2) was constructed by the U.S. Army Corps ofEngineersprimarilyto facilitatenavigation on the Chattahoochee and Flint Rivers. The dam has a navigation lock 25 m wide, with about 9 m of lift from the Apalachicola River into Lake Seminole. The dam also creates storage for a hydroelectric generating plant, which supplies a part of the power needs for the city ofChattahoochee and neighboring communities. The only major tributary ofthe Apalachicola River below Jim Woodruff Dam is the Chipola River. The Chipola is constrained by a low-head, interlocking, sheetpile weir near Wewahitchka, Fla. (fig.3). The resulting pool is called Dead Lake. The drainage area of the Chipola River above Dead Lake is 3,100 km2, exactly one-half of the drainage area of the entire Apalachicola basin. Immediately downstream from the weir, the Chipola is joined by Apalachicola River water flowing through the Chipola Cutoffdistributary. These waters rejoin the main stem of the Apalachicola 21 km downstream. A second major distributary channel of the investigated reach is located near the Sumatra gage at Brickyard Landing (fig. 4). The Brickyard Cutoff conveys water from the Apalachicola River to the Brothers River. The rating curve forthe Sumatra gage is developed from measurements upstream of Brickyard Cutoff and, therefore, representsthetotal flow of-both channels. Twelve km south ofBrickyard Cutoff, the Brothers River joins the Apalachicola. The major part of the Apalachicola River flows 10 km south, where itjoins the Jackson River and flows southeast into Apalachicola Bay. The U.S. Highway 98 bridge across the bay, near the mouth of the Apalachicola River, is used by the U.S. Army Corps ofEngineers asthe mile 0 fornavigationpurposes ontheriver. The flood plain of the Apalachicola River is 454 km2 in area, expanding from a width of 1 km near Chattahoochee to 8 km near Sumatra. The composition ofthe Apalachicolaflood-plain tree community wasestimatedby Leitman and others (1983). Table 1 liststhe 18 mostcommonly observed flood-plain species, in order of abundance. The data represent tree identification from eight cruise transects across the flood plain at widely spaced locations. Leitman and others (1983) recognized 5 major foresttypes (table 2) and47 tree species. Forest-litter production in the flood plain is potentially a major source ofnutrients and organic matterin the Apalachicola system. The flood plain is heavily forested with bottom-land hardwoods dominated by Ogeechee and water tupelo (Nyssa ogeche, N. aquatica) and baldcypress

Nutrient and DetritusTransport in theApalachicola River, Florida C3Figure 2. Jim Woodruff lock and dam (view is to the north).

(Taxodium distichum). Many ofthese species are highly sensitive to the extent and duration offlooding. The vegetation annually produces tons of leaf litter and other organic matter which must be either reincorporated into the system or transported out ofit. Once litter fall reaches the flood-plain floor, annual flooding ofthe forest accelerates decomposition and transport of materials from the flood plain to the main-stream channels (Elder and Cairns, 1982).Using litter-fall measurements collected at two transects between September 1979 and September 1980 and forest type composition data from the eight cruise transects, Elder and Cairns (1982) calculated a mean annual litter production of 800 g/m2

. At this rate, the trees and vines ofthe 454-square-kilometer flood plain produce 3.6x 105 metric tons oflitter fall annually. Much ofthis material decomposes and is recycled to vegetation. It is assumed that some ofthe soluble decomposition products leach through the soil and enter the ground-water system. Another fraction is eroded by seasonal floods and is either redeposited on the flood plain or is captured by the river and carried to Apalachicola Bay. The proportion that is transportedbythe seasonal floodingdependsto agreatextent on the magnitude and duration ofthe seasonal flooding. The residual nutrient content and particle size ofthe transported litter (detritus) are governed largely by the length of time between the litter fall and the flooding episode. The major litter-fall months in the Apalachicola flood plain are October and November (Elder and Cairns, 1982). Peak flooding is normally between January and March. Nutrients and detritus are transported into Apalachicola Bay, which has a complex trophic structure. In an exhaustive data-gathering program, Florida State University scientists (Livingston and others, 1974) are developing adatabasethatdemonstrates the impacts ofvarious physical, chemical, and biological factors on the estuarine ecosystem. The role of the river in affecting the salinity structure, in supplying nutrients to phytoplankton, and in providing detritus is well documented. The relation between the river system and the bay contributes directly to the economic welfare of Franklin County. Oysters (Crassostrea virginica Gmelin) depend on an adequate nutrient supply to sustain their planktonic
C4 Apalachicola River Quality Assessment

### 85°28' 27' 26' 25* 24* 23* 22' 2l' 20* 19* 85°I8'

30°10'

-



### WEWAHITCHKA GAGE

Figure 3. Dead Lake, Chipola Cutoff, and Apalachicola River nearWewahitchka, Florida.

Nutrient and Detritus Transport in the Apalachicola River, Florida C585°I9' 18' 17' 16' 85°I5'

29°58'

57'

56

55'

54

53'

52'

51'

29°50' SUMATRA GAGE

0 I 2 KILOMETERS



# . Figure 4. Apalachicola River, Brickyard Cutoff, and Brothers River near Brickyard Landing.

food supply, and the periodic pulses of freshwater discourage predation by oyster drills (Labyrinthomysa marina) (Menzel and others, 1966). Oyster harvesting is the major industry of the county; the second and third most economically important commercial species of marine life are shrimp (Penaeus sp.) and blue crab (Callinectes sapidus). Both the shrimp and the crab are detrivores.Extensive otter-trawl sampling ofApalachicola Bay organisms (Livingston and others, 1976) identified the 10 dominant species of invertebrates (table 3). The most abundant, the white shrimp (Penaeus setiferus), uses the bay as a nursery ground and depends heavily on detritus and detritus-associated organisms. Five of the six most Table 1. Abundance of18 treespecies intheApalachicola Riverflood plain [ModifiedfromLeitmanandothers, 1983] Species Watertupelo.

.............. Ogeecheetupelo

............ Baldcypress

............... Carolina ash

............... Blackgum.

................ Sweetgum

................ Overcup oak.

.............. Planer-tree

................ Green ash.

................ Waterhickory.

............. Sugarberry

................ Diamond-leafoak

........... American elm

.............. Americanhornbeam.

......... Pumpkin ash1

.............. Water oak

................ Red maple

................ Sweetbay.

................ Relative basal area (in percent)

..... 29.9

..... 11.0

..... 10.6

..... 5.4

..... 5.0

..... 4.8

..... 3.2

..... 2.9

..... 2.9

..... 2.9

..... 2.8

..... 2.5

..... 2.4

. . . . . 2.0

. . . . . 1.9

. . . . . 1.8

. . . . . 1.5

. . . . . 1.0 1 Some trees identified as pumpkinash may have been Carolina ash or green ash. Samaras (winged seeds) had dropped from the trees and seeds of all three species were mixed on the ground beneaththetrees.

abundant species ofinvertebrates in Apalachicola Bay are benthic omnivores and depend heavily on detritus. Gravid female blue crabs from along the entire western coast of Florida migrate to thebay region to spawn (Oesterling and Evink, 1977). Juveniles apparently migrate into Apalachicola Bay. This pattern explains the abundance of juvenile blue crabs (table 3) observed by Livingston and others (1976). Fish are also abundant in Apalachicola Bay. In general, their connection to detritus is indirect; ultimately, however, detritus isjust as vital to the fish as it is to the invertebrates (Livingston and others, 1976). Decayed litter material is colonized by fungi, algae, and bacteria, which are grazed by protozoans. Isopods, amphipods, and decapods use the attached and associated organisms for food and the larger leaf and litter particles for shelter. Many fish feed on these small marine organisms. The higher trophic levels are thus dependent on an abundant nutrient and detrital supply at the base ofthe food web. Although the complex physical, chemical, and biological interactions ofthe bay estuarine system are incompletely understood, the river-derived nutrients and detritus are recognized as essential to the maintenance of the diverse ecosystem.
C6 Apalachicola RiverQualityAssessmentTable 2. Species composition and frequency of five major tree communities in the Apalachicola River flood plain

[Modifiedfrom Leitmanandothers, 1983]

Forest types

A.

. . Predominant

species
Sweetgum Sugarberry Wateroak American hornbeam Possumhaw Associated species

Diamond-leafoak Greenash Americanelm American sycamore Waterhickory Percentage

of223cruisetransect plots 21

D

U Waterhickory Greenash Overcupoak Diamond-leafoak Sweetgum Americanelm Watertupelo Ogeecheetupelo Baldcypress Blackgum Carolinaash Planertree

Watertupelo Blackgum Ogeecheetupelo Baldcypress Carolinaash Pumpkin ash Planertree Sweetbay Watertupelo Baldcypress Carolinaash Planertree Undifferentiated Sugarberry

Redmaple Wateroak Possumhaw American hornbeam Overcupoak Pumpkinash Redmaple Waterhickory Americanelm Green ash Diamond-leafoak Sweetbay 16

21

11

24

Recognition of the scarcity of information that might be used to evaluate potential resource problems on the river and flood plain prompted the Florida Defenders of the Environment to sponsor a symposium on the Apalachicola Drainage System in April 1976. The proceedings were published by the Florida Department of Natural Resources, Marine Research Laboratory (Livingston and Joyce, 1977). An aspect that was emphasized by the conference speakers, but was acknowlTable 3. Ten dominantspeciesof invertebratescollected by otter trawl in Apalachicola Bay [Modifiedfrom Livingstonandothers, 1976] Common name Scientific name Percent White shrimp

.... Penaeussetiferus

. . Grass shrimp.

.... Palaemonetespugio Blue crab.

...... Callinectessapidus. Pink shrimp

..... Penaeusduorarum

. Briefsquid

...... Lolliguncula brevis. Brown shrimp.

. . . Penaeusaztecus.
...... OliveNerite

..... Neritina reclivata...... Swimmingcrab

. . . Portunusgibbesii.

..... Grass shrimp.

.... Palaemonetes vulgaris.

. . Mud crab

....... Rhithropanopeus harrisii. 40.1 20.4 20.2 5.3 4.3 2.6 1.5 1.1 0.8 .5
edged to be poorly defined, was the role ofthe seasonal flooding cycle in the transport oflitter-fall debris fromthe flood plain to the river and, ultimately, to the bay. This aspect was selected as the focus ofthe ApalachicolaRiver Quality Assessment. The ApalachicolaRiver Quality Assessmentwas designed to define the cause-and-effect relation between existing hydrologic fluctuations and the tree community that occupies the flood plain, the production and decomposition ofthe litter fall, andthe effectiveness oflitter-fall transport from the flood plain to the river and the bay. Only when these relations are defined and measured can a rational scientific evaluation of river modifications be determined. 

### Background The Apalachicola River Quality Assessment is unique within the River Quality Assessment Program because it was not conceived ordesigned to address existing problems. The Apalachicola basin is largely undeveloped, and it provides an appropriate setting for study ofnatural processes that might be sensitive to future development. Many ofthe alternative plans ofthe U.S. Army Corps of Engineers (COE) to upgrade navigation have caused concern among inhabitants of the area and State regulatory agencies. There is considerable disagreement about what types ofproblems might arise from different management practices, as described in reports such as the draft COE Environmental Impact Statement (EIS) ofthe rivermodification effects (U.S. Army Corps ofEngineers, 1976), the evaluation of management alternatives by the U.S. Fish and Wildlife Service (1979), and the Estuarine Sanctuary EIS (U.S. Department ofCommerce and State ofFlorida, 1979). These reports differ on the types ofproblems that mightarise.
Nutrientand DetritusTransport in theApalachicola River, Florida C7Conceptual Design

A conceptual design ofthe relations among the program components was developed (Mattraw and Elder, 1980). The design called for work in three broad areas: flood-plain dynamics, nutrient and detritus sources, and nutrient yield. The data-collection procedures employed in the flood-plain dynamics components have been described by Leitman and others (1983). Three ofthe techniques described in that paper those used to measure rainfall, discharge, and flood-plain velocity are directly applicable to an evaluation ofnutrient anddetritustransport. Nutrient and detritus sources include, among others, the vegetation ofthe floodplain. The tree species distribution (Leitman and others, 1983), or, more correctly, the forest type distribution, is an essential component in evaluating nutrient and detritus sources. The techniques used in measuring the leaf production of the five forest types have been described by Elder and Cairns (1982). Decomposition rate studies wereexperiments conducted at field sites under a variety of conditions representative of river and flood-plain conditions. The result ofthese procedures is an estimate ofthe annual potential supply ofnutrients anddetritusderivedfromthe litterfall. The forest-litter material that is actually transported through the flood plain and the river is measured as part ofthe thirdbroad area, nutrient yield. The extent ofinundation and flood-plain velocities during flooding are believed to be the major controls on the fraction ofthe potential nutrient and detritus supply that is transported. The data needs include systematic collection of water-quality samples, discharge, and various size fractions ofparticulate organic matter (detritus). Several additional components dealing with lateral inflow (streams and ground water), atmospheric input, and upstream watersheds are incorporatedintheprogramdesign. Apalachicola basin were made using Chattahoochee, Blountstown, Wewahitchka, and Sumatra gage records; the yields represent their respective parts ofthe basin. A fifth main-stem gage, near Apalachicola, Fla. (fig. 1), is strongly affected by tides and has notbeen rated with sufficientprecision topermitdischarge computations. Determinations ofwater balance and nutrient transport depend on data from discharge gaging stations that can account for flow in the main stem and in tributaries. The main-stem gages separate the basin into three subbasins, as shown in figure 5. With the addition ofboundaries representing the drainage area of each main-stem rivergage, areas are defined forthe subbasins. The subbasins are named according to their downstream order. The upper subbasin, 963 km2 in area, is between the gages at Chattahoochee and Blountstown. The middle subbasin, 593 km2 in area, is between the Blountstown and Wewahitchka gages. The lower subbasin, 476 km2 in area, is between the Wewahitchka and Sumatra gages. The Chipola River basin is actually a 3,100-squarekilometer subbasin of the Apalachicola River basin. For this report, the Chipola subbasin ends where the Chipola River joins the Chipola Cutoff. The part of the Apalachicola River basin south ofthe Brickyard transect was excluded because diel tidal fluctuations made discharge calculations very difficult. Table 5 summarizes the data-collection procedures used to determine nutrient and detrius yield. Included are the frequency of collection and recent references that detail the procedure. As indicated in table 5, the techniques formeasuring flood-plain detritus, suspendeddetritus, and bottom-load detritus are unreferenced. These procedures were devised especially for the flow conditions of the large and swift Apalachicola River and its extensive flood plain.

APPROACH AND METHODS Subbasin Approach Four main-stem stage-discharge gages provided data that could be used to calculate nutient loads to the headwaters of the Apalachicola River below Jim Woodruff Dam and to three points downstream (fig. 1). Thus it was possible to calculate water and nutrient balance for three subreaches of the river and for the system as a whole. This capability lent itself to an attempt to quantify the proportion oftotal loadsderivedfromthe floodplain. Table 4 gives the location, station identification number, drainage area, organization responsible for maintenance, period ofrecord, and average discharge for the 1979 water year for each gage on the Apalachicola River system. The calculations of nutrient yields for the Intensive Data-Collection Transect Approach Two intensive data-collection transects were established to gather detailed information on litter-fall production, leaf decomposition, and water-level fluctuation on the flood plain. The Sweetwater transect (fig. 6) runs perpendicular to the flood-plain corridor and crosses the Apalachicola River 14 km upstream of the Blountstown gage (navigation mile 87). Seven major data-gathering plots (fig. 6) were established to estimate litter fall (Elder andCairns, 1982) forthis upperrivertransect. A second intensive data-collection transectrepresentative of lower river conditions was established near Brickyard Landing (fig. 7). The Brickyard transect crosses the Apalachicola River 1 km downstream of the Sumatra gage (navigation mile 20). Clearly visible in figure 7 is the powerline right-of-way that lies parallel and 150 m north ofthe Brickyard transect. Nine major data-gathering
C8 Apalachicola River Quality AssessmentTable 4. Stage-discharge gage stations on the Apalachicola River, Florida

[Maintenanceresponsibility: USGS,U.S. Geological Survey;NWS, NationalWeather Service;COE, Corps ofEngineers]

Station name and identification number
Apalachicola River at Chattahoochee, C235800. Little SweetwaterCreek near Bristol, C2358685. Apalachicola River near Blountstown, 02358700.

Apalachicola RivernearWewahitchka, 02358754.

Chipola Riverat Dead Lake Outlet nearWewahitchka, 02359101. Apalachicola Rivernear Sumatra, 02359170.

Apalachicola Rivernear Apalachicola, 02359230. Drainage area, in squarekilometers 44,600
6.35 45,600

46,100

3,100 49,800

50,600 Maintenanceresponsibility
USGS
USGS
NWS
COE
COE

USGS
COE

USGS
USGS Period ofrecord

October 1928 through September 1980. June 1979 through September 1980. January 1920 through September 1957 (stage only). October 1957 through September 1980. October 1955 through September 1957 (stage only). October 1965 through September 1980. November 1979 through September 1980. May 1950 through September 1959;April 1965 through April 1966 (stage and miscellaneous discharge measurements). September 1977 through September 1980. July 1978 through September 1980. Average discharge, in cubic meters per second 640
Not determined.

702

728
Not determined.

833
Not determined.

plots were established in this transect to estimate monthly litter-fall production and to measure flood-plain flow and detritus during flooding. Data from the two intensive transects and eight cruise transects were determined to be adequate to support semiquantitative estimates ofthe productivity ofthe entire basin. The approaches,judgments, and statistical analyses of this sampling design were discussed in earlier reports (Elder and Cairns, 1982; Leitman and others, 1983). Discharge Approach Discharge at the main-stem gaging stations represents contributions fromtheentire subbasin. Thereference flood elevation chosen by Leitman and others (1983) was that ofa 2-year, 1-day flood. The extent ofinundation by such a flood correlates closely with the distribution ofbottom-land hardwood forest types. During 1980, the peak discharge at Blountstown occurred on April 2. Its discharge, 3,100 m3/s, has a recurrence interval of approximately4years.
Water-Quality Sampling Approach Sample Location and Frequency Water-quality samples for analysis of nutrients and suspended sediments were collected at each ofthe major gaging stations at least monthly between February 1979 and June 1980. Samples were collected more frequently during the major flooding period in March and April 1980. Because concurrent sampling was not possible, the different sampling sites had different sample intervals. Sample collection dates for each location are listed in table 6.
Nutrient and Detritus Transport in the Apalachicola River, Florida C9C~ -V §§ORG1A__

__ ii^N / FLORIDA ""

EXPLANATION A GAGING STATION -SUBBASIN BOUNDARY

Figure 5.Apalachicola River subbasin components and gaging locations.

C10 Apalachicola River Quality AssessmentTable 5. Data-collection procedures used in determining nutrient and detritus transport

Procedure Number or frequency of collection Reference
Riverflow Stage recorder. Tagline measurement Movingboat Flood-plain flow Price current meter 15 minute orhourly punched tape, graphic recorders (continuous). Each total flow measurement during flood (channels in flood plain). Each flood flow measurement ofmain channel.
Used to measure all flow velocities except movingboat measurements. Buchanan and Somers, 1968. Buchanan and Somers, 1969. Smoot and Novak, 1969.
Buchanan and Somers, 1969.
Ground water Recorder

........... Tape down.

......... Water quality Collection

.......... Composite

.......... Silver filter.

......... 0.45 Aim filter.

....... Preservation

......... Shipping

........... Laboratory analysis

. . . . Detritus Pumped.

........... Bottom load.

........ Flood-plain net
....... Plastic sheets

........ Hourly punched tape. Periodic. Monthly, flood sampling. Each sample. Each sample for suspended organic carbon. Each sample for dissolved constituents (solids, nutrients). Iced. Within 1 day ofcollection. Within 2 days ofreceipt. Monthly. Monthly. Flood sampling. Project period. Buchanan and Somers, 1968. Brakensiek and others, 1979.
Brown and others, 1970. Guy and Norman, 1970. Beetem and others, 1980. Do. Do. Do. Do.

Additional nutrient samples were collected at three other sites, offthe main stem. One site was the Brickyard transect (fig. 7), where a composite sample was taken fromBrickyardCutoff, BrothersRiver, and when flooded, several points across the flood plain. To reach this area, water had to traverse a broad expanse of the flood plain and was, therefore, indicative of flood-plain outflow. Sampling on the Brickyardtransect was done on the same days as atthe Sumatra station (table 6). A second off-channel site was at the mouth of the ChipolaRiverat Dead Lake outlet (fig. 3). Itwas sampled on the same dates as the Wewahitchka station (table 6), except that it was not sampled during the period March 13-April 28, 1980, because Apalachicola flooding produced reverse-flow at the site. The third off-channel site was at Little Sweetwater Creek (fig. 6), a small ground-waterfed stream 10 km north ofBlountstown. Its waterchemistry (low pH, specific conductance, and nutrient content) was very different from that ofApalachicola River water but was similarto that ofother ground-wateroutlets in the basin; hence, it was considered representative of groundwater input. This site was sampled on the same dates as the Blountstown station (table 6) except during the 1980 spring flood, when it was subjecttobackwaterfloodflow.
Sample Handling A schematic diagram ofthe sample handling procedure is shown in figure 8. A point-integrating cable-andreel sampler, US P-61 (Guy and Norman, 1970), was used to obtain 10 or more depth-integrated water-quality samples across the channel width or the flood plain. Each sample was emptied into a large polycarbonate mixing container (churn). When sampling was complete, the cross-sectional composite sample was mixed and total nutrient and total residue samples were drawn into 1-L polypropylene bottles. Additional samples from the churn were pumped through a 0.45-|A membrane filter by a peristaltic pump. The filtered samples were stored in 500- mL polypropylene bottles. All samples wereplaced in icefilledcoolers and shippedtothe analytical laboratory.
Nutrient and DetritusTransport in the Apalachicola River, Florida C11

### EXPLANATIO Qr Sampling plot ATContinual-record £...surface water ?-;^ 1JF*gaging station

Observation well Continual-record observation well

Figure 6. Locations of litter-fall sampling plots and water-level observation sites near the Sweetwater transect.

C12 Apalachicola River Quality Assessment

## Brickyard Landing

EXPLANATION D Sampling, plot A--'. Continualrecord surface-water gaging Station ^ Observation weN Continual record observation well

Figure 7. Locations of litter-fall sampling plots, water-level observation sites, and rainfall gage near the Brickyard transect.

Nutrient and DetritusTransport in theApalachicnla River, Florida C13Table 6. Water-quality sample collection dates atthe major river-gaging stations [Parenthesesindicate dateswhen samplingwas done forNASQANprogram] Month 1979 March

........ April.

........ May

......... June

......... July

......... August

....... September

..... October.

...... November

..... December

..... 1980 January

....... February

...... March

........ April.

........ May

......... June

......... Chattahoochee

27 (6), 14, (19) 3, (10), 24 16, (21) 18 23, (31) 20, (28) (18), 26 (25) (14), 19 18
21, (28) 26 9, 10, 18, (23), 26 2,23 (15), 21 (16), 25 Blountstown

28 14 3,24 16 18 23 20 26 25 19 18

22 27 10 (twice), 12, 18, 26 2,23 20 25 Wewahitchka

28 15 4,25 17 19 24 22 27 24 20 17

22 27 11, 13, 19, 27 3,28 20 24 Sumatra

1, 16 5, 11,26 17 19 24 21 27 2,24 20 17
23,28 28 4, 11, 13, 14, 19, 27 3, 28 19 24

Samples for carbon analysis were placed in a 100- mL stainless-steel pressure filter apparatus with a 0.45-(ji silver filter. Both filtered and unfiltered samples for carbon analyses were collected in 60mL, oven-fired (500°C) glass bottles having aluminum foil cap liners. The 0.45-(ji silver filter containing the suspended material was folded andplaced in apetri dish for shipment. The water-quality constituents analyzed andthe general method of analysis are presented in table 7. Analytical results not presented in this report are published in "Water-Resources Data for Florida, Volume 4, Northwest Florida" (U.S. Geological Survey, 1979, 1980, 1981) and can also be accessedthrough WATSTORE (U.S. Geological Survey computerized water data storage and retrieval system) with the station identification numbers listed in table4.

Bulk Precipitation Approach and Method Bulk precipitation is the solution that results when rainfall incorporates the products of dry fallout (Whitehead and Feth, 1964). Four bulk precipitation collectors (fig. 9) were used in the Apalachicola basin near the main-river sampling sites. Samples were retrieved from the collectors monthly, coinciding with river sampling. It is recognized that the relatively simple design of the collectors did not minimize the various possible sources of error described by Galloway and Likens (1976). It was not practical for this study to collect dry and wet deposition separately or to retrieve samples at daily or weekly intervals. Some potential problems were mitigated, however, by the environmental conditions. Deposition offine dry materials andvarious gases, forexample, was not likely to contribute significantly to atmospheric input in this relatively humid area. Many chemical transformations that might have taken place between sample collections were of little consequence because the samples were analyzed for total organic carbon, nitrogen, andphosphorus only. Atmospheric loading of nutrients to the subbasins for the period June 19, 1979, to June 25, 1980, was calculated using analytical data and National Weather Service rainfall records at the locations indicated in figure 10. Rainfall records for two locations were average for each subbasin to obtain a distributed rainfall depth across each subbasin. Records ofrainfall near Sumatra were not available, so a recording rain gage was installed at the Brickyardtransect toprovide the desiredrainfall coverage. C14 Apalachicola River Quality AssessmentSAMPLER

FILTERED DISSOLVED"

CARBON UNFILTERED "TOTAL"

NITROGEN AND PHOSPHORUS

ANALYTICAL LAB Figure 8. Water-quality sample handling procedures.

Ground-Water Component The ground-water contribution to the Apalachicola River was estimated during the design phases of the Apalachicola River Quality Assessment to be less than 5 percent ofthe dry weather total flow (Mattraw and Elder, 1980). This estimate was based on records of discharge increases between Chattahoochee and Blountstown during low flow. Regional water-level mapping (fig. 11) ofthe principal artesian aquifer (Floridan aquifer) indicated that the steepest ground-water gradient toward the Apalachicola River is between these two main-stem gage locations. Low-flow discharge records and the groundwatergradient ledto the establishment ofseveral wells for observation ofground-water elevations in the Sweetwater transect (fig. 6). In addition, a surface-watergage was established on nearby Little SweetwaterCreek to observe its flow, which was principally ground-water discharge. The creek's drainage basin is 6.4 km2

. Calculations ofgroundwater-contributed load are based on low-flow water-quality samples from Little Sweetwater Creek that were processed like main-stem water-quality samples. Between Chattahoochee and Blountstown, the regional pattern of ground-water contours for the Floridan aquifer (fig. 11) is north and south, parallel to the Apalachicola basin. Farther down river, the ground-water contour direction is more nearly east and west. This indicates that the ground-water contribution in the southern half of the river is much less and is more difficult to measure without an extensive system ofwater-table monitoring wells. Since the gain in information would have had such a small effect on the overall estimates ofnutrient transport in the river system, only afew wells were installed in the lower river basin for qualitative comparisons of river levels with ground-waterlevels.

Detritus Methods Suspended Detritus Several particle-size classifications ofdetritus (particulateorganic matter) arecurrentlyinuse. Themostcommon recognizes three major size ranges: coarse, fine, and veryfine (NaimanandSedell, 1979). Coarsepaniculateorganicmatter(CPOM) isdefinedasorganicparticlesgreater than 1 mm across. Forthis study, particles greaterthan 63 JJL(0.063mm)butsmallerthan 1 mmwereclassifiedasfine paniculateorganicmatter(FPOM). Particlessmallerthan63 JJLbutgreaterthan0.45 |xwereclassifiedasveryfineparticulateorganicmatter(VFPOM). CPOM and FPOM were collected on 1-mm and 63- |x nested sieves attached to the side ofthe sampling boat. Water was pumped from depths of0.5, 1.5, and 3.0 m for 10 minutes each as the boat slowly traversed the river cross section. The pumpingrate was 10L aminute, which produced a detritus sample representing 300 L of river water. The samples were rinsed from the sieves into labeled masonjars. The samples were shippedto the laboratory, where they were oven dried at 105°C andweighed, then ashed at 500°C and weighed again. The weight oforganic matterwas determinedby subtractingthe ash weight from the dry weight. Organic matter weights were converted to organic carbon weights by multiplying by 0.5, a conversion factor arrived at by chemical analysis ofdetrital material from the flood plain (Elder and Cairns, 1982).VFPOM data were obtained from analysis of the 0.45-|x silverfilterthat wasusedto filterthe dissolvedorganic carbon sample. The particulate matter captured on the silver filter was termed "suspended organic carbon" (SOC). This SOC sample included fine and very fine parNutrient and DetritusTransport intheApalachicola River, Florida C15Table 7. Analytical techniques used in the determination of chemical and physical characteristics ofwater samples
Parameter Analytical technique1 Totalorganic carbon

.... Dissolved organic carbon.

. Suspended organic carbon. Totalinorganic carbon

. . . Dissolved inorganic carbon Total organic nitrogen

. . . Dissolved nitrate,nitrite

. . Dissolved ammonia

..... Dissolved organic nitrogen. Dissolved orthophosphate. Dissolved phosphorus.... Totalphosphorus

...... Chloride

............ Dissolved solids.

....... Total solids

.......... Temperature.

..... pH

............ Specific conductance Dissolved oxygen. . . Combustion, infrared absorption by carbon dioxide. Do. Do. Do. Do. Colorimetric, block digester-salicylate. Colorimetric, cadmium reduction-diazotization. Colorimetric,indophenol. Colorimetric, Kjeldahl. Colorimetric, phosphomolybdate. Colorimetric, phosphomolybdate. Do. Colorimetric, ferric thiocyanate. Residue on ignition at 105 C. Do. Thermometer, on site. Water-quality monitor, on site. Do. Do. 1References for organic carbon, Goerlitz and Brown, 1972; for all analyses except organic carbon, Skougstad and others, 1979.

tides; coarse material was excludedbecause ofthe narrow opening on the samplernozzle. Hence, the carbon concentration ofVFPOM was determined by subtracting FPOM as carbon from SOC.

Bottom-Load Detritus CPOM includes all sizes greater than 1 mm. Coarse material transported along the river bottom could not be sampled by the pump-sampling apparatus; yet, it was judged to be too important to be overlooked. Early experimentation led to a stationary net dredge (fig. 12) designed to sample coarse bottom-load particles that are transported along the bed of the river hence the term "bottom-load" paniculate organic carbon (BPOC). The stainless-steel frame ofthe net dredge has an 860-mm by 240-mm opening which holds a 1.5-m-long, 1-mm-mesh nylon net. Four kg oflead weight attached to the bottom edge ofthe frame hold the bottom leading edge flush with the river bed when the boat is anchored in place. The net is lowered to the bottom by a mounted crane and is left in place for 20 minutes. The velocity ofthe waterentering the net is measured with an attached flow meter. The volume of water for the bottom-load sample is calculated from the cross-sectional area ofthe net opening, the velocity ofthe water, andthe time the netis inplace. Several cross-sectional profiles of bottom-load organic carbon were made under different discharge conditions. In all cases, samples fromthe mid-20percent ofthe channel accounted for close to 50 percent of the total BPOC (fig. 13). The monthly, or more frequent, bottomload samples were all collected at midchannel, and all estimates of BPOC were based on the assumption that 50 percent ofthe material was outside ofthe sampled section. The collected organic material was hand picked from the detachable net andplacedin pressure-closure plastic bags. The samples were shipped to the laboratory for oven-dry and ash weights, in the same manner as the other organic carbon size fractions. Flood-Plain Detritus Net collection.The large quantity of litter fall restingontheflood-plainfloorisinvariousstagesofdecompositionwhen seasonalfloodingbegins. Becauseonlyapart ofthe litter fall is transported, a method for estimating the fractiontransportedduringfloodingwasdevised. Figure 14 shows a device developed for sampling detritus moving through the flood plain. Samples were collected during flooding at numerous points in each ofthe two intensive transects. The device was placed well away from stream channels,butcarewastakento avoidareasofdensevegetationwheredetrituswouldbetrapped.
C16 Apalachicola River Quality AssessmentFigure 9. Bulk precipitation apparatus used for collection of total carbon, total nitrogen, and total phosphorus samples.

The flood-plain detritus net (fig. 14) has an opening 300 mm wide by 1.7mhigh. The net is 2 m long andtapers to a 300-mm-diameter opening at the rear. A coarse mesh outer net is used to support an inner 1-mm-mesh collection net. The double net is closed at the trailing end with a drawstring. The side bars ofthe net are constructed of 10-mm threaded steel rod approximately 2 m long. The side bar rods extend about 150 mm below the bottom net support. For detritus collection, these extension rods were driven intothe flood-plain floorby stepping on thebottom net support or when the water was over 1 m deep, by driving the rods from the top with ahammer. Nylon cord attached to the threaded rods above the top net support was attached to nearby trees to achieve a vertical position. The net was flushed of any debris accumulated during emplacement and the drawstring was pulled. The depth of water in the net opening, the time, and the current velocity wererecorded. The net was left in place for 2 to 24 hours, depending on accessibility and water velocity. The depth, time, and current velocity were recorded when the netwas recovered. The depth and velocity used to calculate the volume of water passing through the net were the averages ofthebeginning andendingdepths andvelocities. The entrained material was rinsed to theback ofthe net, the drawstring was opened, and the material was emptied into marked pressure-closure plastic bags. Like theotherdetritus samples, this material was shippedtothe laboratory foroven-dry and ash weights. Plastic-sheet collection. The flood-plain detritus net was used to estimate the proportion of the litter fall that was transported under the conditions at the time the sample was collected. The suspended andbottom-load detritus data collected in the main river channel were designed to estimate the fraction that was captured by the river and ultimately was transported to Apalachicola Bay. All ofthese techniques were relatively short term; collections were madeoverperiodsof20 minutesto 24hours. A method used to supplement short-term detritus data was a long-term collection technique intendedto provide an independent measure ofthe amount ofmaterial in transport but remaining on the flood plain after flooding. The collection material was a 1-square-meterplastic sheet held flush to the ground with eight large nails around the perimeter. Three plastic sheets were installed at randomly selected locations in each of the 16 intensive-plot locations. The sheets were installed in early September 1979. In late December 1979, the litter fall resting on the sheets was sprayed with fluorescent orange paint. After the March-April flood had receded, 31 sheets wererecovered. Seventeen sheets were not recovered because they were lost, destroyed, folded, or in some other manner invalidated.In the laboratory, the presence or absence of fluorescent orange leaves was noted. The sample was weighed, and a subsample was separated into coarse and fine fractions with a 1-mm sieve. These fractions were dried, andtheiroven-dry ash weights were determined.

Data Handling Surface-water-quality and stage-discharge records are routinely collected, prepared, and then stored in the WATSTORE computer file (Hutchinson, 1975). A generalized representation ofthe major steps between the collection ofdata and the nutrient and detritus loadresults presented in this report is shown in figure 15. All waterquality analyses and stage-discharge records are published annually and are also accessible through NAWDEX (Edwards, 1977). The temporary data file labeled ARQA QW (fig. 15) represents the water-quality analytical results which
Nutrient and DetritusTransport in theApalachicola River, Florida C1785°30' 85°I5' 85°00' 84°45' 84°30'

3I °00'

30°45'
-

30°30'
-

EXPLANATION Apclcchicola River basin boundary Drainage divide for gaging stations National Weather Service rain gage location USGS rain gage location Bulk precipitation gage

OF MEXICO 30°I5'
-

30°00' 5

29°45'

-

Figure 10. Locations of National Weather Service and U.S. Geological Survey rain gages and bulk precipitation sample collectors in theApalachicola basin, Florida.
C18 Apalachicola RiverQualityAssessmentPOTENTIOMETRIC SURFACE, IN METERS ABOVE SEA LEVEL
Figure 11.The potentiometric surface ofthe Floridan aquifer in May 1976.

Nutrient and DetritusTransport in theApalachicola River, Florida C19Figure 12. Sampling apparatus used for collection of bottom-load particulate organic material.

were set aside primarily for computation of the water budget and transport of nutrients and detritus. The computer program to calculate transport, ARQA LOAD (fig. 15), accessed the water-quality analytical results and the average daily discharge (ARQADV). In an earlier study of hydraulic and nutrient budgets, Scheider and others (1978) reported on the relative accuracies of various possible methods for determining nutrient input. The best model resulted from the combinationofdiscrete stream nutrientconcentrationdata with continuous discharge data. Since continuous nutrient concentration data are virtually impossible to obtain, the best estimate for an interval is obtainedbyusingtheconcentration at the midpoint ofthe interval. The product of integrated discharge from continuous records and the discrete midpoint nutrient concentration thus gives the best estimate oftransport. The ARQA LOADprogram was written tocalculate the midpoint date between any two sets ofsamples. Each water-quality data point represented the sample interval beginning at the midpoint date between the previous and current samples and ending at the midpoint date between the current and subsequent samples. The sample interval thus defined was used to calculate the mean sample interval discharge, using mean daily discharges computed from continuous streamflow record. Transport for the sample intervals is reported as metric tons ofthe particular constituent. The transportperday is reportedonly forthe particular day the sample was collected and is reported as metrictonsperday. The time period chosen torepresent annual transport (metric tons per year) was June 3, 1979, through June 2, 1980, a period of 366 days. This 1-year span includes a complete spring flood (March-May 1980) as well as some low flows and brief high-water peaks that characteristically occur at other times ofthe year. It also represents a period during which water-quality and detritus sampling was thorough. Although sampling began in February 1979, methods were in the process ofrefinement during the early months of the program. The period selected to represent annual transport also nearly coincides with the September 1979 to September 1980 sample collecting period for litter-fall measurements (Elder and Cairns, 1982).

C20 Apalachicola River Quality AssessmentiJU

uj 40 

# is i°- <z ^< 30 o z
CD DC
PERCENTAGE OF r ORGANIC C/

mnH _ ro



### go o i i

-

-

_

i i i

i i BE 0.9 0.7 0.5 0.3 OF WATER -

-

.

-

O.I Rl \\J\J

80 5 O I DC. Ul Q. 60 w
DC. O Z 40 i-r oc. o CL CO Z IT H 20

0 GHT EDGE OF WATER FRACTION OF WIDTH OF RIVER CROSS SECTION NEAR SUMATRA Figure 13. Results of cross-sectional sampling on July 2, 1979.

RESULTS Because of the movement of water through the river-wetland system, physical transport of nutrients to Apalachicola Bay is possible. The computation ofnutrient transport (weight) requires the collection ofdischarge data (volume) andconcentration data (weight/volume). All data were separated by date into time periods that correspond to different hydrologic conditions during the study year. Subsequently, discharge data, combined with other water input and output information, were used to determine a waterbudget, and nutrient and detritus concentration data were computed on both a seasonal and an annual basis. Estimates of the magnitude and significance of error in thesecomputations were included.

Seven Hydrologic Periods As previously described, the annual budgets were calculatedforafullyearbeginningJune 3, 1979, andending June 2, 1980. The year was subdivided into seven periods, according to hydrologic changes. The periods also varied a great deal in the rate offorest litter fall on the flood plain, which has important effects on nutrient and detritus transport. The seven periods may be characterized as follows: 1. Summer (June 3-September 8; 98 days) Continuous low flow was interrupted only slightly by a minor peak in July; the peak was below flood stage. Litter fall was moderate. Tupelo, the most common tree in the flood plain, beganto shedleavesinJuly. 2. Early autumn (September 9-October 13; 35 days) Heavy rainstorms in the basin produced unseasonally high flows, especiallyinthe lowerriverbasin. Afterthe storm, the flows rapidly decreasedto a low level. Some flooding occurred in the lowerfloodplain. Litterfall increasedsubstantially. 3. Late autumn (October 14-January4; 83 days) A moderate increase in flow in November-December caused some shallow flooding in the lower flood plain in December. Litter fall from most tree species was voluminous and reached maximum levels in November (Elder andCairns, 1982). 4. Winter (January 5-March 8; 64 days) Flow remained at a moderate level, producing continuous shallow flooding in the lower flood plain. Litter fall decreased considerably, but some species, particularly the oaks, planer-tree, and sweetgum, continued to shed leaves duringthe wintermonths. 5. Springfloodrise (March 9-March 16; 8 days) An abrupt increase in flow produced extensive flooding over the entire length ofthe river basin. Discharge increased threefoldin 8 days. Litterfall decreasedto low levels. 6. Springfloodpeaks (March 17-April 20; 35 days) High flow was continuous, well above flood stage inthe entire basin. Three flood peaks occurred, with maximum flow in early April of3,850 m3/s at Sumatra. New leaves appeared on trees and litter fall remained low. 7. Springfloodrecession (April 21-June 2; 43 days) The recession ofthe river flow was interrupted by a secondary peak of 1,900 m3/s in late May. Litter fall increased slightly. These periods were selected to represent different hydrologic events and were not delimited by climatic conditions, fiscal periods, or arbitrary dates. Consequently, their lengths vary considerably. Most ofthem are considerably longer than 1 month, minimizing errors associated with calculations over short time spans (Winter, 1981). The spring flood rise period is necessarily short to represent the rising limb of the flood. During a short period with high flows, only the discharge component of the water budget is significant. Discharge estimates based on stage-dischargerelations atthecontinuous-recordinggages are the most accurate of all water-budget components.
Nutrient and DetritusTransport in theApalachicola River, Florida C21Figure14. Flood-plaindetritus netusedtomeasuretransportedforestlitter.

Therefore, an 8-day period to represent the spring flood rise is acceptable.


### Water Budget An equation that expresses the water budget ofthe ApalachicolaRiversystemis: (1) WO=WI+P

ro+P dp+GW+CR-Ret±r, where allterms representvolumesofwaterand aredefined asfollows: WOequalsoutflowatthedownstreamlimit; WIequalsinflowattheupstreamlimit; P roequalsprecipitationrunoff; P dpequalsdirectprecipitationinriverandfloodplain; GWequalsground-waterdischarge; CRequalsinputfrommouthofChipolaRiver; Retequalsevapotranspirationofriver-derivedwater;and requalsresidual the amountrequiredtobalancetheequation(equivalenttoanerrortermandnotassociatedwithany knowncomponentofthebudget). The equation may be applied to each subbasin or to the entire basin upstream ofthe Sumatra gage. Application of the equation is dependent on accurate estimates ofbudget components for each subbasin and each period. The methods and dataused are described in the following sections. The water budget described by equation 1 is depicted diagrammatically in figure 16. Numbers shown with each component are overall estimates forthe 1979-80 study year; their derivations and seasonal breakdowns are detailed in subsequent tables and text. Several of the major components, shown by large circles, can be subdivided into more specific categories. Only the components or subcomponents thatprovide directinputtooroutflow from the river-wetland system are included in equation 1.
C22 Apalachicola River Quality AssessmentFigure 14. Flood-plain detritus net used to measure transportedforest litter Continued. Figure 15. Majorsteps in datacollectionand handling. (See textforexplanationofsymbols.)

Precipitation (P) in the basin is separated into four categories: P gw equals precipitation-derived water that enters the ground-water system before it has any contact with.the river or the flood plain. Percolation through the soil may alterits chemistry considerably. P ro equals precipitation that enters the riveror floodplain as surface runoff. Any nutrient and detritus contribution made by the upland communities is likely to be transportedbythis route. P dp equals direct precipitation in the river channels and floodplain. P et equals precipitation in the uplandsthatre-enters the atmosphere by evapotranspiration without ever reaching the river-wetland system. Since these are the only subdivisions ofthe precipitation component, it followsthat: Pgw +Pro +Pdp +Pet (la) Similarly, evapotranspiration (ET) is composed of water from two sources: water from precipitation,just defined under the term P

et, and water lost to the atmosphere fromthe river and wetland, termedRet
.

ET=P et+Ret. db) Ground water (GW) is also broken down into two fractions, one that comes from inside the basin, originating as precipitation (P

gw), and another that comes from outside the basin, (GW 0). Ground-water flow can be bidirectional; hence, both GW and GW 0 can be either positive ornegative. dc)
Nutrientand DetritusTransport intheApalachicola River, Florida C23

### PV=QnA:, K 2, (2) where

BASIN BOUNDARY

Figure 16. Representation of Apalachicola water budget. (See text for explanation of symbols; values are in cubic kilometers.)

Streamflow 

### Each subbasin was delimited at its upstream and downstream ends by a continuous-recording stage recorder. Stage-discharge relations have been established for each ofthese sites on the basis ofratings drawn from current-meter measurements. Total period volume was calculatedforeach site fromthe daily discharge data, usingthe equation PVequalsperiodvolume, orflowofwater, inkm3; Qequalsmeandailydischarge duringtheperiod, inft3/s; nequalsnumberofdays intheperiod; KI equalsnumberofsecondsperday (8.64X 104); and K 2equals numberofkm3perft3 (2.83x 10"''). The results ofthese calculations are shown in table 8. At each site, PVbecomes WOfortheupstream subbasin and WIforthedownstream subbasin.

Precipitation 

### The total precipitation for each subbasin was based on National Weather Service data from nearby rain gages (fig. 10). Values ofPwere calculated for each subbasin, andfortheentire Apalachicolabasin, bythe equation

(3)



### where Ru equalsrainfall atupstream site, in inches; Rdequalsrainfall atdownstream site, in inches; A equalstotal areaofsubbasin, inkm2; Ar3equalskilometerperinch (2.54X 10"5).

The computations produced the precipitation estimates shown in table 9. Once the total rainfall in the basin was known, the values of direct precipitation (P dp) could be computed

Table8. Flowvolumesbygagingsitesand theseven periods

[Volumesareincubickilometers]

Period Gaging site Dates Chattahoochee Blountstown Wewahitchka Sumatra Summer.

. .............. Early autumn
............. Winter.

................. Springflood rise

........... Springfloodpeak

.......... Springflood recession

....... Total foryear ........... . . . . . 06/03/79-09/08/79

. . . . . 09/09/79-10/13/79

. . . . . 10/14/79-01/04/80

. . . . . 01/05/80-03/08/80

. . . . . 03/09/80-03/16/80

. . . . . 03/17/80-04/20/80

. . . . . 04/21/80-06/02/80

. . . . . 06/03/79-06/02/80 3.18 1.28 3.09 3.73 1.54 6.39 3.65 22.86 3.67

1.48 3.41 3.68 1.47 6.81 3.61 24.13 3.69

1.74 3.36 4.13 1.12 6.37 3.71 24.12 4.52

2.06 3.96 4.23 1.14 8.06 4.64 28.61

C24 Apalachicola RiverQualityAssessmentTable 9. Precipitation in the seven periods and the Apalachicola basinsfrom June 3, 1979, through June 2, 1980 [Precipitation (P)in cubic kilometers] Subbasin Period Dates Upper Middle

Total foryear, 06/03/79-06/02/80 1.50 1.22 Lower

0.92 Entire basin Summer.

.................. Early autumn
............... Late autumn.
............... Winter.

................... Spring flood rise

............. Spring flood peak

............ Spring flood recession

......... ...... 06/03/79-09/08/79

...... 09/09/79-10/13/79

...... 10/14/79-01/04/80

...... 01/05/80-03/08/80

...... 03/09/80-03/16/80

...... 03/17/80-04/20/80

...... 04/21/80-06/02/80 0.47 0.29 0.14 0.21 0.09 0.20 0.10 0.43

0.29 0.10 0.13 0.06 0.14 0.07 0.30

0.23 0.09 0.10 0.04 0.09 0.07 1.20

0.81 0.33 0.44 0.19 0.43 0.24 3.64

from the ratio offlood-plain area to total watershed area. Other subdivisions of precipitation were computed indirectly. Runoff (P

ro) was determined from historical records of measurements of small tributary streams in the basin. Both Little Sweetwater Creek near Bristol and Flat Creek near Chattahoochee (fig. 10) have been measured on several occasions duringboth base low-flow andhigher flow conditions. Base flows in these streams are attributable to ground-water discharge; hence, the difference between mean annual flow and base flow gives an estimate of the amount contributed by runoff. This may be converted to an annual volume per unit watershed area and extrapolatedto the entirebasin. The term P

et, or the amount ofprecipitation lost by way ofevapotranspiration in the uplands, is computed as part of the overall evapotranspiration estimate, to be described subsequently. Once P et is known, along with P(JP and P

ro, the fraction involved in ground-water recharge (P gw) can be determinedby difference.

GroundWater Ground-waterdischarge occurs as springs in theriver andalongthewestbank, as seepsalongthesteepeastbank, and as streamflow in various small tributaries. Discharge seeps are quite common above Blountstown, where the limestonesoftheFloridanaquiferapproachlandsurface,becomingexposedatvariouspointsintheriverchannelandon bluffs neartheeastbank. Fromthere, thetopofthe aquifer dips to the south until it is about 46 m below sea level at Apalachicola (Kwader and Schmidt, 1978). The Chipola RiverrisesonFloridan limestonesnearDothan, Ala.,flows through DeadLake, andjoinsthe ApalachicolaRivernear Wewahitchka some 90 km south. Much ofthe flow ofthe ChipolaRiverisderivedfromground-waterdischarge. Regional water-level mapping (fig. 11) of the principal artesian (Floridan) aquiferindicates the existence of steep gradients to the Apalachicola and Chipola Rivers in their upper reaches, and flat gradients normal to them in the south. This is consistent with Kwader and Schmidt's (1978) "Top ofFloridan Aquifer" map and area of known ground-water discharge. Pascale and Wagner (1982), in their investigation ofthe waterresources ofthe Ochlockonee River basin, explained the high and steep water levels on the east side of the Apalachicola River. They found recharge to the Floridan to be limited by overlying clay beds and by the aquifer's low permeability andtransmissivity. Estimates ofground-water discharge can be derived from various data taken from flow measurments. A series of low-flow measurements on the main channel of the Apalachicola River at Chattahoochee and Blountstown provides the most reliable data from which to estimate ground-water discharge. Between 1957 and 1980, U.S. Geological Survey personnel made 16 same-day measurements of the two sites during low-flow periods. The mean discharge increase forthe 16 measurements was 20 m3/s, or 0.6 km3/yr. This was attributed to groundwater inflow, because there was no significant contribution from overland runoff or surface-water tributaries. Flow measurements also were made on small streams that empty into the Apalachicola River in the upper subbasin. During dry periods, these streams are almost exclusively sustained by ground-water discharge. Total ground-water discharge of0.4km3/yr was estimated by calculating mean discharge per unit watershed area on the basis of low-flow measurements (table 10) of three streams in theupper subbasin. Since thisestimatedoes not account for seepage, spring flow, or ground-water discharge to the river during other than low-flow periods, it is assumed to be low. It is therefore quite consistent with the estimate of 0.6 km3/yr derived from the river low-flow measurements.
Nutrient and DetritusTransport in the Apalachicola River, Florida C25Table 10. Mean discharge per unit watershed areabased on low-flow measurements [Q=low-flowdischarge;/! =watershedarea] Mosquito Creek, September23, 1976



### A =223km2 Q= 1.28m3Is I.28m3/s

_ 223km2 =0.0057 (m3/s)/km2

FlatCreek, October 18, 1976



### A =64.5km2 =0.54m3/s Q.54m3/s_ 64.5km2 =0.0084 (m3/'s}/km2

LittleSweetwaterCreek, September 16, 1980 !2=0.116m3/s A =6.35 km2 Q'\\6mJ

S =0.0183 (m3/s)/km2

Averagefor three streams 

### 0.0057 + 0.0084 + 0.0183 = 0.0108(w3/s)A;m'

Chattahoochee toBlountstown annualground-waterdischarge



### A = 963km2 1 km' 0.0108 (m3/s)lkm2 X ^hjX 3.1536X 107^L-X 963^m2 =0.33km3/year v 7 10 m year

The middle and lower subbasins presumably show much less ground-water discharge to the riverbecause the water-level gradient shifts toward a direction nearly parallel totheriverflow (fig. 11). In fact, some additional flow measurements from the lower subbasin indicate that ground-water discharge is negligible in that region. The annual water-budgetestimates are therefore asfollows:



### Subbasin Upper

. Middle

. Lower

. 

### Annualgroundwaterdischarge, in km3 0.6 0.1 0

Seasonal fractions of these annual ground-water discharge volumes are determined as the amounts proportional to the time fraction involved. This assumes a constant ground-water flow rate, an assumption made because ofinsufficient data. A more likely relation is that ground-water discharge decreases during initial phases of a flood, then increases during the flood recession. Data are not available, however, to document such a pattern in theApalachicola system. Table 10 values represent estimates for the term GWin equation 1. The fraction that results from recharge within the basin (P

gw) was already determined from precipitation data. The remaining fraction (GW 0) the amount ofdischarge to orrecharge from the ground-water system ouside the basin can be determined by difference. Chipola River Inflow The Chipola River is the only major tributary to the Apalachicola. Flowing south from Alabama, it forms
C26 Apalachicola RiverQualityAssessmentDead Lake, then enters the Apalachicola near Wewahitchka. With a mean annual flow of 100 m3/s, the Chipola River is a major surface-water input to the lower subbasin. Like some ofthe small streams in the upperpart ofthe Apalachicola basin, the Chipola is spring fed at its source nearDothan, Ala. The inflow from the Chipola River, which becomes the CR component in the water budget equation when applied tothe lower subbasin orto the entire basin, is shown in table 11. The upper and middle subbasins obviously have no CR component.

Table 11. Inflow from Chipola River at Dead Lake, June 3,

1979, through June 2, 1980

Period

Summer.

........... Early autumn
........ Late autumn.
........ Winter.

............ Spring flood rise

...... Spring flood peaks

..... Spring flood recession

. . Total foryear ...... of days
98 35 83 64 8 35 43 366 Mean flow

(in cubic meters per second) 68 151 62 80 178 244 125 103 Total flow

(in cubickilometers)
0.58 0.46 0.44 0.44 0.14 0.74 0.46 3.26

Evapotranspiration No data from direct monitoring of evaporation or solar radiation were available. Estimates of evaporation couldbe made, however, on thebasisofambienttemperature andestimatedwater-retention factors ofthe soil. The method ofcalculation ofpotential evapotranspiration, as described by Thornthwaite and Mather (1957), is basedonthe equation

ET= 1.6(10777)' (4) where FTequals monthly potential evapotranspiration, in mm; Tequals mean monthlytemperature, in degrees Celsius; /equals heat index = (775)1 514; and a equals exponent related to the annual heat index, /, by theexpression a=(6.75x 10-7/

3)-(7.71 x lQ-5/

2)+0.01797-0.49. (5) The unadjusted potential evapotranspiration rate resulting from the application of equation 4 is then corrected for month and day length. The result is the maximum potential evapotranspiration that would be expected atthe given temperatures, with high soil-waterretention. In the Apalachicola basin, the wetland area may be expected to have higher ETrates than the uplands. This is because ofthe high soil moisture in large areas that remain permanently saturated or flooded. Water loss from cypress flood-plain forests has been demonstrated to be nearly equal to standard pan evaporation rates (Brown, 1981). The uplands are characterized by mostly sandy soils. Using as estimated 250-mm water-retention factor for sandy soils (Thornthwaite and Mather, 1957), the overall ETrate in the uplands was estimated to be 0.8 of the maximum potential ET. The final computation of monthlyETforabasin or subbasin thenbecomes 

### ET=(ET maxxAw}+(0.8ET

maxxAu\ (6) where ETequals waterloss duetoET, inkm3; ET max equals maximumpotentialET, in km3; Aw equals areaofwetland, inkm2; and Au equals areaofupland, inkm2

. Thetwoterms ontheright side ofequation 6representthe two previously described components of evapotranspiration (fig. 16), Ret andP

el, respectively. Annual ETrates and estimates ofETfor the three subbasins are given in table 12. The ETrates are somewhat higherthan the annual rate of 1,016 mm (40 inches) estimated by Qureshi (1978) for the Apalachicola basin. Summer ETrates, however, are very similar to those determined by Brown (1981) for cypress flood-plain forests, using measurements in polyethylene chambers. Monthly ET varies over an order of magnitude, from 16 mm in Februaryto morethan 160mminJuly.

Table 12. Estimates of annual evapotranspiration (ET) in Apalachicola subbasins, June 3, 1979, through June 2, 1980
Area (km2)

Subbasin

Upper

..... Middle.

.... Lower.

.... Upland

885 429 325 Flood

plain

78 164 151 Mean

annualtemperature in °C

20.0 19.9 19.7 EvapotranspirationMaxiannual rate,millimeters 1,060 1,050 1,040 Estimated volume, in cubickilometers

0.85 0.54 0.44

Nutrient and DetritusTransport in theApalachicola River, Florida C27OverallWater Budget basins and within some periods. In particular, there is an apparentreversal ofthis trend during the spring floodrise. The quantities calculated for each of the budget This may be attributed to lag time in the flood wave (2 components and presented in tables 8, 9, 11, and 12 are to 3 days from Chattahoochee to Sumatra) which becomes combined in equation 1, to produce tables 13-16. Water significant in a short period when flow increases rapidly, inflow (WI) is the dominant contributor to each of the Because of this lag, the rising limb ofthe flood did not subbasins. The ChipolaRiver adds a substantial volume of actually begin at Sumatrauntil March 11. Thus, the spring water in the lower subbasin. The ground-water contribu- flood rise included 2 days of relatively low flow at tion in the upper subbasin is significant, especially during Sumatra. low-flow periods (summer, late autumn, winter). Precipi- Other cases in which the data showed a decrease in tation and evapotranspiration involve a sizable volume of flow downstream were the winter, spring flood rise, and water in the basin, but much ofthat is confined to the up- spring flood recession periods in the upper subbasin and land hydrologic cycle (fig. 16). Their roles in the river- the late autumn, spring flood rise, and spring flood peaks wetland water budget, although significant, are small in periods in the middle subbasin. Although some or all of comparison with streamflow. these reversals may be real, they all may be due to error, The data show a general increase in flow from up- since they are within error limits (see latererror analysis), stream to downstream sites, the increase between Chat- One factor that may contribute to error, particularly in the tahoochee and Sumatra being 5.75 km3/yr, or 20 percent middle subbasin (table 4), isthe existence ofside channels ofthe total flow at Sumatra. Exceptions occur within sub- in the vicinity of the Wewahitchka gage. Such channels

Table 13. Water budget in the upper subbasin (Chattahoochee-Blountstown), by periods, June 3, 1979, through June 2, 1980 [Allvaluesin cubic kilometers. Seetext for beginning and ending dates ofperiods and expalantion ofabbreviations]
Period
Summer.

........... Early autumn
........ Winter.

............ Spring flood recession

. . Total foryear. . . . . . Number ofdays 98 35 83 64 8 35 43 366 WO

3.67 = 1.48 = 3.41 = 3.68 = 1.47 = 6.81 = 3.61 = 24.13 = WI +

3.18 4 1.28 4 3.09 4 3.73 4 1.54 4 6.39 4 3.65 4 22.86 4 pro +

- 0.09 4- 0.06 4-

- 0.03 4-

- 0.04 4- 0.02 4-

- 0.04 4-

- 0.02 4-

- 0.30 4- 

# '*

0.04 0.02 0.01 0.02 0.01 0.02 0.01 0.13 ± GW

+ 0.16 + 0.06 4- 0.14 4- 0.10 4- 0.01 4- 0.06 4- 0.07 4- 0.60 - Ret *

- 0.04 +

- 0.01

- 0.01 +

- 0.005

-
- 0.001

-
- 0.005 4-

- 0.01 4- 0.08 4- r

0.24 0.07 0.15 0.21 0.11 0.31 0.13 0.16

Table 14. Water budget in the middle subbasin (Blountstown-Wewahitchka), by periods, June 3, 1979, through June 2, 1980 [All valuesin cubic kilometers. Seetext for beginningand ending dates ofperiods and explanation ofabbreviations] Period
Summer.

........... Early autumn
........ Winter.

............ Spring flood recession

. . Total foryear. ..... Number ofdays
98 35 83 64 8 35 43 366 WO

3.69 = 1.74 = 3.36 = 4.13 = 1.12 = 6.37 = 3.71 = 24.12 = WI 4

3.67 4 1.48 4 3.41 4 3.68 4 1.47 4 6.81 4 3.61 4 24.13 4' pro +

- 0.07 4-

- 0.05 4-

- 0.02 4- 0.02 4-

- 0.01 4- 0.02 4- 0.01 4- 0.20 4- 

# "dP

0.12 0.08 0.03 0.03 0.02 0.04 0.02 0.34 ± GW

+ 0.03

- 4- 0.01 + 0.02 ~ 4- 0.02

- 4- 0.00

- 4- 0.01 4- 0.01 4- 0.10

- 

# * *

0.08

- 0.02 4- 0.02 0.01 4- 0.003

- 0.01 0.03 4- 0.17

- r

0.12 0.14 0.10 0.39 0.38 0.50 0.09 0.48

C28 Apalachicola River Quality AssessmentTable 15. Water budget in the lower subbasin (Wewahitchka-Sumatra), by periods, June 3,1979, through June 2,1980 [Allvaluesin cubic kilometers. Seetext forbeginningand ending dates ofperiodsand explanation ofabbreviations]
Period
Summer.

........... Early autumn
........ Late autumn.
........ Winter.

............ Spring flood rise

...... Spring flood peaks.

. . . . Spring flood recession

. . Number ofdays
98 35 83 64 8 35 43 366 WO

4.52 = 2.06 = 3.96 = 4.23 = 1.14 = 8.06 = 4.64 = 28.61 = Wl H

3.69 H 1.74 H 3.36 H 4.13 H 1.12 H 6.37 H 3.71 H 24.12 H- pro +

h 0.03 + h 0.03 + h 0.01 + h 0.01 + h 0.004 + h 0.01 + h 0.01 + h 0.10 + 

# pdp

0.10 0.07 0.03 0.03 0.01 0.03 0.02 0.29 ± CR

+ 0.58 + 0.46

- + 0.44

- + 0.44

- + 0.14

- + 0.74

- + 0.46 + 3.26 Ret ±

0.08 + 0.02

- 0.02 + 0.01 0.002

- 0.01 + 0.02 + 0.16 + r

0.20 0.22 0.14 0.37 0.13 0.92 0.46 1.00

Table 16. Water budget in the Apalachicola basin (Chattahoochee-Sumatra), by periods, June 3, 1979, through June 2, 1980 [Allvaluesin cubic kilometers. Seetext forbeginningand endingdates ofperiods and explanation ofabbreviations]
Period
Summer.

........... Early autumn
........ Late autumn.
........ Winter.

............ Spring flood rise

...... Spring flood peaks.

.... Spring flood recession

. . Total foryear. ..... Number ofdays 98 35 83 64 8 35 43 366 WO

4.52 2.06 3.96 4.23 1.14 8.06 4.64 28.61 H

= 3
= 1

= 3
= 1
= 6
= 3

= 22,VI
.18

- .28

- .09

- .73

- .54

- .65

- .86

-+ Pro + f 0.19 + f 0.14 + f 0.06 + f 0.07 + f 0.03 + f 0.07 + f 0.04 + 4- 0.60 + 

### rdp H

0.26

- 0.17

- 0.07

- 0.08

- 0.04

- 0.09

- 0.05

- 0.76

-h GW ±
h 0.19

- h 0.07

- h 0.16

- h 0.12

- h 0.01 i h 0.07

- h 0.08

- h 0.70 H CR

-

\- 0.58

- h 0.46

- h 0.44

- h 0.44

- h 0.14

- h 0.74

- h 0.46

- h 3.26

- Ret

0.20 0.05 0.05 0.02 0.01 0.02 0.06 0.41 +

+

+

. + + + r
0 39 001 0 19 0 19 061 07? 0.42 0,84

may divert water out ofthe channel for short distances, to re-enter at points downstream. These diversions may "hide" some flow from the measurement section and produce low-flow results.

Nutrient Concentrations Nutrient Concentrations in the River The principal elements ofinterest in the analysis of nutrient flow were organic carbon, inorganic and organic nitrogen, and phosphorus. Nutrients can vary as a function oftime, discharge, and location. Both particulate and dissolvedphases were collectedroutinely inriverine samples. Figure 17 illustrates the mean concentration and standard error for total organic carbon, total nitrogen, and total phosphorus at the four main river water-quality collection stations. Variations in concentration withrespectto location were small. The only statistically significant difference (analysis ofvariance) was in total organic carbon between Chattahooch.ee and Blountstown. The large increase in carbon concentrations in the upper subbasin probably resulted from high carbon production in the flood plain and high flood velocities that caused significant transport from the flood plain to the river. The relatively small temporal changes in nutrient concentrations are shown by the standard error. Temporal variations were generally random, with no clear pattern of change with season. Unlike some constituents (Daniel and others, 1979), nutrient concentrations were not closely correlated with discharge.

Bulk-Precipitation Concentrations Bulk precipitation includes dry fallout and rainfall. Concentrations of total organic carbon, nitrogen, and
Nutrient and Detritus Transport in the Apalachicola River, Florida C2910

8
-

UJ o 

# I °
£ 0.10 UJ h- 0.08 Z -I 0.06
Z Z 0.04
0.02
0 TOTAL ORGANIC CARBON

TOTAL NITROGEN

TOTAL PHOSPHORUS

EXPLANATION MEAN CONCENTRATION AND STANDARD ERROR FOR SITES INDICATED

Figure 17. Mean nutrient concentrations for the period February 1979 through July 1980 at the four main river collection stationswith standard error bars. phosphorus in bulk precipitation showed variability over a considerable concentration range. The data were plotted on probability paper (fig. 18) using the method of Velz (1970, p. 522-542). Abrupt slope changes indicated that the frequency distribution of sample concentrations was skewed, probably owing to contamination of some ofthe samples. Calculations of loads based on means from the complete database wouldresultinunreliable bulkprecipitation estimates. A better estimate was provided by the median value for each nutrient for all periods and subbasins. The median values are: total organic carbon, 5 mg/L; total nitrogen, 0.6 mg/L; and total phosphorus, 0.06 mg/ L.
Ground-Water Chemistry Ground-water inflow is a relatively minor part of total water flow in the basin (table 13-16), and its impor

# F I "T

0 aoi 0.9 TOTAL

CARBON

001 0 I 

# "I ,.T 30 SO 70

TOTAL NITROGEN

01 1.0 10 30 50 70 90

TOTAL PHOSPHORUS

01 1.0 10 30 50 70 90

PROBABILITY 99 99.9 99.99
Figure 18. Total carbon, total nitrogen, and total phosphorus concentrations in bulk precipitation samples.

C30 Apalachicola River Quality Assessmenttance as a nutrient source is small. Ground water was found discharging from seeps in the upperreaches ofFlat Creek and Little Sweetwater Creek (fig. 10). Water analysis (table 17) ofLittle Sweetwater Creek suggest that its residence time in the ground was rather short. The low levels ofchloride, dissolved solids, pH, and conductance are similar to those ofother seeps and springs in northern Florida (Rosenau, Faulkner, Hendry, and Hull, 1977). Water analyses ofFlat Creek indicate slightly higherconcentrations of dissolved solids, conductance, and phosphorus. These analyses tend to indicate water movement through the phosphate-rich limestones of the Hawthorn Formation, which crops outin this drainage basin. Chipola River Concentrations of most elements were nearly the same in Chipola River water (Dead Lake Outlet) as in Apalachicola River water (table 17). Total phosphorus was the exception, with 0.02 mg/L in Chipola watercompared with 0.05 mg/L in Apalachicola water. The Chipola Riveris the only large tributary tothe Apalachicola River, and, with nutrient concentrations comparable to those of the Apalachicola, its contribution to streamflow and the transport of nutrients in the Apalachicola system is appreciable. Nutrient Transport The two basic types ofdata described previously discharge and nutrient concentration provide the elements necessary to compute nutrient transport. The term "transport," as used here, is defined as the mass ofmaterial that moves past a given point in a given time span. Otherterms, such as "flux," "load," and "flow," often are used in similar context. The term "yield" refers to total annual transportperunit area. Total organic carbon (dissolved carbon plus suspended organic carbon) concentrations for Sumatra are shown in figure 19. Each sample concentration represents an interval oftime of 1 to 34 days. The mean sample interval discharge, in cubic meters per second (m3/s), is shown below the total organic concentration. Above the mean discharge are the seven periods used previously in the waterbudget summaries. Transport was calculated for each sample interval. The sample interval volume (IV), computed as the mean ofdaily discharge during the sample interval (equation 2), was multiplied by the corresponding sample concentration (Otoobtain nutrienttransport (Y) forthe sample interval
y=(/V)(C). (7)

Table 17. Mean nutrient concentrationsand chemical characteristics ofground water compared with water ofthe

Apalachicola River near Blountstown and the Chipola River nearWewahitchka [Concentrations offirst eight constituents in milligramsperliter. N= number ofsamples; std. dev. = standard deviation] Ground water Surface water

Constituent

Total organic carbon

........... Dissolved organic carbon.

........ Total nitrogen.

............... Dissolved nitrogen

............. Totalphosphorus

............. Dissolved phosphorus.

.......... Chloride

................... Total dissolved solids

........... Flat Creek near Chattahoochee

/V

...... 4

...... 8

...... 3

...... 9

...... 1

...... 6

...... 6 mean

4.8 0.82 .13 .21 .15 3.6 34 std.

dev.
1.7
0.18 .16 .15
1.0 7.6 Little Sweetwater

Creek
/V
16 13 16 12 16 16 11 15 mean
5.5 4.9 0.31 .23 .01 .01 1.9 18 std.

dev. 3.6 3.5 0.19 .15 .01 .01 .5 6 Apalachicola River near Blountstown
/V
23 19 23 22 23 23 22 10 mean 7.4 6.7 0.77 .62 .05 .02 3.9 60 std.

dev. 3.7 3.7 0.26 .18 .02 .01 .5 8 Chipola River nearWewahitchka

/V
17 8 17 13 17 18 18 1? mean
8.6 7.9 0.74 .63 .02 .01 4.5 86 std. dev. 4.5 4.4 0.20 .17 .01 .01 .4 7 Characteristic (range): pH

........................... 12 5.3-7.5 Conductance (micromhos percentimeter).

. 12 35 46 16 4.6-6.8 22 5.7-7.8 16 6.3-7.6 16 10-20 23 57-127 18 80-180

Nutrient and Detritus Transport in the Apalachicola River, Florida C31

### o

&L 5' 

### s (/) 

## i Figure 19. Total organic carbon concen charge, and seven hydrologic periods a

a t/5 c £ 3 o W 3 H "* W " ' 3 o>

T3_ 0) 5' f? 

# I o. DISCHARGE, IN CUBIC METERS PER SECOND



### 979

CD 00 O TOTAL ORGANIC CARBON (DOC+SOC) CONCENTRATION, IN MILLIGRAMS PER LITER

O o o o > 3J H ^j O O * £ ^ 0 - ? z o 'Transport for each of the seven periods was then calculated as the sum of the sample interval transports within the period. Annual transport was the sum of the seven transport periods. The annual transport at Sumatra was defined as the yield forthebasin. Nutrient transport in the Apalachicola River system may be expressed by an equation analogous to that used to describe the waterbudget:

Y 0=Y,.+ Y

dp +Y m +Y gw+Y cr± Y fp±Y r, (8) where Yequals general symbol fortransport ofnutrient C, N, or 

### P-, Y 0 equals outflowing nutrient transport at downstream limit; Yj equals inflowing nutrienttransport atupstream limit; Y dp equals nutrient input by bulk precipitation in the river and floodplain; Y ro equals nutrientrunofffrom upland areas; Y gw equals nutrient inputby ground-waterdischarge; Y crequals nutrient inputby inflow ofthe Chipola River; Y fp equals net nutrientrelease oruptake by the flood-plain ecosystem; and Y r equals residual (includes error and other components such as atmospheric diffusion and anthropogenic sources, alljudgedtobe ofminorimportance).
Nutrient Transport Residual The Y fp term may be eitherpositive ornegative, depending on whether the flood-plain ecosystem acts as a source or a sink for nutrients. This term could be subclassified according to various nutrient-consuming or nutrientrelease processes, such as nitrogen and carbon fixation, cenitrification, and sorption. The important quantity for the nutrient-transport calculations, however, is the overall uptake or release ofthe nutrient, hence the netflood-plain term, Y fp

. The wetland, or flood plain, is the foremost example ofa unit within which both uptake and release processes operate. Litter-fall data gathered as part ofthe present study (Elder and Cairns, 1982) documents the large quantity ofnutritive material deposited each year on the floodplain floor. This is a potential source of 180,000 metric tons of carbon annually. Presumably, a large fraction of this material is retained in the flood-plain soils; however, much remains to be transportedto the river and eventually to the estuary. Quantification of the recycled and floodplain-derived transported fractions was not possible by direct measurement, but transport of material in the flood plain during high-water periods was observed. Detritus movement in the flood plain was documented by use of stationary drift nets, describedearlier. Because there were no direct measurements of Yfp, it mustbe estimated by including it as part ofthe Y rterm. A new term, ±R, is thus created to replace the terms ± Y fp and ± Y

r in equation 8. Because it includes the flood-plain term, which is potentially large, R is likely to have an absolute value considerably greater than the simple residual. The resulting equation is

dp 

### Y

cr±R. (9)

Transport, 1979-80 The results of application ofequation 9 to 1979-80 data from the three Apalachicola subbasins and the entire basin are shown in tables 18-29. In most cases, nutrient transport increased in a downstream direction; that is, Y t tended to be smallerthan Y 0, andR tended tobe positive. Exceptions to this occurred quite frequently within single subbasins and periods, but as the scale is expanded either in space or time, exceptions become fewer. In certain periods and subbasins, negative R values appeared consistently for all three nutrients. Those include the winter in the upper subbasin, the late autumn in the middle subbasin, and the spring flood rise and spring flood recession in the lower subbasin. Of the 12 equations representing annual nutrient transport, only 2 had negative R values: carbon transport in the middle subbasin (table 19) and nitrogen transport in the lower subbasin (table 24). The R term represents a major component in the overall nutrient budget because it includes the flood-plain contribution to nutrient input or uptake. Some large negative R values clearly suggest that there were periods of considerable nutrient retention in the flood plain. These periods were compensated by even greaternutrient release in other periods, however, and the annual basin budget showed positive flood-plain contributions of all three nutrients. As a fraction ofthe annual nonstreamflow nutrient inputs [R/(Y

ro+ Y dp+ Y gw+R)], the residual accounts for 65 percent ofthe carbon, 16 percent ofthe nitrogen, and 78 percentofthe phosphorus. Direct precipitation in the flood plain and runoff from upland areas produced significant inputs to the river during certain periods of the year. This was particularly true during the early autumn, when there was a great deal of local rainfall. Table 21 shows that carbon input from runoff (C

ro) accounted for more than 60 percent of the total nonstreamflow carbon input (C m+C dp+C gw+R) in the early autumn period. Direct precipitation contributed an additional 30 percent of that amount during the same period. For the entire year, these precipitation-related inputs were ofless significance for carbon and phosphorus, but still contributed over halfofthe nonstreamflow nitrogen input. Ground-water discharge contributed all three
Nutrient and DetritusTransport in the Apalachicola River, Florida C33Table 18. Total carbon transport in the upper subbasin, by periods, June 3, 1979, through June 2, 1980 [Allequationvaluesinmetrictons. Seetext forbeginningandendingdatesofperiodsand explanationofabbreviations]
Period
Summer.

............. Early autumn
.......... Late autumn.
.......... Winter.

.............. Spring flood rise

......... Spring flood peaks.

...... Spring flood recession

. . . . Total foryear ........ 1At Blountstown. 2At Chattahoochee. Number ofdays
98 35 83 64 8 35 43 366 C0l

51,600 8,200 19,200 15,300 6,900 63,900 27,800 192,900 = ci

16,000 5,400 12,800 18,300 3,500 64,700 22,000

- 142,700 

# * c*

f 200 f 100 f 50 f 100

- f 50

- f 100 f 50 f 650 + cro

4- 1,170 4- 780 f 390 f 520 f 260 + 520 4- 260 4- 3,900 

### + gw

+ 660 + 250 + 580 + 410 + 40 + 250 + 290 + 2,480 ± R

+ 33,570 + 1,670 + 5,380 4,030 + 3,050 1,670 + 5,200 + 43,170

Table 19. Total carbon transport in the middle subbasin, by periods, June 3, 1979, through June 2, 1980 [Allequationvaluesinmetrictons. Seetext forbeginningand endingdates ofperiodsand explanationofabbreviations]
Period
Summer.

............. Early autumn
.......... Late autumn.
.......... Winter.

.............. Spring flood rise

........ Spring flood peaks

....... Spring flood recession

.... Total foryear ........ 1AtWewahitchka. 2At Blountstown. Number ofdays 98 35 83 64 8 35 43 366 Co'

32,200 7,200 14,300 18,800 10,000 54,800 43,400 180,700 

### - c,.

51,600 8,200 19,200 15,300 6,900 63,900 27,800

= 192,900 + C H dp

+ 600 4 + 400 4 + 150 4 + 150 4 + 100 4 + 200 4 + 100 4 + 1,700 4- C

ro 910 650 260 260 130 260 130

- 2,600 f c

gw f- 120 h 40 h 80 I- 80 H 0 H 40 h 40 f- 400 

# *
21,030

2,090 5,390 + 3,010 + 2,870 9,600 + 15,330 16,900

Table 20. Total carbon transport in the lower subbasin, by periods, June 3, 1979, through June 2, 1980 [Allequationvalues in metric tons. See text forbeginningand endingdates ofperiodsand explanationofabbreviations]
Period
Summer.

.............. Early autumn
........... Late autumn.
........... Winter.

............... Spring flood rise

......... Spring flood peaks.

....... Spring flood recession

..... Total foryear ......... 1At Sumatra. 2AtWewahitchka. 3At Dead Lake. Number ofdays 98 35 83 64 8 35 43 366 Co'

40,100 12,100 17,300 31,000 8,700 73,500 31,100 213,800 = C-2

32,200 7,200 14,300 18,800 10,000 54,800 43,400

= 180,700 + C 4 dp

+ 500 4 + 350 4 + 150 4 + 150 4 + 50 4 + 150 4 + 100 4 + 1,450 4 cro

390 390 130 130 50 130 130 1,350 

## + V ±

+ 7,420

- + 3,830 + + 3,130

- + 2,760 + + 6,650

- + 5,140 + + 640

- + 29,570 + R

410 330 410 9,160 8,050 13,280 13,170 730

C34 Apalachicola RiverQualityAssessmentTable21. Total carbon transportin theApalachicolabasin between Chattahoochee and Sumatra, by periods, June 3, 1979, through June 2, 1980 [Allequationvaluesinmetrictons. Seetextforbeginningandendingdatesofperiodsandexplanationofabbreviations] [Allfiguresrounded]
Period
Summer.

........... Early autumn
........ Late autumn.
........ Winter.

............ Spring flood rise

...... Spring flood peaks.

. . . . Spring flood recession

. . Total foryear ...... 1At Sumatra. 2At Chattahoochee. Number ofdays 98 35 83 64 8 35 43 366 C l 40,100 = 12,100 = 17,300 = 31,000 = 8,700 = 73,500 = 31,100 = 213,800 = Cf <

16,000 H 5,400 H 12,800 H 18,300 H 3,500 H 64,700 H 22,000 H 142,700 H

### > c* <

h 1,300 H h 850 H h 350 H h 400 4 H 200 H H 450 4 H 250 H h 3,800 4- cro H

- 2,470 H

- 1,820 H 780 H 910 H 440 H 910 H 520 H

- 7,850 H

### - c

gw + 780 4 290 4 660 + 490 + 40 + 290 + 330 +

- 2,880 + ccr ±

7,420 + 3,830

- 3,130

- 2,760 + 6,650

- 5,140 + 640 + 29,570 + R

12,130 90 420 8,140 2,130 2,010 7,360 27,000

Table 22. Total nitrogen transport in the upper subbasin, by periods, June 3, 1979, through June 2, 1980 [Allequationvaluesinmetrictons. Seetext forbeginningand endingdatesofperiodsand explanation ofabbreviations]
Period
Summer.

............. Early autumn
.......... Late autumn.
.......... Winter.

.............. Spring flood rise

........ Spring flood peaks.

...... Spring flood recession

.... Total foryear ........ 1At Blountstown. 2At Chattahoochee. Number ofdays 98 35 83 64 8 35 43 366 

## V

1,750 1,110 2,920 2,430 1,200 4,100 5,070 18,580 

# . Nf

2,320 820 2,030 3,580 830 4,280 4,000

= 17,860 + "dp '

f 24 f 12 f 6 f 12 f 6 f 12 f 6 f 78 * Nro

f- 36 )- 24 )- 12 )- 16 1- 8 1- 16 1- 8 1- 120 "H yVQW

+ 43 + 16 + 38 + 27 + 3 + 16 + 19 + 162 ± R

673 + 238 + 834 1,205 + 353 224 + 1,037 + 360

Table 23. Total nitrogen transport in the middle subbasin, by periods, June 3, 1979, through June 2, 1980 [All equationvaluesinmetrictons. Seetext forbeginningand endingdatesofperiodsandexplanationofabbreviations]
Period
Summer.

............. Early autumn
.......... Late autumn.
.......... Winter.

.............. Spring flood rise

........ Spring flood peaks.

...... Spring flood recession

.... Total foryear ........ 1AtWewahitchka. 2AtBlountstown. Number ofdays 98 35 83 64 8 35 43 366 V

2,110 950 2,750 3,110 1,340 4,590 4,800 19,650 

# = Nf

1,750 1,110 2,920 2,430 1,200 4,100 5,070

= 18,580 + "dp 4

+ 72 -\ + 48 4 + 18 4 + 18 4 + 12 4 + 24 4 + 12 4 + 204 4' Nro

28 20 8 8 4 8 4 80 + /V

+ 8 + 3 + 5 + 5 + 0 + 3 + 3 + 27 ± R

+ 252 231 201 + 649 + 124 + 455 289 + 759

Nutrientand DetritusTransportin theApalachicola River, Florida C35Table 24. Total nitrogen transport in the lower subbasin, by periods, June 3, 1979, through June 2, 1980 [Allequationvaluesinmetrictons. Seetext forbeginningandendingdatesofperiodsand explanationofabbreviations]
Period
Summer.

............. Early autumn
.......... Late autumn.
.......... Winter.

.............. Spring flood rise

........ Spring flood peaks

....... Spring flood recession

.... Total foryear ........ 1At Sumatra. 2AtWewahitchka. 3AtDead Lake. Number ofdays 98 35 83 64 8 35 43 366 V

3,340 1,520 2,730 3,630 920 5,670 3,670 21,480 - Hf

2,110 950 2,750 3,110 1,340 4,590 4,800

= 19,650 + N d p 4

+ 60 -\ + 42 -I + 18 4 + 18 4 + 64 + 18 4 + 12 4 + 174 4- N

ro
12 12 4 4 4 4 42 + Ncr3 ±

+ 343 + + 233 + + 398 + 372 + + 472 + 527 + + 215 + 2,560 R

815 283 440 126 900 531 1,361 946

Table 25. Total nitrogen transport in the Apalachicola basin between Chattahoochee and Sumatra, by periods, June 3, 1979, through June 2, 1980 [AH equationvaluesin metric tons. See text forbeginning and endingdates ofperiods and explanation ofabbreviations] Period
Summer.

........... Early autumn
........ Winter.

............ Spring flood rise

...... Spring flood peaks.

. . . . Spring flood recession

. . Total foryear ...... 1At Sumatra. 2At Chattahoochee. Number ofdays
98 35 83 64 8 35 43 366 

# v -

3,340 = 1,520 = 2,730 = 3,630 = 920 = 5,670 = 3,670 = 21,480 = Nj2 H

2,320 H 820 H 2,030 H 3,580 H 830 H 4,280 H 4,000 H 17,860 Hh N

dp H
h 156

- H 102

- h 42 H h 48 H h 24 H h 54 H h 30 H h 456 H> N

ro "
I- 76 4 h 56 4 h 24 4 h 28 H h 14 -\ H 28 -\ h 16 4 h 242 -\

# - *w

51

- 19

- 43

- 32

- 3

- 19

- 22

- 189

-* N

cr +
-
t- 343 + f 233 + f 398 + f 372 t- 472

- f 527 + f 215

- t- 2,560 + R

394 290 193 430 423 762 613 173

Table 26. Total phosphorustransport in the upper subbasin, by periods, June 3, 1979, through June 2, 1980 [Allequationvaluesinmetrictons. Seetextforbeginningandendingdatesofperiodsandexplanation ofabbreviations]

Period
Summer.

.................. Early autumn
............... Late autumn.
............... Winter.

................... Spring flood rise

............. Spring flood peaks.

........... Spring flood recession

......... Total foryear ............. 1At Blountstown. 2At Chattahoochee. Number ofdays

..... 98

. . . . . 35

..... 83

..... 64

. . . . . 8

..... 35

..... 43

..... 366 V = 122 = 69 179 159 106 497 247 1,379 

# ff +

123 + 56 + 147 + 226 + 82 + 485 + 221 + 1,340 + pdp

2.4 1.2 0.6 1.2 0.6 1.2 0.6 7.8 

### + gw

+ 1.8 + 0.7 + 1.5 + 1.1 + 0.1 + 0.7 + 0.8 + 6.7 ± R

5.2 + 11.1 + 29.9 69.3 + 23.3 + 10.1 + 24.6 + 24.5

C36 Apalachicola River Quality AssessmentTable 27. Total phosphorustransport in the middle subbasin, by periods, June 3, 1979, through June 2, 1980

[Allequationvaluesinmetrictons. Seetextforbeginningandendingdatesofperiodsandexplanationofabbreviations]

Period
Summer.

....................... Early autumn
.................... Eate autumn.
.................... Winter.

........................ Spring flood rise

.................. Spring flood peaks.

................ Spring flood recession

.............. Total foryear .................. 1At Wewahitchka. 2At Blountstown.

Table 28. Total phosphorus transport in [All equationvalues in metric tons. See text

Period
Summer.

....................... Early autumn
.................... Eate autumn.
.................... Winter.

........................ Spring flood rise

.................. Spring flood peaks.

................ Spring flood recession

.............. Total foryear .................. Number l ofdays ° 98 165 35 98 83 164 64 204 8 101 35 505 43 300 366 1,537 

# '/ +

122 + 69 + 179 + 159 + 106 + 497 + 247 + 1,379 + 'dp +

7.2 + 4.8 + 1.8 + 1.8 + 1.2 + 2.4 + 1.2 + 20.4 + gw ±

0.3 + 0.1 + 0.2 0.2 + 0.0 0.1 + 0.1 + 1.0 + R

35.5 24.1 17.0 43.0 6.2 5.5 51.7 136.6

the lower subbasin, by periods, June 3, 1979, through June 2, 1980 forbeginningandendingdatesofperiodsandexplanationofabbreviations] Number j ofdays ° 98 164 35 89 83 189 64 284 8 76 35 604 43 246 366 1,652 pl + 165 + 98 + 164 + 204 + 101 + 505 + 300 + 1,537 + Pd

P + 6.0 + 4.2 + 1.8 + 1.8 + 0.6 + 1.8 + 1.2 + 17.4 + P 3 +

cr 10 13 11 + 8 + 11 18 + 4

_ 75 + 1At Sumatra. 2At Wewahitchka. 3At Dead Lake.

Table29. Total phosphorustransport in theApalachicolabasin between Chattahoochee and Sumatra, by periods June 3, 1979, through June 2, 1980 [All equation values in metric tons. Seetext for beginning and ending dates ofperiods and explanation ofabbreviations] Number Period ^ ^ / ofdays Summer.

................ 98 Early autumn
............. 35 Eate autumn.
............. 83 Winter.

................. 64 Spring flood rise

........... 8 Spring flood peaks.

......... 35 Spring flood recession

....... 43 Totalforyear ........... 366 1,

### V = »>
164 = 123 89 - 56 189 = 147 284 = 226 76 - 82 604 = 485 246 = 221 652 = 1,340 

# * v *

+ 15.6 + + 10.2 + + 4.2 + + 4.8 + + 2.4 + + 5.4 + + 3.0 + + 45.6 + gw +

2.1 + 0.8 + 1.8 + 1.3 + 0.1 + 0.8 + 0.9 + 7.8 + Pcr ±

10 + 13 + 11 + 8 + 11 18 + 4 + 75 + R

17.0 26.2 12.2 70.2 36.6 79.2 59.2 22.6

>

R
13.3 9.0 25.0 43.9 19.5 94.8 17.1 183.6 'At Sumatra. 2At Chattahoochee.
Nutrient and Detritus Transport in the Apalachicola River, Florida C37nutrients in amounts somewhat less than the amounts

originating from directprecipitation.

Detritus
Concentrations Mean concentrations of coarse (>1 mm), fine (0.063-1 mm), and very fine (<0.063 mm) paniculate organic carbon are shown in figure 20. Data from the four major gaging sites and six hydrologic periods are included (early and late autumn data were combined because relatively few measurements were obtained during these two periods). Concentrations of coarse paniculate organic carbon (CPOC) ranged from none detectable at Chattahoochee to 0.07 mg/L during the three spring flood periods at Sumatra. CPOC samples obtained at Chattahoochee were consistently less than 0.01 mg/L. A general trend of downstream increase in CPOC mean concentration was observed throughout all periods. The mean concentrations at Blountstown, Wewahitchka, and Sumatra were at least 50 percent higher during the three spring flood periods than during the otherperiods. Fine particulate organic carbon (FPOC) concentrations generally increased from Chattahoochee to Wewahitchka and decreased slightly from Wewahitchkato Sumatra. Averaged over the full year, FPOC concentrations were approximately 12 times greater than CPOC concentrations. Concentrations of very fine particulate organic carbon (VFPOC) increased slightly from Chattahoochee down river, with little change from Blountstown to Sumatra. Averaged over the full year, VFPOC concentrations were approximately 3.4 times greater than FPOC. Concentrations during the three spring flood periods averaged 1.0 mg/L, while the mean concentration during the otherperiods was approximately 0.7 mg/L. A fourth detritus fraction measured with a stationary, 1-mm net dredge was bottom particulate organic carbon (BPOC). Figure 21 shows the period concentrations forthe four main river sampling locations. The capture of BPOC below Jim WoodruffDam near Chattahoochee was less than 0.01 mg/L, except during the spring flood rise. Detectable, but relatively low, concentrations were measured downstream at Blountstown. During most of the year, BPOC concentrations near Wewahitchka were intermediate to those at Blountstown and Sumatra. BPOC mean concentrations were consistently highest for all periods at Sumatra; concentrations in summer were low (0.1 mg/L) and increased twelvefold during the autumn. Concentrations increased even more during the winter and spring flood rise at Sumatra, but decreased during the flood peaks. With the return of flood waters from the floodplain tothe main channel during the spring floodrecession, BPOC concentrations at Wewahitchka and Sumatra reached their highest levels of the year. High BPOC concentrations during the flood rise may have been due to initial removal ofmaterial deposited on or nearthe river bank, whereas the high concentrations during the recession were more likely the result ofrapid drainage from the interiorofthe flood-plain forest.
Transport The particulate organic carbon fraction, known as detritus, is a relatively small part ofthe total organic carbon transport shown in tables 18-21. The transport ofdetrital materials may be further examined by particle-size categories. Detritus transport measurements (fig. 22) showed that there were substantial gains of large-particle detritus (CPOC and BPOC, both having particle sizes greater than 1 mm) from Chattahoochee to Sumatra. The coarse fractions made up only a small part oftotal carbon but showed more than sixtyfold gains from Chattahoochee to Sumatra. The fine particulate fraction (0.063-1.0 mm) also increased, showing a threefold to fourfold gain from Chattahoochee to Wewahitchka and Sumatra. Consistent increase with downstream distance was not exhibited by the very fine particulate fraction. Since VFPOC was the dominant carbon fraction, its downstream changes were closely reflected by the total suspended carbon, and only a slight increase was observed at Sumatra. The relation between detritus transport and time is shown in table 30. The suspended fraction transport rates were generally higher during the three spring flood periods than during earlier, drier periods. Bottom-load POC transport rates increased from summer to winter, then showed only a slight increase during the spring flood rise andrecessionperiods. Flood-Plain Transport The transport of detritus in the flood plain during flooding was verified by trapping transported material in stationary nets, as described previously. Between March 11 and April 28, 1980, 21 flood-plain detritus collections were made in nets randomly located near the intensive plots. All nets collected measurable amounts of detritus, generally about two-thirds organic. The amounts varied greatly, from 0.001 to 0.5 g ofmaterial per cubic meter of water. The mean of the 21 samples was 0.05 g/m3, with a standard deviation of0.10 g/m3

. Data for the individual collections are given in "Supplementary DataI." Deposition on Flood-Plain Floor Estimates ofthe amount ofmaterial deposited in the flood plain were obtained from thirty-one 1-square-meter
C38 Apalachicola River Quality AssessmentMEAN PARTICULATE ORGANIC CARBON, IN MILLIGRAMS PER LITER

orid gure 20

e organ

bon concen 

### Summe

Early and Late Autumn

Winte

SPR Rise

G F Peaks

OOD Recession 

## °

"

~ 

### o 

# $ ^ »< C/>

c



# ° ^ rjoo n n n ^ rjo o 

# Sff 0 3 ^ 3- -* O ±: W 3- O O O 

### ^1 <D



### o o>

rjD



# °(E

UJ

UJ 

### a. CO



### o o z 

### o a: o UJ

ID O

O GO Z UJ 

### 3.5

- 2.5 z o CD 

### or 2.0

1-5

1.0

0.5

0 EXPLANATION

C Ch.attahoochee B Blountstown W Wewahitchka S Sumatra



### W

W

B 

### B W

B



# c W B

Summer Early and Late Winter

Autumn SPRING FLOOD Rise Peaks Recession

Figure 21. Bottom particulate organic carbon concentrations.

C40 Apalachicola River Quality Assessment100,000

50,000

10,000

5000

CO z O O 

### tr fc 1000



### a: o o. CO z < OC

O 00 a: < o o

a: o 500

100

50

10 

### Total suspended

VFPOC



# 1 FPOC CROC 

### Bottomload Organic

Carbon



# I

CHATTAHOOCHEE BLOUNTSTOWN WEWAHITCHKA SUMATRA

Figure 22. Annual paniculate organic carbon transport.

Nutrient and DetritusTransport in the Apalachicola River, Florida C41Table 30. Daily detritusfraction transport at Sumatra, by periods, June 3, 1979, through June 2, 1980

[VFPOC, very fine particulate carbon; FPOC, fine particulate organic carbon; CPOC, coarse particulate organic carbon; BPOC, bottom load particulate organic carbon. Total suspended organic carbon = VFPOC + FPOC + CPOC; slight discrepancies due to rounding. All data shown in metric tonsper day]
Period
Summer.

........................... Autumn (early and late)

................. Winter.

............................ Spring flood rise

...................... Springflood peaks.

.................... Spring floodrecession

.................. Total suspended organic carbon

........ 42

........ 38

........ 52

........ 66

........ 335

........ 130 VFPOC
37 29 37 22 294 114 FPOC

4 8 14 39 32 13 CPOC

0.9 1.1 1.2 4.6 8.8 3.5 BPOC

0.1 0.31 0.90 1.00 0.51 1.05

plastic sheets distributed randomly at 14 plots in the Sweetwater and Brickyard transects (figs. 6 and 7). Summarized results for both inorganic and organic deposition are shown in table 31. Data for the individual collections are given in "Supplementary Data II." The weight of material deposited on the plastic sheets varied widely because the sheets were located in extremely different environments where depth offlooding, velocity of flow, and litter fall differed. Plot 4 was the only sheet location not flooded during the investigation, so it served as a control area. In the flood plain as a whole, most ofthe material deposited was inorganic. By contrast, the organic fraction was predominant at plot 4. The amount of organic material at plot 4 was higher than the amount at most other plots, especially those in swampy areas. Levee plots were subject to a great deal more deposition, both organic and inorganic, than swampplots.

Error Analysis Water Budget Systematic or additive error is error that accumulates in the same direction during each consecutive step. Compensating error occurs when measurement error is both plus and minus, so that the sum ofa series ofoperations may have an absolute error smallerthan many ofthe individual parts. The residuals shown in table 16 are primarily due to independent, nonadditive measurement and estimation errors. The total flow past the Sumatra gage during the various periods included residuals ranging from 54 percent to +9 percent. With the exception of the spring flood rise period, all errors were less than 10 percent. The large negative residual for the spring flood rise period was the result of the 3-day discharge lag and flood-plain storage.The largest positive residual occurred during the spring flood recession, when much ofthe "lost water" was recovered at Sumatra. For the three spring floodperiods, the total residual (+0.53 km3) was 3.8 percent of the total flow past the Sumatra gage during those periods. The residual, or unexplained, discharge for the year was 0.84 km3, or 2.9 percent. Although each component ofthe water budget is associated with an error estimated to be 5 percent or greater, the annual residual is smaller than 5 percent. Error compensation over the long term contributed to the decrease in the annual residual percentage relative to that ofany single period. Similar longterm error compensation is suggested by the residuals of the separate subbasins (tables 14-16). Winter (1981) reported probable error levels for different water balance components and various methods of measurement or calculation. His work dealt with lakes, but many ofthe conclusions apply to any aquatic system. Among the annual water balance error sources, streamflow (determined by a stage-discharge relation using a recording stage gage) was one ofthe most accurate at 5 percent per year. Precipitation (determined by areal averaging ofNational Weather Service rainfall data) is subject to 10 percent error in 1 year. Evaporation errors range from 10 to 15 percent per year. These may be reasonable estimates of the errors associated with the Apalachicola water-budget terms WO or VV7, P, and £T, respectively. Evapotranspiration was not determined by the methods discussed by Winter, but data from other studies (Qureshi, 1978; Brown, 1981) indicated that ET rates in Florida flood-plain environments are quite consistent for any given month. The ETterm is thusjudged accurate to at least 25 percent. Ground-water estimates are probably the most uncertain of any of the Apalachicola water-budget terms; however, the amount of water involved is only 0.7 km3, or 2.4 percent of the 28.61 km3 measured discharge for the entire basin. In the upper subbasin, there are enough data to make ground-water estimates fair to good; a 30 percent errorperyear is presumed adequate. In the middle and lower subbasins, the ground-water component is near C42 Apalachicola River Quality AssessmentTable 31. Deposition of material during 9 to 11 months1 on plastic sheets randomly located at intensive plots [Plot4 wasnever flooded] Deposition, in grams per square meter
Plots

All

............... 4

................ All except 4

......... Swamp2

........... Levee3

............ Number of sheets

....... 31

....... 4

....... 27

....... 14

....... 17 Organic
Mean
150 180 140 60 220 Standard

deviation 180 50 190 60 210 Range

1.5-851 137 -232 1.5-851 1.5-175 18 -851 Mean

2,200 110 2,500 520 3,500 Inorganic

Standard deviation 5,100 30 5,400 540 6,700 Range

15-20,570 80- 152 15-20,570 15- 1,856 80-20,570 1All sheets were in place during the heavy litter-fallperiod andthe spring flood. Dates ofremovalofthe sheets varied (see "Supplementary Data II"). 2Plots 1, 7, 12, 13, 15, 16, 17, and 18 (seefig. 6 and 7). 3Plots 3,4, 5,6, 11, and 14 (see fig.6 and 7).

zero, and percentage errors become meaningless. An error of ±0.3 km3 peryear is estimated in these reaches. Combining the three subbasins, the error, ifadditive, could be 100percent. All stream discharge terms (WO, WI, and CR) are likely to be accurate, in part because they are based on frequent measurements. Stage readings recorded hourly are translated to daily discharge means, which are averaged over longer time periods. With such frequent measurements, independent, nonadditive measurement errors become negligible overthe longterm. Systematic errors in discharge estimates are possible. An inaccurate discharge measurement, for example, might displace the stage-discharge rating curve, affecting most or all daily means with errors of the same sign. All Apalachicola main channel sites have been frequently measured at various stages, however, giving strong documentation ofthe ratings.

Nutrient and Detritus Concentrations As one means ofevaluating the accuracy of waterquality data, a set ofsamples from two Apalachicola sites, Chattahoochee and Sumatra, were used for a standard-addition recovery test. Water samples were injected with measured volumes of standards from the EPA Environmental Monitoring Laboratory. Separate tests were conducted for nitrate, ammonia, and organic nitrogen, dissolved and total phosphorus, and total organic carbon. Each injected sample was accompaniedby a natural sample (not injected), andboth were handled and analyzed in the usual fashion. Reliability ofthe data wasjudged by how closely the results for injected samples reflected the sum of the natural concentration plus the known standard additions. All standard-addition recoveries ofnitrogen, carbon, andtotal phosphorus were within 11 percentofactual concentrations. The recovery efficiency for dissolved orthophosphate was lower, primarily because the concentrations were near the analytical detection limits and the precision ofthe analyses was ±0.01 mg/L. The absolute discrepancies were the same magnitude for dissolved and total phosphorus, but when converted to percentage recoveries, they are much betterfortotalP. Precision for some of the nutrient analyses was given by the U.S. Geological Survey Water Quality Laboratory's Services Catalog (Beetem and others, 1980). At the levels found in Apalachicola water, precision values for analyses ofdissolved nitrogen fractions and dissolved orthophosphates ranged between 14 and 20 percent. No precision estimates were given fortotal carbon analyses. An additional source ofdatausedto evaluate the accuracy of phosphorus data came from having parallel analyses of reactive phosphate performed by a separate laboratory. Results from the Department ofOceanography laboratory at Florida State University were provided by P. N. Froelich (written commun., 1981) for samples collected in March andJune 1980. Twelve values were available for comparison with results on duplicate samples from the U.S. Geological Survey National Water Quality Laboratory, Atlanta, Ga. After rounding all values to the nearest 0.01 mg/L, 8 ofthe 12 samples producedthe same results from both laboratories: two were different by 0.01 mg/L and two, by 0.02 mg/L. The probable maximum errors for the nutrient-concentration data were estimated on the basis ofcontrol data from standard-addition tests and from the laboratories of USGS and Florida State University. Carbon and nitroNutrient and Detritus Transport in the Apalachicola River, Florida C43gen data are estimated to be subject to 15 percent error,

and phosphorus data, to a 25 percent error. Assuming these are random errors, as samples are pooled, the expected relative error becomes smaller. Hence, concentration data collected the same way and averaged over several months ora full year are subjectto smallererrors. Detritus measurements are subject to considerable sampling error because of the probability of nonuniform distribution of the material in the natural environment. Analytical methods to determine dry and ash weight of suspended material, however, are simple and nearly free ofinterference. Detritus sampling methods were original for this investigation; thus there is no documentation as to their accuracy. Discrepancies between replicate detritus samples could be the result ofeither natural variability orinconsistencies in sampling procedures. Field tests ofvarious detritus sampling techniques obtained results such as those illustrated in figure 13, suggesting that these methods were adequate for characterizing the detritus transportprocess. It is assumed that a 15 percent error may be associated with paniculate carbon transport. Even ifsubstantially different, this error will have little effect on the overall carbon budget since most carbon transport is in soluble form.

Transport By using the nutrient transport model derived from continuous streamflow records and discrete nutrient concentration measurements at interval midpoints, transport calculation errors were minimized (Scheider and others, 1978). Errors associated with measurement of discharge and the precision ofchemical analyses, however, are carried over into the calculation of transport. Using percentage error estimates for discharge and nutrient concentrations, transport errors are computed for each sample interval (the length oftime represented by one waterchemistry sample). The total transport error for a particular sample interval (combining discharge and concentration errors), orover ahydrologic period (combining errors forincluded sample intervals), are computedbythe equation

E= (10)

where Eequals total error; GJequals error for/th component or sample interval; and n equals numberofcomponent or sample intervals. This formula was suggested by Winter (1981) as a good estimator for combining errors from various components. It can also beused to combine interval errors to determine long-term error, provided that the component errors (e/) are independent and not additive. This requirement is met by these data since both discharge and concentration data depended on measurements that were totally independent and were equally likely to be erroneous in either a high or a low direction. The results ofcalculation or errors using equation 10 with regard to annual nutrient transport are illustrated in figure 23. The error bars about each annual transport for the four main-stem river gage locations and the Chipola River below Dead Lake Outlet provide a means by which to judge differences among transport rates at different locations. A general downstream increase in nutrient transport is apparent, particularly for carbon. The actual increase between any two adjacent sites should not be overemphasized because of theoverlapping errorbars computed with equation 10.
DISCUSSION Flood-Plain Role in Nutrient Transport A central purpose ofthis investigation is the assessment ofthe role ofthe flood plain in nutrient transport in the Apalachicola River. Direct measurements ofthis role were not possible, but the various kinds ofdata that were gathered provided pieces ofinformation that could be considered together to arrive at clues pertaining to wetland functions. An enormous nutrient source is present in the Apalachicola flood plain. The dense bottom-land hardwood forest contains more than 1,500 trees per hectare (Leitman and others, 1983). This vegetation produces some 800 g/m2 of litter fall annually, which places it among the most productive of forests in warm temperate regions (Elder and Cairns, 1982). Much ofthe littermaterial is subject to rapid decomposition to both soluble and small-detrital nutrientresidues. The hydrology ofthe Apalachicola system, coupled with its high productivity, is critical to the potential nutrient flow from the flood plain. Leitman and others (1983) found that 57 percent of 223 sample points in the flood plain were in environments that are generally saturated or flooded during the dry season (autumn) and that all but 3 ofthe 223 points were below the 2-year, 1-dayhigh flood stage for the period 1958-80. During inundation, velocities in the flood plain range from 0 to 0.3 m/s, with most points subject to velocities of at least 0.1 m/s (Leitman and others, 1983). In channelized areas in the flood plain, velocities almost as high as the river flow may be observed duringhigh flood stages.
C44 Apalachicola River Quality AssessmentCO Z O

## ho trtUJ 

### 2 5 TRANSPORT,

h- ^» NUTRIEh 200,000

160,000
120,000

80,000

40,000

0

20,000

16,000

12,000

8000

4000

0

1600

1200

800

400

0 i i i i i



# I

"

- 

## CARBON x

j I I -*" NITROGEN

EXPLANATION t Mean concentration -L and standard error for sites indicated

-

"*"



# I *
- 1 *

- 

## PHOSPHORUS

CHATTA- BLOUNTS- WEWA- DEAD SUMATRA HOOCHEE TOWN HITCHKA LAKE Figure 23. Annual nutrient transport at four Apalachicola River sites and the Chipola River Outlet at Dead Lake, showing error ranges.
Nutrient and Detritus Transport in the Apalachicola River, Florida C45These hydrologic characteristics of the flood plain

are important not only for transport of nutrients and detritus, but also, over the long term, for the very existence ofthe vegetation that produces that detritus. Leitman and others (1983) found high statistical correlations between forest type distribution and nine different water parameters, such as flood depths, velocity, and duration offlooding. Hence, hydrologic characteristics influence the type ofdetritus produced as well as the quantitytransported. High productivity ofdense vegetation in the floodplain forest implies active uptake of nutrients, tending to counterbalance nutrient and detritus release. Nutrient uptake is likely to diminish concentrations ofdissolvednutrients more than particulates (Stanley and Hobbie, 1981). The trends shown in figures 21-23 indicate that concentrations ofdetritus increase in a downstream direction much more than do concentrations ofdissolved or total organic carbon. This means that the solute:paniculate ratio, although largethroughoutthe river, decreases appreciably in a downstream direction. The flood plain is the primary producer and consumer of carbon in the basin and must have a great deal to do with the change in solute:paniculate ratio. One ofthe net effects ofthe flood plain is conversion of some organic carbon from dissolved to paniculate species due to vegetative assimilation of dissolved carbon and subsequent release oforganic material through litterdeposition. The annual residuals shown in tables 21, 25, and 29 are all positive, indicating that nutrient input to the river cannot be totally balanced by the sum of precipitation, ground-water, and surface-water inflow. The residual values incorporate the combined errors ofall components, but in the cases of carbon and phosphorus, such errors would not likely be additive such that we would observe the high positive R values shown on the tables. Floodplain-derived nutrients probably make up the difference. This seems an especially plausible explanation since the highest relative R value is for carbon, which is less likely to be retained by the wetland than is nitrogen or phosphorus (Peverly, 1982). Export of the three elements has also been documented in studies by Day and others (1977) of a swamp system in Louisiana very similar to the Apalachicola floodplain. The nitrogen budget (table 25) shows a nearly precise balance between nitrogen import and export in the wetland. The annual nitrogen residual, although positive, was less than 1 percent ofthe total outflow at Sumatra and may be attributed to error. Wetlands do have the capacity, under certain circumstances, to retain nitrogen from through-flowing waters (Brinson, 1977; Sloey and others, 1978). As an essential plant nutrient, nitrogen is likely to be retained in the forest ecosystem, at least during the growing season (Vitousek and Reiners, 1975). The waters of the Apalachicola system are nitrogen rich; however, with a nitrogen:phosphorus ratio in excess of 10, the system is probably not nitrogen-limited. Nitrogen fixation and denitrification within the flood-plain forest could provide most of the internal nitrogen needs. Excess nitrogen input might flow through the system quite readily under such conditions. Variable values such as those for Blountstown may mean the values were correct or were artifacts caused by sampling or analytical error. It is assumedthat all data are correct unless there is evidence oferror, such as a sampling inconsistency. Data also may be rejected ifthey are so inconsistent with other data that they arejudged unrealistic. In the case ofthe Blountstown carbon data, however, there was no justification for rejecting the data. The results serve to illustrate the value in considering increased time and area; as the perspective is changed from one period and subbasin to the full year and the entire basin, the fluctuations are more likely to balance each other and more realistic estimates maybe derived. A notable case in which a high negative R value was caused by abnormally low concentration is shown in table 24. In May 1980, the total nitrogen concentration was 0.68 mg/L at Sumatra, somewhat less than its usual range of0.75-1.00 mg/L. A low nitrogen outflow estimate for the lower subbasin produced a high negative R value for the spring flood recession and for the entire year's budgetforthat subbasin. Large negative residuals occurred in the spring flood rise period for all three nutrients in the lower subbasin (tables 20, 24, and 28). This was a reflection of the flood wave lag that produced a similar negative residual in the waterbudget for that period (table 16). The lag effect disappeared when data from all periods were combined into an annual value. The phosphorus export:import ratio in the Apalachicola system (table 29) is comparable to that of carbon. The annual residual is positive and is an appreciable fraction (11 percent) of total transport at Sumatra, suggesting an overall export from the flood plain. This result is in contrast with some other studies (Brinson, 1977; Mitsch and others, 1979; Peverly, 1982) which show either net retention ofphosphorus or a fluctuation between import and export. The large amount of detritus output from the Apalachicola flood plain may be a factor contributing to phosphorus export by providing a surface for sorption ofthe element. In examining the entire set ofdata in tables 18-29, the reader should keep in mind that the main purpose of these data is to arrive at some realistic estimates for annual riverine yield. The purpose is not to highlight changes over short lengths of time or small geographic areas. Focusing on the narrow perspective reveals considerable variability in water flow and nutrient concentration. For example, table 19 shows that in the summer period, carbon inflow (C

7) at Blountstown was 60 percent higher than carbon outflow at Wewahitchka. This produced a
C46 Apalachicola River Quality Assessmentlarge negative R value for that period and, eventually, for the entire year. The high C, at Blountstown in the summer period resulted from three extraordinarily high total organic carbon (TOC) concentrations in the samples collected at Blountstown in June, July, and August all of them greater than 12 mg/L. These high concentrations were not matched at other sites. A similar high TOC concentration at Blountstown occurred in November 1979, producing the high C/ in the late autumn season and subsequenthigh negativeR value (table 19).

River Basin Nutrient Yield Figures 24, 25, and 26 illustrate cumulative nutrient transport and changes with season, over the full yearfrom June 3, 1979, through June 2, 1980. The scope is the entire basin. Y

0 represents outflow at Sumatra, and Y,- represents inflow at Chattahoochee. It is evident that nutrient inflow was the largest single contributor to nutrient yield in the basin. The percentage of Y 0 contributed by Y/ ranged from 40 percent (carbon in early September and nitrogen in late August) to more than 100 percent (phosphorus in early July). The sum of the remaining components, which were estimated from field data, is represented on the graphs (figs. 24-26) by the separation between the two lowermost curves. Nearly all ofthis quantity in each case is attributable to surface-water inflow fromthe ChipolaRiver, embodied inthe Y crterm. Seasonal effects on nutrient transport were minor except during the spring flood periods. Rapid increases in cumulative transport occurred during the early stages of the spring flood, in March and April. Although carbon and phosphorus transport increased rapidly in the early flood stages, the inputs diminished considerably in the latter stages (late April and May), leaving a difference between input and outflow. This gap is the residual, shown by the shaded part in the illustrations. This residual amounts to 13 percent ofthe total annual carbon transport and 11 percent of the annual phosphorus transport; it is presumed to come principally from the flood plain. Floodinduced carbon export from the flood plain appears to have occurred primarily during the latter peaks and recession ofthe spring flood. The nitrogen residual was 1 percent of the annual transport, reflecting an approximate balance between export and import. Transport ofparticulate organic matter is especially prone to sharp surges due to flooding. To illustrate this, figure 27 compares cumulative transport ofall fractions of carbon at Sumatra with the transport curves that would be observed if the rates were constant throughout the year (using January 4, 1980, as the date for determining constant rate). Observed data in the spring months of 1980 were offset considerably from the constant rate curves. On close inspection, the most critical "flushing periods" for the different fractions appear to be quite distinguishable. Forexample, the principal CPOC surge occurred in April, while the FPOC was released somewhat earlier and began to slow down in April. Bottom-load material (BPOC) showed one ofits greatest surges in November, coinciding with the period ofheaviest litter fall, then increased again in the winter and spring periods as greater areas became inundated. The characteristics ofthe waterbudget are such that the flood-plain role in nutrient transport is critical. The Apalachicola River water budget is heavily dominated by streamflow; all inputs and losses within the basin are small relative to the flow in the main channels. In the absence of major pollution sources, nutrient inputs associated with precipitation, ground water, and overland runoffare unlikely to appreciably augment the huge nutrient pool in the river water. The flood plain, with its substantial nutrient production and its direct, prolonged interaction with the flowing river water, is therefore the only factorin the basin that is likely to have considerable influence on the nutrient and detritus yieldofthe river. It is not accurate to inferfrom this analysis thatprecipitation, ground-water flow, evapotranspiration, and other means of water and nutrient exchange in the Apalachicola basin are unimportant. They are minor only when compared with the total pool associated with streamflow. Rainfall and evapotranspiration rates in this warm temperate zone are higher than in most areas ofthe country (Qureshi, 1978), but they nevertheless have relatively little effecton overall streamflow (table 16). Tables 21, 25, and 29 show that annual transport of carbon, nitrogen, andphosphorus was substantially greater at Sumatra than at Chattahoochee. Streamflow at Sumatra was also greater than at Chattahoochee (table 16). Ifthe Sumatra outflow:Chattahoochee inflow ratios are derived from the annual basin-wide budgets oftables 16, 21, 25, and 29, and figure 22, the results are as follows: 

### Constituent Outflow:in flow ratio Water

...................... 1.25 Carbon

...................... 1.50 Nitrogen

..................... 1.20 Phosphorus

................... 1.23 Total detritus

.................. 1.41 VFPOC

..................... 1.25 FPOC

...................... 3.50 CPOC

..................... 70 Increased water flow without simultaneous nutrient inputs would simply result in lowernutrientconcentrations and no change in nutrient transport. The outflow:inflow ratios show that this did not happen. Instead, there was a nutrient input that matched flow increase in the cases of nitrogen and phosphorus and exceeded flow increase in the case ofcarbon.

Nutrient and Detritus Transport in the Apalachicola River, Florida C47

## o

o 

# a: H UJ 

# u_ o o z
O X 

### 250



# a: o z < a:
o oo oc < o UJ



### D 

### 2 o 

## 200

150

100

50 I T I I I I I I



# CARBON C0 (outflow)

C (inflow) 

# B;;;::i..:r:l Estimated flood plain

carbon contribution

JUNE JULY AUG SEPT OCT NOV DEC JAN FEB MAR APR MAY



## 1979 I960 Figure 24. Cumulative carbon transport in the Apalachicola River basin from June 3,1979, through June 2, 1980.

C48 Apalachicola River Quality Assessment

### >

o 7Q

K3 Ul 

### n c 3 c_ o> n>

o era 

### CUMULATIVE NITROGEN TRANSPORT, IN THOUSANDS OF METRIC TONS

~ =. ** 

### o m o m o 10 m

cr o>

o c era

D Is5 VO 

### (D (0

GO c_ C Z 

### m c_ C

> C 

### o (O 

### m D

o o

o < o m o c_ 

### >
n m CD

> ?)
> 1) 7) 

# 5(O



### o
o

### IUJ

(O 

### o z < (O 

### 3 o X



### to: o Q. CO 

### z < o:tco ID 

### o: o x Q. (O O X Q. UJ 

### 2.0



# PHOSPHORUS P0 (outflow)

Pi (inflow)

0.5
-

ID O 

### JUNE JULY AU6 SEPT OCT NOV DEC JAN FEB MAR APR MAY 

## 1979 1980

Figure 26. Cumulative phosphorus transport in the Apalachicola River basin from June 3,1979, through June 2,1980.

C50 Apalachicola RiverQuality Assessment£ 10,000

5000

1000

500

100

50

10 EXPLANATION

TPOC Total particulate organic matter 0 VFPOC Veryfine particulate organic matter x FPOC Fine particulate organic matter D CPOC Coarse particulate organic matter ® BPOC Bottom particulate organic matter . 0

. 0

_ _ _ _

1 r U L


### VFPOC



### FPOC



# CPOC
/

a 

### / BPOC

/ 

### /

/ / 

### /

1 1 1 1 1 

### JUNE JULY AUG SEPT OCT NOV DEC JAN FEB MAR APR MAY JUNE



### 1979 1980 Figure 27. Observed versus constant rate (dashed line) transport of five particulate organic carbon fractions in the Apalachicola River basin from June 3, 1979, through June 2, 1980.

Nutrient and Detritus Transport in the Apalachicola River, Florida C51The overall conclusion from this analysis is that the

Apalachicola wetland functions as a natural transformerfiltration system for waters passing through the basin. Exchanges result in some net increase in organic carbon and phosphorus transport, much ofit in the form ofparticulate matter (detritus), but no net increase or decrease in nitrogentransport. The implied effects of such a wetland role on estuarine ecology are that it favors secondary productivity and a detrital-based food web. Primary productivity is usually limited by phosphorus in estuarine systems, particularly during spring runoff (Taft and Taylor, 1976). This is especially likely in the Apalachicola system, with its high nitrogen:phosphorusratio which is not appreciably altered by interaction with the flood plain. With the limitation on primary production, heterotrophic activity assumes relatively greater importance in the estuarine food web. The heterotrophs depend on a plentiful source oforganic material. Detrital loads in the river water discharging to the bay provide an excellent substrate for bacterial growth (Fenchel, 1970) and a base for support ofa thriving population ofdetrital feeders (Darnell, 1961), including many economically valuable shellfish species. An alternative view might be suggested by the total organic carbon data. If the dissolved fraction is the main energy source for the estuary, the flood-plain role would appear much less significant. As shown by the outflowiinflow ratio and the data in figure 22, the total organic transport at Sumatra is not greatly different from that at Chattahoochee. If the flood plain were not there, the riverine yield oftotal organic carbon might not be greatly reduced. This interpretation requires several assumptions: (1) dissolved organics are not converted to particulates in the river channel by such processes as precipitation, adsorption, and bioassimilation; (2) dissolved organics are not changed in the river channel to forms that are less bioavailable; and (3) dissolved rather than particulate organics are most important in sustaining the estuarine productivity. Further research would be needed to determine the validity ofthese assumptions. 

### Sources of Nutrients Considerable attention has been given thus far to nutrient inflow from the flood plain to the river. It is important that other sources be examined also to approach a full understanding of the interaction of various components.Currently (1981), nearly all nutrients entering the Apalachicola streamflow by intrabasin pathways, such as ground water and surface runoff, are natural inorigin. Anthropogenic sources are minor owing to the relatively undisturbedcharacterofthebasin. Wastewatereffluents consist primarily of a few treatment plants serving small municipalities. Industry and agriculture are more prevalent in the basins ofthe two headwater rivers, the Chattahoochee and the Flint. Effects ofagriculture in southwest Georgia were studied recently by Radtke and others (1980). They found that agriculture did not produce high concentrations of chemical constituents in stream water, even during periods of storm runoff. They attributed this to the permeability of the soil, which permits extensive percolation and adsorption of materials from the water deposited on agricultural lands. A recent investigation of the upper Chattahoochee River basin (Stamer and others, 1978) foundthat nonpoint sources of nutrient loads contributed more nutrients to streamflow than point sources. Atmospheric deposition, as precipitation and dry fallout, contributes significant amounts of nitrogen and phosphorus to the Apalachicola-Chipola basin. As shown in tables 18-29, however, these inputs are quite small relative to total nutrient loads in the river. Atmospheric inputs often constitute a major chemical influence on any lakes in the area that do not undergo a large water exchange. Such impacts of atmospheric deposition have been observed elsewhere (Elder and Home, 1978; Dethier, 1979). The Apalachicola River system, however, is continually replenishedby the Chattahoochee andFlint Rivers, and atmospheric sources ofnutrients are not significant. Recent studies ofprecipitation chemistry in Florida have shown that nitrogen and phosphorus concentrations elsewhere in the state are generally somewhat higher than concentrations in the precipitation of the Apalachicola basin, while organic carbon concentrations arehighly variable. Hendry and Brezonik (1980) found mean concentrations of organic carbon, nitrogen, and phosphorus at Gainesville, Fla., to be 9.5, 0.82, and 0.085 mg/L, respectively, all somewhat higher than the median concentrations found in this study at the Apalachicola sites (fig. 18). Irwin and Kirkland (1980) monitored 24 bulk precipitation sites in Florida; a Tallahassee site had nitrogen and phosphorus concentrations comparable to those of the Apalachicola basin, but organic carbon concentration was considerably lower. Central and southern Florida nutrient concentrations were generally higher than Tallahassee concentrations. In general, the analytical results of Apalachicola bulk precipitation samples were consistent with what might be expected for a relatively undisturbed, densely forested area.


### Flood-Plain Detritus Contributions Some approximation of detritus transport can be drawn from detritus nets and plastic sheets used in the flood plain. Although these approaches give only rough estimates, they serve as a test of the determinations of flood-plain contributions to detritus and total detritus transport in the system. It is emphasized that the values
C52 Apalachicola River Quality Assessment

### derived are for the sole purpose oftesting earlier calculations; they are not quantitative and should not be treated as such.
Flood-Plain-Net Estimate of Detritus 

### tons at Sumatra. Coarse particulate carbon flow from the flood plain as estimated by the net collectors was, therefore, nearly equal to measured transport near the Sweetwater transect but more than an order ofmagnitude smallerthan measuredtransport nearthe Brickyardtransect.
The data from the nets usedto collect detritus in the flood plain ("Supplementary Data I") can be used to estimate the amount of coarse particulate carbon transported from the flood plain. The data show considerable variability, as would be expected because ofthe differences in the sites where the detritus was collected; however, overall mean weights provide information that serves as a comparison with carbon transportmeasuredin theriver. The amount of flood-plain water flow during the 1980 flood rise and peak can be estimated from flow distribution data given by Leitman and others (1983, figs. 25 and 26). The flood-plain part of the discharge at the Sweetwater transect was 27 percent at high stage (<2=2,490 m3/s on March 18) and 10 percent at medium stage (<2= 1,640 m3/s on March 11). At the Brickyard transect, the corresponding values were 44 percent (0=2,920 m3/s on March 19) and 35 percent (Q= 1,980 m3/s on March 14). These percentages may beusedto estimate actual flow in the flood plain during the 1980 flood, assuming that the maximum percentage applies to the floodpeaks period andthe mid-stagepercentage applies to the flood rise and recession periods. Flow percentages multiplied by total discharge values at Blountstown and Sumatra (WO in tables 13 and 15) give the following estimates forflood-plain flow: Flood-plain flow, _3 in torf
Period Sweetwater Rise.................. .0.15 Peaks..................1.84 Recession.............
. . 36 Total 1980 flood 2.35 Brickya.rd 0.40 3.55 

### L£l 5.57


### The mean concentration of coarse particulate organic material capturedin the flood-plain nets was 0.09 g/ m3 at Sweetwater and 0.02 g/m3 at Brickyard ("Supplementary Data I"). Multiplying these values by the floodplain flowjust calculated and by the factor0.5 to account for the concentration ofcarbon in organic matter, one arrives at the estimates of 100 metric tons CPOC transport at Sweetwater and 60 metric tons CPOC transport at Brickyard. Actual transport determinations from the CPOC and BPOC samples collected in theriverduringthe entire flood period were 160 metric tons at Blountstown (slightly downstream of Sweetwater) and 1,000 metric Plastic-Sheet Estimate of Detritus 

### The organic deposition on plastic sheets (table 31) was considerably less than the 800 (g/m2)/yrlitter-fall rate foundby Elder and Cairns (1982). Presumably, the differences are due to losses from the sheets resulting from decomposition and flood scouring and, perhaps, to some other factors such as removal by animals or wind. It should be noted that the plastic sheets were in place for somewhat less than a full year (9 to 11 months); hence, the litter fall on them would be slightly less than the annualrate. The organic deposition on the sheets at plot 4 was somewhat higher than the mean deposition at all other plots (table 31), suggesting that the lack of flooding at plot4 resulted in less removal oflitterfall. Underthis assumption, the removal caused by flooding can be estimated by comparing plot 4 data with data from all other plots, after first correcting for such effects as collection time andforest-covertype. The collection time effect, caused by the sheets being in place for less than 1 year, was corrected by subtracting from annual litter-fall amounts (Elder and Cairns, 1982) the amounts for the months that were not sampled by the sheets. For example, the sheets at plot 4 were removed in early June 1980, after being in place for 9 months, so the amount oflitter-fall duringJune, July, and August was subtracted from the annual total to estimate actual litterfall onthe sheets. The plot locations do not correspond proportionally tothe differentforest-covertypes inthe intensivetransects (Leitman and others, 1983). Atthe Brickyardtransect, for example, two ofthe nine plots are on levees, yet only 5 percent ofthe transect is composed of levee forest-cover types. Thelitter-fall data, as well astheplastic-sheetdata, must be weighted according to the transect distance represented by each plot to more accurately characterize the entire transect. When this is done, the mean plastic-sheet sample weight (organic material only) forplots otherthan plot4is 89g/m2

. Theresults ofthese calculations are as follows:

Plastic Litter sheet fan sample Loss (grams per square meter) Plot 4.... All other plots... ,733

.831 182

89 551

742 Percent age los 75 89
Nutrient and Detritus Transport in the Apalachicola River, Florida C53A greater removal of organic material, amounting to 14

percent ofthe total, is calculated forthe flooded sites. Assuming that this difference is due to flood scouring, the annual carbon loss from the entire flood plain can be calculated. The organic material is considered to be 50 percent carbon. (0.14)x [800(g/m2)/yr]x(0.5)=

56g C/m2/yr=56 metric tons C/km2/yr The area of the flood plain above Sumatra is 393 km2; hence: 56 metric tons C/km2/yrx393 km2^ 22,000 metric tons C/yr This compares closely with the estimate of27,000 metric tons C/yr (table 21) previously determined as the flood plain yieldplusresidualR. Significanceof Flood-Plain-Net and Plastic-Sheet Estimates The flood-plain nets and plastic sheets provide two sources ofdata from within the flood plain which supplement the paniculate carbon transport measurements in the river. Both approaches depend on random samples taken at locationsthatdiffer widely in environmental conditions. The data are thus subject to considerable variability and should be treated as qualitative supporting evidence that substantial amounts ofthe riverine detritus originate in the floodplain. The flow ofcoarse detritus in the flood plain, as determined by the net sampling, could account fornearly all CPOC and BPOC transport measured in the river. At the Sweetwater transect, the estimated detrital flow of 100 metric tons in the flood plain was quite close to the total riverine transport of 160 metric tons measured at Blountstown. Presumably, the amount found at Blountstown had been transported into the river from the flood plain upstream. Some ofthe detritus sampled at the Sweetwater transect may have entered the river above Blountstown, and some may have entered below. Farther downstream, as the detrital load increases in the river owing to inputs along the way, the flood-plain detrital flow would be expected to become a continually smaller fraction of riverine detrital flow. The estimates from the Brickyardtransectconfirmthisexpectation. The plastic-sheet approach to estimating flood-plain carbon flow further corroborates the findings ofthe other approaches. The factthatthe final estimate of22,000 metric tons of particulate organic carbon transport/year is quite close to the river sample amount of 27,000 metric tons/year is an indication that the method does provide realistic estimates. Neitherthe stationary netsnortheplastic sheetsprovide data that show how far the organic particles move. The fact that they do move, however, suggests that some must move from the flood plain to the stream channels. The general flow downstream and toward the channels should prevent complete recycling ofthe materials within the flood-plain ecosystem.


### Nutrient Yields for the Apalachicola-Chattahoochee-Flint River System Annual nutrient yield converted to an areal basis (g/m2/yr, equivalent to metric tons/km2/yr) reveals sharp differences among various basins and the flood plain (table 32). Compared with the entire Apalachicola-Chattahoochee-Flint basin, the Apalachicola flood plain is extremely high in carbon andphosphorusyieldperunit area. Carbon and phosphorus areal yields from the flood plain are more than 15 times greater than from the basin as a whole. The Apalachicola and Chipola basins exhibit more areal nutrient yield than the Chattahoochee-Flint basin. The nutrient yields ofthe Chattahoochee-Flint watersheds are apparently affected by nutrient retention in the 16 reservoirs in the system. The nitrogen budget of the Apalachicola-Chattahoochee-Flint system is clearly distinct from the carbon and phosphorus budgets, as shown bythe data intable 32. Nitrogen yield from the Apalachicola flood plain is the same as the yield from the basin as a whole. Anotherdistinction is seen in the comparisons of the Apalachicola and Chipola drainage areas. The Apalachicolayields more carbon and phosphorus, but less nitrogen, than the Chipola. It should be stressed that these yields apply to net yield rather than gross yield, since they are based on output minus input. Hence, the data do not indicate whether actual nitrogenyield fromthe floodplain was low ornitrogen retention washigh. Carbon transport rates on an areal basis have been reported for a number ofother systems and provide an interesting comparison with those shown in table 32. Schlesinger and Melack (1981) compiled the results of numerous studies from various ecosystem types and found that, with few exceptions, the carbon output from river watersheds ranges from 1 to 10 g/m2 annually. Factors that seemed to favorhigh yield included steep topographic relief, high runoff, high primary productivity, andproduction ofdetritus as litter fall rather than below ground productivity in root systems (as in grasslands). Wetland watersheds were shown to be among the most productive. A regression of total organic carbon transport versus watershed size indicated that the mean annual world carbon export rate from watersheds shouldbe 7.2 g/m2

. Most measured amounts are found to be lower than this, however, with the exception ofwetland areas. C54 Apalachicola River Quality AssessmentTable 32. Nutrient yields, on an areal basis, for various drainage areas ofthe Apalachicola-Chattahoochee-Flint River system
Drainage basin
Apalachicola-Chattahoochee-Flint

. . Chattahoochee-Flint

........... Apalachicola-Chipola

........... Apalachicola.

................ Chipola

.................... Apalachicola flood plain

......... Area (km2)
50,800 44,600 6,200 3,100 3,100 393 Annual output minus input (tons) Carbon 213,800 142,700 71,100 41,500 29,600 27,000 Nitrogen

21,480 17,860 3,620 1,060 2,560 170 Phosphorus

1,652 1,340 312 237 75 180 Carbon

4 3 12 13 10 69 Areal yield

(g/m2/yr) Nitrogen 0.4 .4 .6 .3 .8 .4 Phosphorus

0.03 .03 .05 .08 .02 .46

Further evidence ofthe high nutrient yield of wetlands was provided by Mulholland and Kuenzler (1979). Compiling data from various wetland and upland watersheds, they found a close linear relation between annual runoffand carbon transport. The relation was quite different for the two watershed types, however, with the resulting conclusion that, given equal runoff, wetland watersheds would be expected to yield five times more carbon per unit area than upland watersheds. A large number of other studies, including those of Odum and de la Cruz (1967), Heald (1971), and Day and others (1977), have demonstrated high rates of carbon export from wetland systems. By contrast, Woodwell and others (1977) reported net carbon import in a Long Island salt marsh, an inconsistency that adds credence to the argumentthat wetlands can act as both sinks and sources oforganic material (de laCruz, 1979). The carbon export from the Chattahoochee-Flint basin, limited as it is by the dams on the rivers, is less than the 7.2 g/m2/yrpostulatedby SchlesingerandMelack (1981) as a world average. The output from the Apalachicola part ofthe system is 13 g/m2/yr, well above average. The 69 g/m2/yr yield from the flood plain gives strong evidence that the wetland yield accounts for the high overall yieldofthe whole Apalachicolabasin. Areal yield ofphosphorus in the Apalachicola basin is higher than in most other systems. Mitsch and others (1979) reported a phosphorus output of0.34 g/m2/yr from an Illinois cypress swamp, which is 0.18 g/m2/yr lower than the Apalachicola flood-plain output. Other studies (Richardson and others, 1978; Whittaker and others, 1979) have shown phosphorus export rates considerably lower (less than 0.02 g/m2/yr) for other, more dissimilar systems. Most reported nitrogen export rates from the same systems are also lowerthan thatofthe Apalachicola, although there is considerable variability. Such variability may be partially attributed to nitrogen assimilation rates, which can have enormous seasonal variability (Stanley andHobbie, 1981). It is commonly believed that wetland environments generally function as sinks for nitrogen and phosphorus (Brinson, 1977; Simpson andothers, 1978). This hasbeen documented (Sloey andothers, 1978) where wetlands may be utilized for sewage treatment orothernutrient assimilation roles. The Apalachicola system shows an overall annual export of phosphorus and nearly a balance between import andexportofnitrogen. In view ofthe seasonal variability seen for the various hydrologic periods and the changing output/input ratios described in the nutrienttransport section, it seems likely that the system does act as a nutrient sink for certain periods during each annual cycle.


### Long-Term Factors Influencing Nutrient Transport There is evidence that the nutrient and detritus transport measured in the 1979-80 study yearmay be considered a good indicatorofwhat may be expectedin other years. A greatdeal ofhistorical stage anddischarge record was examined by Leitman and others (1983). They found that during the entire period ofrecord (1929 to 1980), the seasonal distribution offlow shows a strong tendency for flows greater than 1,000 m3/s to occur in the spring months each year. The completion of the Jim Woodruff Dam in 1957 did not appreciably alterthis pattern. Regulation by dams, however, did have some effect in diminishing the extremes, as shown by slightly flatter flowduration curves since 1957. The 1980 mean discharge was slightly higherthan the average for 1958-80, andthe 1980 spring flood had a 1-day peak of4-year recurrence interval (0.25 probability). Nutrient and DetritusTransport in the Apalachicola River, Florida C55The 1979-80 nutrient data, in the context ofthe historical hydrologic record, suggest a long-range pattern of nutrient transport that is stimulated annually by spring floods. The annual flooding and the extensive natural bottom-land hardwood forest are the critical elements for continual high productivity and mobilization of nutrients in the system. The dams on the Chattahoochee and Flint Rivers and the Jim Woodruff Dam at the headwaters of the Apalachicola apparently have had little effect on the nutrient flow pattern, but any new dam or other construction in the Apalachicola basin that alters the integrity of the flood plain is likely to disrupt nutrient flow considerably. There were no hurricanes or extremely severe rainstorms in the Apalachicola basin during 1979-80; hence, the effects ofmajor storms could notbe quantified. Hurricanes have struck the northwest Florida coast in the vicinity of the city of Apalachicola approximately 25 times during the past century. Such storms would presumably produce extremely high rainfall and, in some cases, extreme winds which would dramatically alter the normal water and nutrient flow through the Apalachicola system. An example of the effects of a severe rainstorm in 1969 in the adjacent Ochlockonee Riverbasin was describedby Bridges and Davis (1972). The amount ofrainfall in that storm exceededthe 1 in 100-yearprobability, and Ochlockonee River floods substantially exceeded 50-year flood levels. Significant amounts of the discharge flowed through the flood plain during the storm. It should be noted that the hurricane season is between June and November. These storms, therefore, would have the effect ofadding an additional floodin a normal low-flow period, ratherthan compoundingtheusual spring flood.
SUMMARY The Apalachicola River in northwest Florida is formed by the confluence ofthe Chattahoochee and Flint Rivers and has a 50,800-square-kilometer drainage system encompassing parts of three states. With an average discharge of 640 m3/s at Chattahoochee, Fla., the Apalachicola is the largest river in Florida and ranks 21st in magnitude of discharge in the conterminous United States. The river falls 12 m in its 172-km course from Lake Seminole, at the Florida-Georgia state line, to Apalachicola Bay in the GulfofMexico. Each winter and spring, its rising waters flood the adjacent wetlands for 3 to 5 months. The floodplain, which broadens downstream from 1 km widejust below Lake Seminole to more than 8 km wide near the mouth, is thickly forested with cypress, tupelo, and mixed hardwood trees, which thrive on the periodic inundation. At the end ofits course, the river empties into the Apalachicola Bay, which is one of the mostproductive shellfishregions in the United States. The bottom-land hardwood forest, which occupies the 454 square mile Apalachicola River flood plain, has experienced several generations of cutting but retains the same variety and general distribution of tree species that existed prior to timber harvest. The production, decomposition, and transport of leaf litter byproducts in the Apalachicola basin are considered representative ofundisturbed bottom-land hardwood ecosystems. The description of the flood-plain contribution to the overall transport of nutrients and detritus to Apalachicola Bay includes the following specific findings: 1. The water budget ofthe Apalachicola basin is heavily streamflow-dominated; water volumes involved in precipitation, ground-water flow, surface-waterrunoff, and evapotranspiration are relatively minor compared with main-stem flow. 2. Small errors ofrating curves atthe fourmain-stem gaging stations accounted for most of the possible waterbudget error. Total annual errors appeared very small because flow errors were largely compensating rather than additive. Water-budget calculations for seven time periods between June 3, 1979, and June 2, 1980, for three subbasins showed that the most satisfactory balances were obtained when longer periods and all three subbasins oftheriver/floodplain were combined. 3. Annual flooding, which usually occurs on the Apalachicola in late winter or early spring, causes appreciable surges in nutrient transport, especially in particulate organic form. During the 86-day flood event in 1980, approximately half of the annual outflow of organic carbon, nitrogen, and phosphorus and 60 percent of the detritus were transported past Sumatra, the final main-stem gaging station. 4. Total annual organic carbon outflow at Sumatra in 1979-80 was 50 percent higher than inflow at Chattahoochee. This increase was greaterthan the 25 percent increase in streamflow. Nitrogen and phosphorus increases, on the otherhand, were similarto the discharge increase, indicating that the basin input of these elements to the riverjust matched the river's gain in water volume. 5. Flood-plain detritus nets used to estimate flood-period transport of coarse particulate organic carbon measured substantial flood-plain transport at the Sweetwater and Brickyard transects. Bottom load and suspended detritus transport in the main-stem river channel increased downstream. 6. Plastic sheets were used in combination with litter-fall estimates to make a passive net estimate of detritus transport. The amount ofannual organic carbon removal calculated from these data was close to the amount determinedby actual measurements. 7. On an areal basis, the Apalachicolabasin exports greater quantities of carbon (13 g/m2/yr) and phosphorus (0.08 g/nr/yr) than most watersheds. Some nutrient exC56 Apalachicola River Quality Assessmentport can be attributed to flood-plain contributions, although the flood plain also acts as a nutrient sink during certainperiods ofthe year. 8. Over the long term, the system is dependent on annual spring floods and a healthy, productive, bottom-land hardwood forest in the flood plain to maintain nutrient anddetritus flow to the bay. Inthe absence ofmajoralterations to the system, the floods and the flood-plain forest will continue to be present each year and the annual nutrient-flow pattern should continue.

SELECTED REFERENCES Avery, T. E., 1967, Forest measurements: New York, McGrawHill, 290 p. Beetem, W. A., Friedman, L. C., Ferryman, G. R., and Watterson, C. A., eds., 1980, 1981 Water Quality Laboratory services catalog: U.S. Geological Survey Open-File Report 80- 1279, 251 p. Brakensiek, D. L., Osborn, H. B., and Rawls, W. J., coordinators, 1979, Field manual forresearch in agricultural hydrology: U.S. Department ofAgriculture, Agriculture Handbook 224, 547 p. Bridges, W. C., and Davis, D. R., 1972, Flood of September 20-23, 1969, in the Gadsden County area, Florida: Florida Bureau ofGeology Information Circular79, 37 p. Brinson, M. M., 1977, Decomposition and nutrient exchange of litter in an alluvial swamp forest: Ecology, v. 58, no. 3, p. 601-609. Brown, Eugene, Skougstad, M. W., and Fishman, M. J., 1970, Methods for collection and analysis ofwater samples for dissolved minerals and gases: U.S. Geological Survey Techniques of Water-Resources Investigations, Book 5, Chap. Al, 160 p. Brown, Sandra, 1981, A comparison of the structure, primary productivity, and transpiration of cypress ecosystems in Florida: Ecological Monographs, v. 51, no. 4, 403-427. Buchanan, T. J., and Somers, W. P., 1968, Stage measurement at gaging stations: U.S. Geological Survey Techniques of Water-Resources Investigations, Book 3, Chap. A7, 28 p. 1969, Discharge measurements at gaging stations: U.S. Geological Survey Techniques ofWater-Resources Investigations, Book 3, Chap. A8, 65 p. Daniel C. C., Ill, Wilder, H. B., and Weiner, M. S., 1979, Water quality ofthe French Broad River, North Carolina; An analysis ofdata collected at Marshall, 1958-77: U.S. Geological Survey Water-Resources Investigations 79-87, 53 p. Darnell, R. M., 1961, Trophic spectrum ofan estuarine community based on studies ofLake Pontchartrain, Louisiana: Ecology, v. 43, no. 3, p. 553-568. Day, J. W., Butler, T. J., and Conner, W. H., 1977, Productivity and nutrient export studies in a cypress swamp and lake system in Louisiana, in Wiley, M. L., ed., Estuarine processes, v. 2: New York, Academic Press, p. 255-269. de la Cruz, A. A., 1979, Production and transport ofdetritus in wetlands, in Wetland functions and values The state ofour understanding: National Symposium on Wetlands, Lake Buena Vista, Florida, 1978, Proceedings, p. 162-174. Dethier, D. P., 1979, Atmospheric contributions to stream water chemistry in the North Cascade Range, Washington: Water Resources Research, v. 15, no. 4, p. 787-794. Edwards, M. D., 1977, The National Water Data Exchange (NAWDEX): U.S. Geological Survey Open-File Report 77- 259,9 p. Elder, J. F., and Cairns, D. J., 1982, Production anddecomposition of forest litter fall on the Apalachicola River flood plain, Florida: U.S. Geological Survey Water-Supply Paper 2196, Chap. B, 42p. Elder, J. F., and Home, A. J., 1978, Ephemeral cyanophycean blooms and their relationships to micronutrient chemistry in a southern California reservior: University of California, Sanitary Engineering Research Laboratory Report 78-1, 182PFenchel, Tom, 1970, Studies on the decomposition of organic detritus derived from the turtle grass Thallassia testudinum: Limnology andOceanography, v. 15, no. 1, p. 14-20. Galloway, J. N., andLikens, G. E., 1976, Calibration ofcollection procedures for the determination ofprecipitation chemistry: Water, Air, and Soil Pollution, v. 6, p. 241-258. Goerlitz, D. F., and Brown, Eugene, 1972, Methods foranalysis oforganic substances in water: U.S. Geological SurveyTechniques of Water-Resources Investigations, Book 5, Chap. A3, 40 p. Greeson, P. E., ed., 1978, River-quality assessments: American Water Resources Association symposium, Tucson, 1977, Proceedings, 191 p. Guy, H. P., and Norman, V. W., 1970, Field methods formeasurement of fluvial sediment: U.S. Geological Survey Techniques of Water-Resources Investigations, Book 3, Chap. C2, 59 p. Heald, E. J., 1971, The production oforganic detritus in a south Florida estuary: University of Miami Sea Grant Program, Technical Bulletin 6, 110 p. Hendry, C. D., and Brezonik, P. L., 1980, Chemistry ofprecipitation at Gainesville, Florida: Environmental Science and Technology, v. 14, p. 843-849. Hutchison, N. E., compiler, 1975, WATSTORE user's guide: U.S. Geological Survey Open-File Report 75- 426, v. 1, 300p. Irwin, G. A., and Kirkland, R. T., 1980, Chemical andphysical characteristics of precipitation at selected sites in Florida: U.S. Geological Survey Water-Resources Investigations 80- 81, 70p. Kilkus, S. P., LaPerriere, J. D., and Bachman, R. W., 1975, Nutrients and algae in some central Iowa streams: Journal of Water Pollution Control Federation, v. 47, no.7, p. 1870- 1879. Kwader, Thomas, and Schmidt, Walter, 1978, Top ofthe Floridan aquifer of northwest Florida: Florida Bureau ofGeology Map Series 86. Leitman, H. M., Sohm, J. E., and Franklin, M. A., 1983, Wetland hydrology and tree distribution of the Apalachicola River flood plain, Florida: U.S. Geological Survey WaterSupply Paper 2196, Chap. A, 52 p. Livingston, R. J., Iverson, R. L., Estabrook, R. H., Keys, V. E., and Taylor, John, Jr., 1974, Major features of the

Nutrient and Detritus Transport in the Apalachicola River, Florida C57Apalachicola Bay system physiography, biota, and resource

management: Florida Scientist, v. 37, no. 4, p. 245-271. Livingston, R. J., and Joyce, E. A., Jr., eds., 1977, Proceedings ofthe conference on the Apalachicola drainage system; Florida Department of Natural Resources: Marine Research Laboratory, Research Publication 26, 177 p. Livingston, R. J., Kobylinski, G. J., Lewis, F. G., Ill, and Sheridan, P. F., 1976, Long-term fluctuations of epibenthic fish and invertebrate populations in Apalachicola Bay, Florida: Fishery Bulletin, v. 74, no. 2, p. 311-321. Mattraw, H. C., Jr., and Elder, J. F., 1980, Nutrient yield of the Apalachicola River flood plain, Florida River-quality assessment plan: U.S. Geological Survey Water-Resources Investigations 80-51, 21 p. Menzel, D. W., Hulings, N. C., and Hathaway, R. R., 1966, Oyster abundance in Apalachicola Bay, Florida, in relation to biotic associations influenced by salinity and other factors: GulfResearch Reports, v. 2, no. 2, p. 73-96. Mitsch, W. J., Dorge, C. L., and Wiemhoff, J. R., 1979, Ecosystem dynamics and a phosphorus budget of an alluvial cypress swamp in southern Illinois: Ecology, v. 60, no. 6, p. 1116-1124. Mulholland, P. J., and Kuenzler, E. J., 1979, Organic carbon export from upland and forested wetland watersheds: Limnology and Oceanography, v. 24, no. 5, p. 960-966. Naiman, R. J., and Sedell, J. R., 1979, Characterization ofparticulate organic matter transported by some Cascade Mountain streams: Journal of the Fisheries Research Board of Canada, v. 36, no. 1, p. 17-31. Odum, E. P., and de la Cruz, A. A., 1967, Paniculate organic detritus in a Georgia salt marsh Estuarine ecosystem, in Lauff, G. H., ed.. Estuaries: Washington, D.C., American Association forthe Advancement ofScience Pub. 83, p. 383- 388. Oesterling, M. L., and Evink, G. L., 1977, Relationship between Florida's blue crab population and Apalachicola Bay, in Livingston, R. J., andJoyce, E. A., Jr., eds.. Proceedings of the conference on the Apalachicola drainage system; Florida Department of Natural Resources: Marine Research Laboratory, Research Pub. 26, p. 101-121. Pascale, C. A., andWagner, J. R., 1982, Waterresources ofthe Ochlockonee River area, northwest Florida: U.S. Geological Survey Water-Resources Investigations Open-File Report 81- 1121, 114p. Peverly, J. H., 1982, Stream transport of nutrients through a wetland: Journal of Environmental Quality, v. 11, no. 1, p. 38-41. Qureshi, Zia, 1978, Surface water resources of northwest Florida: WaterResources Bulletin, v. 14, no. 3, p. 710-718. Radtke, D. B., McConnell, J. B., and Carey, W. P., 1980, A preliminary appraisal of the effects of agriculture on stream quality in southwest Georgia: U.S. Geological Survey WaterResources Investigations Open-File Report 80-771, 40p. Richardson, C. J., Tilton, D. L., Kadlec, J. A., Chamie, J. P. M., andWentz, W. A., 1978, Nutrientdynamics ofnorthern wetland ecosystems, in Good, R. E., and others, eds., Freshwater wetlands, ecological processes and management potential: New York, Academic Press, p. 217-241. Rosenau, J. C., Faulkner, G. L., Hendry, C. W., Jr., and Hull, R. W., 1977, Springs ofFlorida: Florida Bureau ofGeology Bulletin 31 (revised), 461 p. Rosenau, J. C., and Meadows, P. E., 1977, Potentiometric surface of the Floridan aquifer in the Northwest Florida Water Management District, May 1976: U.S. Geological Survey Water-Resources Investigations Open-File Report 77-2, map. Scheider, W. A., Moss, J. J., and Dillan, P. J., 1978, Measurement and uses of hydraulic and nutrient budget, in Lake restoration, proceedings ofthe national conference, August 22- 24, 1978, Minneapolis, US EPA 440/5-79-001, p. 77-83. Schlesinger, W. H., and Melack, J. M., 1981, Transport oforganic carbon in the world's rivers: Tellus, v. 33. no. 2, p. 172-187. Simpson, R. L., Whigham, D. F., and Walker, Raymond, 1978, Seasonal patterns of nutrient movement in a freshwater tidal marsh, in Good. R. E.. and others, eds.. Freshwater wetlands, ecological processes and management potential: New York, Academic Press, p. 243-257. Skougstad, M. W., Fishman, M. J., Friedman, L. C., Erdmann, D. E., and Duncan, S. S., eds., 1979, Methods for determination ofinorganic substances in water and fluvial sediments: U.S. Geological Survey Techniques of Water-Resources Investigations, Book 5, Chap. Al, 626p. Sloey, W. E., Spangler, F. L., and Fetter, C. W., Jr., 1978, Management offreshwater wetlands for nutrient assimilation, in Good, R. E., and others, eds.. Freshwater wetlands, ecological processes and management potential: New York, Academic Press, p. 321-340. Smoot, G. F., and Novak, C. E., 1969, Measurement of discharge by the moving-boat method: U.S. Geological Survey Techniques of Water-Resources Investigations, Book 3, Chap. All, 22 p. Stamer, J. K., Cherry, R. N., Faye, R. E., and Kleckner. R. L., 1978, Magnitudes, nature, and effects ofpoint and nonpoint discharges in the Chattahoochee River basin, Atlanta to West Point Dam, Georgia: U.S. Geological Survey Open-File Report 78-577, 74p. Stanley, D. W., and Hobbie, J. E., 1981, Nitrogen recycling in a North Carolina coastal river. Limnology and Oceanography, v. 26, no. 1, p. 30-42. Taft, J. L., and Taylor, W. R., 1976. Phosphorus dynamics in some coastal plain estuaries, in Wiley, M. L., ed., Estuarine processes, v. 1: New York, Academic Press, p. 79-89. Thornthwaite, C. W., and Mather, J. R., 1957, Instructions and tables for computing potential evapotranspiration and the water balance: Drexel Institute in Technology Laboratory of Climatology, Publications in Climatology, v. 10, no. 3, p. 185-306. U.S. Army Corps of Engineers, Mobile District, 1976, Apalachicola, Chattahoochee, and Flint Rivers, Alabama, Florida, and Georgia, Final impact statement operation and maintenance: Mobile, Ala. 179 p. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Office ofCoastal Zone Management, and State of Florida, Department of Environmental Regulation, Bureau of Coastal Zone Managment, 1979, Final environmental impact statement, Apalachicola River and bay estuarine sanctuary: Washington, U.S. Government Printing Office, 48 p. 13 app. U.S. Fish and Wildlife Service, 1979, Evaluation ofalternatives report for Corps ofEngineers study ofnavigational improveC58 Apalachicola RiverQualityAssessmentments of the Apalachicola River below Jim Woodruff Dam, Florida: Unpublished report on file in Panama City, Fl., office ofU.S. Fish and Wildlife Service, 82 p. U.S. Geological Survey, 1980-82, Water resources data for Florida Northwest Florida: Annual reports as follows: 1980, Water-Data Report FL79-4; 1981, Water-Data Report FL80- 4; 1982, Water-Data Report FL81-4. Velz, C. J., 1970, Applied stream sanitation: New York, Wiley Interscience, John Wiley & Sons, 619p. 1978, River-quality assessment A rational scientific basis for pollution control and water-quality management, in Greeson, P. E., ed., River-quality assessments, Tucson, Ariz., 1977, Proceedings: Minneapolis, Minn., American Water Resources Association, p. 3-10. Vitousek, P. M., and Reiners, W. A., 1975, Ecosystem succession and nutrient retention A hypothesis: Bioscience, v. 25, no. 6, p. 376-381. Whitehead, H. C., and Feth, J. H., 1964, Chemical composition of rain, dry fallout, and bulk precipitation an Menlo Park, California, 1957-59: Journal ofGeophysical Research, v. 69, p. 3319-3333. Whittaker, R. H., Likens, G. E., Bormann, F. H., Eaton, J. S., and Siccama, T. G., 1979, The Hubbard Brook ecosystem study Forest nutrient cycling and element behavior: Ecology, v. 60, No. 1, p. 203-220. Winter, T. C., 1981, Uncertainties in estimating the water balance oflakes: Water Resources Bulletin, v. 17, no. 1, p. 82- 115. Woodwell, G. M., Whitney, D. E., Hall, C. A. S., and Houghton, R. A., 1977, The Flax Pond ecosystem study Exchanges ofcarbon in waterbetween a salt marsh and Long Island Sound: Limnology and Oceanography, v. 22, no. 5, p. 833-838.

Nutrient and Detritus Transport in the Apalachicola River, Florida C59SUPPLEMENTARY DATA I Flood-plain detritusdatafromstationary netslocatedrandomly onthe flood plain during the spring flood, 1980. Alllocationswereon ornear the Sweetwater and Brickyardtransects. Datecollected (1980)

3/11 3/12 3/12 3/18 3/18 3/26 3/26 4/02 4/02 4/23

3/14 3/14 3/17 3/17 3/19 3/19 3/27 3/27 4/03 4/28 4/28 Duration

of sampling (hrs:min)

1:00 5:10 21:00 1:30 21:00 4:00 3:10 4:30 6:30 2:40

23:05 24:00 7:30 4:35 4:10 5:10 5:30 4:05 3:30 4:15 5:50 Flowthrough volume (m3)
Sweetwatertransect 537 119 2,068 393 378 1,116 734 2,254 725 1,290 Brickyard transect 4,741 1,399 1,321 1,194 1,511 861 1,170 1,300 308 667 242 Detritus concentration,

in mg/m3 Inorganic

160 110 0.3 16 18 2 9 4 30 4

34 1 62 3 0.6 6 2 2 12 3 10 Organic

260 390 0.6 22 20 i 14 6 49 8

54 2 108 6 1.4 9 6 4 26 5 20

C60 Apalachicola River Quality AssessmentSUPPLEMENTARY DATA II Deposition on plastic sheets randomly placed in Sweetwater and Brickyardplotson orabout September 1, 1979, and collected on the date indicated. Coarse (>1 mm) and fine (<1 mm) fractions are given for most samples;for others,onlytotalsampleswereanalyzed. Theareaofall sheetswas 1 m2,except4D,whichwas4m2

.

Plot


## 1

. . . . 3

. . . .

4

. . . .

5

. . . .

6

. . . .

7

....

11

.... 12

.... 13

.... 14

....

15

.... 16

.... 17

.... 18

.... Sheet

A.

. . . . A.

. . . . B

. . . . . C

. . . . . A.

. . . . B

. . . . . C

. . . . . D.

. . . . A.

. . . . B

. . . . . C

. . . . . A.

. . . . B

. . . . . C

. . . . . A

. . . . . B

. . . . . C

. . . . . A.

. . . . B

. . . . . C

. . . . . A.

. . . . C

..... A.

.... B

..... C

..... A.

.... B

..... 

## c A.

.... B

..... A.

.... Collection date (1980) 8/4 6/3 6/3 6/3 6/3 6/3 6/3 6/3 6/3 6/3 6/3 6/3 6/3 6/3 6/3 6/3 6/3 7/9 8/5 8/5 8/5 8/5 5/6 6/6 5/6 8/5 O 1C Q/t) 8/5 8/5 8/5 8/5 Inorganic deposition, in grams per square meter Coarse 31

4 143 101 86
91 70 45 112 169 0.3 1.1 3 379 22 53 11 36 38 255 12 1 53 73 75 45 10 Fine

320

223 9 6 3
122 230 823 1,378 287 424 122 1,853 205 419 509 195 769 18,699 11,643 20,559 106 38 1,403 58 581 5 Total

351 1,075 1,787 227 152 107 89 80 213 828 300 868 1,490 456 424 123 1,856 584 441 562 206 805 18,737 11,898 20,571 107 91 1,476 133 626 15 Organicdeposition,

ingrams persquaremeter Coarse 58

- 2 230 208 145
24 24 14 95 68 0.2 0.8 2 81 23 60 15 47 25 179 14 1 21 49 38 17 6 Fine

94

16 2 4 2

6 8 68 135 24 2.4 0.7 11 22 36 44 17 81 319 369 179 9 3 126 5 58 1 Total

152 284 851 18 232 212 147 137 30 130 32 82 230 92 2.7 1.5 13 103 59 104 32 128 345 548 193 10 24 175 43 75 7

Nutrient and DetritusTransport in theApalachicola River, Florida C61Metric Conversion Factors For readers who prefer to use inch-pound units rather than metric units, the conversion factors for the terms used in this report are listed below: Multiply metric unit

jum (micrometer) mm (millimeter) m (meter) km (kilometer) m/s (meter per second)

m2 (square meter)

ha (hectare) km2 (squarekilometer)

m3 (cubic meter)

L (liter) m3/s (cubic meterper second) km3 (cubickilometer)

mL (milliliter)

mg (milligram) g (gram) kg (kilogram) t (metricton) t/ha (metricton perhectare) t/km2 (metricton per squarekilometer)

g/m2 (gram persquare meter)

°C (degree Celsius)

mg/L (milligrams perliter) Mg/L (micrograms perliter) By Length
0.00003937 .03937 3.281 1.094 .6214 3.281 Area 10.76 1.196 0.0002471 2.471 0.3861 Volume 35.31 1.308 0.0008107 264.2 1.0567 35.3145 0.2399 810,700 264,200 0.0338
Mass 0.0000353 0.0353 0.0022 2.2046 2,204.6 1.1023 892.18 0.4461 8.9218 0.004461 8.9218 Temperature 1.8 (+32°) Concentration 1.0 1.0 Toobtain inch-pound unit

in. (inch) in. (inch) ft (foot) yd (yard) mi (mile) ft/s (Foot per second)

ft square foot yd2 (square yard) acre acre mi2 (square mile)

ft3(cubic foot) yd3 (cubicyard) acre-ft (acre-foot) gal (gallon) qt (quart) ft /s (cubic foot per second) mi3 (cubic mile) acre-ft (acre-foot) Mgal (million gallons) oz (fluid ounce)

oz (ounce) oz (ounce) Ib (pound) Ib (pound) Ib (pound) short (ton) Ib/acre (pound per acre) ton per acre Ib/acre (poundsper acre) tons per acre Ib/acre (pound per acre)

F (degree Fahrenheit)

ppm (parts permillion) ppb (partsperbillion)

C62 Apalachicola River Quality Assessment

U.S. GOVERNMENT PRINTING OFFICE: 1984-461-433:410