Suwannee River Basin and Estuary

Integrated Science Workshop:

September 22-24, 2004

Cedar Key, Florida

Compiled by Brian Katz and Ellen Raabe

This workshop is co-sponsored by

U.S. Geological Survey

Suwannee River Water Management District

Florida Marine Research Institute

Open-File Report 2004-1332

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2004

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Katz, B.G., and Raabe, Ellen, Compilers, 2004, Suwanee River Basin and Estuary Integrated Science Workshop:

September 22-24, 2004: U.S. Geological Survey Open-File Report 2004-1332, 65 p.
CONTENTS

Map of Suwanee River Basin ...................................................................................................................... vi

Introduction to Suwannee River Basin and Estuary Initiative ................................................................ vii

HYDROGEOLOGY ISSUES

The future of the Suwannee River Sill - A review and update

By S.B. Aicher ............................................................................................................................... 2

Surface and ground water mixing along the Cody Scarp: An example from the Santa Fe River 

sink-rise system

By J.B. Martin, E.J. Screaton, and P.J. Moore......................................................................... 3

Using synthesized data to quantify surface-water / ground-water relationships between 

Madison Blue Spring and the Withlacoochee River of north Florida

By J.C. Schneider, S.B. Upchurch, K.M. Champion, J. Good, and D. Hornsby ................... 4

Development of minimum levels and flows for Blue Spring, Madison County, Florida

By S.B. Upchurch, M. Farrell, A. Janicki, J. Good, R.A. Mattson, D. Hornsby, 

J. Schneider, D. Wade, and K. Malloy.......................................................................... 6

Delineation of the Fanning and Manatee Spring Basins in the Suwannee River Water 

Management District

By R. Ceryak... 8

Extension of minimum flows from the lower Suwannee River to upstream tributaries and 

springs using a reach-based method

Exchanges of water between the Upper Floridan aquifer and the lower Suwannee and 

lower Santa Fe Rivers, Florida

By J. Good and Robert Mattson ................................................................................................. 9

By J.W. Grubbs and C.A. Crandall, C.A. .................................................................................... 11

Geologic setting, depositional environments, and geologic history of the Suwannee River 

Delta; Present understanding and proposed work

By A.C. Hine, S.D. Locker, E.E. Wright, and S.L. Goodbred .................................................... 12

Ecological characteristics and forcing functions of the Suwannee River Estuary

By R.E. Edwards and E.A. Raabe................................................................................................ 13

Toward a hydrologic observatory in the Suwannee River watershed

By J.B. Martin 14

WATER QUALITY AND GEOCHEMISTRY

Hydrodynamics and salt transport in the Suwannee River estuary

By J. Bales ..... 16

The impact of nutrient loading and hydrodynamics on algal biomass in the Suwannee 

River Estuary

Understanding contaminant sources, ground-water residence time and flow patterns in a 

karstic springshed

By E.L. Bledsoe and E.J. Philips ................................................................................................. 17

Source tracking and microbial water quality in three Florida springs

By D.W. Griffin and M.A. Gray..................................................................................................... 18

Risk of phosphate movement from soils in the Suwannee River Basin

By W. Harris and V. Nair .............................................................................................................. 19

By B.G. Katz, R. Copeland, T. Greenhalgh, W. Swanka, and S.B. Upchurch....................... 20
Impacts of riparian ecosystems on water quality in the western upper Suwannee 

River watershed

By R. Lowrance, G. Vellidis, D. Bosch, J. Sheridan, R. Williams, and R. Hubbard............. 21

Assessment of nitrate-nitrogen variability in soils of the Santa Fe River watershed in 

north-east Florida

Evidence for rapid transport of recharge from onsite sewage treatment and disposal systems 

to groundwater at Manatee Springs State Park

By E. Roeder, H.S. Harden, J.P. Chanton, and M. Hooks ........................................................ 22

Identifying water-quality domains near Ichetucknee Springs, Columbia County, Florida

By S.B. Upchurch, K.M. Champion, J.C. Schneider, D. Hornsby, and R. Ceryak ................ 24

By S. Lamsal, S. Grunwald, C.M. Bliss, I. Lopez-Zamora, N.B. Comerford, 

and M.W. Clark .............................................................................................................................. 25

ECOSYSTEM DYNAMICS

Long-term and large-scale trends in mercury bioaccumulation in the Suwannee River 

Basin, Florida

By L.C. Chasar, T.R. Lange, J.W. Grubbs, and J.P. Chanton ................................................... 28

Gulf sturgeon

Benthic macroinvertebrate and periphyton monitoring in the Suwannee River Basin in Florida 1: 

Overview and biogeography

Aquatic invertebrate communities as tools for establishing minimum flows and levels in 

Suwannee River Basin streams

By R.A. Brooks, and K. Sulak ...................................................................................................... 29

By R.A. Mattson, D. Wade, and K. Malloy ................................................................................. 30

Benthic monitoring in the Suwannee basin in Florida 2: Relationships between physical and 

chemical variables and biology

By K. Malloy, D. Wade, T. Janicki, and R.A. Mattson .............................................................. 31

Benthic monitoring in the Suwannee basin in Florida 3: Spatial and temporal trends

By D. Wade, K. Malloy, T. Janicki, and R.A. Mattson .............................................................. 32

By G.L. Warren and T. Ferring ..................................................................................................... 33

Submerged aquatic vegetation mapping in the Ichetucknee Springs and river system, Florida

By R.C. Kurz, R.C., P. Sinphay, W.E. Hershfeld, and D.C. Woith ............................................. 34

Factors influencing the submersed aquatic vegetation of the Ichetucknee River

S.K. Notestein and T.K. Frazer. .................................................................................................... 35

Lower Suwannee River floodplain, Florida: Hydrology, topography, and soils of riverine and 

tidal floodplain forests and ecological consequences of potential flow reductions

By H.M. Light . ............................................................................................................................... 36

Structural and dynamic habitat in the Suwannee Estuary: An application of remotely sensed 

imagery to integrated habitat mapping

The Florida Fish and Wildlife Conservation Commission’s Fishery-Independent Monitoring 

Lower Suwannee River floodplain, Florida: Canopy, subcanopy, and ground cover vegetation 

and potential impacts of flow reductions on plant distribution

By M.R. Darst. ............................................................................................................................... 37

By E.A. Raabe, R.E. Edwards, and C.C. McIvor........................................................................ 38

The Florida Salt Marsh Vole on the Lower Suwannee National Wildlife Refuge

By S.E. Barlow, and M.W. Mitchell. ........................................................................................... 39

Program, Cedear Key, Florida

By D. Nemeth. ............................................................................................................................... 40
Gulf Sturgeon - The central role of an iconic species in the Suwannee River Initiative

By R.E. Edwards, K.J. Sulak, M.T. Randall, and R.A. Brooks.................................................. 41

The Florida manatee in the Suwannee River and estuary: Past, present, and future

By C.A. Langtimm, A. Beck, R.K. Bonde, and J.P. Reid ........................................................... 42

Effects of water level fluctuations on year class strength of sport fish in four Florida rivers

By M.S. Allen and T.F. Bonvechio............................................................................................... 44

“Where are the fish?” An angler survey of the Lower Suwannee River

By D.P. Dorosheff .......................................................................................................................... 45

Application of the Physical Habitat Simulation Model (PHABISM) to the Santa Fe River

By E. Nagid, and G. Warren......................................................................................................... 46

INFORMATION MANAGEMENT, MODELING, NEW TOOLS

Suwannee River Partnership

By K.B. Webster............................................................................................................................ 48

Watershed assessment model (WAM) evaluation of the Suwannee River Basin

By A.B. Bottcher, B.M. Jacobson, and J.G. Hiscock. ............................................................. 49

A Suwannee River Basin geodatabase archetype

By A.W. Coffin, and A.M. Foster................................................................................................. 50

Integrating information for watershed management: A Suwannee River Basin watershed atlas

By B.S. Poore. 51

Existing geospatial data sets covering the Suwannee River Basin

By M. Crane ... 52

An airborne high resolution thermal infrared and multi-spectral mapping system trials 

over the Suwannee River Basin, FL (2002)

By D. Stonehouse ......................................................................................................................... 53

POSTERS

Stable carbon and nitrogen isotope composition of organic aggregates produced by salinity 

induced flocculation of dissolved organic matter from the Suwannee River

By E.R. Hall, T.K. Frazer, J.P. Montoya, and J.J. Delfino.......................................................... 56

Utilization of GIS methodologies to evaluate the relationship between land use and aquatic 

ecosystem health

By A.M. Foster, N.J. Kernaghan, and R.A. Mattson ................................................................ 57

Florida’s first magnitude springsheds

By T.H. Greenhalgh ....................................................................................................................... 58

Seagrass mapping within the Big Bend region

By K. Patterson and M. White .................................................................................................... 59

Occurrence of herbicide degradation compounds in streams and ground water in 

agricultural areas of south Georgia, 2002

By J.R. Pittman and M.P. Berndt................................................................................................. 60

Pesticide fate and transport in coastal plain watersheds

By T.L. Potter, D.D. Bosch, D. Sullivan, and R.D. Wauchope.................................................. 61
Map of the Suwannee River Basin

vi
SUWANNEE RIVER BASIN

AND ESTUARY INITIATIVE

In response to the growing number of environmental concerns in the mostly pristine Suwannee 

River Basin and the Suwannee River Estuary system, the States of Florida and Georgia, the Federal 

government, and other local organizations have identified the Suwannee River as an ecosystem in need 

of protection because of its unique biota and important water resources. Organizations with vested 

interests in the region formed a coalition, the Suwannee Basin Interagency Alliance (SBIA), whose 

goals are to promote coordination in the identification, management, and scientific knowledge of the 

natural resources in the basin and estuary. To date, an integrated assessment of the physical, biological, 

and water resources has not been completed. 

A holistic, multi-disciplinary approach is being pursued to address the research needs in the basin 

and estuary and to provide supportive data for meeting management objectives of the entire ecosystem. The USGS is well situated to focus on the larger concerns of the basin and estuary by addressing 

specific research questions linking water supply and quality to ecosystem function and health across 

county and state boundaries. A strategic plan is being prepared in cooperation with Federal, State, and 

local agencies to identify and implement studies to address the most compelling research issues and 

management questions, and to conduct fundamental environmental monitoring studies. 

The USGS, Suwannee River Water Management District and the Florida Marine Research Institute 

are co-sponsoring this scientific workshop on the Suwannee River Basin and Estuary to: 

• Discuss current and past research findings, 

• Identify information gaps and research priorities, and 

• Develop an action plan for coordinated and relevant research activities in the future. 

This workshop builds on the highly successful basin-wide conference sponsored by the Suwannee 

Basin Interagency Alliance that was held three years ago in Live Oak, Florida. This year’s workshop 

will focus on identifying information needs and priorities and developing partnerships. The USGS is 

seeking to define the role of the USGS Florida Integrated Science Center (FISC) in conducting integrated research in the Suwannee River Basin, and to establish a cooperative program with other agencies. 

Participants interested in river, floodplain, springs, estuary, or basin-wide issues are encouraged to 

attend. Topics for this year’s workshop include: 

• Water quality and geochemistry: nutrient enrichment, reduction of nutrient loading to ground 

water, contaminants, and land use, 

• Hydrogeology: interactions among ground water, surface water and ecosystem, modeling, and 

baseline mapping, 

• Ecosystem dynamics: structure, process, species, and habitats (estuarine, riverine, floodplain, 

and wetland), and 

• Information management: data sharing, database development, geographic information system 

(GIS), and basin-wide models. 

vii

HYDROGEOLOGY ISSUES

1
The Future of the Suwannee River Sill –

A Review and Update

Sara B. Aicher

Biologist, Okefenokee National Wildlife Refuge, Rt 2, Box 3330

Folkston, GA Tel. 912-496-7366 ext 236 Fax 912-496-3332 email: sara_aicher@fws.gov

In 1998, an Environmental Assessment of the future management of the Suwannee River Sill was 

completed. The Suwannee River Sill was found to not serve its intended purpose of holding water 

within the Okefenokee Swamp during droughts to reduce the spread of fires. Further, if it did reduce 

fire occurrence, it would be detrimental to the swamp under current management philosophy. The 

preferred action proposed to remove the two existing concrete water control structures and create four 

breaches within the 4.8 mile long earthen levee pending the results of hydrologic monitoring. The U.S. 

Fish and Wildlife Service that has responsibility for the Suwannee River Sill within the boundaries of 

the Okefenokee National Wildlife Refuge (NWR) contracted with the U.S. Geological Survey (USGS) 

to monitor potential downstream effects related to re-establishing a free-flowing river channel as it 

exits from the Okefenokee Swamp. USGS (Giese, 2004) found 1) no significant changes in groundwater levels at wells measured downgradient from the sill, 2) no significant change in concentrations of 

water-quality constituents in flows at the sill, 3) no significant changes in stream water levels downstream from the sill, 4) the sill increased the base water levels immediately upstream of the sill by 

about 6 ft, 5) the sill decreased the peak flows from the sill to Fargo, Georgia, and 6) the sill increased 

the base flows due to reduced gradients within the swamp and leakage through the sill. Based on these 

findings, the preferred alternative will continue to be pursued. Congressional action modifying the 

original sill legislation is needed along with approximately $5 million to complete this wetland restoration project. Natural hydrologic conditions will be partially restored by allowing water to pass freely 

through openings created by the removal of the water control structures and additional breaches. Okefenokee NWR will continue to provide bank fishing opportunities, access to the Suwannee River, and 

promote other recreational opportunities at this location.

Giese, G.L., 2004, Effects of alterations to the Suwannee River sill on the Suwannee River flow and water-quality 

regime, Florida and Georgia, U.S. Geological Survey Open File Report 2004-1237.

2
Surface and Ground Water Mixing along the

Cody Scarp: An Example from the Santa Fe River

Sink-Rise System

Jonathan B. Martin, Elizabeth J. Screaton, and Paul J. Moore,

Department of Geologic Sciences, University of Florida, PO Box 112120, 241 Willliamson Hall 

Gainesville, FL 32611-2120 email: jmartin@geology.ufl.edu screaton@geology.ufl.edu pjm13@ufl.edu

The Cody Scarp represents the erosional edge of the Miocene Hawthorn Group, which confines 

the Floridan aquifer in north-central Florida. The scarp cuts across the Florida Peninsula from northwest to southeast, with the confined Floridan aquifer located to the northeast of the scarp. Surface 

water is common in the confined region but sinks underground where it flows across the Cody Scarp 

onto unconfined Floridan aquifer rocks. At this boundary all streams with the exception of the Suwannee River sink into the subsurface, and the Suwannee River becomes a losing stream at the boundary. 

A good example of a sinking stream at the Cody Scarp is the Santa Fe River. The river is captured by 

a sinkhole at all times except during extreme floods when a portion of the river returns to an overland 

flow path. The river reemerges at the surface at a first magnitude spring ~5 km to the south of where 

it sinks into the subsurface. Numerous karst windows intersect conduits between the River Sink and 

River Rise and a combination of cave diving exploration and chemical and thermal tracing have shown 

that conduits connect the River Sink and River Rise.

Discharge measurements at the River Sink and River Rise demonstrate that during base- and lowflow conditions, more water emerges from the River Rise than flows into the Sink, but during periods 

of high discharge, more water enters the Sink than reemerges at the Rise. These differences in discharge indicate that water is alternately stored and released from the aquifer during variations in flow 

conditions. The most likely location for the storage is in the intergranular porosity of the matrix rocks, 

which for the Floridan aquifer is greater than in many other well studied karst aquifers. Water emerging at the Rise at flood conditions is chemically similar to water flowing into the Sink, which would be 

expected if water flows from the conduits and is stored in the matrix porosity. At base-flow conditions, 

chemical compositions of water discharging from the River Rise differ strongly from water flowing 

into the Sink, which would be expected if substantial amounts of water flow into the conduits from the 

matrix porosity. Although gain and loss of water from the matrix porosity can be measured by differences in discharge at the Sink and Rise, as well as observed in the chemical composition of the water, it 

is more difficult to determine how much water exchanges with the matrix porosity, where this exchange 

may occur, and what conditions control the exchange. The quantity of water exchanged between 

matrix and conduit porosity is critical for protection of the water resources of the Floridan aquifer, but 

information on the quantity of the water that is exchanged might be estimated with an injected dye 

trace study and sampling for monitoring wells close to the conduits.

Eight monitoring wells have been drilled in the gap between the River Sink and River Rise. The 

wells are located at known distances from the conduits and several are instrumented with continuous 

water level recorders. Water levels fluctuate in the wells in response to changes in head in the conduit 

as estimated from water level at the River Rise and reflect pressure pulses from the conduits. Chemical compositions of some of the monitoring wells change only slightly during high discharge events 

suggesting that water flowing from the conduits is not sampled by these wells. Other wells show large 

changes in their composition and may reflect water that has flowed from the conduits into the matrix 

porosity. Differences in the behavior of the wells likely reflect heterogeneous permeability distribution in the Floridan aquifer. Numerous other similar locations where sinking streams are connected to 

springs exist along the Cody Scarp and would provide good locations to compare with results obtained 

from the Santa Fe Sink-Rise system.

3
Using Synthesized Data to Quantify SurfaceWater/Ground-Water Relationships Between

Madison Blue Spring and the Withlacoochee River

of North Florida

James C. Schneider1, Sam B. Upchurch1, Kyle M. Champion1, John Good2, and David Hornsby2

1

SDII Global Corporation, Tampa, FL 

2

Suwannee River Water Management District, Live Oak, FL

Madison Blue Spring is a first magnitude spring located on the western bank of the Withlacoochee 

River in Madison County, Florida. The spring has been the focus of a recent study, with the ultimate 

objective of setting a minimum flow and level (MFL) to protect this resource. A major obstacle in 

this study was the almost complete lack of any hydrologic data for the spring. Nearby gauges on the 

Withlacoochee River were also significantly lacking in data. To overcome this, a time-series of data for 

the river and spring were generated, utilizing all other available and relevant hydrologic data.

At the beginning of this study, the available data set for Madison Blue Spring consisted of 

22 discharge measurements dating from 1932 to 2003. All available related hydrologic data were 

collected and analyzed for potential relationships to river and spring discharge. Unfortunately, most of 

these data coincided temporally with only a small percentage of the 22 spring discharge measurements, 

if at all. Ground-water level data for monitored wells in the spring basin were sporadic and therefore 

not useful. Daily rainfall was available, but a good relationship between this and spring or river 

discharge was not observed. 

Madison Blue Spring contributes a significant portion of the total discharge to the Withlacoochee 

River, particularly during low flows. A relationship between spring discharge and river discharge 

was expected, however, the only gauge located downstream from the spring (the Withlacoochee River 

near Lee) has only been present since late 2000. The closest gauging station, located just upstream 

from the spring (the Withlacoochee River near Madison) has never been regularly monitored. The 

gauges located on the Withlacoochee River near Pinetta (10 miles upstream from the spring) and on the 

Suwannee River at Ellaville (just downstream from the mouth of the Withlacoochee) have been monitored since 1932. Step-wise multiple linear regressions, utilizing the stage data from the Pinetta and 

Ellaville gauges, were used to generate a time-series (1932-2003) of stage data for the gauges near Lee 

and near Madison. 

The Withlacoochee River downstream from Madison Blue Spring frequently experiences backwater conditions due to the nearby confluence with the Suwannee River. Therefore, discharge is often not 

a simple function of stage along this reach of the river, but rather a function of stage and fall (or slope). 

A stage-fall-discharge rating was developed for the gauges on the Withlacoochee River near Madison 

and near Lee. These ratings were used to generate a time-series (1932-2003) of discharge data for 

these two gauges.

Another complicating factor in this study is the fact that Madison Blue Spring is an estavelle; the 

spring is flooded when the river rises above a certain level, and flow can even reverse during large river 

floods. An analysis of the synthesized data for the Madison and Lee gauges shows a complex relationship between surface-water/ground-water interactions, stage at the Withlacoochee River near Madison, 

and the fall on the river (representing the backwater conditions) within this reach. The range of inflows 

to/outflows from the river increases with increasing stage. The range of fall along this reach also 

4
increases with increasing river stage. For a given stage, the river experiences an influx from the aquifer 

below some level of fall, and discharges water to the aquifer above that level of fall.

The 22 Madison Blue Spring discharge measurements were compared with the synthesized 

discharge for the Withlacoochee River near Lee. A good relationship between the two data sets was 

observed; this was used to generate a partial time-series of spring discharge. This relationship was not 

valid at high river discharge (greater than 2500 cfs). Also, a plot of total inflows or outflows to the 

river versus this predicted spring discharge showed this relationship was not accounting for backwater 

conditions. 

A better relationship was found when the 22 Madison Blue Spring discharge measurements were 

plotted against the inflows to the river. Towards the end of this study, some additional spring discharge 

data from a newly installed and calibrated acoustic flow meter became available. Comparison of the 

simulated spring discharge (from the relationship with total inflows to the river) with this new discharge data showed good agreement. This synthesized data set allowed for the determination of a MFL 

for Madison Blue Spring. 

5
Development of Minimum Levels and Flows for

Blue Spring, Madison County, Florida

Sam Upchurch1, Mark Farrell2, Anthony Janicki3, John Good4, Rob Mattson4, David Hornsby4,

James Schneider1

, David Wade3, and Kate Malloy3

1

 SDII Global Corporation, 4509 George Rd., Tampa, FL 33634

2

 Water Resource Associates, Inc., 14502 N. Dale Mabry Hwy., Ste 226, Tampa, FL 33618

3

 Janicki Environmental, Inc., 1155 Eden Isle Drive, N.E., St. Petersburg, FL 33704 

4

 Suwannee River Water Management District, 9225 County Road 49, Live Oak, FL 32060

As required by Florida Statutes (§373.042 F.S.), the Suwannee River Water Management District 

(SRWMD) is currently developing minimum flows and levels (MFLs) for surface water bodies and 

springs within the District. The first spring in the SRWMD for which a MFL is being developed is 

Madison Blue Spring (MBS), a first-magnitude spring located in Madison County, Florida. The spring 

consists of a single vent on the west bank of the Withlacoochee River, which is a major tributary of the 

Suwannee River.

As described by Schneider (this symposium), there was little discharge or stage data from the 

spring, and the spring is an estevelle, so spring discharge reverses at high river stages. Consequently, 

stage and discharge data from gauges on the river were used to simulate spring discharge and stage 

data. Simulated river and spring data closely fit measurement data, indicating a high level of confidence in the simulated data. The data are also consistent with ground-water data from within the 

springshed.

The river exhibits hysteresis and backwater effects as it interacts with the Suwannee and the karstic 

limestone that makes up the river channel. Because of the estevelle behavior of the spring, river and 

spring discharge data were stratified to isolate low spring discharge as a result of high river stage from 

analysis. Flow duration analysis of the measured and synthesized spring and river data was utilized to 

determine the duration of occurrence of low flows and the relative contributions of spring discharge to 

the river during low-flow events. At low river stage, MBS appears to contribute approximately 

25 percent of the base flow in the river. Therefore, it was determined that reductions in MBS discharge 

may create adverse consequences to river water quality or ecological conditions.

As part of the study, six representative shoals in the river downstream from MBS were surveyed 

to determine depths for fish passage and total area of wetted shoal, which constitutes important aquatic 

habitat for benthic invertebrates and algae. These data were utilized in conjunction with historic and 

simulated discharge and stage data to simulate low-flow conditions and identify event durations and 

frequencies with HEC-RAS. Since MBS contributes significant percentages of the river water downstream from the spring during low-flow conditions, the spring’s ability to maintain these habitats was 

considered an important factor for MFL development.

Based on the 10 ecological and water-resource “values” suggested for determination of 

“significant harm” according to Section 62-40.473 Florida Administrative Code, five potential 

applicable values were identified for determination of significant harm. These values were, in order 

of decreasing priority: (1) fish and wildlife habitats and the passage of fish, (2) maintenance of freshwater storage and supply, (3) recreation in and on the water, (4) aesthetic and scenic attributes, and, 

possibly, (5) water quality. It was determined that the effects of MBS discharge on water quality in the 

Withlacoochee River did not result in a potential for significant harm. Since MBS is a first magnitude 

spring and a Florida State Park, maintenance of first magnitude status was considered important for 

water supply, recreational, and aesthetic reasons, but identification of significant harm criteria based 

6
on ecological needs to justify maintenance of first magnitude status could not be established at this 

time. A critical, low-flow MFL was identified for the spring that will prevent significant harm to fish 

and wildlife habitats (i.e., total wetted shoal area) and protect the passage of fish during low flow in the 

river.

Simulations of the number and duration of potential minimum MBS discharge events and 

comparisons with predicted inundation of the shoals and water depths in channels utilized for fish 

passage were utilized to determine the minimum MBS discharge that would support appropriate depths 

over shoals and in channels within the shoals while preserving the first magnitude spring status of 

MBS. Thus, maintenance of fish and wildlife habitats and the passage of fish in the Withlacoochee 

River downstream of MBS were chosen as the principal values for which significant harm could be 

demonstrated and an MFL could be developed.

The proposed MFL has been peer reviewed on behalf of the District, and is presently being 

considered by District staff.

7
Delineation of the Fanning and Manatee Spring

Basins in the Suwannee River Water

Management District

Ron Ceryak, P.G.

Suwannee River Water Management District, 9225 CR 49, Live Oak FL 32060 

email: ceryak_r@srwmd.state.fl.us

Fanning Springs and Manatee Springs are first magnitude (flow > 100 cfs) springs that flow from 

the Floridan aquifer into the Suwannee River in Levy County, Florida. Increasing concentrations of 

nitrate in spring discharge has prompted the FDEP and the SRWMD to begin a “District Springs Initiative” project, designed to identify the areas in the spring basin that are most vulnerable in terms of 

recharge and contamination of ground water traveling to the springs. This information will lead to the 

development of a final management plan for each spring basin.

The first step in the process was to attempt to delineate the spring basin. The primary methodology was to create a dense ground-water levels network that would define the potentiometric surface on 

one – foot contour intervals. This task was complicated by the presence of a diurnal tidal influence that 

can reach a magnitude of 1.5 feet. The flow lines derived from the potentiometric contours define the 

spring basins. Ground-water chemistry, cave maps, and topography also enhance the understanding of 

ground-water flow to the springs.

8
Extension of Minimum Flows from the

Lower Suwannee River to Upstream Tributaries

and Springs using a Reach-based Method

John Good and Rob Mattson

Suwannee River Water Management District, 9225 CR 49, Live Oak, FL 32060

email: ceryak_r@srwmd.state.fl.us

The purpose of this paper is to present an approach being considered by the Suwannee River Water 

Management District (SRWMD) to extend minimum flows and levels (MFLs) being established for the 

lower Suwannee River under §373.042, Florida Statutes (F.S.), to associated upstream tributaries and 

springs.

For a river system it is possible to establish river MFLs at a downstream location of interest 

(typically at a long-term gage), and then use that control and regulate all withdrawals upstream to the 

headwaters. In 1993, the SRWMD began a research project to obtain the data necessary for adequate 

determination of MFLs for the lower Suwannee River. This effort is nearing completion. However, for 

a large river system like the Suwannee, which crosses varying physiographic regions with 

multiple large and small tributaries, with a high degree of ground-water/surface-water interaction, and 

high ecological diversity, the possibility exists that an important upstream ecological value could be 

compromised without different regulatory levels than those provided by the downstream control 

location.

Recognizing this problem, in 2003 District staff were charged with developing a methodology 

for efficiently determining MFLs throughout the District, especially for the Suwannee basin. The 

approach was to be implemented quickly (within five years), with minimal field work beyond that 

currently underway as part of the District’s normal data collection networks. The approach also had 

to include setting MFLs for the many springs in the region. For the Suwannee River and associated 

springs this meant finding a way to leverage the intensive data collection and study efforts that have 

been expended in the lower Suwannee River into a basin-wide effort, from downstream to upstream. 

The methodology was initially conceived for use on the rivers like those of the SRWMD, which 

have two key characteristics. First, they are structurally unregulated, and will likely remain so into the 

foreseeable future under current District goals and management programs. Second, District rivers, and 

the Suwannee system in particular, exhibit a high degree of ground-water/surface-water interaction. 

For many reaches the only pickup is from ground-water discharge; for all practical purposes direct 

surface water runoff doesn’t occur.

In understanding the proposed method, it should also be recognized that the District is pursuing 

a multiple minimum flow and level, or a minimum flow regime, as opposed to a single valued MFL. 

This results in an MFL-based time series that represents the historic river flow pattern at a gage as if 

the MFLs had been in place during the period of record and all water flow exceeding the MFL time 

series had been withdrawn.

Given the prior establishment of an MFL regime at a downstream location, the first step in the 

method is a desktop procedure; an upstream reach is identified, then the downstream MFL is projected 

to the upstream location at the head of the reach using a relatively simple hydraulic calculation. One 

method for accomplishing this follows. From the historic and MFL time series, flow duration curves 

(FDCs) are constructed. For each exceedance probability the ratio of MFL discharge to historic 

9
discharge is determined. These ratios are then applied to the historic FDC at the upstream location 

establishing an upstream MFL FDC. This FDC can then be inverted to construct the upstream MFL 

time series. Thus four time series result: the historic and MFL series at both the head and bottom of a 

river reach.

The next step in the approach is to check the proposed upstream MFL against the water requirements of any environmental values within the reach. Any local ecological values in the reach were not 

included in the establishment of the downstream MFL and may not be adequately protected by the 

initial proposed regime. If any such ecological considerations are identified, the MFL regime is 

modified as necessary to include adequate protection.

Once the upstream and downstream MFL regimes are final, the allocable water in a reach and the 

reach MFL can be computed. This is done by determining the ground-water pickup in the reach under 

both historic and MFL conditions. The allocable water is the difference between the historic flow 

pickup and the MFL pickup. The reach MFL is the ratio between the MFL pickup and the historic 

pickup. At this point the task for water managers becomes one of evaluating the cumulative impact of 

withdrawals versus the allocable water and reach MFL.

However, in any given reach points of interest (such as springs) may exist for which point-specific 

protection is required. Discrete spring vents may have special characteristics; magnitude, ownership, 

threat, etc., or supports a specific environmental value in or near their run or discharge point that needs 

protection. Such springs would have specific MFLs established based on the characteristics needing 

protection.

For other springs that have no specific characteristic needing protection the MFL would be based 

on the cumulative reach MFL ratio (R) defined above. For example, withdrawals in the ‘springshed’ of 

one of these springs would not be allowed to reduce the flow of the spring (as determined under 

non-backwater, free-flowing conditions) to less than R percent of its unimpacted (or historic) flow at 

any time. The rational behind this approach is the assumption that many springs serve the primary 

purpose of supporting the stream base flow, and thus the environment of instream locations, and have 

no inherent site-specific resources requiring protection above and beyond that of the reach itself.

Once the reach MFL and any specific spring MFLs are set the entire process is repeated for the 

next upstream location of interest. In this way interim MFLs at all contributory points of interest in the 

river are established.

The proposed methodology is under review for further development by the District.

10
Exchanges of Water Between the Upper

Floridan Aquifer and the Lower Suwannee

and Lower Santa Fe Rivers, Florida

J.W. Grubbs and C.A. Crandall

U.S. Geological Survey, Tallahassee, FL

Exchanges of water between the Upper Floridan aquifer and the Lower Suwannee River were 

evaluated using historic and recently collected hydrologic data from the Lower Suwannee River Basin 

and adjacent areas which contribute ground-water flow to the lowest 76 miles of the Suwannee River 

and the lowest 28 miles of the Santa Fe River. These and other data were also used to develop a computer model that simulated the movement of water in the aquifer and river, and surface-water/groundwater exchanges between these systems over a range of hydrologic conditions and a set of hypothetical 

water-use scenarios.

Long-term data indicate that at least 15 percent of the average annual flow in the Suwannee River 

near Wilcox (at river mile 36) is derived from ground-water discharge to the Lower Suwannee and 

Lower Santa Fe Rivers. Model simulations of ground-water flow to this reach during water years 1998 

and 1999 were similar to these model-independent estimates, and indicated that ground-water discharge 

accounted for about 12 percent of the flow in the Lower Suwannee River during this time period.

The simulated average ground-water discharge to the Lower Suwannee River downstream from the 

mouth of the Santa Fe River was about 2,000 cubic feet per second during water years 1998 and 1999. 

Simulated monthly average ground-water discharge rates to this reach ranged from about 1,500 to 

3,200 cubic feet per second. These temporal variations in ground-water discharge were associated with 

climatic phenomena, including periods of strong influence by El Niño-associated flooding, and 

La Niña-associated drought. These variations showed a fairly consistent pattern in which the lowest 

rates of ground-water inflow occurred during periods of peak flood levels, when river levels rise faster 

than ground-water levels, and after periods of extended droughts, when ground-water storage was 

depleted. Conversely, the highest rates of ground-water inflow typically occurred during periods of 

receding levels that followed peak river levels.

11
Geologic Setting, Depositional Environments, and

Geologic History of the Suwannee River Delta;

Present Understanding and Proposed Work

A.C. Hine1, S.D. Locker1, E.E. Wright2, and S.L. Goodbred3

1 College of Marine Science, University of South Florida, St. Petersburg, FL 33701

2 Department of Marine Science, Coastal Carolina University, Conway, SC 29526

3 Marine Science Research Center, State University of New York, Stony Brook, NY 11794

Research along the 300 km-long, Big Bend coast of northwest Florida in the 1980s and mid1990’s by our group has defined the overall geologic setting and primary processes active along this 

low-energy, sediment-starved, marsh-dominated coastline. The Big Bend coast is generally a Juncas 

roemerianus marsh supported by a thin (0-2 m thick) organic -rich mud veneer overlying an irregular 

karstified limestone surface. Fine-grained sediments are recycled by being eroded along the marsh 

front facing the open Gulf of Mexico and carried back onto the marsh top through the tidal creeks. 

This bedrock surface consisting of sinkholes, springs, dissolved fracture lines, and elevated rocky nubs, 

control coastal morphology, distribution and pattern of tidal creeks, and the distribution of plants. This 

incipient, epicontinental sea coastline lacks barrier islands and tidal inlets seen to the north and the 

south due to the regional absence of sand-sized sediments. 

At the center of this coastline is the Suwannee River Delta—the only significant point source of 

sediment in the Big Bend area. The result is a marsh/tidal creek system dominated by sands thus reducing the influence of the underlying bedrock as compared to the rest of the Big Bend coastline. The 

influx of fresh water from the river insures the development of large oyster bioherms. During sea-level 

lowstands, the Suwannee River extended at least 20 km out across the modern shelf. Additionally, arid 

conditions at that time allowed parabolic dunes to form. During the ensuing sea-level rise, these sandy 

eolian bedforms were flooded forming today’s underwater, seagrass-dominated sand shoals, sandy 

beaches, and elevated marsh islands covered by less salt-tolerant plants such as pines, oaks, palmettos, 

and other indigenous species.

This previous work provides the basis for launching new research to define the distribution of benthic environments and habitats both in the nearshore delta, into the estuary and up the Suwannee River 

itself. New technologies and techniques such as very shallow-water, very high- resolution seismic and 

side-scan sonar profiling, as well as acoustic bottom classification techniques, allow us to develop very 

accurate and detailed benthic habitat maps on spatial scales previously unattained. A decade ago, using 

uncontrolled (not georeferenced) analog side-scan sonar, we were able to demonstrate the complexity 

of estuarine/riverbed substrate types. Distinct and predictable patterns of active bedform-mantled sand 

bodies and exposed bedrock surfaces revealing fracture patterns were clearly shown on the bottom. 

We propose that a new map series of the delta front—inner shelf/estuarine/riverbed be generated using 

a package of multiple, digital geoacoustic tools tied to meter-scale navigation accuracy. Such a map 

would be ground-truthed using bottom sampling techniques with appropriate laboratory analysis. A 

data product would provide the spatial distribution of benthic environments, which could be overlain 

by the benthic biology providing a benchmark for comparison for future years to detect and measure 

temporal changes.

12
Ecological Characteristics and Forcing

Functions of the Suwannee River Estuary

Randy E. Edwards1, Ellen A. Raabe2

1

University of South Florida, College of Marine Science, St. Petersburg, FL

2

U.S. Geological Survey, Center for Coastal and Watershed Studies, 

Florida Integrated Science Center, St. Petersburg, FL

The limited scientific information available about the Suwannee River Estuary System (SRES) 

indicates that its ecology is controlled by a suite of physical characteristics and ecological forcing 

functions that distinguish it from most rivers and estuaries in the southeast. The Suwannee River forms 

a large, unusual estuarine system at its confluence with the Gulf of Mexico. The greatest area of 

estuarine conditions is everted, lying outside the river mouth along an open coast. This main estuarine 

zone, Suwannee Sound, is a shallow offshore area enclosed by a semi-continuous arc of oyster reefs. 

Within the river, transition from high to low salinity usually occurs over very short distances. A subsystem of tidal creeks and marshes south of the river mouth comprise another component of the estuary 

and receives fresh water from different sources and under various conditions. At high-river stage, 

fresh water overflows the low-elevation marshes to the south and flows into estuarine tributaries. This 

major forcing function of freshwater inflow at high-river stage subjects vast areas south of the river to a 

relatively sudden transition from estuarine to freshwater conditions. At lower stage, estuarine tributaries receive fresh water from possibly substantial, but yet unidentified, ground-water inflow. At almost 

all stages, the estuarine tributaries, especially to the south, receive some fresh water on incoming tides 

via tidal advection of discharged Suwannee fresh water, as mixed masses or lenses of fresh water. The 

hydrologic forcing functions of direct flow, ground-water inflow, and freshwater advection, result in 

complex physical and ecological dynamics in the estuary and intertidal zone. These dynamics are 

further complicated by tide, which also is an important forcing function, due to its 1-m range, distinct 

seasonal patterns, and wind-driven characteristics. Seasonality of freshwater inflow is another unusual 

characteristic of the SRES. Most estuarine systems in the region experience lowest salinity levels during the meteorological “wet season,” typically starting around June and peaking in September. 

However, peak-stage conditions in the Suwannee typically occur in March or April, resulting in low 

salinities during the spring, when other regional estuaries experience high salinities. The reverse is true 

in mid- or late summer, when SRES salinity is high due to low river stage, and salinity in other 

estuaries is low. The seasonal difference is undoubtedly significant to estuarine fauna and flora. 

Additionally, low-gradient topography and open coastline expose the SRES to episodic major storm 

surges of high-salinity water that also can impact flora and fauna. Low topography makes the SRES 

highly sensitive to surface alterations, such as roads, that interrupt local freshwater inflow, impound 

saline waters, and result in forest morbidity. The SRES is a unique, highly productive, and valuable 

ecosystem that arises from an unusual combination of physical, geological, hydrological, and biological factors. Thorough study and assessment of this large and important system is necessary if it is to 

be well understood, managed, and conserved.

13
Toward a Hydrologic Observatory in the

Suwannee River Watershed

Jonathan B. Martin1 and Wendy Graham2

1

Department of Geologic Sciences, University of Florida, P.O. Box 112120, 241 Willliamson Hall 

Gainesville, FL 32611-2120 email: jmartin@geology.ufl.edu 2

Department of Agricultural and Biological Engineering, University of FL, P.O. Box 110570 

120 Rogers Hall, Gainesville, FL 32611-0570 email: wgraham@ufl.edu

The Consortium of Universities for the Advancement of Hydrologic Sciences (CUASHI) is a 

non-profit organization incorporated June 2001 in Washington DC and funded entirely by the National 

Science Foundation (NSF). Its purpose broadly includes coordinating hydrologic research efforts in 

the US through advisement to the NSF and by developing program ideas and managing infrastructure. 

CUASHI is organized around a concept called HydroView which is composed of four elements: 

Information Systems, Data Synthesis, Instrumentation infrastructure, and Hydrologic Observatories. 

Each of these elements is interlinked with data gathering programs organized around Hydrologic 

Observatories, which are to be developed within an individual watershed, focusing on the hydrologic 

cycle. NSF expects to fund two Hydrologic Observatories following evaluation of proposals to be 

submitted in spring 2004.. Three additional observatories will be funded each year between 2008 and 

2010. Support for observatories is planned to consist of approximately $3 million annually for 

operating expenses and $10 million over five years for infrastructure development.

The overarching design concept of hydrologic observatories is that they will serve as a 

community resource with core data collected and made available through a common interface, equal 

access to the site, and support for remote investigators. The observatories will be sufficiently large 

to explore all interfaces including land surface and atmosphere impacts on global circulation models. 

Consequently, observatories are expected to be at a minimum 10,000 km2

. The five observatories will 

be linked in a national network, with common data collected and exchanged throughout the network. 

The observatories will be overseen by Observatory Design Teams that will determine the best way 

to characterize the site, delineate core data, and develop a work plan for data collection. The daily 

operation of the observatory will be conducted by a professional staff led by a director and technicians 

capable of field data collection, data handling, and information technology.

A group of researchers from Florida and Georgia plan to propose the Suwannee River watershed 

as a Hydrologic Observatory. At present, the group includes faculty from UF, FSU, USF, and UGa and 

staff from Suwannee River Water Management District, USDA-ARS, and USGS. The Suwannee River 

is ideal for an observatory, in part because it is the last major river in the United States with unrestricted 

flow and good water quality. This pristine nature is threatened by rapid population growth. The watershed is divided into confined and unconfined regions at the Cody Escarpment leading to variable but 

extensive interactions between ground and surface waters, including the world’s greatest density of first 

magnitude springs. In selected regions across the watershed, long-term site-specific programs study 

and collect data to address linkages between water quality, water storage, water and nutrient fluxes, 

ecosystems, and environmental stressors. No centralized program links, compares, or coordinates these 

efforts. A Suwannee River Hydrologic Observatory could provide that centralized program and linkages to the USGS Suwannee River Basin and Estuary Initiative would strengthen both programs.

14
WATER QUALITY AND GEOCHEMISTRY

15
Hydrodynamics and Salt Transport

in the Suwannee River Estuary

Jerad Bales

U.S. Geological Survey, Raleigh, NC

Living resources in the Suwannee River estuary are highly dependent on the presence of a suitable 

salinity regime for habitat, growth, and reproduction. Salinity, in turn, is affected by a complex interaction among tides, weather, river flow, ground-water discharge, morphology, and perhaps vegetation. 

Such a dynamic system is difficult to measure in sufficient spatial and temporal detail to understand the 

individual roles of each of these controlling processes. Hence, determination of the effects of a change 

in one or more of the physical processes controlling the salinity regime requires application of a predictive model that has been accurately calibrated to current conditions and can be confidently applied to 

possible future scenarios. 

A three-dimensional, unsteady, numerical model of hydrodynamics and salt transport in the 

Suwannee River estuary was developed by the U.S. Geological Survey, in cooperation with the 

Suwannee River Water Management District. The model includes the capability to predict timevarying water level, currents, and salinity on an orthogonal, curvilinear, finite-difference grid. 

Computational cell sizes range from about 60 meters by 60 meters in the river to about 1,000 meters 

by 1,000 meters in the western part of the model domain in the Gulf of Mexico. A total of 2,385 

computational cells are contained within each of the 6 model layers. The model domain includes the 

downstream-most 10 kilometers of the Suwannee River, including East, West, Alligator, Wadley, and 

Northern Passes. From the mouth of Alligator Pass, the model domain extends northward along the 

Gulf of Mexico shoreline about 23 kilometers to Horseshoe Point, southward about 26 kilometers to 

Piney Point, and westward about 20 kilometers into the Gulf of Mexico. 

The model was developed and tested using comprehensive data on water level, velocity, flow, and 

salinity. The primary data-collection period extended from October 1999 through September 2000. 

Hydrologic data included continuous (15-minute interval) measurements of water level at 5 sites in the 

study area, flow velocity at 3 locations, flow calculated from velocity and water level at 3 locations, 

wind speed and direction at 1 site, and near-surface and near-bottom salinity at 6 locations in the study 

area. In addition, vertical profiles of water temperature and salinity were measured at 15 sites more 

than 50 times under a wide range of flow and tidal conditions. 

Water levels were simulated accurately (generally within 0.1 meter of measured values, with very 

little phase shift) at all measurement sites. The accuracy of simulated flows varied over the tidal cycle, 

with more accurate simulations for flood flows than ebb flows; similarly, simulated flows during neap 

tides were more accurate than those during spring tides. Within the river, simulated salinities were 

more accurate for West Pass than East Pass. Simulated top-to-bottom differences in salinity were in 

good agreement with measurements, but simulated salinities generally were lower than measured 

values. Measured and simulated salinities were within 1 – 3 parts per thousand at Red Bank Reef, 

located in the Gulf about 2 kilometers from the mouth of the river. The model currently is being 

applied by the Suwannee River Water Management District to simulate the effects of changes in low 

flows on salinities at key locations in the river and nearshore areas. The model could also prove useful 

in simulating the nutrient transport in the Suwannee, coupling delivery from terrestrial and atmospheric 

sources to estuarine response, with the addition of appropriate water-quality algorithms.

Ground-water discharge to the model domain is not included in the model. Although there is currently little data on ground-water discharge rates, addition of this source of freshwater could produce 

more realistic simulations. Likewise, addition of the many small tidal creeks and drainages located 

along the Gulf of Mexico shoreline within the model domain could improve model performance in 

those areas. Currently, the only source of freshwater in the model is the Suwannee River. 

16
The Impact of Nutrient Loading and

Hydrodynamics on Algal Biomass in the

Suwannee River Estuary

E.L. Bledsoe and E.J. Phlips

University of Florida, Dept. of Fisheries and Aquatic Sciences, 7922 NW 71st Street, Gainesville, FL 32653 

Tel. (352) 392-9617 email: spider4@ufl.edu phlips@ufl.edu

Like many estuaries subject to major riverine inputs, the ecology of the Suwannee River Estuary is 

closely tied to the water quality characteristics of the Suwannee River. Nutrients entering the 

estuary from the river support primary production, but in excess can also lead to significant environmental problems like algal blooms. In an effort to address the consequences of nutrient loading, the 

objective of this study was to define the relationships between changes in nutrient loading and the 

response in algal biomass. 

Prior studies of the Suwannee River and its estuary indicate high nutrient concentrations in the 

Suwannee River and subsequent transport and use of these nutrients in the estuary. We hypothesized 

that algal biomass would be related to spatial and temporal patterns of nutrient availability. The results 

from the first year of our study generally supported this hypothesis. Shifts in the algal assemblages, 

however, suggested the role of major meteorological events, such as El Niño and La Niña in altering 

the basic features (e.g., color, flow rate and depth) of the river and estuary. 

Hydrodynamic properties such as tidal amplitudes, riverine outflow and current patterns also 

influence the spatial patterns and abundance of phytoplankton biomass. Flushing rates are a major 

factor in the control of phytoplankton standing crop in the Suwannee River estuary. Regions of the 

estuary within the oyster reefs exhibited enhanced phytoplankton biomass, indicating nutrient availability and the potential for slower flushing rates. Periods of exceptionally high phytoplankton biomass 

(> 30 μg chl L-1) were associated with on-shore wind events that may decrease flushing rates within the 

estuary. 

The consequences of nutrient loading from natural and anthropogenic sources within the watershed are of great concern to the ecological state of the Suwannee River and estuary. From this study, 

it is clear that large-scale meteorological events such as drought events affect the spatial and temporal 

abundance and composition of primary producer communities. The results from this study could be 

used to help water managers in their effort to set meaningful and reasonable targets for nutrient loading, as well as for land managers in fulfilling their responsibility to guide future agricultural and urban 

development in the region. 

17
Source Tracking and Microbial Water Quality

in Three Florida Springs

Dale W. Griffin and Mike A. Gray

USGS, 600 4th St. South, St. Petersburg, FL 33701

Microbiological sampling and viral-source tracking were conducted in tandem with geochemical 

studies at Hornsby, Poe, and Manatee Springs. Standard and alternate microbial water quality indicators (fecal coliforms, E. coli, Clostridium perfringens and enterococci) were used to screen water 

samples to determine if spring waters (Poe and Hornsby Springs) were being impacted by fecal 

sources. Source tracking assays were employed to differentiate between human and animal (agricultural) fecal contamination using human- and bovine-specific virus assays. Microbial data sets from 

three sample dates demonstrated good water quality (at drinking-water standard levels for Hornsby and 

Poe Springs) on the first two dates. On the third date, elevated indicator numbers were observed at all 

of the sites. In addition, human enteroviruses were detected in all of the springs on the third date via 

reverse transcriptase-polymerase chain reaction. These data indicate that water emanating from these 

springs may be susceptible to sporadic contamination by human wastewater through local groundwater-recharge dynamics. 

18
Risk of Phosphate Movement from Soils

in the Suwannee River Basin

Willie Harris and Vimala Nair

Soil and Water Science Department, P.O. Box 110290, University of Florida 

Gainesville, FL 32611-0290 email: apatite@ufl.edu vdna@ifas.ufl.edu

The karst areas within the Suwannee River Basin (SRB) are vulnerable to transport of 

agriculturally-applied nitrate and phosphate (P) that could potentially have ecological impacts on 

springs and ultimately the Suwannee River estuary. Risk of impact is heightened by karst hydrology 

and the sandy, permeable nature of soils that occur above the limestone. Nutrients move vertically in 

these areas such that runoff-based risk assessment models are not applicable. The vertical pathway 

means that soil retention capacity for nutrients exerts far greater control of mobility than is the case 

for a surface runoff pathway. Nitrate contamination risks are particularly acute in the SRB because of 

minimum denitrification and very low retention by soils. Therefore, nitrate is an immediate health and 

environmental concern. However, excessive P application could also ultimately result in environmental 

problems. Phosphate is reactive with soils and its “breakthrough” at springs would take longer than 

nitrate, but once it reached springs its influence would continue for a much longer time than in the case 

of nitrate. The degree to which phosphate is being retained in four SRB soils is being monitored over 

a 36-month period of manure (dairy wastewater and poultry solids) application. Data collected thus far 

suggest that the safe “lifespan” of a manure application site can be predicted with reasonable accuracy 

given sufficient knowledge of soil and loading variables. This lifespan is influenced by soil factors such 

as P retention capacity and previous loading history. Even a site with minimum previous P application 

may have a short safe P-application lifespan (e.g., a few years) if P retention capacity is low. Vertical 

P movement continues slowly even after application ceases. Therefore, applications should be discontinued before the measured P migration reaches the depth of concern, in order to minimize the risk of 

eventual elevated solution P concentrations at that depth. The latter requires a mindset of planning to 

avoid future problems. 

19
Understanding Contaminant Sources,

Ground-Water Residence Time and Flow

Patterns in a Karstic Springshed

Katz, B.G.1 , Copeland, R.,2 Greenhalgh, T.2, Zwanka, W.,3 and Upchurch, S.4

1

U.S. Geological Survey, 2010 Levy Ave., Tallahassee, FL 32310 email: bkatz@usgs.gov 2

Florida Geological Survey, Tallahassee, FL

3

Suwannee River Water Management District, Live Oak, FL

4

SDII Global Corp., Tampa, FL

Human health and ecological concerns have arisen due to a steady increase in nitrate-N 

concentrations (0.29 to 4.5 mg/L) during the past 40 years in Fannin Springs, a regional discharge 

point (mean flow 2.8 m3

/s) for water from the karstic Upper Floridan aquifer (UFA). Multiple chemical tracers (3

H/3He, CFCs, SF6, 15N and 18O of nitrate; dissolved gases; 66 pesticides and degradates; 

and 64 organic compounds typically found in domestic and industrial wastewater) were analyzed in 

samples from three ground-water flow transects and in spring water to identify contaminant sources 

and estimate ground-water age. A preliminary ground-water contributing area for Fannin Springs 

(590 km2

) was delineated from a potentiometric surface map (0.3 m contours) of the UFA based on 

high-resolution water level data. Nitrate-N concentrations were highly variable in the oxic UFA and 

ranged from <0.02 to 4.7 mg/L. Delta 15N-NO3

 values (3.4 to 9.9‰) indicated that local sources of 

nitrate included both inorganic fertilizer and human/animal wastes. Higher nitrate concentrations in 

spring water relative to water from upgradient wells indicate that fertilizers or septic tank effluent 

inputs likely enter parts of the aquifer that contain conduits close to the spring. Other evidence for 

agricultural sources included the presence of atrazine at slightly above or below analytical reporting 

limits (0.007 μg/L) in water from Fannin Springs and three upgradient wells. An atrazine degradate, 

deethylatrazine, was detected at concentrations less than 0.006 μg/L in the spring water and in one well 

water sample. Wastewater sources of contaminants to ground water included the quantifiable presence of very low concentrations of disinfectants, fragrances, flame retardants, and insect repellants.

Estimated recharge ages were younger in ground-water samples taken closer to the spring (<8 years 

compared to 10-50 years for water from other wells) indicating that these wells likely intersect conduits 

containing more recent recharge. 

20
Impacts of Riparian Ecosystems on

Water Quality in the Western

Upper Suwannee River Watershed

Richard Lowrance1, George Vellidis2, David Bosch1, Joseph Sheridan1,

Randall Williams1

, Robert Hubbard1

1

Ecologist, USDA-ARS

2

Professor, University of Georgia 

1

Hydrologist, USDA-ARS

1

Hydraulic Engineer, USDA-ARS 

1

Agricultural Engineer, USDA-ARS

1

Soil Scientist, USDA-ARS 

Riparian ecosystems strongly influence the quantity and quality of water in streams forming the 

western portion of the upper Suwannee River Watershed. The Withlacoochee, Alapaha, and Little 

Rivers begin in the Tifton-Vidalia upland in Georgia and their upper reaches are dominated by direct 

surface runoff and interactions with shallow surficial ground water. In many of these watersheds, 

naturally occurring riparian forest ecosystems typically comprise about 30 percent of the watershed 

area and agriculture including row-crops and pastures comprise about 70 percent of the watershed. 

In this watershed setting, riparian zones have been shown to retain 68 percent of the N, 30 percent 

of the P, 39 percent of the Ca, 23 percent of the Mg, and 6 percent of the K that is being transported 

from surrounding agricultural areas of the watershed. On a mass basis, denitrification and vegetation 

uptake were of similar importance for N removal. Very poorly drained soils had higher potential than 

poorly drained ones to remove nitrate by denitrification and could remove more than the present load 

of nitrate. Watershed scale studies of existing forest buffers showed that long-term sediment deposition rates ranged from 35 to 256 Mg/ha/yr, consistent with the low-sediment delivery ratios for Coastal 

Plain streams. When implemented as part of farm scale landscape management, managed and restored 

forest and grass buffers controlled nitrogen and phosphorus movement from conventional row crops 

and from areas of intensive manure management including dairy and swine lagoon effluent applications. Managed and restored forest and grass buffers also removed herbicides (atrazine and alachlor), 

that moved primarily in the dissolved phase of surface runoff from row crops. Because of land use patterns that have tended to preserve naturally occurring riparian forest buffers there is not a general need 

for riparian ecosystem restoration in the western upper Suwannee Watershed. But, understanding and 

modeling chemical and sediment transport from these heavily agricultural watersheds requires understanding and modeling the impacts of riparian zones. 

21
Evidence for Rapid Transport of Recharge from

Onsite Sewage Treatment and Disposal Systems

to Ground Water at Manatee Springs State Park

Eberhard Roeder1, Harmon S. Harden2, Jeffrey P. Chanton2, Mark Hooks1

1

Florida Department of Health Bureau of Onsite Sewage Programs Bin #A08, 4052 Bald Cypress Way, 

Tallahassee, FL 32399-1317

2

Department of Oceanography, Florida State University Tallahassee, FL 32306-4320 

Given the karstic nature of much of the Suwannee watershed, recharging water should reach 

ground water quickly. Rapid transport, e.g., via conduit flow, also limits the potential for natural 

attenuation of any contamination present in the recharging water. These hypotheses, rapid transport and limited attenuation, were investigated at two onsite sewage treatment and disposal system 

(OSTDS) sites at Manatee Springs State Park, Levy County, in 2003/2004.

Two conventional septic systems with drainfields at the Magnolia and Hickory campgrounds were 

studied. Magnolia represents a river front landscape position with a shallow water table, while Hickory 

represents a more upland/hammock situation with a deep water table. Ground Penetrating Radar surveys at both sites indicated the presence of paleo-sinkholes. Monitoring wells with 10-ft screens were 

installed downstream of the drainfields in shallow ground water. One monitoring well at the Hickory 

site was installed into a paleo-sinkhole. Tracer tests, one at each location, consisted of injections of 

50-gallon slugs of water containing two tracers, sulfur hexafluoride and fluorescein, into the drainfield. 

Monitoring wells were sampled for the tracers for up to a year. Sampling of the monitoring wells 

for nitrate, nitrite, ammonia, TKN, total phosphorous and fecal coliforms continued over a one-year 

period. 

The results of this study clearly confirmed that there are rapid connections between the nearsurface drainfields and the underlying karst aquifer at both the OSTDS sites. Tracer was observed 

at each site in monitoring wells within hours of the injection into the drainfields. Flow velocities, as 

determined by traveltimes to individual monitoring wells, were in tens of feet per day. At Magnolia 

campground, flow rates varied from 5 to 100 feet per day and at Hickory campground they varied from 

1 to 280 ft/day. Tracer from the Hickory tracer test was detected in Manatee Spring shortly after the 

beginning of the test.

On the other hand, the complexity of transport in karst, likely due to multiple porosities, was 

indicated by more than one peak in many monitoring well concentration time series and persistently 

high tracer concentrations up to a year after begin of the tracer test. The more volatile sulfur hexafluoride showed both earlier and later peaks than fluorescein. 

Elevated nutrients were found in wells surrounding the septic systems with nitrate 

concentrations in impacted wells as great as 20 to 60 mg/L at both the Magnolia and Hickory sites. 

In the most impacted well at Magnolia, concentrations ranged up to 55 mg/L nitrate, 0.92 mg/L total 

phosphorus and 930 fecal coliform colonies/100 ml. The well installed in a paleo-sinkhole was the 

most impacted at Hickory, with concentrations ranging up to 56 mg/L nitrate, 4.9 mg/L total phosphorus and 99 fecal coliform colonies/100 ml. The greatest concentrations observed in background wells 

were only 1.6 mg/L nitrate, 0.47 mg/L total phosphorus and <2 fecal colonies/100 ml. Elevated 

nutrient concentrations were found directly in the flow path of the effluent as indicated by the tracer 

experiments. 

22
A conclusion of this study is that the good connections between surface and groundwater in the 

underlying karst aquifer allows rapid transport in the direction of the next surface-water body or spring. 

EPA’s Gulf of Mexico Program and FL DOH’s Onsite Sewage Research Program provided funding 

for this study.

23
Identifying Water-Quality Domains near

Ichetucknee Springs, Columbia County, Florida

Sam B. Upchurch1, Kyle M. Champion1, James C. Schneider1, David Hornsby2, and Ron Ceryak2

1

SDII Global Corporation, Tampa, FL

2

Suwannee River Water Management District, Live Oak, FL

Water-quality data collected at nearly 100 wells and 6 major springs in southern Columbia and 

eastern Suwannee counties were investigated using factor analysis, hierarchical analysis, star diagrams 

and WATEQ4F. These analyses were used to identify geochemical facies within the Floridan aquifer 

near Ichetucknee Springs. The factor analysis suggests that six factors help explain more than 

75 percent of the variability in the data. These six factors reflect flow path and recharge characteristics, 

as well as water-rock interactions, in the Floridan aquifer near the springs. 

The variables that best represent these six factors are alkalinity, chloride, magnesium, nitrate, 

ammonium, and phosphorus. Hierarchal analyses of these six factors suggest that the wells and 

springs can be grouped into three distinct water-quality domains. These domains indicate areas where: 

1) clay-rich sediments of the Hawthorn Group influence the water chemistry in the Floridan aquifer, 

2) regional flow paths appear to be emerging, and 3) ground-water flow paths are short in the Floridan 

aquifer. This last domain can be further subdivided into two sub-domains with two distinct water 

quality types each.

Star diagrams representing the relative importance of each factor for each well and spring show the 

three major domains occupy distinct geographic areas. The first domain is located beneath the Northern Highlands, where the Hawthorn Group acts as a confining unit. The second domain is concentrated 

around the Santa Fe River, where upwelling of deep aquifer water is expected. The third domain 

occupies most of the study area, where the Floridan aquifer is poorly confined or unconfined. The 

subdivisions of this domain do not indicate any spatial patterns, but rather indicate areas characterized 

by distinct chemical fingerprints, identify areas susceptible to ground-water contamination, and locate 

regions where surface-water recharge is occurring.

The water-quality data collected from six major springs along the Ichetucknee River suggest that 

the spring water is mostly derived from areas near the springs characterized by rapid recharge and 

shallow flow paths. These regions supply base flow to the springs while conduit flow supplies ground 

water that has recently recharged the aquifer through swallets in the Cody Scarp.

Supplemental analysis of the water-quality data using WATEQ4F suggests that much of the ground 

water and spring water is at or near saturation with respect to calcite. However, in areas where Factor 1 

is low (<1), such as in the Cody Scarp, the ground water tends to be undersaturated with respect to 

calcite. These areas tend to be characterized by the presence of disappearing springs, where surface 

water has not reached chemical equilibrium with the limestone aquifer.

24
Assessment of Nitrate-Nitrogen Variability in

Soils of the Santa Fe River Watershed in

North-East Florida

S. Lamsal, S. Grunwald, C.M. Bliss, I. Lopez-Zamora, N.B. Comerford, and M.W. Clark

Soil and Water Science Department, University of Florida, Gainesville, FL

The Santa Fe River (SFR) has been contributing to elevated loads of nitrate-nitrogen in the ground, 

spring and surface water of the Suwannee River Basin. Sustainable land use management in the 

Suwannee Basin preserving water resources requires to upscale site-specific observations of nitratenitrogen to watershed-scale and to understand relationships between nitrate-nitrogen and environmental 

factors such as land use, soils, parent material, and landscape position. Our objective was to model the 

space-time variability of nitrate-nitrogen across the SFR watershed using point measurements and its 

relationship with environmental factors. Geospatial data from the Soil Survey Geographic Database 

and land use derived from Landsat-TM satellite imagery was used to compute soil-land use categories 

(SLC). We used a stratified random sampling design for selecting sites proportional to the aerial extent 

of individual SLC and targeting “high-risk” SLC categories expected to contribute to high nitrogen 

loads. Soil sampling started in September 2003 and will continue for 2 years including 6 synoptic 

soil sampling events. Soil samples have been collected in composites, proportional to the support size, 

from four different depth increments (0 to 30, 30 to 60, 60 to120 and 120 to180 cm). Nitrate-nitrogen 

measured at individual sites was averaged along soil profiles. We used Classification Trees to classify nitrate-nitrogen based on environmental factor combinations. Tree models were used to upscale 

site-specific observations to watershed-scale. The minimum and maximum average nitrate-nitrogen 

values were 0 and 6.54 μg/g soil and highly skewed with a mean of 0.71 μg/g soil and standard deviation of 1.3 for the September 2003 event. Many sites showed absence of nitrate-nitrogen (values below 

detection limit (DL). We used various exhaustively available data layers of soil, land use and terrain 

attributes to develop a classification tree model predicting the presence (values > 0) or absence (values 

< DL) of nitrate-nitrogen. The derived classification tree model showed that land use, soil type and 

upslope drainage area are useful predictor variables. Land uses such as crops, feedlot, improved pasture 

and rangeland contributed to the tree branch predicting presence while urban, wetland and upland forests were associated with the tree branch predicting values < DL. The classification model successfully 

predicted 92 sites out of 100 sites in training mode, while the cross validated results showed correct 

classifications for 75 sites out of 100 sites. The January 2004 sampling also indicated a highly skewed 

nitrate-nitrogen distribution, with some higher nitrate-nitrogen values compared to the September 2003 

data. The high values were associated with improved pasture, crops and rangeland. The future sampling 

will provide information about the seasonal variation of nitrate-nitrogen in soils across the watershed 

and explores the importance of environmental variables to explain nitrate-nitrogen variability. The final 

research output will contribute to better understand the space-time variability of nitrate-nitrogen at 

watershed scale and develop recommendations to improve the soil and water quality in the SFR 

watershed.

25
26
ECOSYSTEM DYNAMICS

27
Long-Term and Large-Scale Trends in

Mercury Bioaccumulation in the

Suwannee River Basin, Florida

Lia C. Chasar1, Ted R. Lange2, J.W. Grubbs1, Jeffrey P. Chanton3 

1

United States Geological Survey, Florida State University Research Foundation Building B 

2010 Levy Avenue, Tallahassee, FL 32310 Tel. (850) 942-9500 ext. 3010 

email: lchasar@usgs.gov tgrubbs@usgs.gov 2

Florida Fish and Wildlife Conservation Commission (FFWCC), Eustis Fisheries Research Laboratory 

Eustis, FL 32737 Tel. (352) 742-6438 email: Ted.Lange@fwc.state.fl.us 3

Department of Oceanography, Florida State University, Tallahassee, FL 32306

email: chanton@ocean.fsu.edu

The Suwannee River exhibits strong gradients in land use and water chemistry along its 245 mile 

course, providing a unique opportunity for the study of mercury bioaccumulation in lotic systems. To 

evaluate temporal trends in mercury burden of largemouth bass (Micropterus salmoides), muscle tissue 

was analyzed for total mercury concentration in fish collected from the lower Suwannee River Basin 

annually from 1987 to present. As a preferred prey item crayfish (Procambarus sp.) were collected in 

1993 and 2001, and muscle tissue was analyzed for methylmercury. Spatial trends in bioaccumulation 

were evaluated by analyzing mercury burden, δ13C, and δ15N in crayfish, sunfish (Lepomis auritis) and 

largemouth bass collected in 2001 from stations 15 to170 miles upstream of the river mouth. Mercury 

levels in largemouth bass (age standardized, EHg3

) decreased from 0.80 (1989) to 0.25 μg/g (2001), 

although values peaked in 1992 and 1999. Mercury levels in crayfish also decreased by approximately 

60 percent from 1989 to 2001. Mercury body burden is apparently related to river stage; regression 

models indicate that mercury in largemouth bass is significantly correlated to the number of days at 

or exceeding flood stage (days overbank, i.e., streamflow exceeding 75 percent duration flow) 

during the life of the fish. Mercury concentration in the muscle tissue of sunfish and largemouth bass 

increased with increasing river miles upstream. Preliminary analysis of stable isotope data indicates 

little difference in trophic position for largemouth bass among all stations (δ15Nlmb – δ15Ncray = 4-6 ‰), 

suggesting that bioaccumulation rates are more tightly controlled by mercury source/transport, and 

local biogeochemical processes.

28
Gulf Sturgeon

R. Allen Brooks and Ken Sulak 1

U.S. Geological Survey, Center for Aquatic Resources, 7920 NW 71st Street, Gainesville, FL 32653

Gulf sturgeon, Acipenser oxyrinchus desotoi, forage extensively in the Suwannee River Estuary 

following emigration out of the Suwannee River. While in the estuary, juvenile sturgeon primarily feed 

on benthic infauna. In June-July, 2002, and February-April, 2003, random sites within the estuary were 

sampled for benthic macrofauna (2002, n=156; 2003, n=103). A mean abundance of 2,562 individuals/m2

 (s.e. + 204) was found in the summer, with significantly reduced macrofaunal abundance in the 

winter (mean density of 1,044 individuals/m2, s.e. + 117). Benthic biomass was significantly higher 

in the summer with an average summer sample dry wt. of 5.92 (s.e. + 0.82) g/m2 compared to 3.91 

(s.e. + 0.67) g/m2 in the winter. Amphipods and polychaetes were the dominant taxa collected during 

both sampling periods. A Principal Food estimate indicated that the potential food resource value for 

juvenile Gulf sturgeon is spatially heterogeneous within the Suwannee River Estuary.

29
Benthic Macroinvertebrate and Periphyton

Monitoring in the Suwannee Basin in Florida 1:

Overview and Biogeography

R.A. Mattson1. D. Wade2, K. Malloy2

1

Suwannee River Water Management District, 9225 County Rd. 49, Live Oak, FL 32060 

email: mattson_r@srwmd.state.fl.us. 2

Janicki Environmental, Inc., 1155 Eden Isle Drive, N.E., St. Petersburg, FL 33704

email: JanickiEnv@aol.com. 

This and two other papers will summarize the results of a long term program, begun in 1989, to 

monitor water quality, benthic macroinvertebrates and periphytic algae in the Suwannee River and its 

major tributaries in Florida. Invertebrates and algae were sampled quarterly as a subcomponent of a 

comprehensive water quality monitoring effort. Six stations on the Suwannee mainstem, four sites 

on the Santa Fe, two on the Withlacoochee and one sampling site on the Alapaha River have at least 

12 years of continuously collected algal and/or invertebrate data, which were collected by the same 

firm and analyzed by the same taxonomists for the entire period. These biological data were collected 

concurrent with water chemistry sampling, and in many cases, at sites where continuous river stage 

and discharge were monitored as well. This permits examination of biological responses to changes in 

physical/chemical conditions. Algae were sampled with glass slide settling racks (periphytometers), 

and macroinvertebrates were sampled with multiple gear types; primarily Hester-Dendy multiplate 

samplers, but also petite ponar grabs and dip nets.

A diverse algal flora has been documented to occur in the Suwannee River and its tributaries 

in Florida. These plants probably account for the majority of the primary production in the riverine 

aquatic ecosystem. Diatoms generally dominate the taxa composition (by both relative richness and 

relative abundance). Dominant taxa include Achnanthes, Cocconeis, Gomphonema and Melosira, all 

indicative of hard, bicarbonate freshwater conditions. Green algae and blue-green bacteria make up 

the remainder of the periphytic algal communities in the river system, and form a greater fraction of 

the algal community in the upper reaches of the Suwannee and Santa Fe, where the water chemistry is 

more dominated by surface-water runoff (low pH and conductivity, low alkalinity).

Benthic macroinvertebrates in the Suwannee drainage fulfill several ecological roles. Primarily, 

they serve as the key link between autochthonous and allochthonous primary production and secondary production at higher trophic levels (e.g., fish, reptiles, and birds). Benthic invertebrates comprise 

a sizeable fraction of the total animal biodiversity of the Suwannee River in Florida. Chironomids 

dominate the taxa richness and relative abundance throughout the system.

30
Benthic Monitoring in the Suwannee Basin

in Florida 2: Relationships Between Physical

and Chemical Variables and Biology

K. Malloy1, D. Wade1, T. Janicki1, and R. Mattson2

1

Janicki Environmental, Inc., 1155 Eden Isle Drive, N.E., St. Petersburg, FL 33704 

email: kmalloy@janickienvironmental.com 2

Suwannee River Water Management District, 9225 County Road 49, Live Oak, FL 32060

This paper is the second in a series of three papers that summarizes the results of a long-term 

monitoring program, begun in 1989, to monitor water quality, benthic macroinvertebrates, and 

periphytic algae in the Suwannee River and its major tributaries in Florida. This paper presents the 

relationships between physical and chemical variables and biology.

Physical and chemical variables influence the biological components of the Suwannee River 

system. Algae and benthic invertebrates serve a variety of ecological roles in river and tributaries, 

including primary (algae) and secondary (invertebrate) production, food for higher organisms, and 

transformation of energy and nutrient cycling. Both algae and invertebrates act as indicators of 

ecosystem health, with algal communities being more immediate indicators of environmental stress, 

while the benthic invertebrate community responds to environmental conditions integrated over a 

longer time period. 

The Suwannee River Water Management District has been collecting long-term stream discharge, 

water-quality, and biology data (algal and invertebrate) at numerous stations throughout the District 

since 1989. From these data, we identified existing relationships between the physical/

chemical variables and biology and assessed the relative strengths of these relationships through an 

extensive series of bivariate plots and Spearman correlation statistics. Logistic regression analysis was 

also conducted to examine relationships between water quality and physical factors and the resulting 

distribution (presence/absence) of taxa. 

31
Benthic Monitoring in the Suwannee River Basin

in Florida 3: Spatial and Temporal Trends

D. Wade1, K. Malloy1, T. Janicki1, and R. Mattson2

1

Janicki Environmental, Inc. 1155 Eden Isle Drive, N.E., St. Petersburg, FL 33704 

email: dwade@janickienvironmental.com 2

Suwannee River Water Management District, 9225 County Road 49, Live Oak, FL 32060

This paper is the third in a series of three papers that summarize the results of a long-term monitoring program, begun in 1989, to monitor water quality, benthic macroinvertebrates, and periphytic algae 

in the Suwannee River and its major tributaries in Florida. This paper presents the spatial and temporal 

trends observed in the long-term monitoring data.

Algae and benthic invertebrates serve a variety of ecological roles in the Suwannee River system. 

Observed community responses indicate whether an ecosystem is experiencing stress or is relatively 

healthy. Periphytic algae and benthic macroinvertebrate data were evaluated to assess community 

similarity over time and between river systems (or groups of rivers) within the Suwannee River Water 

Management District. Trend analysis was applied to all sampling sites with 5 or more years of data to 

identify and quantify the significance, direction and magnitude of trends in algal and invertebrate taxa 

richness and abundance. Cluster analysis and other multivariate analyses were performed to identify 

patterns and trends at selected sampling sites and to identify the most influential physical variables 

with respect to the observed biological responses. These analyses represent a comprehensive review 

of trends in the Suwannee and its major tributaries in Florida.

32
Aquatic Invertebrate Communities as Tools

for Establishing Minimum Flows and Levels in

Suwannee River Basin Streams

Gary L. Warren and Tracy Ferring

Florida Fish and Wildlife Conservation Commission, University of Florida 

Department of Fisheries and Aquatic Sciences, 7922 NW 71st Street, Gainesville, FL 32653

email: gary.warren@fwc.state.fl.us

Florida’s five water management districts are required by statute (373.042 F.S.) to establish 

minimum flows and levels (MFLs) for water bodies within their boundaries. The statute mandates 

that MFLs be set at levels that prevent significant harm to Florida’s ecological resources. Development-related increases in consumptive water use have prompted water managers throughout the state to 

predict significant flow reductions in many lotic systems. In response to these predicted reductions, the 

Florida Fish and Wildlife Conservation Commission has implemented an instream flow program with 

the dual purposes of determining flow requirements of stream-dwelling communities and providing 

the water management districts with MFL recommendations that are protective of the biotic integrity 

of stream ecosystems. The Commission has identified streams within the karst area of the Suwannee 

River Basin of north-central Florida as particularly vulnerable to impacts from increased ground-water 

withdrawals related to agriculture and human population growth. Three streams within the Suwannee 

Basin, the Santa Fe River, the Withlacoochee River, and the Ichetucknee Springs and River complex, 

have been chosen as study areas for development and evaluation of MFL determination methods. A 

principal tool chosen for derivation of these methods is aquatic invertebrate community structure. 

Invertebrate communities were selected because they are flow-sensitive and are integral to the normal 

functioning of stream systems; invertebrate community structure is a proven sentinel of aquatic ecosystem health. Within each study stream, invertebrate communities will be sampled in areally dominant 

natural habitats within several stream reaches. A suite of physicochemical measurements, including 

current velocity, depth, and substrate type, will be recorded concurrently with the collection of each 

individual sample. Data compiled from the collections will provide a baseline for future flow-related 

evaluations. Taxa sensitive to flow will be identified using multivariate methods such as canonical 

correspondence analysis. Invertebrate abundance data and physicochemical data will be combined to 

produce habitat suitability curves for indicator species and selected community metrics. The utility 

of using locally derived habitat preference curves coupled with the PHABSIM model for determining 

usable habitat areas at different streamflows will be evaluated.

33
Submerged Aquatic Vegetation Mapping in the

Ichetucknee Springs and River System, Florida

Raymond C. Kurz1, Phinla Sinphay1, Wendy E. Hershfeld1, and Debra C. Woithe2

1

PBS&J, Sarasota, FL 

2

Debra Childs Woithe, Inc, Palmetto, FL

In 2003, the Suwannee River Water Management District (SRWMD) began collecting ecological 

data within the Ichetucknee Springs and River to provide baseline information regarding the current 

health of this aquatic ecosystem. This presentation describes the mapping and monitoring of 

submerged aquatic vegetation (SAV) in this spring system. Water quality and SAV biomass were also 

sampled and will be presented as a separate paper for this conference. The goals of the Ichetucknee 

Springs mapping project were to provide a map of the spatial distribution of SAV in the Ichetucknee 

Springs and River, and compare existing coverages with a study performed in 1979 by Dutoit. 

Approximately 78 percent of the Ichetucknee River bottom was covered by SAV in 2003, an 

increase of approximately 23 acres or 353 percent compared to the 1979 Dutoit survey. The most 

common species encountered (in order of percent cover) in the Ichetucknee Springs and River were 

Sagittaria kurziana, Zizania aquatica, Vallisneria americana, Chara sp., Myriophyllum heterophyllum, 

Ludwigia repens, and Hydrocotyle sp. In 2004, portions of the river which are exposed to intensive 

recreational use (e.g., docks used for entry and exit points by tubers, swimmers, and canoeists) were 

remapped and a change analysis of these areas was performed to compare SAV map data between 

2003 and 2004. Maps were also created for river depth, flow, reach and tree canopy shade, and analyzed with respect to 2003 SAV maps. SAV coverage declined by approximately 454 m2

 or 0.1 acres 

between 2003 and 2004 in the intensive recreational use areas. This represents an approximate 2 percent loss within the remapped areas. Overall, changes in SAV coverage were minimal between the two 

mapping periods and the majority of loss can be explained by temporary impacts associated with the 

reconstruction of the take out area near U.S. 27. Other losses were the result of conversion of former 

SAV polygons to emergent polygons, likely due to lower river water levels observed during the drier 

2004 mapping period. 

Based on the spatial mapping analyses for the river, the vast majority of the river is less than 

2 m deep. Just over 50 percent of the river is less than 1 m deep (75,000 m2

), with a slightly smaller 

area (62,000 m2

) between 1 and 2 m deep. The 2 to 3 meter interval is small (5,000 m2, less than 

5 percent) and occurs in Reach 3 (Rice Marsh) and the lower reaches. In general, flow follows the same 

trends as the depth, with more rapid flow in areas with greater depth. With respect to river reach, tree 

canopy shade decreases from reach 1 to 3, increases to reach 6, then decreases again, although more 

gradually, to reach 9. The decrease in shade around reach 3 is due to the greater width of the river in 

this area, and the presence of Zizania beds beyond the tree canopy. These two characteristics result in 

more open surface area away from the fringing tree canopy. The decrease in shade in reaches 8 and 9 

appear to be due in part to the more east-west orientation of the river.

Dutoit, C. H., 1979, The carrying capacity of the Ichetucknee Springs and River: Masters Thesis, University of 

Florida, Gainesville, Fla, 176 p.

34
Factors Influencing the Submersed Aquatic

Vegetation of the Ichetucknee River

Sky K. Notestein and Thomas K. Frazer

University of Florida, Department of Fisheries and Aquatic Sciences

 Annual surveys (2003 and 2004) of the Ichetucknee River were made for a variety of 

parameters with the goal of measuring baseline conditions and relating the effects of stream depth, 

flow and terrestrial canopy cover to the abundance of submersed aquatic vegetation (SAV) and 

periphyton in the river. Additionally in 2004, nitrogen and phosphorus concentrations were measured in the main river and several feeder springs to explore the relations between nutrients, SAV and 

periphyton. SAV coverage was correlated to stream depth and terrestrial canopy. SAV biomass was 

correlated to stream depth, flow and terrestrial canopy. Periphyton abundance was correlated to depth 

and flow as well. Nutrient concentrations were not correlated to SAV or periphyton abundance in the 

main river; however, in the feeder springs, phosphorus availability was positively correlated to periphyton abundance. Also of interest, periphyton abundance was negatively correlated to both SAV coverage and biomass, suggesting that increases in periphyton may cause declines in the SAV community. 

These observations provide insight into the roles of physical and chemical parameters in shaping the 

SAV community as well as a framework for long-term monitoring. 

35
Lower Suwannee River Floodplain, Florida:

Hydrology, Topography, and Soils of Riverine

and Tidal Floodplain Forests and Ecological

Consequences of Potential Flow Reductions

Helen M. Light

U.S. Geological Survey, 2010 Levy Avenue, Tallahassee, FL 32310 

Tel. 850-942-9500 ext. 3008 email: hlight@usgs.gov

Increased water withdrawals from the Suwannee River Basin could reduce river flow, resulting 

in decreased floodplain inundation and an upstream movement of the saltwater interface. Impacts of 

hypothetical flow reductions on wetland forests were estimated in a study of hydrology, soils, and 

vegetation of the lower Suwannee River floodplain conducted by the U.S. Geological Survey, in 

cooperation with the Suwannee River Water Management District, from 1996 to 2000. 

Hydrology, topography, soils, and vegetation were described from transects and plots in the floodplain of the Suwannee River from its confluence with the Santa Fe River to the tree line near the Gulf 

of Mexico. Flood depths and duration of inundation and saturation varied with land-surface elevations, 

which ranged from 13-24 ft above mean sea level at the most upstream site to 1-4 ft above mean sea 

level at downstream tidal sites. Surface soils were predominantly mineral in riverine forests and predominantly organic and saturated in tidal forests. Hydrologic conditions and soil characteristics were 

described for each of 13 wetland forest types. 

Forest composition in river floodplains, which is primarily determined by flood depths, duration 

of inundation and saturation, and salinity, could change if flows were reduced. If forests became 

significantly drier or more saline due to flow reductions, upland species would invade bottomland 

hardwood forests, bottomland hardwood species would invade swamp forests, and tidal species would 

migrate upstream. Alteration of wetland hydrology could have other ecological consequences such 

as invasion of floodplain forests by exotic plants. Decreased soil saturation may result in oxidation of 

organic soils in riverine swamps, reducing water-holding capacity and pollution-filtering ability, and 

increasing vulnerability to fire. In riverine swamps, flow reductions at low flows could decrease aquatic 

habitat for floodplain fishes and aquatic invertebrates at a time when that habitat is already scarce. Flow 

reductions at high flows may decrease the abundance of fishes that are seasonally dependent on flooded 

forests for food, and may adversely affect aquatic organisms in the river and estuary that depend on 

nutrient and detritus exports from the floodplain. 

36
Lower Suwannee River Floodplain, Florida:

Canopy, Subcanopy, and Ground Cover

Vegetation and Potential Impacts of Flow

Reductions on Plant Distribution

Melanie R. Darst

U.S. Geological Survey, 2010 Levy Ave., Tallahassee, FL 32310 

Tel. 850-942-9500 email: mdarst@usgs.gov

Plant communities in the lower Suwannee River floodplain were described in a study conducted 

by the U.S. Geological Survey, in cooperation with the Suwannee River Water Management District, 

from 1996 to 2000. The distribution of plant species in the floodplain was related to flow-dependent 

hydrologic characteristics such as flood depth, soil saturation, and salinity. Principal data collection 

sites were transects that were permanently marked for future ecological studies. Major forest types 

were defined from vegetative sampling and digitized aerial photography. A detailed forest map was 

created and an interactive version of the map was published on compact disc.

Floodplain forest types include 1 upland and 13 wetland types. A total of 77 canopy and 

subcanopy species were identified in floodplain wetland forests (n = 8,576). Bald cypress was the 

most important canopy species in the floodplain by basal area. Cabbage palm and pumpkin ash 

increased in importance in tidal reaches, and red cedar and sweetbay were found only in the lower tidal 

forests. The distributions of tree species by river mile may be due primarily to differences in flood 

depths and salinity. Flow reductions will lower flood depths and result in the increased importance in 

bottomland hardwood forests of species with less flood tolerance such as hackberry. Flow reductions 

will also increase the potential for higher salinities in tidal reaches, resulting in a retreat upstream of 

species that are less salt-tolerant such as water tupelo. 

Ground cover density and species richness in wetland forests were analyzed by reach and forest type. The riverine reach had the greatest species richness (n = 203). The upper tidal reach had the 

lowest species richness (n = 116) and lowest density of ground cover. Density was greatest in the lower 

tidal reach where floods are shallow and usually of short duration. The distribution of ground cover 

species may also demonstrate the influences of flood depth, salinity, and soil saturation, and these 

distributions can be expected to change if flow reductions occur. Some species, such as poison ivy, that 

have a wide tolerance to hydrologic conditions, may increase in abundance in altered habitats if other 

species decrease.

37
Structural and Dynamic Habitat in the Suwannee

Estuary: An Application of Remotely Sensed

Imagery to Integrated Habitat Mapping

Ellen A. Raabe1, Randy E. Edwards2, and Carole C. McIvor1

1

U.S. Geological Survey, Florida Integrated Science Center, St. Petersburg, FL

2

University of South Florida, College of Marine Science, St. Petersburg, FL

This study characterized and mapped the shallow and nearshore benthic and intertidal habitats of 

the Suwannee River Estuary and identified potential relations between benthic habitat, hydrology, and 

ecological function. Submerged and emergent habitat characteristics were detected and evaluated from 

12 bands of 4-m hyperspectral imagery flown in fall 2002. These data were combined with hydrologic, 

topographic, and tidal data to interpret structural and dynamic habitat and its potential as essential fish 

habitat. Categories and geomorphology of the intertidal zone depicted channels, submerged aquatic 

vegetation (SAV), oyster bars, vegetation differences, and flooding stages within the nearshore and 

intertidal zones. Morphologic derivatives such as tidal creek sinuosity and drainage density were also 

obtained from the imagery.

It was hypothesized that habitats north and south of the river are dynamically and structurally 

different, because the influence of the Suwannee River is greater to the south. Image analysis shows 

that the northern creeks support more flooded low marsh accessible to small mobile organisms, more 

creek edge and coarse sediment, lower runoff rates, and possibly prolonged discharge during low tide. 

Barnett Creek and its tributaries are straighter, fresher, and deeper than the northern creeks. Field 

observations suggest that the southern creeks have more exposed limestone substrate and Vallisneria

beds, but these features were not detected with the imagery. Hydrologic monitoring confirmed fresher 

conditions in the southern creeks and a net influx of ground water to both northern and southern creeks, 

but the source and timing of freshened ground water are incompletely documented. Observed intertidal 

habitat differences between northern and southern creeks point to differences in underlying geology 

and hydrology, especially overland and ground-water flow.

Fish were collected in early April 2003 with three methods: rivulet nets, seines, and throw traps. 

Forty-five species were collected, 41 species from the southern creeks and 30 species from the northern 

creeks. Whereas the fish sampling effort in this study was insufficient to make definitive statements 

about species assemblages or habitat use, fish sampling does suggest that southern creeks were utilized by more freshwater species. In addition, fishery habitat value of northern and southern creeks for 

estuarine species may be indistinguishable, a conclusion that is supported by earlier independent FMRI 

fishery sampling. Additional analysis of seasonal variation and specific habitat use, and refined habitat 

mapping would help clarify the effects of Suwannee River discharge on habitat and species assemblages. Further assessment of the dynamic interaction between geology, tide, ground water, and river 

discharge in the estuary and their combined role in habitat suitability is needed. The successful detection and interpretation of detailed habitat characteristics from airborne imagery serves as an example of 

the application of hyperspectral imagery to aquatic and wetland mapping and monitoring.

38
The Florida Salt Marsh Vole on the

Lower Suwannee National Wildlife Refuge

Steve E. Barlow and Mike W. Mitchell

Wildlife Biologist and Assistant Refuge Manager, U.S. Fish and Wildlife Service

Lower Suwannee National Wildlife Refuge, 16450 NW 31 Place, Chiefland, FL 32626 USA

email: Steve_Barlow@fws.gov Mike_Mitchell@fws.gov

The Florida salt marsh vole (Microtus pennsylvanicus dukecampbelli) was first described in 1982 

from a single site on private lands in Waccasassa Bay, near Cedar Key in Levy County, Florida (Woods 

et al. 1982). Subsequent surveys failed to locate any other populations within Florida’s Big Bend 

region (Bentzien 1989, Doonan and Morgan 2002, Woods 1988). Prior to our effort, only 15 Florida 

salt marsh voles had been captured and all were trapped at the same site in Waccasassa Bay (Doonan 

and Morgan 2002, Smith 1990, Woods et al. 1982). We conducted an initial survey of salt marsh habitats on the Lower Suwannee National Wildlife Refuge to determine if Microtus populations could be 

present. We surveyed several potential trapping sites and prioritized them based on plant species composition, distance to tree line, distance to open water, site protection, patch size, and proximity to the 

known Microtus population. The survey site that ranked highest was an area dominated by salt grass 

(Distichlus spicata) with a patch size of approximately 3 hectares, located near the southern boundary of the refuge. At this study site we established a grid of 40 traps. Using accepted live-trapping 

techniques we captured 1 adult male Florida Salt Marsh Vole, 1 sub-adult male, and 1 adult female. 

Our study site was approximately 12 kilometers northwest of the original Waccasassa Bay site. Future 

plans call for continued surveys on the refuge to determine if other areas may contain Microtus populations, along with an in depth population and life history study of the newly discovered population. 

Bentzien, M. M., 1989. Florida salt marsh vole survey: Unpub. Rep., U.S. Fish and Wildlife Service, 

Jacksonville, Fla., 5 p.

Doonan, T. J., and G. L. Morgan, 2002, Abundance and distribution of the Florida salt marsh vole (Microtus 

pennsylvanicus dukecampbelli): Final project rep. Project 9314 221 1000, Florida Fish and Wildlife 

Conservation Commission.

Smith L.H. 1990, The saltmarsh vole: Florida Naturalist, Winter 1990. p. 5-8.

Woods, C.A., 1988, Status surveys of the Florida salt marsh vole: Report to the U.S. Fish and Wildlife Service 

under cooperative agreement, No. 14-16-0009-1544, 6 p.

Woods, C.A., Post, W., and Kilpatrick.C.W., 1982, Microtus pennsylvanicus (Rodentia: Muridae) in Florida: A 

Pleistocene relict in a coastal saltmarsh: Bull. Florida State Mus., Biol. Sci. 28(2):25-52. 

39
The Florida Fish and Wildlife Conservation

Commission’s Fishery-Independent

Monitoring Program, Cedar Key, Florida

Doug Nemeth

Research Administrator, George Kirkpatrick Marine Lab, Cedar Key, FL

The fishery-independent monitoring (FIM) program began in the Cedar Key area during 

June 1996. The program was designed to monitor the relative abundance of fishery resources in 

Florida’s major estuarine, coastal, and reef systems. Cedar Key is one of seven areas in the state 

where the FIM program operates.

The FIM program utilizes a multi-gear approach within a stratified random sampling design to 

collect data on fishes and selected invertebrates from a wide range of habitats and life history stages. 

A 21.3m center bag seine with 3 mm mesh is used to collect juvenile and small adult fishes in shallow 

water 0.3 – 1.5 m deep, a 6.1 m otter trawl with a 3 mm mesh liner is used to collect juvenile and adult 

fishes in water 1.8-7.6 m deep, and a 183 m haul seine with 38 mm stretch mesh is used to collect 

juvenile and adult fishes along shorelines in water less than 2.5 m deep. 

The Cedar Key sampling universe is divided into 3 sampling zones based on geographic and 

logistic criteria. Each zone is subdivided into 1 nm2

 grids and each grid is further subdivided into 

100 micro grids. Every month, 66 sites identified by microgrids, are randomly selected from this 

universe to be sampled with the suite of gears mentioned above. The Cedar Key sampling universe 

extends from Bumblebee Creek (north of the Suwannee River), to Porpoise Creek (south and east of 

the Cedar Keys). It also includes the lower Suwannee River up to the Gopher River and all tidal 

creeks . The western boundary is the NOAA 3-nautical -mile demarcation line. 

At each sample location, all species of fish and selected invertebrates are identified (quality 

control procedures are in place to ensure proper identification) and all or a subsample are measured 

and released. Environmental data is also taken including location (latitude and longitude), water quality, habitat characteristics and other physical parameters. Depending upon research and management 

needs, some specimens may be brought back to the lab for otolith extraction, tissue samples, etc.

Data collected by the FIM program can be used to describe the spatial and temporal distribution of 

fishes, relating fish distribution and abundance to macrohabitat parameters, and tracking relative fish 

abundance through time, among other uses. 

40
Gulf Sturgeon – The Central Role of an Iconic

Species in the Suwannee River Initiative

Randy E. Edwards1, Kenneth J. Sulak2, Michael T. Randall3, and R. Allen Brooks2

1

University of South Florida, College of Marine Science

2

U.S. Geological Survey, Center for Aquatic Resources, Florida Integrated Science Center, Gainesville, FL

3

AScI Corporation, USGS Center for Aquatic Resources, Florida Integrated Science Center, Gainesville, FL

The Gulf sturgeon (Acipenser oxyrinchus desotoi) is an ESA-listed threatened species having 

known reproducing populations in seven river systems along the Gulf of Mexico. The Suwannee 

population is by far the largest and is critical to this anadromous species’ survival and recovery. The 

Suwannee population seems relatively stable – reflecting the generally unaltered ecological conditions 

in the lower 220 km portion of the 386-km long river and its estuary, all of which provides critical 

habitats for various life stages. Gulf sturgeon is undoubtedly the most important protected species in 

the Suwannee River system, and the condition of its population is both dependent on and an indicator 

of the health of the Suwannee.

USGS researchers and collaborators have been studying Suwannee River Gulf sturgeon for almost 

two decades and have made many important scientific contributions with regard to the species’ biology, 

ecology and protection. These include: determination of seasonal adult movement patterns within the 

river, identification of juvenile habitats in the river mouth and estuary, first robust estimates of population size, development of a long-term data base, identification of spawning habitats (over 200 km up 

river from the mouth) and conditions, determination of fall migration and movement patterns within the 

estuary and Suwannee Sound, first determination of winter marine migrations and habitats (during its 

half-year period of marine residency), contribution to critical habitat designation, acoustic analyses of 

jumping behavior, analyses of potential effects of flow/stage on reproductive success, testing and refutation of thermal barrier/springs holding area hypotheses, assessment of benthic prey distributions, and 

investigations of potential for inter-river transfers between the Suwannee population and other systems.

Despite these advances, many important questions remain, and their answers are essential to the 

long term conservation and protection of Suwannee River Gulf sturgeon. These include: identification of freshwater habitats of young of the year (YOY), full delineation of juvenile habitat in the river 

mouth and estuary, determination of prey resources of YOY and juveniles, impacts of dredging and 

other man-made changes on critical habitats, impacts of eutrophication (including effects of episodic 

benthic algal mat overgrowth on sturgeon feeding ability, prey distribution, and dissolved oxygen). 

Additionally, much remains to be done to protect the critically important spawning sites, including 

protection from direct impacts of nearby development or alteration, as well as from general ecological impacts on water quality and quantity (minimum flows) within the basin upstream of the mid-river 

spawning sites and nursery habitats.

The health and well being of the Suwannee River ecosystem and this magnificent fish species are 

intimately intertwined. Sturgeon are dependent on conservation of the ecosystem, and in turn, their 

protection can assist efforts to conserve the system. Gulf sturgeon should have a central role in any 

initiative aimed at understanding and conserving the Suwannee River. 

41
The Florida Manatee in the Suwannee River

and Estuary: Past, Present, and Future

Catherine A. Langtimm, Cathy A. Beck, Robert K. Bonde, James P. Reid

Sirenia Project, U.S. Geological Survey, Florida Integrated Science Center, Gainesville, FL

The Florida manatee is a federal- and state-listed endangered marine mammal, inhabiting 

near-shore marine areas and coastal rivers of the southeastern U.S. It is dependent on freshwater for 

drinking, seagrass and freshwater vegetation for forage, and warm-water refuges to survive cold 

winters. Early historical reports (Bartram, 1791) attest to the species long-term use of the lower 

Suwannee River system. In the 1980s, research by the USGS Sirenia Project (radio-telemetry, photoidentification, aerial surveys) identified the estuary and the lower Suwannee as a primary summer 

foraging areas for manatees in northwest Florida (Powell and Rathbun, 1984, Rathbun et al., 1990). A 

review of past studies and current data on summer and winter distributions identified Manatee Spring 

as an important area consistently used by small numbers of manatees throughout the year, but particularly during fall and spring cold spells when animals are dispersed away from the primary winter 

refuges near springs in the Crystal and Homosassa Rivers. 

Research to monitor manatee population parameters and to assess population status indicates 

that presently manatees in the region are doing well. USGS estimates of survival, reproduction, and 

population growth rates from photo-identification data show an increasing population over the past 10 

years (Runge et al., 2004). Northwest Florida, along with the Upper St. Johns River region, is the least 

impacted by human interactions and development. Over the years, the number of manatee deaths from 

watercraft strikes and cold stress has been low. 

Optimism over the growing regional population, however, is tempered with concern over 

maintaining quality and quantity of habitat for the long-term viability of the species, particularly winter 

warm-water refuges and summer foraging areas. Several Working Groups under the U.S. Fish & 

Wildlife Service’s Florida Manatee Recovery and Implementation Team (Warm-water Task Force, 

Habitat Working Group, and Population Status Working Group) are now coordinating to address 

habitat/population/management issues. USGS research to develop new models of manatee population dynamics that incorporate habitat variables show considerable promise. However, to advance our 

understanding of manatee population ecology, interdisciplinary research is needed to identify and 

quantify the ecological linkages of population dynamics to biotic and abiotic processes across the 

landscape. A larger ecosystem-based approach to research and management was recently identified as 

a high priority for all marine mammals by the U.S. Commission on Ocean Policy. 

The inclusion of manatees into a larger Suwannee River Ecosystem Research Plan undoubtedly 

can provide important data for manatee researchers and managers, but it can also provide important 

data to researchers in other disciplines. Long-term monitoring of manatees in the region for over 

20 years with photo-identification, aerial surveys and telemetry provides historical data for comparison 

to the present and future. Because of their reliance on winter warm-water refuges and summer 

foraging areas, the manatee could prove to be a key indicator of effects from perturbations to the 

Suwannee ecosystem. 

Bartram, W., 1791, Travels of William Bartram: Philadelphia, James and Johnson, Dover reprint edition, 1955. 

Powell, J.A., and Rathbun, G.B., 1984, Distribution and abundance of manatees along the northern coast of the 

Gulf of Mexico: Northeast Gulf Science, vol. 7, p. 1-28.

42
Rathbun, G.B., Reid, J.P., and Carowan, G., 1990, Distribution and movement patterns of manatees (Trichechus 

manatus) in northwestern peninsular Florida: Florida Marine Research Publication No. 48, 33 p.

Runge, M. C., C. A. Langtimm, and W. L. Kendall, 2004, A stage-based model of manatee population dynamics, 

Marine Mammal Science, vol. 20, p. 

43
Effects of Water Level Fluctuations on

Year Class Strength of Sport Fish in

Four Florida Rivers

Dr. Mike S. Allen and Tim F. Bonvechio

Department of Fisheries and Aquatic Sciences, University of Florida 7922 NW 71st Street 

Gainesville, FL 32563

We evaluated how annual and seasonal flows and water levels were related to year class strength 

of selected sportfishes across four Florida Rivers. The four rivers included the Santa Fe, Ochlockonee, 

Withlacoochee North, and Withlacoochee South. Residuals from catch curves were used as an index 

of year class strength and related to water levels/flows in each system. Species investigated included 

bluegill Lepomis macrochirus, largemouth bass Micropterus salmoides, redbreast sunfish L. auritus, 

and Suwannee bass M. notius. 

Relations between flow and year class strength differed among fish species. For example, largemouth bass and Suwannee bass year class strength was negatively related to flow and stage in the 

Santa Fe River. Suwannee bass residuals combined from two systems indicated that year class strength 

was negatively correlated with annual and seasonal flow rates (N = 8, all P < 0.10), and models 

explained 38-51 percent of the variation. Conversely, redbreast sunfish year class strength was 

positively related to flow and stage in the Ochlockonee River. Redbreast sunfish residuals were 

positively correlated with flow rates in the Fall season prior to spawning in three lotic systems combined (N =12, both P < 0.10), and models explained 25 and 31 percent of the variation in year class 

strength. Thus, high flow rates were generally beneficial for redbreast recruitment but were negatively 

related to black bass year class strength in rivers. Low water levels in these rivers may have improved 

nesting success or habitat characteristics such as aquatic macrophytes. High flows at least once every 

three years in the fall may allow inundation of floodplain habitat, producing favorable environmental 

conditions for Lepomis spp. reproduction. Low flows for three or more consecutive years should be 

prevented, and thus, MFLs should consider biological impacts to short-lived fishes.

44
“Where are the fish?”

An Angler Survey of the Lower Suwannee River

Daniel P. Dorosheff

Fisheries Biologist II, Florida Fish and Wildlife Conservation Commission 

North Central Regional Office, 3377 East U.S. Hwy 90, Lake City, FL 32055

This study quantitatively and qualitatively describes the sport fishery within a section of the lower 

Suwannee River, Florida, between the confluence of the Santa Fe River and the town of Fanning 

Springs (51.8 km). Data from angler surveys conducted in 1971, 1990, 1995, 1999-2004 is being used 

by the Florida Fish and Wildlife Conservation Commission (FWC) to broaden the understanding of 

trends associated with recreational fishing in this section of the river and to document the value of this 

resource. Since 1998, weekly river stage (mean sea level) information has been monitored, seeking 

to ascertain correlations between sport fishery descriptions and hydrologic regime. This multifaceted 

study is providing supporting data for future Minimum Flow and Level (MFL) recommendations. A 

roving, non-uniform, survey design based on a 12-week sample period covering the spring peak fishing season was used. Four randomly selected weekdays and one weekend day were surveyed during 

each 14-day period. Each sample day consisted of two six-hour periods (a.m. and p.m.), which were 

randomly selected by weighted probabilities based on actual fishing pressure. The data shows that the 

majority of the angling effort focuses on panfish species, with the redbreast sunfish (Lepomis auritus) 

being the dominant specie. Redbreast sunfish represent a five-year average of 81 percent of all harvested panfish, ranging from 70 percent to 93 percent. Other panfish species contributing to the total 

harvest include bluegill (Lepomis macrochirus), redear sunfish (Lepomis microlophus), spotted sunfish 

(Lepomis punctatus), and warmouth (Lepomis gulosus). Five-year average success rates for all panfish 

within the study area are 1.62 fish/hr. ranging from 1.24 fish/hr. to 2.12 fish/hour in 2003, which is 

considered exceptional. The 2004 survey shows a decrease in angling effort directed towards panfish; 

565 hrs/km in comparison to 639 hrs/km in 2003. In addition, the 2003 survey documented the highest 

levels of effort, harvest, and success for panfish since survey inception, irrespective of drought conditions presiding since 1999. An identical survey was conducted concurrently (2003 and 2004), in the 

downstream area from Fanning Springs to East Pass (48 km). This area is considered a control zone 

for MFL related research because tidal influence keeps water levels from staying below bank-full even 

during extended low water periods, thus allowing for continued utilization of available edge and emergent vegetation by fish. The ratio of redbreast sunfish compared to spotted sunfish harvested within 

this section drops, indicating a gradual change within the freshwater fish community as the lower 

Suwannee River actually becomes the upper estuary. Total panfish success (fish/minute) within this 

section for 2004 was 23 percent greater than the up-stream survey zone.

45
Application of the Physical Habitat Simulation

Model (PHABSIM) to the Santa Fe River

Eric Nagid and Gary Warren

Florida Fish & Wildlife Conservation Commission, 7922 NW 71st Street

Gainesville, FL 32653

The Physical Habitat Simulation Model (PHABSIM) produces an incremental analysis of a 

species’ usable area per given river discharge. The success of this model however, has been limited to 

shallow (<2 m), high gradient, clear rivers, and primarily on cold-water fishes and invertebrates. Thus, 

the application to Florida river systems requires investigation. The objectives of this study are to 

(1) develop life-stage specific habitat suitability indices for the Suwannee bass Micropterus notius and 

the net-spinning caddisflies (Hydropsychidae), (2) model the relationships between hydrologic and 

habitat (macro and micro) variables in selected river segments, and (3) incorporate the species’ suitability, hydrologic, and habitat models into the PHABSIM framework to predict the usable area of the 

Suwannee bass and net-spinning caddisflies under variable flows and levels. The goal of this study is 

to produce species-specific flows and levels recommendations for minimum flows and levels (MFL) 

determinations, and evaluate the use of this model for future MFL development.

46
INFORMATION MANAGEMENT,

MODELING, NEW TOOLS

47
Suwannee River Partnership

Kirk B. Webster

Suwannee River Water Management District, 9225 CR 49, Live Oak, FL 32060

Tel. (386) 362-1001 email: webster_k@srwmd.state.fl.us

The Suwannee River Partnership was originally formed to reduce nitrogen loading from fertilizers, 

animal waste and human waste in the Middle Suwannee Watershed located in Suwannee and Lafayette 

Counties, Florida. Now its programs have expanded to other watersheds in north Florida. The Partnership, with a current membership of 50 organizations, emphasizes the use of voluntary, incentive 

based programs, including the implementation of agricultural Best Management Practices, to reduce 

nitrogen in groundwater, springs and rivers. In the Middle Suwannee 37 of 40 dairies and 136 of 140 

poultry farms have conservation plans that meet Natural Resource Conservation Service requirements. 

The Partnership is also sponsoring research to evaluate the effectiveness of Best Management Practices. Outcomes from Partnership projects are evaluated through a Quality Assurance Program that 

determines if BMPs are being properly implemented and through a regional water quality monitoring 

program that will determine if reductions in nutrients are occurring. 

48
Watershed Assessment Model (WAM)

Evaluation of the Suwannee River Basin

Adelbert B. Bottcher1, PhD, PE1, Barry M. Jacobson, PhD, PE1, and Jeffery G. Hiscock, PE2

1

Soil & Water Engineering Technology, Inc.

2

JGH Engineering

WAM was utilized to estimate the nitrogen, phosphorus, BOD, and TSS loads discharged from 

basins located within the Suwannee River Water Management District (SRWMD). A previous version 

of this model, called SR-WAM (Suwannee River Watershed Assessment Model), was developed in 

1997, but was limited to average annual assessments and did not include stream routing. Though the 

original WAM-SR provided good general assessment information, it is not able to provide the reach 

specific information needed for completing TMDL assessments. Therefore, the objective of this 

project was to upgrade the existing WAM-SR model to a new version of WAM that includes daily 

stream routing and ground-water/spring flow subbasins. The simulation period was also extended 

through 2000 with the results comparing favorably with observed data collected throughout the 

District. This work was completed to assist FDEP staff in their TMDL work within the watershed by 

interactively simulating and assessing the environmental effects of various land-use changes and 

associated land-use practices. 

49
A Suwannee River Basin Geodatabase Archetype

Alisa W. Coffin1 and Ann M. Foster2

1

University of Florida, Gainesville, FL / U.S. Geological Survey, Gainesville, FL

Department of Geography, Land Use and Environmental Change Institute (LUECI), TUR 3141 

P.O. Box 117315, Gainesville, FL 32611-7315 Tel. 352-846-2860 email: acoffin@ufl.edu 2

U.S. Geological Survey, 50, Gainesville, FL 32601 Tel. 352-372-2571 ext. 27 Fax 352-374-8080

email: alisa_coffin@usgs.gov

Several federal and state agencies, including the Suwannee River Water Management District, 

USFWS, USGS, Florida Fish and Wildlife Conservation Commission and the Florida Department of 

Environmental Protection are involved with research and management of the Suwannee River Basin. In 

addition to these agencies, the Suwannee River Basin extends through 13 counties in Florida and 

20 counties in Georgia, encompassing numerous metropolitan areas and local planning units. With the 

number of diverse agencies working on the river, we feel that there is a need to identify these groups 

and compile existing data into one comprehensive database, which will facilitate research and subsequent management decisions regarding the future of the basin. A basin-wide geodatabase for the 

Suwannee River can provide a unified and consistent system of geographic information management 

for both scientists and local stakeholders concerned about land use and water resources at the regional 

scale. 

The geodatabase developed for the Greater Everglades Ecosystem project demonstrates the 

capability of a geodatabase to manage several types of geographic data in one database. A prototype 

geodatabase for the Suwannee River Basin is presented here, modeled on the Everglades geodatabase. 

Data used in these examples include thematic data, such as demographic information, and quantitative 

data, such as an elevation model, detailing the physical as well as social characteristics of the region. 

50
Integrating Information for Watershed

Management: A Suwannee River Basin

Watershed Atlas

Barbara S. Poore

Center for Coastal and Watershed Studies, U.S. Geological Survey, 400 6th Street South, 

St. Petersburg, FL 33701 Tel: 727-803-8747 ext. 3095 email: bspoore@usgs.gov

The Suwannee River Basin covers 10,000 mi2 in the states of Florida and Georgia. Threat of 

habitat alterations due to competing water needs among users has resulted in the formation of the 

Suwannee Basin Interagency Alliance (SBIA), a cooperative planning venture between the two states. 

The SBIA works with many state and local agencies, private businesses, and local land owners to 

promote the cooperative management of water and land resources in the basin. To assist in this effort, 

the U.S. Geological Survey (USGS) proposes to help the SBIA and the groups associated with it 

construct a watershed atlas—an online repository of maps, scientific data, and historical and cultural 

information about the Suwannee River Basin. The watershed atlas will provide scientific information 

for decision makers and at the same time serve to strengthen watershed identity. 

In recent years, the watershed has become the focus of study among natural and social scientists 

as a holistic unit for integrating different community viewpoints and disciplinary knowledges in 

ecosystem and resource management. As an example, the National Watershed Forum of 2001 

(http://www.epa.gov/owow/forum/finalrpt.pdf) brought together community leaders, government 

officials, environmental activists, and scientists to discuss cooperative action to sustain watersheds. 

A key recommendation of this forum was to foster the use of information technologies for better 

communication among citizen groups, state and local officials, and scientists. Increased access to 

scientific, social, cultural, and historical information about a watershed can potentially promote a 

cohesive watershed identity and lead to better stewardship. 

In a quest for a sustainable future, many watershed groups have produced participatory watershed 

atlases that provide access to data and information for decision making. These atlases range in technical sophistication and scope of geographical coverage and content. Many are established by citizen 

groups and serve as clearinghouses for community voluntary activity and data gathering. Educational 

institutions and governmental organizations commonly help community groups assemble these atlases. 

Studies of a sampling of these atlases show that they enhance community awareness of the holistic 

nature of the watershed if there is sufficient community participation in the creation and ongoing 

maintenance of the atlas. The author’s previous research on the use of the Internet for data sharing and 

watershed-data integration in the Pacific Northwest salmon crisis demonstrates the common dilemma 

of watershed management—community participation. 

With its scientific background and data-management skills, the USGS is uniquely poised to 

provide support for the development of a participatory, interactive watershed atlas as part of its 

proposed Suwannee River Basin and Estuary Initiative. This atlas would build on ongoing work of 

such organizations as the SBIA, which is primarily driven by governmental agencies and the Upper 

Suwannee River Watershed Initiative, a citizen group. The atlas would strive for strong community 

involvement by including data and information from a wide range of stakeholders as well as scientific 

information organized into a geodatabase. The National Map of the USGS would supply the common 

base data. Such a watershed atlas would integrate knowledge about the entire watershed, helping to 

break down institutional and organizational boundaries, offering interpretive material for residents, and 

providing common information for decision makers.

51
Existing Geospatial Data Sets Covering

the Suwannee River Basin

Michael Crane

U.S. Geological Survey, EROS Data Center, Sioux Falls, SD 57198

Tel. (605) 594-604 Email: 1mpcrane@usgs.gov

A number of key geospatial data sets provide existing coverage for the Suwannee River Basin. 

Included are a variety of remote sensing data ranging from daily coarse resolution AVHRR and 

MODIS, to sixteen-day repeat moderate resolution Landsat, to infrequent high-resolution aerial 

photography. Elevation data is available from the National Elevation Database and from the Shuttle

Radar Topography Mission. The National Land Cover Database contains land cover for 1992, and 

2001 data will be available in the near future. Other data sets available include phenologic trends, fire 

potential index, NDVI biweekly greenness, urban areas, transportation routes, and political 

boundaries. Web sites for accessing these data are presented.

52
An Airborne High Resolution Thermal Infrared and

Multi-Spectral Mapping System Trials over the

Suwannee River Basin, Florida (2002)

David Stonehouse

MET, VeriMap PLUS Inc, Tel. (403) 228-1235 Fax (403) 244-5580 

e-mail: david_s@verimap.com website: www.verimap.com

There is a requirement for monitoring the environment thermally, to locate natural springs and 

cold or warm water seeps. This is a difficult and time-consuming task by ground search methods only. 

By using a suite of sensors and technology on an economical aerial platform, great areas of land and 

wetlands is rapidly mapped. We have combined High Resolution Digital Thermal Imaging, and Digital 

Color IR Cameras to Map the wetlands and vegetation very accurately and rapidly, without the need 

of air photo ground control. This enables our custom software to generate accurate geo-tiff electronic 

GPS-moving-maps used to “navigate” directly to the suspect anomaly, to scientifically ground truth its 

dynamics. The methods used to collect and process the imagery data is done in a way that takes 

advantage of a custom alignment procedure of sensors to INS, (a highly accurate inertial navigation 

system gyro); Real-Time Differential GPS, and custom LINUX automated software processing 

routines. This method produces fully ortho-rectified imagery mosaics that are ready for insertion into 

any GIS or AM/FM system as a mosaic .geoTIFF imagery tile. The imagery is processed on-site for 

rapid delivery of electronic maps to hand held GPS devices and laptops with GPS to navigate to areas 

of interest.

The VeriMap system is an airborne, rapid delivery, Multi-Sensor, Digital Imaging System with 

specialized software called IMAPPS. This software processes the images rapidly into a seamless, 

rectified computer maps for use in any Geographic Information System; GIS. The electronic maps can 

be printed out to color plotter or printers in any size and resolution for use in planning and/or operations. The simplest way to describe our system is that collects, assembles and presents several imagery 

types, (different wavelengths) at precisely the same position/time, with the same field of view. The 

combined rectified imagery bands provide a more comprehensive “detailed picture” of artifacts on the 

ground, in different wavelengths. 

The VeriMap system was developed to speed delivery time of traditional FILM ortho-photo 

mapping while maintaining image resolution. As well, it was developed to combine multiple sensors 

to increase economics of data collection while adding to the quality and amount of decisions that could 

be made with the data collected. The Ortho-photo is the process of correcting imagery with inherent 

distortions and orientation errors by rectifying known positions of accurate photo targets on the ground, 

shooting aerial film photography, correcting, triangulating and converting the film to a computer 

system later. These tasks are very time consuming and are labor intensive. 

VeriMap PLUS has achieved that Survey Industry Milestone with our Solution without any ground 

control requirement today. The system was first flown in 1997 as a trial prototype. Today, we can collect and process imagery onboard the plane and email rectified imagery from the plane without landing 

to field technicians onsite with digital wireless hand held devices or laptops with wireless capabilities.

53
54
POSTERS

55
Stable Carbon and Nitrogen Isotope Composition

of Organic Aggregates Produced by Salinity

Induced Flocculation of Dissolved Organic

Matter from the Suwannee River

Emily R. Hall1, Thomas K. Frazer2, Joseph P. Montoya3, and Joseph J. Delfino1

1

University of Florida, Department of Environmental Engineering

2

University of Florida, Department of Fisheries and Aquatic Sciences

3

Georgia Institute of Technology, School of Biology

The Suwannee River, which originates in the Okefenokee Swamp in Georgia, is highly colored as 

a consequence of elevated concentrations of dissolved organic substances (predominantly humic and 

fulvic acids). These dissolved substances are derived largely from decaying terrestrial vegetation in the 

Okefenokee Swamp and are transported seaward towards the Gulf of Mexico where they are subject 

to further transformation by a suite of physical, chemical and biological processes. Salinity induced 

flocculation of dissolved organic matter likely occurs in the upper estuary and results in the formation 

of organic aggregates of a size suitable for filter- and suspension-feeding organisms such as clams and 

oysters. Flocculation of dissolved organic matter in several estuarine systems has been documented 

previously. Organic aggregates were produced in our laboratory by adding salts to fresh surface water 

collected from the Suwannee River. Based on these findings, experiments were performed to determine if the natural abundance of stable carbon and nitrogen isotopes might be used as markers to characterize organic aggregates and identify their potential role as a food source for fauna in the Suwannee 

River estuary.

Organic aggregates were produced by adding synthetic sea salts (Instant Ocean®) to unfiltered 

surface water collected from freshwater portions of the Suwannee River. The aggregates were analyzed 

for stable nitrogen and carbon isotope composition (�15N and �13C, respectively) as well as elemental 

composition. As salinity was increased, the �15N signature of the aggregates increased by approximately 

4 to 6‰ in each of four experiments (two with source water from the upper Suwannee River and two 

with source water from the lower Suwannee River). In contrast, �13C signatures of organic aggregates 

remained relatively uniform in any given experiment and maintained a signature typical of terrestrial 

derived organic matter, i.e., -26 to -29‰. The calculated C:N ratios ranged from 6 to 17, indicative of 

a relatively high quality food source. These findings indicate that the �15N signatures might be used as 

a tracer of organic aggregate development as they are formed as a result of increasing salinity. More 

importantly, however, our results suggest that�13C signatures of organic aggregates might be used to 

quantify their role as a food source for estuarine fauna. 

56
Utilization of GIS Methodologies to

Evaluate the Relationship Between Land Use

and Aquatic Ecosystem Health

Ann. M. Foster1, Nicola J. Kernaghan2, and Robert Mattson3

1

U.S. Geological Survey, 412 NE 16th Avenue, Room 250, Gainesville, FL 32601 

email: ann_foster@usgs.gov 2

University of Florida, P.O. Box 113225, Gainesville, FL 32611 email: nikkik@ufl.edu 3

Suwannee River Water Management District, 9225 County Road 49 Live Oak, FL 32060 

email: mattson_r@srwmd.state.fl.us

We explored the relationship between land use and its effect on aquatic biota in the Suwannee 

Basin. As an initial pilot project, this approach looked at three sites on the Santa Fe River. Variables 

used in assessing the health and reproductive status of select species included body condition 

factors, glycogen content, total protein levels, sex, reproductive sex steroids and reproductive stage. 

The following species were evaluated based on their relative trophic level placement: freshwater mussels, Elliptio icterina and Villosa vibex (Mollusca: Bivalvia); Florida Apple snail, Pomacea 

paludosa (Mollusca: Gastropoda); Crayfish, Procambarus paeninsulanus (Arthropoda: Malacostraca); 

and largemouth bass, Micropterus salmoides (Chordata: Osteichthyes). We discuss the usefulness of 

this approach in evaluating the wide-variety of impacts this watershed is presently undergoing.

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Florida’s First Magnitude Springsheds

Thomas H. Greenhalgh

Florida Geological Survey, Florida Department of Environmental Protection, 903 W. Tennessee St., 

Tallahassee, FL 32304-7700 email: tom.greenhalgh@dep.state.fl.us

At the May 2002, Workshop to Develop Blue Prints for the Management and Protection of 

Florida’s Springs (Workshop) held in Ocala, panelist Hal Davis of the U.S. Geological Survey (USGS) 

stated that he felt a map of Florida’s springsheds should be generated. A springshed was defined at this 

workshop as “those areas within ground-water and surface-water basins that contribute to the discharge 

of the spring.” The Florida Geological Survey’s (FGS) Hydrogeology Section decided to act on 

Mr. Davis’s suggestion and took the lead in this effort. Working in conjunction with staff from the 

Northwest Florida, Suwannee River, St. Johns River and Southwest Florida Water Management 

Districts (all of which have first magnitude springs within their districts), and the USGS, the FGS has 

produced the “Florida’s First Magnitude Springs” poster.

Quality, and possibly the quantity of water discharging from Florida’s first magnitude springs are 

declining. The purpose of the poster is to inform citizens and decision makers (e.g., county commissioners, legislators, and local and state agency personnel) about the importance of appropriate land use 

within a springshed and to establish a baseline for the further refinement of the springshed boundaries. 

Land use within springsheds can have profound effects of the quality of the water and in some cases, 

the quantity of water recharging the aquifer(s) that ultimately discharge at the springs. An understanding of this is paramount to the protection and the restoration of the springs that are now impacted.

It should be noted that the springshed maps were developed with currently available information. 

Therefore, maps on the poster should only be used as a guide. As ongoing and future research 

provides additional information, more accurate springshed boundaries for these first magnitude springs 

can be developed. It is anticipated that maps for the individual first magnitude springsheds will be 

generated; however, the “Florida’s First Magnitude Springs” poster probably will not be updated.

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Seagrass Mapping within the Big Bend Region

Keith Patterson and Michael White

Avineon, Inc.

The poster will show and describe the methods currently being utilized for the mapping of 

seagrass habitat within the Big Bend region of Florida. Field methods, photogrammetric processes, 

photointerpretation, GIS and accuracy assessment methods will be presented on the poster.

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Occurrence of Herbicide Degradation

Compounds in Streams and Ground Water in

Agricultural Areas of South Georgia, 2002

John R. Pittman and Marian P. Berndt 1

U.S. Geological Survey, 2010 Levy Ave., Tallahassee, FL 32303

email: jpittman@usgs.gov mberndt@usgs.gov

Water samples were collected in 2002 from 2 streams and 28 wells located in agricultural areas 

in southern Georgia and analyzed for over 180 pesticides (including herbicides, insecticides, and their 

degradation compounds). The most frequently detected pesticides in stream samples were the herbicide 

degradation compounds metolachlor ethane sulfonic acid (ESA) (74 percent of samples), metolachlor 

oxanilic acid (OA) (61 percent), and alachlor ESA (61 percent). In contrast, the parent compounds, 

metolachlor and alachlor, were not detected in stream samples (at a reporting level of 0.05 micrograms 

per liter (μg/L)). Atrazine was detected in 45 percent of stream samples and the atrazine degradation 

compound, deethyldeisopropylatrazine, was detected in 13 percent of stream samples. In ground water, 

metolachlor ESA (67 percent of samples), alachlor ESA (48 percent), and metolachlor OA (33 percent) 

were the most frequently detected pesticides. In contrast, metolachlor was detected in only 7 percent of 

ground-water samples and alachlor was not detected in any ground-water samples. Concentrations of 

metolachlor did not exceed 0.13 μg/L in ground water; however, metolachlor ESA concentrations were 

as high as 19 μg/L and metolachlor OA concentrations were as high as 4.42 μg/L in ground water. The 

higher detection rates and higher concentrations of the metolachlor and alachlor degradation compounds relative to their parent compounds, highlight the importance of including herbicide degradation 

compounds in water-quality assessments to more fully evaluate the environmental fate of herbicides in 

hydrologic systems.

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Pesticide Fate and Transport in

Coastal Plain Watersheds

Thomas L. Potter1, David D. Bosch1, Dana Sullivan1, and R. Don Wauchope1

1

USDA-ARS Southeast Watershed Research Laboratory, P.O. Box 946, Tifton, GA 31793

Tel. 229-386-7073 Fax 229-7292 email: tpotter@tifton.usda.gov

The Southeast Watershed Research Laboratory is committed collecting data which can be used to 

more accurately assess pesticide fate and transport in agricultural watersheds in the southern portion 

of the Atlantic Coastal Plain. Peanuts and cotton are produced intensively in the region. The 334-km2

Little River Watershed (LRW) which is located the upper most portion of the Suwannee River Basin 

is our principal experimental unit. We are intensively monitoring pesticide residue levels at the watershed outlet (beginning in 2003), developing pesticide use estimates, and assessing land cover. This is in 

addition to on-going precipitation and stream-flow monitoring spanning more than 35 years. The goal 

is to develop comprehensive data sets to calibrate watershed scale pesticide and fate models that reflect 

Coastal Plain conditions. Initial findings show that residue levels in surface water are extremely low 

(parts per trillion) even through estimated pesticide use rates exceed 1 kg ha-1yr-1 conventional active 

ingredient over the entire watershed. Results appear explainable in part by field and laboratory 

dissipation studies which show that widely used active ingredients degrade rapidly. In several studies 

we have shown that soil half-lives are 3 to 100 times faster than values reported in pesticide 

registration documents. The rapid rates of degradation rates likely result in relatively small amounts 

remaining available for runoff and discharge to surface waters.

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