U.S. Department of the Interior The Suwannee River Basin Pilot Study: U.S. Geological Survey Issues for Watershed Management in Florida

Introduction grams that are coordinated among Federal, Monitoring Programs State, and local agencies in addressing the key issues related to monitoring water in the Basin In most watersheds (river basins) in resources. The ITFM previously found The Suwannee River basin in Florida Florida the interactions between ground that information gaps existed in State and comprises an area of 4,230 mi2 (fig. 2). water and surface water typically result in Federal monitoring programs and recom- a single dynamic flow system. This direct mended that these gaps be addressed by The basin is characterized by karstic wet- hydraulic linkage results from numerous developing an integrated, voluntary, land and lowland topography, a small num- karst features (such as sinkholes, conduit nationwide strategy for water-quality ber of tributary streams, and an abundance systems in the underlying limestone, and monitoring. The ITFM recommended the of discharge as springs from the UFA. His- springs) that facilitate the exchange of watershed approach as a highly effective torically, ground-water and surface-water water between the surface and subsurface way to manage water resources because systems in the Suwannee River basin have (fig. 1). Unique problems can been monitored as separate media arise in protecting water quality DIRECTION OF under specific programs, with the in karst areas because of the GROUND-WATER exception of a small number of FLOW direct and rapid transport of local studies. During the past 30 recharge through conduits to the years, a considerable amount of subsurface and through resur- SINKHOLE hydrologic data (such as river SINKHOLE GROUND-WATER gence by springs. In some areas, SURFICIAL SANDS DISCHARGE TO stage and ground-water level) was A SPRING/RIVER recharge from unknown drainage AND CLAYS collected as part of extensive sur- pathways to areas of discharge face-water and ground-water net- may contribute to chemical and works. biological contamination of water The Suwannee River Water supplies. Such contamination in UPPER FLORIDAN AQUIFER Management District (SRWMD) karst areas has been documented in cooperation with the FDEP and M by many studies. CONDUIT SYSTE U.S. Geological Survey (USGS), Legislation enacted in 1993 maintains extensive monitoring mandated the Florida Depart- Figure 1. Generalized cross section in the Suwannee River networks for surface water and ment of Environmental Protection basin showing karst features that facilitate the exchange of water ground water in the Suwannee between the surface and subsurface. (FDEP) to develop and imple- River basin. As part of a surface- ment measures to protect the functions of this approach integrates ground-water and water network, water levels are being mea- the State’s ecosystems. Watershed man- surface-water systems. sured regularly at 17 lakes, river stage and agement is one of the main components of The Suwannee River basin pilot discharge are monitored at 18 sites, and a program designed to protect and manage study is attempting to provide answers to daily rainfall is recorded at 34 stations. Florida’s ecosystems. The FDEP has critical watershed-management questions Surface-water quality samples are collected identified several key objectives to effec- monthly or bimonthly at 52 sites by the such as: (1) Can boundaries be delineated tively address watershed management SRWMD as part of the Surface Water issues: (1) more coordinated management for ground-water and surface-water Improvement and Management Program. of ground- and surface-water resources, basins and do these boundaries change Currently, ground-water levels are being (2) more effective partnerships with local, depending upon hydrologic conditions? measured at 328 sites in the basin, which regional, State, and Federal government (2) What does existing information tell includes monthly measurements at 43 wells agencies, (3) coordination of ground- and about the hydrochemical interaction and continuous measurements (using surface-water monitoring efforts to assess between ground water and surface water water-level recorders) at 32 wells. Since the quality and quantity of the water in the basin? (3) Can natural processes 1987, extensive information on ground- resources and delineate the boundaries of provide a remediation of elevated concen- water quality is being collected as part of three-dimensional watersheds, and (4) the trations of nitrate in the Upper Floridan the Florida Ground Water Quality Monitor- development and maintenance of compre- aquifer (UFA) during high or low flow ing Program (FGWQMNP), which con- hensive statewide data bases for water conditions and or mixing of surface and tains 107 wells designed to monitor resource information and monitoring net- ground water? and (4) Can a framework background water quality of the principal works oriented toward targeted water- aquifers. Water from these wells is sam- be developed in this study for evaluating sheds. pled every three years for major ions, nutri- The Suwannee River basin in Florida the interactions between ground water and ents, trace elements, and selected organic is one of several watersheds in the U.S. surface water and for delineating water- compounds (Maddox and others, 1992). that was chosen for a pilot study by the shed boundaries that can be extrapolated Also as part of the FGWQMNP, the effects Intergovernmental Task Force on Monitor- to other watersheds within Florida and of various land-use practices on ground- ing Water Quality (ITFM) to evaluate the nationwide that have similar hydrogeo- water quality are being investigated at a effectiveness of current monitoring pro- logic conditions? mixed urban-industrial site and at an agri-

84° 83° 82° such study in the Santa Fe River basin, the GEORGIA degree of interconnection among springs

Withlacoochee NASSAU that discharge from Ginnie Springs Park to FLORIDA r

e the Santa Fe River was investigated using River v

i MADISON R rhodamine dye tracing experiments. a JEFFERSON h a HAMILTON ap Al Based on the dispersion of dye to more than one spring, Wilson and Skiles (1988) BAKER DUVAL concluded that there is an extensive net- COLUMBIA work of three-dimensional braided con- SUWANNEE Suw TAYLOR an duits in the aquifer system and unique n e e ground-water drainage divides do not exist 30° R i UNION CLAY v G e u r BRADFORD within a few hundred meters of the spring l f LAFAYETTE anta S Fe discharge points. o Riv f er

M PUTNAM e GILCHRIST ALACHUA Interactions Between x i GA c DIXIE Ground Water and Surface o EXPLANATION SUBBASINS OF THE SUWANNEE Water in the Basin RIVER WATERSHED IN FLORIDA WITHLACOOCHEE ALAPAHA

UPPER SUWANNEE SANTA FE STUDY LEVY In some cases, the linkage between AREA FLA LOWER SUWANNEE ground water and surface water can be MARION MONITORING SITES FOR obvious, as when water levels in the UFA GROUND-WATER LEVELS 02040MILES BACKGROUND GROUND-WATER respond directly to changes in stage of a QUALITY nearby river. One such example is a moni- 0 20 40 KILOMETERS 29° toring well located near the Alapaha River Figure 2. Location of monitoring sites and subbasins in Suwannee River watershed, Florida. (fig. 3). There is a high correlation between stage of the river and water levels cultural area in the Suwannee River from potentiometric-surface maps of the in the aquifer. As the stage increases in basin. As part of the National Water Qual- UFA constructed for low flow and high the Alapaha River, ground water sampled ity Assessment Program (NAWQA), the flow conditions. These patterns were at the Alapaha Tower well sometimes rep- superimposed on surface water drainage USGS has sampled water from six wells resents a mixture of river water and areas for the major subbasins in the in its regional background network for the ground water. However, additional Suwannee River basin. Generally, the surficial aquifer system. Seven sites on geochemical evidence is needed to deter- the Suwannee River in Florida and one regional flow patterns indicate that bound- mine the extent of mixing of river water site on the Santa Fe River are being sam- aries for ground-water basins do not coin- with water from the UFA. pled by NAWQA for bed material, water cide with surface-water drainage In other cases, the interaction quality, and biological species. subbasins except in some parts of the lower Suwannee River basin and the Santa between ground water and surface water Fe River subbasin. There are several areas can be subtle and tracers have been used to establish the relation. For example, sev- Comparison of ground- in the basin where ground water that origi- eral local studies have effectively used nat- water and surface-water nates outside of the Suwannee River basin urally occurring radionuclides, such as crosses surface-water basin boundaries basin boundaries uranium (238U and 234U), radium (226Ra), during both low flow and high flow condi- and radon (222Rn), to trace the amount of tions. However, the measured ground- The accurate delineation of karst ground water influx to rivers and amount drainage basins represents a considerable water levels were part of a network whose of streamflow losses to ground water. challenge because of complex patterns of objective is to delineate the regional These studies rely on the fact that the surface-water and ground-water flow. In potentiometric surface of the UFA. The mobility of U, Ra, and Rn is controlled by studies of karst areas in other parts of the wells in this network are open to different different geochemical and physical pro- world it was determined that surface water depths in the aquifer and probably inter- cesses that lead to their separation or frac- basins typically do not coincide with cor- cept more localized ground-water flow tionation in ground-water and surface- responding ground-water basins. For systems. Therefore, the wells in the water systems. For example, 222Rn is a example, streams that sink within one sur- present network (approximately 250 wells gas and, hence, its concentration in ground face drainage basin can reappear in a dif- in the basin) are not adequately distributed water is about 1,000 times that in surface ferent basin. Ground-water divides are to accurately define two-dimensional water. Based on measurements of 222Rn controlled by aquifer properties as well as ground-water basin boundaries in most in ground water and in a 2-kilometer reach by topographic conditions. areas of the Suwannee River basin. of the Santa Fe River, a tributary to the Two-dimensional boundaries for sur- To more accurately define drainage Suwannee River, Kincaid (1994) reported face-water and ground-water subbasins in areas, the connection between discharge that as the river discharge increased, corre- the Suwannee River basin were compared areas (such as springs) for the UFA and sponding increases were observed for for two different hydrologic conditions: surface water must be determined for dif- ground-water discharge to springs, stream- low-flow conditions during December ferent flow conditions using tracer tech- flow losses to ground water, and input to 1990 to January 1991 and high-flow niques involving dyes and naturally springs from resurgent streamflow. One conditions during April to May 1984. Pat- occuring isotopes and, in some cases, particularly noteworthy finding was that terns of ground-water flow were derived human exploration (cave diving). In one even though the regional potentiometric-

surface map of the UFA indicates 120 farms, cropland, and silvaculture. In that the Santa Fe River is a gaining ALAPAHA RIVER STAGE 1990, 1991, and 1994, 18 wells tap- stream, streamflow is actually being 100 ping the UFA and 7 springs that dis- lost to the UFA in many places charge into the Suwannee River were along the river. Siphons that are vis- sampled for major dissolved inor- 80 ible at the surface also provide direct ganic constituents, trace elements, evidence of stream water being nutrients, and volatile and nonvolatile diverted to the subsurface. As much 60 organic compounds as part of the as 55 percent of spring discharge at FGWQMNP. In the study area, the Devil’s Ear basin was supplied 40 ground-water flow patterns remained by resurgent surface water that origi- relatively unchanged during 1990,

ALTITUDE, IN FEET ABOVE SEA LEVEL WATER LEVEL IN ALAPAHA FIRE TOWER WELL nated in the the overlying Santa Fe 20 1991, and 1994, even though large River and not water from the UFA. III IV I II III IV I II III IV I II III IV I II III IV I II 19891990 1991 1992 1993 1994 fluctuations in ground-water levels Crane (1986) used differences were observed. For example, mea- in the 234U/238U activity ratio (UAR) Figure 3. Comparison of Alapaha River stage and water sured ground-water levels in 1991 level in Alapaha Fire Tower well. and uranium (U) concentrations in increased by as much as 20 feet at ground water and surface water to deter- Several of the first-order magnitude some wells following three months of 226 mine the source and amount of recharge springs have relatively high Ra concen- above normal rainfall, compared to water for different parts of the aquifer and trations (0.155 to 0.917 disintegrations per levels in 1990. ground-water contributions to the Suwan- minute per liter) and the concentration of Nitrate concentrations in ground nee River. Most sampled sites produced 226Ra in these springs progressively water had large fluctuations from one sam- waters with low activity ratios and high U increased in a downstream direction. This pling period to the next and were associ- concentrations, which are typically associ- trend was attributed to the increasing con- ated with areas of the UFA that are uncon- tribution of water from deeper parts of the ated with fluctuations in water levels in the fined and where recent and intense UFA that supply spring water to the lower UFA. For instance, the median and range dissolution of aquifer minerals is occur- reaches of the river. (in parentheses) of nitrate concentrations in water samples from the UFA, in milli- ring, such as in places where material over- An ongoing study that began in 1994 grams per liter as nitrogen, were: April- lying the UFA has been breached by is investigating the connection between sinkholes. For example, three water sam- the Suwannee River and the unconfined May 1990, 1.52 (<0.02-17); March 1991, ples (the Little River springs and wells UFA along a 75-kilometer reach from 0.20 (<0.05-9.5); and June 1994, 2.0 upgradient) from the Little River basin (in Ellaville to Branford, as part of the (<0.02-22.). Substantially lower concen- which material overlying the UFA has NAWQA study, in collaboration with the trations of nitrate were measured in water undergone recent and fairly intense disso- SRWMD and the University of Florida. from 76 percent of wells sampled in 1991 lution) had very low activity ratios (0.57) Based on existing data from ten wells, compared to 1990, and probably resulted and high U concentrations (1.76 micro- sampled as part of the FGWQMNP during from denitrification reactions. The process grams per liter). Many springs had activity 1991 to 1994 for water levels and water- of denitrification involves the transforma- ratios greater than 0.75, which Crane quality constituents, Hirten (1995) found tion of nitrate by bacteria (present in the attributed to a mixture of waters from areas that water-level data indicate that the soil and aquifer) to nitrogen gases, result- of high recharge with those from areas of direction of the hydraulic gradient is away ing in lower amounts of nitrogen. Based little or no recharge. The Suwannee River from the river during high-flow condi- on extensive analysis of chemical and has UAR values and U concentrations that tions, in contrast to low flow conditions hydrologic data, evidence for denitrifica- are anomalous when compared to those of when the direction of the hydraulic gradi- tion in water from the UFA was indicated other river systems of the world (Crane, ent is toward the river. The effect of ele- by increased concentrations of dissolved 1986). The anomalous values result from vated river stage on the potentiometric organic carbon, a decrease in measured mixing of some surface runoff (high UAR, surface may extend as much as 8 kilome- redox potential, and an increase in pH and low U concentration) with large amounts ters away from the river. dissolved iron concentrations. Dilution of of ground-water flow from springs and nitrate concentrations in ground water was seeps (generally low UAR and high U con- centrations). Natural Remediation of unlikely because concentrations of chlo- ride and other major ions did not show a The input of water to the Suwannee Contaminants in corresponding decrease from 1990 to River from large springs south of Bran- Ground Water 1991. In fact, chloride concentrations ford, Fla., was traced using 226Ra (Bur- nett and others, 1990). They found that High nitrogen loading from wastes increased in water samples from 75 per- stream stations north of Branford, Fla., generated by poultry and dairy farms, and cent of the wells in which nitrate concen- tended to have a lower mean concentration fertilizers applied to cropland along the trations decreased from 1990 to 1991. of 226Ra (0.189 disintegrations per minute Suwannee River in Lafayette and Suwan- Thus, the combination of higher ground- per liter) compared to the mean concentra- nee Counties has resulted in elevated nitrate water levels in 1991 with increased tion for stations south of Branford (0.270 levels in the river and in parts of the UFA. amounts of organic carbon and decreased disintegrations per minute per liter). Even Changes in water quality and flow patterns amounts of dissolved oxygen in ground though 226Ra has a strong affinity for in the UFA are being evaluated in a 73- water created conditions favorable for the adsorption on aquifer minerals, the con- square kilometer study area in Lafayette natural reduction of nitrate in ground centration of 226Ra in ground water is gen- County, which is located near the Suwan- water. As a result, less nitrate was dis- erally several times to several orders of nee River and consists mainly of agricul- charged by ground water to the Suwannee magnitude higher than in surface waters. tural land use, such as dairy and poultry River.

Lessons Learned always coincide with boundaries and document this preliminary available, in the foreseeable for surface water basins; that is, finding. future, to conduct statewide delin- there is flow of ground water • Insufficient information exists eation and mapping of zones of The vast amount of across surface-water basin at present to determine the lateral interaction between ground water information that has been divides. However, to more pre- extent of mixing of river water and surface water. One solution to this problem would involve the gathered on ground-water and cisely define ground-water basin with water in the UFA during periods of high flow conditons. establishment of watershed coali- surface-water systems in the boundaries, additional wells are ¥ The Suwannee River is both a tions, involving the private sector Suwannee River basin pro- needed to refine the map of the vides an extensive data base gaining and losing stream stakeholders, that could be respon- potentiometric surface for the UFA sible for generating the necessary from which water-resource depending on the stage of the and obtain data to determine more river. However, the existing spa- resources for proper watershed managers can begin to under- detailed flow patterns. tial distribution of wells in the assessments. The watershed coali- stand the importance of the ¥ Complex ground-water flow UFA is not sufficient to delineate tions will benefit their communities hydraulic and hydrochemical patterns can be revealed only areas of ground water flow to the by participitating in, not only iden- linkage between ground water through consistent monitoring river and areas where the river tifying, the threats to watersheds and surface water in the basin. over time and during varying recharges the aquifer. health and function, but also by However, to address specific hydrologic conditions. Sampling ¥ A combination of naturally being a part of the solution to existing problems. management issues, several of ground water and surface- occurring tracers (isotopes, chemical constituents), artificially gaps have been identified water should be coordinated and where more information is introduced tracers (dyes), and performed during changing critically needed: detailed water-level data could U.S. Department of the Interior hydrologic conditions, such as provide much needed information U.S. Geological Survey • It is difficult to use existing data periods of high and low flow. on hydaulic interactions between Fact Sheet FS-080-96 to evaluate basin boundaries and ¥ Reduction in nitrate concen- ground water and surface water, the extent of interaction between trations in ground water by deni- such as the amount of recharge to AUTHORS: ground water and surface water trification processes is likely to the aquifer from surface-water Brian G. Katz because these data were collected inflow, the amount of resurgent occur naturally during periods of U.S. Geological Survey by different agencies for programs surface water in spring flow to the high flow conditions (high water and with different monitoring objec- river, and the amount of ground- Rodney S. DeHan tives. Existing information indi- levels in the UFA and high stages water flow to the river during low in the river and its tributaries). Florida Department of cates that ground-water basin and high stages. Environmental Protection divides, as delineated from potenti- More detailed investigations, ¥ It is unlikely that adequate ometric-surface maps, do not however, are needed to confirm State and Federal funding will be

Ongoing Studies in the Little River Basin REFERENCES

Burnett, W.C., Cowart, J.B., and Deetae, S., 1990, Two studies are currently gathering detailed information on the hydro- Radium in the Suwannee River and estuary: Bio- chemical interaction between ground water and surface water in the Little River geochemistry, v. 10, p. 237-255. basin, a tributary basin to the Suwannee River. One study, which is part of the Crane, J.J., 1986, An investigation of the geology, NAWQA Program, is investigating the extent of the mixing zone between the Suwan- hydrogeology, and hydrochemistry of the lower Suwannee River Basin: Florida Geological Sur- nee River and ground water during various flow conditions. Another study, which is a vey Report of Investigations No. 96, 205 p. cooperative effort among the FDEP, the SRWMD, and the USGS, is investigating the Hirten, J.J., 1995, Influence of the Suwannee River on hydrochemical linkage between the UFA and the Little River where the river disap- ground water height in the Upper Floridan aquifer, pears underground through a series of sinkholes. Results from these studies are Geological Society of America, Annual Meeting, Abstracts with Programs, v. 27, no. 6, p. A-181. expected to provide important information on ground-water basin boundaries, the Kincaid, T.R., 1994, Groundwater and surface water hydrochemical effect of surface water migration into the aquifer during various interaction in the western Santa Fe River basin hydrologic conditions, and natural processes that could remediate contaminants in the near High Springs, Florida: Masters Thesis, Uni- aquifer and surface water. versity of Florida, Gainesville, Florida, 186 p. Maddox, G.L., Lloyd, J.M., Scott, T.M., Upchurch, S.B., and Copeland, R., eds., 1992, Florida’s ground-water quality monitoring program: back- ground hydrogeochemistry. Florida Geological For more information on this and related studies, contact: Survey Special Publication no. 34, 364 pp. John Vecchioli, District Chief Mimi Drew, Director Wilson, W.L., and Skiles, W.C., 1988, Aquifer char- U.S. Geological Survey Division of Water Facilities acterization by quantitative dye tracing at Ginnie 227 N. Bronough St. Florida Department of Environmental Protection Suite 3015 2600 Blair Stone Road Spring, northern Florida: The Proceedings of the Tallahassee, FL 32301 Tallahassee, FL 32399-2400 Second Conference on Environmental Problems (904) 942-9500 (904) 488-3601 in Karst Terranes and Their Solutions, Nashville, Tennessee, Association of Ground Water Scien- tists and Engineers, p. 121-141