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.