Situated within Ordway-Swisher Biological Station (OSBS) in Putman County, Barco Lake is an oligotrophic (i.e., has low nutrient levels) acidic seepage lake in the mantled karst, a landscape formed by the dissolution of soluble rocks, of north central Florida.
Surface area, elevation & depth
Barco Lake is 0.12 km2 in surface area, at an elevation of 28 m and sits within a 0.9 km2 watershed. Barco Lake has a maximum depth of 7.1 m and a mean depth of 4.3 m.
Estimated to be at least 1000 years old, Barco Lake is classified as a lentic sandhill upland lake underlain by sandy substrate and organic deposits that increase with depth. It is underlain by the Floridan Aquifer dominated by a limestone and dolomite geology. The limestone geology is overlain by a thick mixture of sand, gravel, clay, phosphate, and carbonate deposited during the Pleistocene interglacials. The overlying sands are highly weathered and have very low cation-exchange capacity.
Barco Lake is a typical lentic water body without significant surface inflows or outflows. Instead, water may be largely derived from lateral groundwater seepage through the surrounding well-drained uplands and/or from artesian sources via connections with the underlying limestone aquifer. There is no discernible inflow or outflow to Barco Lake, although there is some evidence of water inflow from the northern edge of the lake with a flow pattern to the S and SE. Virtually all the water inflow to Barco Lake is groundwater, with up to 8 inches per year: the main flow of groundwater is NE to SW and groundwater flow is downward beneath most of Barco Lake. Fluctuation in the water table is generally between 1 to 1.5 m but can reach up to 3 to 4 m during storm event.
The immediate watershed of Barco Lake is characterized by a forest of widely spaced pine trees (Pinus clauda) and a sparse understory of deciduous oaks. Fairly dense ground cover of grasses and herbs is typical of these environments. Fire is a dominant factor in the ecology of this community.
Common animals include tiger salamander, barking treefrog, spadefoot toad, gopher frog, gopher tortoise, worm lizard, fence lizard, mole skink, indigo snake, coachwhip snake, pine snake, short-tailed snake, crowned snake, eastern diamondback rattlesnake, bobwhite, ground dove, red-headed woodpecker, rufous-sided towhee, fox squirrel and pocket gopher. Barco Lake is an important breeding areas for terrestrial amphibians, including the threatened gopher frog, as well as many unusual or endemic insects, as well as an important watering holes for a number of mammals and birds, including ducks and wading birds.
Barco Lake is an oligotrophic acidic lake (pH 4.5). The lake is clear with a dissolved organic carbon (DOC) concentration of ~ 2 mg L -1 . The water chemistry is highly influenced by the rainwater and interactions with groundwater. Total phosphorous and nitrate concentrations are ~ 39 μg L -1 and 14 μg L -1 , respectively, and SO4 2- ~ 2.18 mg L -1 . Chlorophyll a concentration is ~ 2.74 μg L -1 (James, 1991). Upgradient of Barco Lake the water remains oxic as it moves downward. Downgradient of Barco Lake, the oxic groundwater mixes with lakewater leakage in a highly reducing (methanogenic, low-sulfide), silicate-carbonate mineral environment.
Resources & additional readings
- James, R.T. 1991. Microbiology and chemistry of acid lakes in Florida: II. Seasonal relationships. Hydrobiologia, 213: 227-240
- Katz, B.G. 2002. Demystifying Ground-water Flow and Contaminant Movement in Karst Systems Using Chemical and Isotopic Tracers. U.S. Geological Survey Karst Interest Group Proceedings, Shepherdstown, West Virginia, August 20- 22, 2002
- Lee, T.M., 1996, Hydrogeologic controls on the groundwater interactions with an acidic lake in karst terrain, Barco Lake, Florida: Water Resources Research, v. 32, p. 831-844
- Lee, T.M., 2002, Factors Affecting Ground-Water Exchange and Catchment Size for Florida Lakes in Mantled Karst Terrain. U.S.G.S. Water-Resources Investigations Report 02-4033
- Winter, T.C., J.W. Harvey, O.L. Franke, and W.M. Alley, 1998, Ground Water and Surface Water A Single Resource. U.S. Geological Survey Circular 1139