Wetlands Hydrology in Relation to the Surrounding Landscape in the North Landing River Natural Area Preserve, Virginia

by M. J. Focazio and G. K. Speiran

Hydrologic interactions between protected wetlands and the surrounding landscape of the North Landing River Natural Area Preserve were investigated from spring of 1994 to fall of 1996. The U.S. Geological Survey cooperated with the Virginia Department of Conservation and Recreation and The Nature Conservancy to investigate the potential of nearby land uses on the ecosystem of the protected wetland areas.

Water levels were monitored and water samples were collected in wells and piezometers in the water-table and underlying confined aquifers along a transect that crosses an agricultural upland, a forested wetland that includes a mixed stand of Atlantic white-cedar (Chamaecyparis thyoides) and pond pine (Pinus serotina), a series of short and tall pocosins, and a low salinity marsh. The geohydrologic framework of the study area was determined by use of peat cores, hand-augured well borings, published geologic maps, water levels, and water-chemistry data including concentrations of tritium, major ions, and major nutrients. These data were also used to help determine ground-water-flow patterns and water quality. Specific conductance, precipitation and wind speed and direction, were continuously monitored at selected ground- and surface-water sites for various time periods to investigate the role of wind-induced tidal fluctuations on the wetland system.

Individually, the water-level and water-chemistry data corroborate that the pocosins receive water entirely by direct precipitation. This ombrotrophy is caused by the low to nonexistent horizontal ground-water gradients, the downward ground-water gradients under the pocosins (indicating that the pocosins recharge the underlying confined aquifer), and the absence of surface-water inputs. The marsh and forested wetland adjacent to the pocosins are clearly minerotrophic, and mixing of marsh surface water with surface water in the forested wetland was documented during extreme wind events. These hydrologic controls have important implications for management of the pocosins and surrounding wetlands. Currently, land-use practices in the wetlands and uplands that border the pocosins do not affect the hydrology of the ecosystem due to the isolation within the landscape. The forested wetland and marsh; however, are minerotrophic and therefore could be affected by nearby land-use practices.

Focazio, M.J., and Speiran, G.K., 1999, Wetlands hydrology in relation to the surrounding landscape in the North Landing River Natural Area Preserve, Virginia [abs.], Society of Wetland Scientists Annual Meeting, Norfolk, Virginia: Bulletin, Society of Wetland Scientists, Supplement, v. 16(2), p. A-46 - A-47.

Contact: GS-W-VArmd_webmaster@usgs.gov
U.S. Department of Interior, U.S. Geological Survey
Privacy Statement
Disclaimer