Date of Award

Fall 1990

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Geological Sciences

Committee Director

G. Richard Whittecar

Committee Member

Joseph H. Rule

Committee Member

Randall S. Spencer

Call Number for Print

Special Collections LD4331.G4H57

Abstract

Ground-water-fed interdunal ponds in Nags Head Woods Ecological Preserve lose as much as 7600 m3 yr-1 of water through evaporation. This withdrawal of groundwater is sufficient to significantly alter flow patterns through the surficial aquifer on Bodie Island, N.C. Statistical analyses of evaporation estimates derived by various methods indicate a weak correlation, (r2=0.4-0.5) between pan evaporation data from Aurora, N.C. and pond evaporation at Nags Head Woods calculated by water budget analyses.

Results of stratigraphic and pedologic analyses in and around the ponds indicate that the ponds formed after development of multiple generations of dunes. This dune field rests upon a Holocene regressive barrier island segment with a 10 m thick surficial aquifer. Peat on the bottoms of two ponds is up to 0.25 m thick, being thickest close to the ponds' edges. Permeameter tests indicate permeabilities of 0.15cm/day for the peat, approximately ten times less than the permeability of the surrounding dune sand.

Water level data gathered weekly from thirteen pairs of monitoring wells around the ponds reveal that water table gradients can vary irregularly in magnitude and direction. Heads in wells close to ponds generally mimic lake levels although hydraulic responses are influenced by low peat permeability. A numerical model of the pond-aquifer interface indicates that heads in monitoring wells within 10m of a pond require more than 24 hours to rise to increased pond levels following an intense rainstorm. Heads in wells beyond 10 m show virtually no effects of such bank storage but show relatively large fluctuations caused by impulses of water infiltrating through the unsaturated zone. Generalized trends in gradient data indicate that groundwater enters these ponds along their northern and eastern sides and exits towards the south and west.

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DOI

10.25777/t259-7s29

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