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Investigating Regional Hydrogeology of the Mid-Atlantic Coastal Plain

Martin B. Farley
P. Lee Phillips
Rachel McBroom*

Department of Geology & Geography, *Department of Biology
University of North Carolina-Pembroke
Pembroke, NC 28372

This activity uses maps we modified from U.S. Geological Survey publications; specific references are provided in the exercise text.
This material is replicated on a number of sites as part of the SERC Pedagogic Service Project

Summary

Exercise to recognize general groundwater characteristics in the Mid-Atlantic Coastal Plain. The initial phase is an investigation of the Coastal Plain and its stratigraphy using hydrostratigraphic units. The second phase includes interpreting groundwater levels and flow before and after human withdrawals. Students then can interpret likely impacts on the groundwater system, especially for depletion and saltwater intrusion.

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Learning Goals

  1. Determine the regional distribution of coastal plain aquifers and confining units from map data.
  2. Interpret basic flowlines in regional groundwater systems using knowledge of basic pressure characteristics of aquifers.
  3. Interpret the impact of humans on regional groundwater systems from analysis of flowpaths and potentiometric surface levels.
  4. Develop skills in reading and interpreting maps and cross-sections.

Context for Use

This activity is a lab exercise for students in an introductory geoscience course for basic hydrogeologic concepts. In addition to freshman-level college students, we have used it to introduce basic concepts to high school science teachers with no geologic background.

Teaching Materials

The document "Investigating Regional Hydrogeology of the Mid-Atlantic Coastal Plain.doc" contains the basic text and exercises for the students. It refers to the twelve figures (four for each part); these are briefly described in "List of figures for exercise."

Assignment handout and notes (Microsoft Word 36kB Jul25 07)
List of figures for exercise (Microsoft Word 22kB Jul25 07)
Outcrop of the Atlantic Coastal Plain aquifer (Acrobat (PDF) 906kB Aug24 07)
Dip section of Coastal Plain aquifers (Acrobat (PDF) 160kB Jul25 07)
Strike section of Coastal Plain aquifers (Acrobat (PDF) 244kB Jul25 07)
Correlation chart for Atlantic Coastal Plain aquifers (Acrobat (PDF) 157kB Aug24 07)
Illustrations of impacts on coastal aquifers (Barlow aquifer context) (PowerPoint 1.6MB Aug24 07)
Potentiometric surface of PeeDee-upper Cape Fear aquifers before pumping (Acrobat (PDF) 166kB Jul25 07)
Potentiometric surface of PeeDee-upper Cape Fear aquifers after pumping (Acrobat (PDF) 195kB Aug24 07)
Potentiometric surface of Black Creek aquifer in 1980 (Acrobat (PDF) 137kB Aug24 07)
Water production from PeeDee-upper Cape Fear aquifers in 1980 (Acrobat (PDF) 187kB Aug24 07)

Teaching Notes and Tips

The exercise assumes students understand:
1) what an aquifer, confining unit, and cones of depression are
2)what a potentiometric surface is
3)the relation, in the NC Coastal Plain, of the potentiometric surface of Cretaceous deep aquifers to topographic contours (i.e., they're commonly very close).

We generally precede this exercise with one that introduces these concepts, using paper maps with local data on one of the Cretaceous aquifers.

We have commonly projected the Powerpoint figures in Part 2 (Figures 2-1 to 2-4) in introducing the hydrogeology exercise and not printed them out for the students.

Note that Figure 3-1 (potentiometric surface before pumping) implies that flow might have been updip in some areas of central North Carolina before pumping. See the "island" of the 100' potentiometric surface.

The embayment of the 100' potentiometric contour in Bladen and Cumberland Counties is where it crosses the valley of the Cape Fear River. As the potentiometric surface is close to the land surface, it V's upstream as do the topographic contours.

Acknowledgments: Development of this exercise has been supported by NSF Grant EAR 05-03592. In addition, Paul Barlow (USGS) generously provided figures from his Circular on saltwater effects on aquifers.

Assessment

The exercise contains questions to direct student inquiry and their answers can be used for assessment.

References and Resources

Barlow, P.M., 2003, Ground Water in Freshwater-Saltwater Environments of the Atlantic Coast: U.S. Geological Survey Circular 1262, 113 p.

North Carolina Division of Water Resources, August 2004, Central Coastal Plain capacity use area status report: North Carolina Division of Water Resources, Environmental Management Commission, 31 p. (available as of June 14, 2007 as a pdf from http://www.ncwater.org/Reports_and_Publications/GWMS_Reports/

Trapp, H., Jr. and Horn, M.A., 1997, Ground Water Atlas of the United States--Delaware, Maryland, New Jersey, North Carolina, Pennsylvania, Virginia, West Virginia: U.S. Geological Survey Report Hydrologic Atlas HA730-L.