Hydrogeology (or “groundwater hydrology”) is the study of tracking the flow of water as it "works" through the soil and into underground systems.
Once rainwater (or snow, ice, hail, etc.) soaks into the subsurface of the earth, a process called recharge, it moves downward, passing between particles of soil, sand, gravel, or rock until it reaches a depth where the ground is filled, or saturated, with water. The area that is filled with water is called the saturated zone and the top of this zone is called the water table. All water below the water table depth is known as groundwater. In the Piedmont and Mountains, the entire saturated system, including the soil, saprolite and bedrock, together compromise what is known as the aquifer.
The Upper Piedmont Research Station is a 680-acre tract owned and operated by North Carolina State University and the North Carolina Dept. of Agriculture and Consumer Services. The station is located adjacent to the Betsy-Jeff Penn 4-H Center and the historic Chinqua-Penn Mansion. There are many historic structures located on the station such as historic log horse barns and a 200-foot long stone dam.
The UPRS is one of five hydrogeologic research stations in the fractured rock of the Piedmont and Mountains of North Carolina. A range of hydrogeological data, including groundwater chemistry and age dating, groundwater flow differences down “dip slope” vs. down “scarp slope”, effects of groundwater on surface water, and effects of agricultural land uses on groundwater quality, is gathered from samples taken bi-annually from the 19 monitoring wells on site.
The UPRS hydrogeologic research is focused on the Piedmont Province aquifers. Most of this province, like the adjoining Blue Ridge Province, is underlain by dense, almost impermeable bedrock that yields water primarily from secondary porosity and permeability provided by fractures. The bedrock in both provinces is partly covered by glacial deposits, which include productive sand and gravel aquifers.
The Piedmont Province is bounded on the southeast by the Fall Line, which is a zone of rapids or waterfalls that marks the position where streams flow from the consolidated rocks of the Piedmont onto semiconsolidated to unconsolidated rocks of the Coastal Plain. The western and northwestern boundaries of the Piedmont Province are, for most of their length, the base of a mountain ridge. This ridge is the highlands of the Reading Prong from northern New Jersey to northeastern Pennsylvania and the Blue Ridge Mountains from southern Pennsylvania to North Carolina. In the gap between the two mountain ridges, the Piedmont Province is adjacent to the Valley and Ridge Province, and the boundary between the provinces is the northwestern edge of the early Mesozoic Gettysburg and Newark Basins.
The Piedmont Province is underlain by three principal types of bedrock aquifers - crystalline-rock and undifferentiated sedimentary-rock aquifers, aquifers in early Mesozoic basins, and carbonate-rock aquifers. The rocks in the Piedmont of North Carolina are primarly igneous and metamorphic and are considered as part of the crystalline aquifer system. This aquifer system is the most widespread system in the Piedmont and Blue Ridge Provinces, extending over 49,000 square miles, or about 86 percent of the area. Running just north and west of this area is the Dan River/Danville Basin, where the aquifers are found in the early Mesozoic rift basins.
Most of the rocks that compose the crystalline-rock and undifferentiated sedimentary-rock aquifers are crystalline metamorphic and igneous rocks of many types. The main types of crystalline rocks are coarse-grained gneisses and schists of various mineral composition; however, fine-grained rocks, such as phyllite and metamorphosed volcanic rocks, are common in places. Most of the metamorphic rocks were originally sediments; some, however, were igneous rocks or volcan-ic tuff, ash, and lava flows. The degree of heat and pressure to which the original rocks were subjected, the nature of the fluids that have been in contact with the rocks, and the degree of folding and shearing that they have undergone have produced their present texture and mineralogy. Most of the metamorphic rocks have undergone several periods of metamorphism. Locally, they contain highly mineralized zones, some of which are ore bearing. During and after metamorphism, igneous rocks intruded the metamorphic rocks and are present as dikes, sills, and large to small plutons.
One interesting aspect of the UPRS project is the nature of the local groundwater flow system. The geologic structure dips consistently to the south and southeast across the site. Land surface in the northern portion of the property faces steeply north (opposite the dip direction), while land surface in the southern portion faces gently south (in the same direction as the dip), setting up a modified dip-slope and cut-slope scenario. Examples of the southerly dip of bedrock can be seen in outcrops around the walking trail.
To Receive Credit for this Earthcache:
• Four of the monitoring wells on the UPRS are easily accessible off of the Chinqua Penn Walking Trail. Post a picture of you and your group with your GPSR standing with one of the two pairs of monitoring wells located at either:
N 36* 23.471, W 079* 42.275 or N 36* 23.388, W 079* 42.212
• AND Email us the answers to the following questions, using the informational sheets posted on the kiosk at the parking lot.
The answers are no longer posted on the kiosk. Use the highlighted information below to answer question #2 and post your picture!
1. Monitoring wells are generally grouped into clusters of three. What are the three traditional classifications or depths of these wells? Shallow (regolith), Intermediate (transition zone), Deep (bedrock)
2. Using the well-depths listed on the tags on the two monitoring wells where you took the photograph, which of the three classifications above do you believe they fall into? 30 feet (shallow), 70 feet (intermediate), 260 feet (deep), 300 feet (deep)
3. What are some of the variables that can affect the water table’s depth? droughts, area ground water usage, etc.
4. According to the age dating sampling, the groundwater on the UPRS fell as rain or other precipitation how many years ago? between 10 and 50 years ago
5. How many people in this area of North Carolina rely on groundwater as their principle water supply? over 2 million people
6. Think about where you live… is groundwater your principle water supply? If not, what do you think is?
References Cited:
Baloochestani, Farshad. Estimation of Hydraulic Properties of the Shallow Aquifer System for Selected Basins in the Blue Ridge and the Piedmont Physiographic Provinces of the Southeastern U.S. Using Streamflow Recession and Baseflow Data. Thesis (Ph. D.)--Georgia State University, 2008.
Hollyday, E. F., and G. E. Hileman. Hydrogeologic Terranes and Potential Yield of Water to Wells in the Valley and Ridge Physiographic Province in the Eastern and Southeastern United States. Regional aquifer-system analysis--Appalachian Valley and Piedmont, C. Washington, D.C.: U.S. G.P.O.], 1997.
Upper Piedmont Research Station Fact Sheet
U.S. Geological Survey, 1997, HA-730: Ground Water Atlas of the United States (Delaware, Maryland, New Jersey, North Carolina, Pennsylvania, Virginia, West Virginia), Trapp, Henry Jr. and Horn, Marilee A.
U.S. Geological Survey, 2009, 2009-5149: Characterization of Groundwater Quality Based on Regional Geologic Setting in the Piedmont and Blue Ridge Physiographic Provinces, North Carolina, Harden, Stephen L., Chapman, Melinda J., and Harned, Douglas A.
Photos from the U.S. Geological Survey Open File Report 93-642
A special thanks to Snoopinaround for the help and education!