Geometry of the Water Table

Similar in shape to land surface, but

more subdued

Groundwater flows down slope of water table

Slope of the Water Table Influences Groundwater Flow

Slower

Steeper slope = faster flow

Groundwater divideFaster

Types of Aquifers

Confined aquifer overlain by less permeable materials

Unconfined aquifer open to Earth’s surface and to infiltration

Perched aquifer underlain by low-permeability unit

Artesian aquifer: water rises in pipe (maybe to surface)

Fractures can contain groundwater

May be the only pathways for water, if interconnected

More fractures = more water

Groundwater in Fractures

17.03.a2

(Cunningham & Daniel, 2001)

Bedrock Aquifer

http://www.usgs.gov/envirohealth/geohealth/v09_n03/ - Arsenic and Other Natural Contaminants in New England Drinking Water Wells

Bedrock Aquifer

Limestone (Karst) Aquifers

Groundwater is slightly acidic

Limestone is soluble

Above water table, cave may be dry

Below water table water further dissolves materialNOT where most

groundwater occurs

http://nc.water.usgs.gov/reports/ofr041025/report.html

Generalized geology of NC

Aquifers of eastern NC

How Does Water Move Between the Surface and Subsurface?

Water table intersects surface

Why is there water in streams when it’s not raining?

How Are Lakes and Wetlands Related to Groundwater?

Water table intersects surface

Perched above water table

Wetlands at water table or perched

How Do Streams Interact with Water Table?

Stream higher than water table

Stream lower than water table Gaining stream

Losing stream

http://pubs.usgs.gov/circ/circ1139/htdocs/natural_processes_of_ground.htm

http://pubs.usgs.gov/circ/circ1139/htdocs/natural_processes_of_ground.htm