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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
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