Introduction to Groundwater, Karst and the Edwards Aquifer

Water color by Kathy Rottier

Groundwater Zones

Alternate image of groundwater zones

Porosity

Permeability

Types of groundwater flow

Aquifer Recharge and Discharge

Groundwater flow timescales

Artesian groundwater systems

Water: the great dissolver and precipitator

Dissolves: Precipitates:

Limestone, gypsum, salt (makes caves and landscapes these rocks)

Cave deposits (stalactites, travertine, etc)

Cements that hold sedimentary rocks together (calcareous, siliceous, and ferruginous)

Few minerals from sandstones, shales, and igneous and metamorphic rocks (does not make caves in these rocks)

Spring and geyser deposits

Concretions and geodes

Limestone Dissolution

H2O + CO2 = H2CO3

water + carbon dioxide = carbonic acid

H2CO3 + CaCO3 = Ca++ + 2 HCO3-

carbonic acid + calcium carbonate (limestone) = calcium ions + bicarbonate ions

Karst Development: Initial Stage

Karst Development: Intermediate Stage

Karst Development: Late Stage

Karst Terrain

Mike Warton

Geologic History of the Edwards Aquifer

Uplifting and Earthquakes

The Edwards Aquifer

Barton Springs Segment (map view)

Barton Springs Segment (cross-section view)

Inner Space Caverns

Photos by Marsha WillisPhotos by Marsha Willis

Longhorn CavernsLonghorn Caverns’’Photos by Larry JayroePhotos by Larry Jayroe

Photo Credit: City of Austin <http://www.ci.austin.tx.us/watershed/images/

bartonaerial.jpg>,accessed September 22, 2008

Barton Springs Pool

Example Hydrograph

Discharge at Barton Springs January 1980 – September 2008

Source: USGS <http://waterdata.usgs.gov/tx/nwis/uv/?site_no=08155500>,accessed September 19, 2008

Source: Source: http://media.point2.com/p2a/htmltext/d51f/3a57/e5a5/4d13a91fhttp://media.point2.com/p2a/htmltext/d51f/3a57/e5a5/4d13a91fbcd071034cf8/original.jpg, accessed September 22, 2008bcd071034cf8/original.jpg, accessed September 22, 2008

The EndThe End