Fresh WaterFresh Water

and Karst Topographyand Karst Topography

Hydrologic cycleHydrologic cycle

On a On a globalglobal basis: basis:

Water from atmosphere to earth

(Precipitation)

Water from earth to atmosphere

(Evaporation andTranspiration)

=

Surface WaterSurface Water

lakeslakes

streamsstreams

overland flowoverland flow

Ground waterGround water

soilsoil

pores in rockspores in rocks

regolithregolith

sedimentssediments

Ground waterGround water

Water stored beneath the surface, in Water stored beneath the surface, in rock, regolith, soil, sedimentsrock, regolith, soil, sediments

– Flows to surface waterFlows to surface water– Is Is rechargedrecharged (fed) by surface streams (fed) by surface streams

Water percolates downward from soil as Water percolates downward from soil as gravitational water through gravitational water through aerated aerated zonezone; reaches ; reaches water tablewater table, which is the , which is the top of the top of the saturated zonesaturated zone

aquifer:aquifer: rock or sediment that rock or sediment that holds a body of free-flowing holds a body of free-flowing

ground waterground water

Ground water utilization: Ground water utilization:

well pumping causes well pumping causes cone of depressioncone of depression; ;

may cause water table may cause water table drawdowndrawdown

Water table and climateWater table and climate

Karst TopographyKarst Topography

movement of ground water through movement of ground water through limestone produces limestone produces karst karst landscapes.landscapes.

Characteristics:Characteristics: SinkholesSinkholes

CavesCaves SpringsSprings

Lack of surface waterLack of surface water

Requirements:Requirements:(Not all limestone regions are karst regions)(Not all limestone regions are karst regions)

““pure” limestone pure” limestone – (>80% calcium carbonate)(>80% calcium carbonate)

abundant rainfallabundant rainfall complex joint patterns in complex joint patterns in

limestonelimestone

Carbonation process:Carbonation process:

1. carbon dioxide + water 1. carbon dioxide + water carbonic carbonic acidacid

2. carbonic + 2. carbonic + calciumcalcium calciumcalcium

acidacid carbonatecarbonate bicarbonatebicarbonate

in limestone

soluble

Soluble product of the reaction is Soluble product of the reaction is carried away in groundwatercarried away in groundwater

As groundwater seeps through As groundwater seeps through joints, rock is gradually dissolved; joints, rock is gradually dissolved; beginning of cavern formationbeginning of cavern formation

Tube passageTube passage

As rock dissolves, surface loses As rock dissolves, surface loses underlying support and subsides or underlying support and subsides or collapses:collapses:

SINKHOLE developsSINKHOLE develops

TravertineTravertine

Calcite that has precipitated out of Calcite that has precipitated out of groundwater as a mineral depositgroundwater as a mineral deposit

carbonation in reverse carbonation in reverse ::

calcium calcium calcite + CO calcite + CO2 2 + + HH22OO

bicarbonatebicarbonatetravertine

Some types of travertine:Some types of travertine:

soda strawssoda straws draperiesdraperies stalactitesstalactites stalagmitesstalagmites columnscolumns