The Hydrologic Cycle and Groundwater

Total amount of water on the Earth's surface 1.46x 106 km3

Where is the water ? How is it distributed?

Oceans 1.4 x 109 km3 95.6%

Glaciers 2.97%

Undergound waters 1.05%

Lakes and rivers .009%

Atmosphere .001%

Biosphere .0001%

But water is dynamic on the Earth's surface motion described by the the Hydrologic Cycle.

Hydrologic Cycle

Precipitation

factors humidity , cooling; cooling caused in various ways:

Cold fronts; orographic cooling (and rain shadows), convectional cooling (S. Florida)

Runoff -

what forms rivers this is what is left over after evaporation and infiltration - streams, rivers and lakes; artificial lakes are reservoirs behind dams(these are simply a way of controlling runoff).

Infiltration depends on state of ground, whether vegetated or bare, slope etc

Groundwater

Porosity and Permability

Porosity

capacity of rock to hold water

pore structure; reduce porosoty and with decreasing grain size and cementation

fracture porosity

porosity = (volume available for water / total volume) x 100 %

Permeability

Rock body with high permeability and porosity is called an aquifer

Rock body with low permeability is called an aquitard (aquiclude).

Aquifers and the behaviour of the water table

Unsaturated (vadose) zone; Saturated (phreatic zone)

Surface between these two is the Water Table

Unconfined aquifer:

Recharge and discharge

Speed of flow - slow

Behaviour of Wells

Cone of depression

Confined aquifers and Artesian wells

Aquiclude caps and auifer so that water cannot freely flow upward

Floridan aquifer situation Water sinks N of Orlando, rises in Artesian wells in John Pennekamp Park, (Chekika Park)

Oases

Coastal aquifers

Salt water intrusion

Erosion by Groundwater - Karst terrains

Caused by soultion of soluble rocks limestone, gypsum, salt

Chemical solution of limestone

H2O + CO2 ------> H2CO3 (Carbonic acid)

H2CO3 + CaCO3 ----> Ca(HCO3)

"Hard" water is water with calcium bicarbonate

Caves

solution of limestone forms conduits a.k.a. caves

Sinks, Risings

Suface features of karst terranes

closed depressions, lack of surface streams

Pollution and water quality in karst terrains

Water moves fast and no filtering effect compared to non karst groundwater

Catastrophic Sinkholes

Occur in central Florida where there are two water tables. Loose, sandy aquifer overlies clay aquiclude (Hawthorne Formation) which in turn overlies limestone aquifer