Hydrosphere

Global Water Inventory

97.2% Oceans

2.15% Ice Caps and Glaciers

0.0625% Subsurface water

• 0.005% Soil Moisture
• 0.52% Groundwater

0.017% Surface Water

0.009% Freshwater Lakes 0.008% Saline lakes and inland seas 0.0001% Rivers and Streams

0.001% Atmospheric Water Vapor

Freshwater Inventory:

Glaciers and Ice 84.9%

Groundwater 14.2%

Lakes, reservoirs 0.5%

Soil moisture 0.3%

Atmosphere 0.05%

Rivers 0.004%

Groundwater

Definition - water contained in the pore spaces within rock.

Only represents 0.62% of total water on earth, but represents 14.2% of freshwater inventory

Most important source of water for drinking and irrigation

Much concern exists about groundwater contamination from sewage, human garbage, fertilizers, pesticides, and industrial wastes.

The Water Table

Voids in soil or rock can be occupied by either air or water

Above the water table in the zone of aeration, open spaces are mainly filled by air

Below the water table in the zone of saturation, open spaces are filled by water

The water table is therefore the upper limit of the zone of saturation.

Water table is not a level surface and generally mirrors surface topography

Swamps occur when the water table is at the surface

Water table moves up and down in time in response to rainfall

Movement of Groundwater

Groundwater moves within rock formations at slow velocities (centimeters per day or kilometers per year)

Gravity provides the energy for water movement and water tends to migrate to the point of lowest pressure (usually, but not always, downslope)

The ability of a rock to hold and transmit water is determined by its porosity and permeability

Porosity - % pore volume to the total volume of the rock. Depends on size and shape of grains, packing, degree of sorting, and amount of cement.

Permeability - ability of rock to transmit a fluid. How well are the pore spaces connected?

Aquifers - permeable rock strata or sediment that transmit groundwater freely

Aquiclude - rock layers that have low permeability. Blocks the movement of water.

Recharge zone - place on the Earth surface where surface water seeps into or recharges the aquifer. Recharge zones are environmentally sensitive because it is easy to contaminate groundwater supply.

Where does our water come from?

Gainesville well field -- NE 53rd Ave

8 wells drilled into the Florida aquifer. Groundwater is pumped to large water tanks and distributed to our homes.

Floridan Aquifer - soft, permeable limestone (known as the Ocala Limestone) that yields large quantities of water

In North Florida, Ocala limestone is overlain by an aquiclude known as the Hawthorne Formation consisting of mainly clays.

The Hawthorne aquiclude is overlain by Pleistocene sands that constitute the surficial aquifer.

The zone of recharge for Ocala Formation occurs to the west.

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