Groundwater Systems

Importance of Groundwater

•Groundwater usage–Drinking water for > 50% of the population

–Accounts for 40% of the Irrigation water

–Provides 25% of industry’s needs

Groundwater

Other FreshW ater94

%

6%Freshwater – no

Glaciers

•Excluding glaciers, groundwater is 94% of the available freshwater.

Glaciers

Groundwater

Other FreshWater

14%

85%

Freshwater•Although groundwater is only 0.6% of the Earth’s water it is 14% of the fresh water.

Ocean Water

Fresh Water

97%

3% Earth’s Water

•Only 3% of the Earth’s water is fresh & potable.

Daily Assignment

• Using the terms below complete the concept map.

A) saturated zone

B) unsaturated zone

C) partially saturated zone

D) sandstone

E) shale

F) confining unit

G) unconfined aquifer

H) confined aquifer

I) porosity

J) permeability

K) aquifer

M) water table

L) infiltration

Rock/Sediment

3. 4.

5.

8.6. 7.

9. 10.

With high 1) _______(storage of water) & high 2) _________ (transmission of water)

With low 1) _______ & low 2) _________

Forexample

Forexample

Pores are filledwith water

Pores are filledwith water & air

Between 2confining layers

Near thesurface

How does water get below the Earth’s surface

• Water infiltrates in recharge areas – areas at the Earth’s surface that allows water to move through it

Is groundwater an underground river?• Groundwater occurs

everywhere• Zone of Saturation –

all the pore space is filled with water

• But not all the ground is saturated

• Zone of Aeration – pores are filled with air and water

• Water Table – upper surface of the zone of saturation

• Porosity– Percentage of total volume

of rock or sediment that consists of voids (pores)

– Function of • Size and shape of the grains

• The packing of the grains

• Sorting of the grains

Where is groundwater stored?

Permeability

• Ability of a material to transmit a fluid (water)

• The interconnectedness of the pores

– Shales have a low permeability

– Sandstones have a high permeability

• Unconfined Aquifer – top of the aquifer is exposed to the atmosphere

• Confined Aquifer – an aquifer lying between two aquitards, water is under pressure

• The water table is a subdued replica of the topography

Groundwater movement

• Groundwater is not stagnant, it responds to climatic changes

• i.e. the water moves up wet periods & moves down during dry periods

Energy Drives Water Movement

• Groundwater moves from high “energy” to low “energy”

• Groundwater has two types of energy– Potential (stored) energy – controlled by elevation &

gravity – how far can the water drop– Kinetic (in motion) energy – controlled by pressure and

velocity (very small can be ignored)

• Total of potential and kinetic energy is hydraulic head

• Groundwater is moving, but slowlyslowly

Artesian Conditions

Artesian is applied to any situation where the groundwater in a well rises above the level where it is initially encountered.

Associated with confined aquifers – due to excess pressure from overlying material