Earth’s Water

Only 1% of the Earth’s water is usable and accessible for

consumption.

• Evaporation: Process of changing from a liquid to a gas– Two factors affecting evaporation

• Temperature• Surface area

• Transpiration: process by which plants release water vapor into the atmosphere

• Evapotranspiration: How the atmosphere gets moisture as a combination of evaporation and transpiration.

• Infiltration: water seepage thru the ground

The Water Table

• Water Table: boundry that separates the zone of saturation from the zone of aeration

The Water Budget

1. Precipitation (P) – Main Source of water

2. EP (Potential evaportation) = Heat

3. P/EP ratio = P divded by EP = Climate type of area4. Storage (st) = Amount of water stored in the ground5. Δ storage = change in storage

• If negative – Δ st = usage (evaporation)• If positive + Δ st = rechagre infiltration

6. Ea (actual evapotranspiration) – amount of moisture that actually evaporates

7. Deficit = shortage of water = drought8. Surplus = extra water = runoff

Factors of Infiltration

1. Ground Saturation – saturated ground means no infiltration, unsaturated ground means infiltration

Factors of Infiltration

2. Slope of Land – Steep Slope = little

infiltration– Gentle Slope = a lot of

infiltration

Factors of Infiltration

• Permeability (rate of infiltration)– Larger particles =

greater permeability = large pore space

Infiltration Vs. Permeability

0

1

2

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4

5

Infiltration

Pe

rme

ab

ility

Line 1

Infiltration Vs. Slope

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1

2

3

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5

Infiltration

Slo

pe

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Infiltration Vs. Ground Saturation

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Infiltration

Gro

un

d S

atr

ura

tio

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Runoff

• Runoff: Water that does not infiltrate

• This occurs when:1. Ground is saturated

2. Steep Slope

3. Impermeable ground (water can’t get through)

4. No vegetation

Porosity

• Porosity: percent of pore space

• NOT EFFECTED BY PARTICLE SIZE

• Equation:– water volume ÷ total volume of sediments x

100

Porosity Factors

• Shape of particles– Round sediments = more porosity– Angular sediments = less porosity

Porosity Factors

• Packing of Sediments– Well packed = less

porosity– Poorly packed = more

porosity

Porosity Factor

• Sorting of sediments– Well sorted = more

porosity– Poorly sorted = less

porosity

Porosity Factors

• Size has a constant relationship– Sediment size does not affect porosity at all

Porosity and Sediment Size

0

0.5

1

1.5

2

2.5

Small Medium Large

Sediemnt Size

Po

ros

ity Small

MediumLarge

Capillarity

• Capillarity- water rises thru small pore spaces

Capillarity Vs. Pore space size

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12

Small Meduim Large

Pore Size

Ca

pill

ari

ty

Line 1

Think of a straw in a soda

Ground water experiment• Which tube has:

– Greatest Permeability and the least permeability– Greatest porosity and lowest porosity– Greatest capillarity– Greatest runoff– Retain the least water?