Water in the Earth

The Water Cycle• Earth has been recycling

its water supply for 4 billion years.

• 97.2% = Ocean salt water• 2.8% = fresh water

• When precipitation falls, four things can happen:

1. Water retention

2. Infiltration

3. Runoff

4. Evapotranspiration

Factors Affecting Infiltration1. Slope of the land – the steeper the slope, the less

infiltration.

Factors Affecting Infiltration2. Degree of Saturation – the more saturated the

ground is, the less infiltration there will be.

1.) Zone of aeration pores are partly filled with air and water.

2.) Zone of saturation pores are completely filled with water.

Regolith

Solid Rock

How old is your water?

Factors Affecting Infiltration3. Porosity: the percentage of open space in a

material compared to its total volume.– The greater the porosity, the greater the infiltration.

Porosity depends on:a) Shape - Rounded particles have greater porosity

than angular. Rounded shapes do not fit together tightly.

Porosity depends on:b) Packing:– Closely packed = lower porosity. – Loosely packed = higher porosity.

Porosity depends on:c) Sorting: • All the same size (sorted) has higher porosity.

• All different sizes (unsorted) has lower porosity. Smaller particles can fit between larger particles.

• Size DOES NOT affect porosity!!!

Few pore spaces, but they are very large.

Many pore spaces, but they are very small.

Same Porosity

Factors Affecting Infiltration4. Permeability: the ability of a material to allow

fluids to pass through**How WELL CONNECTED are the pore spaces?**

Permeable: Allows fluids to pass through

Impermeable:Fluids cannot pass through easily

Impermeable Impermeable Permeable

Factors Affecting Infiltration5. Capillarity: the attractive

force between water molecules and the surrounding Earth materials.

• Results in the movement of water up against gravity

Zone of Aeration

Factors Affecting Infiltration6. Vegetation: more plants = more infiltration

Factors Affecting Infiltration7. Land Use:– Creation of

impermeable surfaces– Removal of vegetation

Surface RunoffOccurs when:• Precipitation rate > infiltration

rate• Surface material is saturated • Slope too steep• Surface water has not yet

evaporated/sublimated

**Most runoff makes it to streams, which carry water back to the oceans.

Surface RunoffStream Discharge: the volume of water flowing past a

certain spot in a stream in a specific amount of time.

Surface Runoff• Flooding: occurs when a stream overflows its

normal channel.– Precipitation rate > infiltration rate– Hurricane’s storm surge– Rising of sea

level– Sinking Land– Tides moving

water onto land

• Flooding of the Walsbash River in Indiana inundates Highway 63 for 3/4 mile on June 13, 2004. Birds and Crane in the foreground are watching a 2-foot carp (fish) cross the road. Photo Credit: Photo by Marvin Nauman, FEMA News Photo