Water In Deserts

Question 1

What are the sources of water in hot deserts?

Answer 1

• Exogenous rivers
• Endoreic rivers
• Empemeral rivers
• Episodic flash floods
• Fog (Atacama)

Question 2

Exogenous rivers

Answer 2

Are rivers that have their source in mountains, outside desert regions

• They have sufficient water to flow continuously despite the high rates of evaporation
• E.g. The Nile, the Colorado

Question 3

Episodic flash floods

Answer 3

Are infrequent rainfall events that tend to involve torrential, conventional storms unleashing large amounts of water in a very short period of time

• The sunbaked soil results in large amounts of overland flow that is capable of carrying out significant erosion, particularly in mountains where steep gradients increase the rates of flow.
• During such high magnitude events, huge amounts of sediment can be washed out of the mountains to be deposited as vast alluvial plains on the lowlands below.

Question 4

Episodic flash floods - Types of flooding

Answer 4

Sheet flooding - water flows as a sheet over the landscape
Channel flash flooding - when water makes its way into channels in the landscape

Question 5

Endoreic rivers

Answer 5

Are rivers that flow into deserts but terminate usually in a lake or inland (dead) sea

• such as the River Jordan, which drains into the dead sea

Question 6

Ephemeral rivers

Answer 6

Are rivers or streams that flow intermittently (on and off) in desert regions.

• They might flow after storm events or they might be fed my snowmelt in the spring adjacent from the mountains
• Flow rates can vary dramatically and in times of flood ephemeral river can be powerful forces of erosion

Question 7

Alluvial fan

Answer 7

This is a depositional feature formed by water flowing out of a mountain range onto the flat desert plane.

• The sediment has been eroded form the mountains then transported along a river channel before being deposited on the edge of a desert plain.

Question 8

Water action (sheet wash/ flooding) processes

Answer 8

• Splash erosion
• Sheet erosion
• Rill erosion
• Gully erosion
• Bank erosion

Question 9

Water action (river) processes

Answer 9

• Erosion
• Transportation
• Deposition

Question 10

Erosion

Answer 10

• Hydraulic action
• Abrasion
• Corrasion
• Solution

Question 11

Transportation

Answer 11

• Traction
• Saltation
• Suspension
• Solution

Question 12

Splash erosion

Answer 12

The force of falling water displacing soil particles

Question 13

Sheet erosion

Answer 13

Water running as a sheet over impermeable surfaces or compacted soil washing away disturbed particles

Question 14

Rill erosion

Answer 14

Sheet wash wears down the soil to form a definite path to form rivulets in the soil called rills

Question 15

Gully erosion

Answer 15

Over time, rills become wider and deeper to form gullies

Question 16

Bank erosion

Answer 16

Fast water flow wears away the stream sides, causing the banks to collapse and the channel to widen

Question 17

Hydraulic action

Answer 17

The sheer force of water

Question 18

Abrasion

Answer 18

Sandpaper effect of loose rocks being ground over bedrock

Question 19

Corrasion

Answer 19

Fragments of rock carries by water gouging or sculpting bedrock

Question 20

Solution

Answer 20

Dissolving of soluble rocks such as limestone

Question 21

Traction

Answer 21

Rolling sediment along the surface or channel bed

Question 22

Saltation

Answer 22

Bouncing or leaping motion of particles

Question 23

Suspension

Answer 23

Sediment carried within the body of water

Question 24

Solution

Answer 24

Dissolved sediment

Question 25

Deposition

Answer 25

Takes place where velocity drops, such as on the inside of meander bends or where streams flow out of a mountain onto flat desert plains (alluvial fan)