Running water and groundwater

Question 1

What are the processes involved in the water cycle?

Answer 1

• Precipitation
• Evaporation
• Infiltration (water into cracks/soil/pores)
• Runoff
• Transpiration (from plants into ground/air)

Question 2

What is the earth’s water balance?

Answer 2

Average annual precipitation over Earth

EQUALS

Amount of water that evaporates

Question 3

What percentage of the earths water is fresh?

Answer 3

2.8%

• 2.15% glaciers
• 0.62% groundwater
• 0.009% freshwater lakes
• etc

Question 4

What is a streams gradient?

Answer 4

The slope or steepness of a stream channel

Question 5

What factor most influence the power of a stream to erode and transport material?

Answer 5

The stream’s velocity

Question 6

How do gradient and dischard change between a stream’s headwaters and its mouth?

Answer 6

While

GRADIENT DECREASES

between a stream’s headwaters (in mountains) and mouth (at the ocean or lake),

DISCHARD INCREASES

because more and more tributaries (streams that empty into other streams) enter the main channel.

Question 7

What is a stream’s Base Level?

Answer 7

Base level is the lowest point to which a stream can erode its channel.

A temporary base level might include a lake, layer of resistant rock, and main streams. At these points, the streams velocity approaches zero, so they can’t erode their channels anymore.

The ultimate base level is the level at which the mouth of a stream enters the ocean, lake, or another stream.

Question 8

How do streams erode their channels?

Answer 8

By

• lifting loose particales by abrasion,
• grinding,
• and by dissolving soluble material.

Question 9

What are the 3 ways streams transport sediment?

Answer 9

1. in solution
2. in suspension (cloudy)
3. scooting or rolling along the bottom.

Question 10

What two factors influence a stream’s ability to carry a load (sediment)?

Answer 10

1. Stream’s competency: measure of the largest particals it can carry. Increases with the square of the stream’s velocity.
2. Stream’s capacity: total load capacity is related to the volume of water in a stream (i.e. its discharge).

Question 11

What is disposition? When does it occur?

Answer 11

Disposition is when sediment begins to drop out (largest particles first). This occurs as a streamflow drops below the critical settling velocity of a certian particle size. The sediment in that category begins to settle out.

Question 12

What are the two types of stream valleys?

Answer 12

1. Narrow: V-shaped, which shows the river has been mainly downcutting towards base level. Lots of waterfalls and rapids (caused by variations in erosion).
2. Wide: Usually when a Narrow valley reaches near base level, it starts to widen out creating a floodplain.

Question 13

What is a floodplain?

Answer 13

When a river overflows its banks, the plain it floods is the floodplain (a wide valley).

Question 14

What is a natural levee? How do they form?

Answer 14

A landform parallel to a river formed by pile ups of sediment deposited from repeated overflows of the river.

Question 15

What is a Delta?

Answer 15

When a stream nears a lake or ocean and slows down, it deposits lots of sediment and forms what is called a delta. (Delta is greek for change.)

Question 16

What causes floods?

Answer 16

Most floods are caused by rapid spring snow melts or storms that bring heavy rains over a large region.

Question 17

What are 3 measures used to control flooding?

Answer 17

1. Artificial levees (earthen mounds built on the banks of rivers).
2. Flood-control Dams (store and slowly let out flood waters).
3. Limiting development (preserving floodplains in their natural state)

Question 18

What is a drainage basin?

Answer 18

Thew land area that contributes water into a stream.

Question 19

What is the zone of saturation?

Answer 19

The area where water fills all of the open spaces in sediment and rock.

The upper limit of the zone of saturation is called the WATER TABLE.

Question 20

Where is ground water and how does it move?

Answer 20

Groundwater is water within the saturation zone. It moves by twisting an turning through interconnected small openings. Groundwater moves more slowly when pore spaces are small.

Question 21

What is an aquifer?

Answer 21

Permeable rock layers (those with lots of pore spaces) or sediments that trasmit groundwater freely.

Question 22

What is a spring? Where do they form?

Answer 22

Springs forms whenever the water table intersects the ground surface.

Question 23

What is a geyser? How do they work?

Answer 23

An intermittent hot water spring the shoots up a column of water.

1. Start with an extensitve underground network of chambers in HOT igenous rock.
2. Cold water fills the chambers and heat up, but the weight of the water increases the boiling temperature of the water below.
3. The hot water expands which forces water out of the surface.
4. As water gets pushed out, presure drops until the water below can vaporize/boil.
5. The sudden great expansion of the boiling water causes the geyser to erupt.
6. Cold water starts entering the chamber again…

Question 24

What are some threats to groundwater?

Answer 24

• If you pump out water too fast, the ground subsides and compacts.
• Polution from sewage (bacteria), pesticides, fertilizer, highway salt, etc.

Question 25

How and where do most caverns form?

Answer 25

Erosion forms most caverns at or below the water table in the zone of saturation. Water containing small abouts of carbonic acid (from rain water + CO2 in air) disolve limestone following cracks, etc.

Question 26

What is a Karst Topography?

Answer 26

Areas largely shaped by the disolving power of GROUNDWATER are called Karst Topographies. They typically has irregular terrains with may depressions called SINKHOLES.