Hydrological Cycle and Rivers

Question 1

Why is the global hydrological system a closed system?

Answer 1

The main output (evaporation) is balanced with the main input (precipitation). Water is continually circulating through the system.

Question 2

What is the global water budget?

Answer 2

The annual balance of water fluxes (the flows between stores)

Question 3

What is groundwater otherwise known as?

Answer 3

Fossil water

Question 4

What percentage of the worlds water is accessible immediately in rivers and lakes?

Answer 4

0.01%

Question 5

What are the inputs of the drainage basin system (1)?

Answer 5

Precipitation

Question 6

What are the outputs of the drainage basin system (2)?

Answer 6

• channel flow

* evapotranspiration

Question 7

What are the stores of the drainage basin system (4)?

Answer 7

• soil moisture storage
• groundwater storage
• surface storage
• interception storage

Question 8

What are the transfers of the drainage basin system (6)?

Answer 8

• through flow
• surface runoff
• groundwater flow
• channel storage
• infiltration
• percolation

Question 9

What is the rate of infiltration influenced by? (2)

Answer 9

• amount of precipitation and vegetation

* degree of soil saturation

Question 10

What is groundwater affected by (2)?

Answer 10

• the angle of the rock strata. Steeper = gravity

* rock porosity. More porous = more flow

Question 11

What human action can stop infiltration?

Answer 11

Urbanisation

Question 12

What can lessen interception?

Answer 12

•deforestation/ removal of forest canopy

Question 13

Equation for a balanced water budget

Answer 13

P=Q+E(+/-)S
•P=precipitation 
•Q=river discharge 
•E=evapotranspiration 
•S=change in storage

Question 14

What do water budgets show?

Answer 14

If areas experience a soul moisture surplus and deficit at certain times of the year

Question 15

What is a river regime?

Answer 15

The seasonal variability in a rivers discharge throughout the course of a year in response to precipitation, temperature and evapotranspiration

Question 16

What is a simple regime?

Answer 16

When the river experiences a period of seasonally high discharge followed by low discharge

Question 17

What type rivers typically have a simple regime? Give an example

Answer 17

Rivers where inputs depend on glacial meltwater or seasonal storms
•Rhône France

Question 18

What is a complex regime ?

Answer 18

Where larger rivers cross several different relief and climatic zones and experience the effects of different seasonal climatic effects

Question 19

Give an example of a river with a complex regime

Answer 19

The Mississippi

Question 20

Factors that cause changes to the regime of the River Rhône (5)

Answer 20

• differing local climates
• glacial melt
• Atlantic air masses
• confluence
• summer evaporation

Question 21

What does a storm hydrograph show?

Answer 21

Variations in a rivers discharge at a specific point over a short period of time (before,during and after a storm)

Question 22

What are the two types of storm hydrographs?

Answer 22

• Flashy- rapid increase in discharge and high risk of flooding
• subdued- the opposite

Question 23

Three types of rainfall

Answer 23

• frontal
• orographical
• conventional

Question 24

How does drainage basin size affect a storm hydrograph?

Answer 24

the smaller the basin the more rapidly the water will reach the channel as it has shorter distance to travel

Question 25

How does drainage basin shape affect a storm hydrograph?

Answer 25

for circular basins it takes less timefor water to reach the channel as all the extremeties are equidistant from the channel while elongated basins, water will take longer

Question 26

How does drainage basin relief affect a storm hydrograph?

Answer 26

Steeper slopes mean water flows downhill and reachs channel more quickly

Question 27

What drainage basin characteristics affect a storm hydrograph (3)?

Answer 27

1. size
2. shape
3. relief

Question 28

How does soil type affect a storm hydrograph?

Answer 28

thin soils become saturated quickly while thick soils allow more inflitration

Question 29

How does rock type affect a storm hydrograph?

Answer 29

with impermeable rock, water cannot percolate, increasing surface runoff

Question 30

How does drainage density affect a storm hydrograph?

Answer 30

High drainage density means a large number of surface streams per km^2 meaning the storm water will reach main channel quickly

Question 31

How does natural vegetation affect a storm hydrograph?

Answer 31

Forest and woodland mean high rates of evapotranspiration and more infiltration so less water reaches the channel and more slowly

Question 32

How does land use affect a storm hydrograph?

Answer 32

Urban areas will have more hard surfaces and drains which carry water quickly and directly to river

Question 33

How does precipitation intensity affect a storm hydrograph?

Answer 33

high intensity precipitation means surface runoff occurs and transports water rapidly to the channel

Question 34

How does precipitation duration affect a storm hydrograph?

Answer 34

Prolonged rainfall means the water table rises and soil becomes saturated, causing runoff, which travels quickly to channel

Question 35

How does snowfall affect a storm hydrograph?

Answer 35

Fast snowmelt means meltwater cannot infiltrate into frozen ground so flows to channel rapidly

Question 36

How does evapotranspiration affect a strom hydrograph?

Answer 36

Low rates results in fewer losses from the drainage basin which increases discharge into the river channel