5.2

Question 1

What type of system is the drainage basin?

Answer 1

Open system, within the global hydrological cycle.

Question 2

What is precipitation?

Answer 2

The input into a drainage basin system. It includes all forms of moisture entering: hail, snow, frost, sleet and rain.

Question 3

What is interception storage?

Answer 3

The storage of water when it lands on vegetation (or structures like buildings) before it reaches the soil. It is a temporary store before evaporation or stem-flow.

Question 4

What is surface storage?

Answer 4

The storage of water on the surface including puddles, ponds and lakes.

Question 5

What is soil water (sub-surface) store?

Answer 5

The storage of water in soil. Water is held in small gaps between soil particles.

Question 6

What is groundwater storage?

Answer 6

The storage of water in the ground rocks of permeable rock. The water is held in cracks (limestone) bedding planes (sedimentary rock) or pores (chalk). Rocks with lots of water storage are called aquifers.

Question 7

What is channel store?

Answer 7

The storage of water in the river channel. As water is being transported to the sea it is a storage of water.

Question 8

What is vegetation store?

Answer 8

The storage of water in the vegetation. Plants and trees take up water through their roots and water is stored here.

Question 9

What is surface run-off?

Answer 9

The horizontal flow of water over the surface of the land either in little channels or over the whole surface - this is usually a quick flow.

Question 10

What is throughflow/stem flow?

Answer 10

The downwards flow of water moving downwards from interception storage to the surface

Question 11

What is soil throughflow?

Answer 11

The horizontal flow of water moving through soil (between the particles) towards the river

Question 12

What is infiltration?

Answer 12

The downwards movement of water from the surface into the soil.

Question 13

What is percolation?

Answer 13

The downwards movement of water from the soil to the permeable ground rock

Question 14

What is groundwater flow?

Answer 14

There horizontal movement of moving through the rocks (cracks/bedding planes/pores) slowly towards the river. This is the movement of water below the water table sideways to the river.

Question 15

What is channel flow?

Answer 15

The movement of water in the river channel moving towards the sea.

Question 16

What is evaporation?

Answer 16

The output of water when water is heated and turned from a liquid into a gas.

Question 17

What is transpiration?

Answer 17

The output of water where moisture is taken into plants through their roots, moved to the leaves by capillary action and then evaporates from the leaves into a gas.

Question 18

What is evapotranspiration?

Answer 18

The combined output of water from evaporation and transpiration.

Question 19

What is river discharge?

Answer 19

The output of water from a river channel out to sea.

Question 20

What is the dew point?

Answer 20

The point of which water turns from gas to liquid.

Question 21

Describe the process of conventional rainfall?

Answer 21

1. The Earth’s surface heats the air above it.
2. The heated air rises, expands and cools. This causes condensation to take place.
3. Further ascent causes more expansion and more cooling to take place.
4. Cool air descends and replaces the warm air.

Question 22

Describe the process of cyclonic rainfall?

Answer 22

1. Warm air front rises over cold air (as it is less dense).
2. It then expands cools and condenses.
3. This means clouds and rain form.

Question 23

Describe the process of orographic rainfall?

Answer 23

1. High mountains force air to higher altitudes.
2. This causes the air to cool & condense.
3. Clouds and rain forms
4. As a result a rain shadow forms past the mountain.

Question 24

How does interception affect flows in a drainage basin?

Answer 24

Interception:

• Level of rainfall
  (High levels = overcome maximum storage capacity)
  (Low levels = Allows leaves and stems to be able to storage precipitation, before it evaporates, without reaching the surface)
• Volume of vegetation
  (High volumes of plants = high levels of interception and increased effectivity)
  (Also different types of vegetation influences interception amounts - e.g. denser types of vegetation (coniferous forests) intercept more than less dense vegetation (deciduous forests).

Question 25

Describe the characteristics of an environment where maximum infiltration would take place?

Answer 25

• Medium duration of rainfall
• Small raindrops
• Deciduous trees (low levels of interception
• Forest/Moorlands
• Sandy soil
• Very porous soil
• No slope
• Dry soil

Question 26

What is the difference between saturated overland flow and infiltration-excess overland flow?

Answer 26

Saturated overland flow - When water accumulates in the soil until the water table reaches the surface.

Infiltration-excess overland flow - When rainfall intensity exceeds the infiltration capacity, forcing surface run-off. This then delivers water downstream very quickly, increasing the risk of flooding.

Question 27

What are outputs in the drainage basin?

Answer 27

Temperature:
Increased temp = increased evaporation

Wind:
Increased wind = less humidity

Vegetation cover:
More vegetation = Higher transpiration
Darker vegetation = More evaporation

Channel flow discharge:
High levels of precipitation = more water in channel
Sunny weather = less water in channel

Soil moisture:
High levels = High levels of transpiration potential

Evapotranspiration:
High levels of wind = High levels of evaporation

Question 28

How do humans disrupt the drainage basin?

Answer 28

Cloud seeding - Dispensing of substances for the formation

Deforestation - Lower levels of interception = higher risk of flooding

Dams - Increase evaporation, while reducing downstream water discharge

Increased crop farming - Increased interception = decreased infiltration, which leads to drought

Industrialisation and Urbanisation - Increase in impermeable surface = increased surface run-off = higher risk of flooding