1.1. The drainage basin system

Question 1

Outputs in the drainage basin system

Answer 1

Evaporation, evapotranspiration and river discharge.

Question 2

Stores in the drainage basin system

Answer 2

Interception, soil water, surface water, ground water, and channel storage.

Question 3

Flows in the drainage basin system

Answer 3

• Above ground – throughfall, stemflow, overland flow, and channel flow.
• Below ground – infiltration, percolation, throughflow, groundwater, and baseflow.

Question 4

Underground water in the drainage basin system

Answer 4

Water tables, ground water, recharge, and springs.

Question 5

Drainage Basin

Answer 5

The area drained by a river and its tributaries.

Question 6

Watershed

Answer 6

A ridge, like that formed by a chain of mountains, which sends water to two different rivers on either side.

Question 7

Precipitation

Answer 7

The main input into the drainage basin system. It is the conversion and transfer of moisture in the atmosphere to the land. It includes rainfall, snow, frost, hail and dew.

Question 8

Hydrological cycle

Answer 8

The movement of water between air, land and sea.

Question 9

Interception

Answer 9

Precipitation that is collected and stored by vegetation.

Question 10

Throughfall

Answer 10

Water that either falls through gaps in the vegetation or which drops from leaves, twigs or stems.

Question 11

Stemflow

Answer 11

Water that trickles along twigs and branches and finally down the main trunk.

Question 12

Interception less

Answer 12

Water that is retained by plant surfaces and which is later evaporated away or absorbed by the plant.

Question 13

Evaporation

Answer 13

The transformation of liquid water from the Earth’s surface into a gas (water vapour).

Question 14

Transpiration

Answer 14

Water loss from vegetation to the atmosphere.

Question 15

Evapotranspiration

Answer 15

The combined loss of water to the atmosphere through transpiration and evaporation.

Question 16

Potential Evapotranspiration

Answer 16

The amount of evaporation that would occur if a sufficient water source were available.

Question 17

Actual Evapotranspiration

Answer 17

The quantity of water that is actually removed from a surface due to the processes of evaporation and transpiration.

Question 18

Antecedent Precipitation

Answer 18

The water in the soil that is retained after a period of rainfall.

Question 19

Surface Runoff

Answer 19

The water flowing over the surface of the land.

Question 20

Throughflow

Answer 20

The lateral (sideways) transfer of water through the soil layer.

Question 21

Groundwater flow

Answer 21

The lateral transfer of water through bedrock.

Question 22

Channel Runoff

Answer 22

The flow of water in streams, rivers and other channels.

Question 23

Groundwater Storage

Answer 23

The water that is stored between the cracks and pore spaces in the underlying rock layers.

Question 24

Soil Storage

Answer 24

The water contained between soil particles.

Question 25

Surface Storage

Answer 25

Where water lies above the ground on the Earth’s surface such as in lakes, rivers, ponds, puddles.

Question 26

Percolation

Answer 26

The downward movement of water through the soil and the underlying bedrock.

Question 27

Zone of Saturation (Phreatic Zone)

Answer 27

The area in an aquifer, below the water table, in which relatively all pores and fractures are saturated with water.

Question 28

Aquifer

Answer 28

Rocks that store large quantities of groundwater

- saturated zone beneath the water table.

Question 29

Recharge

Answer 29

The process by which water moves downward from surface water to groundwater.

Question 30

Factors affecting parts of the hydrological cycle

Answer 30

1) Duration of rainfall
2) Vegetation Cover
3) Antecedent soil moisture
4) Raindrop Size
5) Soil Porosity
6) Slope Angle

Question 31

Duration of rainfall (Factors affecting parts of the hydrological cycle)

Answer 31

Longer duration of rainfall:

• Surface run off increases
• Infiltration decrease

Question 32

Vegetation Cover (Factors affecting parts of the hydrological cycle)

Answer 32

In a forest:
- Surface run off is fairly low throughout, but does increase slowly
- Decreases slowly over time in a rain shower
On bare earth:
- Surface run off increases rapidly at the start of a rain shower and stays constantly high throughout
- Infiltration decreases rapidly in a rain shower and stays low

Question 33

Antecedent soil moisture (Factors affecting parts of the hydrological cycle)

Answer 33

If the soil is saturated with moisture:

• Surface run off increases
• Infiltration is lower

Question 34

Raindrop Size (Factors affecting parts of the hydrological cycle)

Answer 34

Bigger Raindrop size:

• Surface runoff increases
• Infiltration decreases

Question 35

Soil Porosity (Factors affecting parts of the hydrological cycle)

Answer 35

High Porosity:

• Surface run off decreases
• Infiltration increases

Question 36

Slope Angle (Factors affecting parts of the hydrological cycle)

Answer 36

Steeper slopes:

• Surface run off increases
• Infiltration decreases