Booklet 3 - Drainage Basin

Question 1

Inputs into a Drainage Basin

Answer 1

Precipitation

Question 2

What is Precipitation

Answer 2

Any form of water that falls from the atmosphere and reaches Earth’s surface, including rain snow, hail, dew and frost

Question 3

Outputs out of a Drainage Basin

Answer 3

Evaporation, Transpiration, Evapotranspiration, River Discharge (Flow Rate)

Question 4

What is Evaporation

Answer 4

The process by which liquid water turns into gas.

Question 5

What is Transpiration

Answer 5

Evaporation of water from plant leaves.

Question 6

What is Evapotranspiration

Answer 6

Combination of evaporation and transpiration

Question 7

What is River Discharge

Answer 7

The output of a river, calculated as the speed of the river in m/s multiplied by the river’s cross sectional area in m squared

Question 8

Flows within a Drainage Basin

Answer 8

• Infiltration
• Overland flow
• Drip flow
• Stem flow
• Infiltration
• Through flow
• River/Channel/Stream flow
• Groundwater flow
• Base flow
• Percolation

Question 9

What is Infiltration

Answer 9

Water soaking into the soil

Question 10

What is Overland Flow

Answer 10

Also known as runoff, occurs when precipitation exceeds infiltration

Question 11

What is Drip Flow

Answer 11

Water dripping from one leaf to another

Question 12

What is Stem Flow

Answer 12

Water flowing down the stem of the vegetation

Question 13

What is Infiltration

Answer 13

Water seeping through the soil to the water table

Question 14

What is Through Flow

Answer 14

Water moving laterally through the soil

Question 15

What is River/Channel/Stream Flow

Answer 15

Water moving through a river

Question 16

What is Groundwater Flow

Answer 16

Water flowing slowly below the water table through permeable rock

Question 17

What is Base Flow

Answer 17

Groundwater flow that feeds into rivers through river banks and beds

Question 18

What is Percolation

Answer 18

Water flowing downhill through permeable rock above the water table

Question 19

Stores in a Drainage Basin

Answer 19

• Interception Storage
• Soil Water Storage
• Surface Storage
• Groundwater Storage
• Channel Storage
• Vegetation Storage

Question 20

What is Interception Storage

Answer 20

When some precipitation lands on vegetation or other structures (buildings/tarmac) before it reaches the soil

• Temporary store a it will evaporate
• Significant store in woody areas

Question 21

What is Vegetation Storage

Answer 21

Water that has been taken up by plants and is all the water contained by plants at any one time

Question 22

What is Surface Storage

Answer 22

Includes water in puddles (depression storage), ponds and lakes

Question 23

What is Soil Storage

Answer 23

Includes moisture in the soil

Question 24

What is Groundwater Storage

Answer 24

When water is stored underground in soil and rock

Question 25

What is Channel Storage

Answer 25

The water held in a river or stream channel

Question 26

What is water balance?

Answer 26

The difference between the inputs and the outputs (and the subsequent change in storage) in the drainage basin

Question 27

When will there be a positive water balance?

Answer 27

If precipitation exceeds runoff and evapotranspiration

Question 28

When will there be a negative water balance?

Answer 28

When will there be a negative water balance? If runoff and evapotranspiration exceed precipitation

Question 29

Water Balance Equation?

Answer 29

Precipitation = Evapotranspiration + Runoff +/- Change in Storage

Question 30

What is the soil moisture budget?

Answer 30

The change in the amount of water stored in the soil throughout the year

Question 31

River Wye (example of a drainage basin):

Answer 31

- total length of 215km - fifth longest river in UK - mid- Wales to Chepstow - AONB

Question 32

What does a flashy flood hydrograph look like?

Answer 32

Short lag time and high peak

Question 33

Factors Affecting Flood Risk

Answer 33

HUMAN: - Deforestation/Afforestation/Reforestation - Land Use - River Channel Straightening - Channel Widening/Deepening - Relief Channel - Pollution - Storm Drains PHYSICAL: - Permeable Rock - Relief - Temperature - Vegetation - Ground/Soil Type - Natural Dams (beavers) - River Channel depth or width - Antecedent Rainfall - Saturated Soil - Snow Melt