River Discharge

Question 1

What is it measured in?

Answer 1

Cubic metres per second (cumecs) (m3/s)

Question 2

What affects river discharge?

Answer 2

Precipitation
Hot weather
Removal of water (from river)

Question 3

How does precipitation affect discharge?

Answer 3

More precipitation means higher discharge.

Question 4

How does hot weather affect river discharge?

Answer 4

Higher temperature means lower discharge as rate of evapotranspiration is higher.

Question 5

How does the removal of water affect river discharge?

Answer 5

Reduces discharge.

Question 6

What does a hydrograph show?

Answer 6

River discharge over a period of time.

Question 7

What do Storm hydrographs show?

Answer 7

River discharge around the time of a storm event

Question 8

What are the 4 key stages of a storm hydrograph?

Answer 8

Peak discharge
Lag time
Rising limb
Falling limb

Question 9

What is peak discharge?

Answer 9

The highest point on the graph

When river discharge is greatest

Question 10

What is lag time?

Answer 10

The delay between peak rainfall and peak discharge.

Question 11

What is the rising limb?

Answer 11

The part of the graph up to peak discharge.

Question 12

What is the falling limb?

Answer 12

The part of the graph after peak discharge.

Question 13

What are the 7 physical factors affecting storm hydrographs?

Answer 13

• drainage basin characteristics
• amount of water already present
• rock type
• soil type
• vegetation
• precipitation
• temperature

Question 14

How do drainage basin characteristics affect storm hydrographs?

Answer 14

Larger drainage basins catch more precipitation - higher peak discharge

Smaller drainage basins - shorter lag time as precipitation has less distance to travel

Steep-sides basins - shorter lag times than shallower basins, water flows quicker downhill

Question 15

How does the amount of water already present affect storm hydrographs?

Answer 15

Grounds are already waterlogged - infiltration is reduced - surface runoff increases - faster than through flow or baseflow - rainwater reaches river more quickly = reducing lag times

Question 16

How does rock type affect storm hydrographs?

Answer 16

Impermeable rocks are don’t store water not let it run through - infiltration reduces - increases surface runoff - reduces lag time

Question 17

How does soil type affect storm hydrographs?

Answer 17

Sandy soils all a lot of infiltration

Clay souls have very low infiltration rates - increases surface runoff - reducing lag time

Question 18

How does vegetation affect storm hydrographs?

Answer 18

It intercepts precipitation and slows it’s movement to river channel - increased lag time

Question 19

How does precipitation affect storm hydrographs?

Answer 19

Intense storms will generate more precipitation - greater discharges than lighter rain showers

Question 20

How does temperature affect storm hydrographs?

Answer 20

Hot, dry conditions and Coke, freezing conditions mean a hardened ground - reduces infiltration - increases surface runoff

Question 21

What two human activity ways can affect the hydrograph?

Answer 21

Urban areas

Man made drainage systems

Question 22

How do urban areas affect the hydrograph?

Answer 22

Soil is covered in man-made impermeable materials(concrete) - water can’t infiltrate - increases surface runoff - water flows quicker into river = short lag time - increases peak discharge

Question 23

How do man made drainage systems affect the hydrograph?

Answer 23

Water flows down the drains into the river before it can evaporate or infiltrate = shorter lag time - increased peak discharge.

Question 24

What is river discharge?

Answer 24

The volume of water flowing in a river per second