Lesson Aims:

1. To understand how the river basin hydrological cycle works.

2. To understand the factors that effect the amount of water in the river

Water Flows

• Impermeable – water can’t permeate through it (e.g. tramac, etc.)

• Permeable – water can permeate through it (e.g. soil)

Drainage basin hydrological cycle (p108)

INPUTS OUTPUTS PROCESSES STORES

How does all this water get into the rivers?

How does all this water get into the rivers?

• On the mini white board draw a drainage basin with a main river and tributary.

• Then add ‘real rain’ and show how it moves down the rivers.

• What will make the ‘rain’ flow faster into the main rivers?

EXPERIEMENT TIME!How could we collect rainfall

data during a storm?

EXPERIEMENT TIME!How could we collect data from

a river during a storm?

Hydrographs

• These are graphs that show the amount of rainfall and the volume of water discharged during a storm by a river.

• Label your diagram

0 12 24 36 48 30 72

Hours from start of rain storm

3

2

1

Dis

charg

e (

m3/s

)

0 12 24 36 48 30 72

Hours from start of rain storm

3

2

1

Dis

charg

e (

m3/s

)

mm4

3

2

Rainfall shown in

mm, as a bar graph

0 12 24 36 48 30 72

Hours from start of rain storm

3

2

1

Dis

charg

e (

m3/s

)

mm4

3

2

Discharge in m3/s, as a line graph

0 12 24 36 48 30 72

Hours from start of rain storm

3

2

1

Dis

charg

e (

m3/s

)

Ris

ing

lim

b

mm4

3

2

Rising limbThe rising

flood water in the river

0 12 24 36 48 30 72

Hours from start of rain storm

3

2

1

Dis

charg

e (

m3/s

)

Ris

ing

limb

mm4

3

2

Peak flow

Peak flowMaximum

discharge in the river

0 12 24 36 48 30 72

Hours from start of rain storm

3

2

1

Dis

charg

e (

m3/s

)

Ris

ing

limb

Recession

limb

mm4

3

2

Peak flow

Recession limbFalling flood water in the

river

0 12 24 36 48 30 72

Hours from start of rain storm

3

2

1

Dis

charg

e (

m3/s

)

Ris

ing

limb

Recession

limb

Basin lag time

mm4

3

2

Peak flow

Basin lag timeTime

difference between

the peak of the rain

storm and the peak

flow of the river

0 12 24 36 48 30 72

Hours from start of rain storm

3

2

1

Dis

charg

e (

m3/s

)

Base flow

Ris

ing

limb

Recession

limb

Basin lag time

mm4

3

2

Peak flow

Base flowNormal

discharge of the river

0 12 24 36 48 30 72

Hours from start of rain storm

3

2

1

Dis

charg

e (

m3/s

)

Base flow

Through flow

Overland flowR

isin

g

limb

Recession

limb

Basin lag time

mm4

3

2

Peak flow

Overland flow

Through flow

+

=Storm Flow

What factors effect the discharge (volume) of water in any river?

What factors would influence the flood hydrograph in this area?

What factors would influence the flood hydrograph in this area?

What factors would influence the flood hydrograph in this area?

What factors would influence the flood hydrograph in this area?