Storm hydrograph

Question 1

Base flow on storm hydrograph is…

Answer 1

the regular flow of a river, when there is no rainfall.

Question 2

Smaller drainage basin:(compared to larger)

Answer 2

-shorter lag time
-higher peak
Water reaches the channel more rapidly as water has a shorter distance to travel.

Question 3

More circular drainage basin:(compared to more elongated)

Answer 3

-shorter lag time
-higher peak discharge
It takes less time for the precipitation to reach the channel.

Question 4

Circular drainage basin means…

Answer 4

that all points on the watershed are equidistant from the channel, so it takes less time for water to reach the channel.

Question 5

Steeper basin:(Relief)

Answer 5

-shorter lag time
-higher peak
Water reaches the channel faster as it travels more quickly downhill.

Question 6

Type of precipitation:

Answer 6

The lag time and peak are lower after a snowfall, as the water is stored on the ground surface.

Question 7

If the snow melts…

Answer 7

the water will reach the channel quickly as infiltration is impeded if the ground is frozen.

Question 8

Intense rainfall causes…

Answer 8

excess-overland flow.

Question 9

Prolonged rainfall causes…

Answer 9

saturated overland flow.

Question 10

Impermeable rock is…

Answer 10

saturated more quickly than porous rock. Saturated overland flow is common.

Question 11

Vegetation intercepts a large…

Answer 11

proportion of rainfall. In forested drainage basin, the lag time and peak are lower.

Question 12

In areas of sandy soil…

Answer 12

the lag time and peak are lower. Sandy soil has larger pores than clay soil. Infiltration is more rapid.

Question 13

In urban areas, there is higher…

Answer 13

surface run-off as there are more impermeable surfaces and sewers take water rapidly to rivers.

Question 14

In a deforested basin, there is less…

Answer 14

interception, evapotranspiration and surface-runoff.

Question 15

Water quality decreases due to deforestation as…

Answer 15

more eroded topsoil enters the channel(may contain fertilisers)

Question 16

Increased nitrate levels encourage…

Answer 16

aquatic plant growth, resulting in eutrophication(choking) of the river.

Question 17

Cattle bred in a deforested area…

Answer 17

remove remaining vegetation and increase the surface runoff.

Question 18

Deforestation increases the light…

Answer 18

intensity, wind speed. The area becomes drier and maybe desertified.

Question 19

Irrigation can decrease…

Answer 19

the water table.

Question 20

Large expanses of irrigated land may increase…

Answer 20

evapotranspiration rates, thus increasing precipitation and in some cases tornado frequencies.

Question 21

Interception loss is…

Answer 21

part of rain retained by an aerial portion of vegetation(canopy)

Question 22

As the agricultural crop density increases…

Answer 22

the interception loss as well, especially from cereal crops.

Question 23

Coniferous(evergreen) trees intercept more…

Answer 23

than deciduous trees in the winter, but less in the summer.

Question 24

Coniferous trees have relatively high…

Answer 24

surface area. Pine needles allow for water to accumulate.

Question 25

After a certain amount of water on the leaf…

Answer 25

the leaf bends down and water drops.

Question 26

Different trees have different…

Answer 26

interception loss. E.g. spruce has higher annual interception compared to the beech.

Question 27

The 3 Ps

Answer 27

• porosity
• permeability
• perviousness

Question 28

Porosity is…

Answer 28

a measure of the distance between rock particles. (the size of the pores).

Question 29

Permeability is…

Answer 29

a measure of the ability to transmit water through porous rock.

Question 30

Perviousness is…

Answer 30

something which allows water to pass through it due to cracks or defects in the rock.

Question 31

Antecedent soil moisture is…

Answer 31

the pre-existing levels of moisture, before rainfall.

Question 32

River regime is…

Answer 32

annual variation in the discharge of a river.