Lesson 2 - Drainage Basins

Question 1

What is a drainage basin?

Answer 1

An area of land that is drained by a river and its tributaries, and separated from neighbouring drainage basins by an area of highland called a watershed.

Question 2

How is a drainage basin an open system?

Answer 2

It has eternal inputs and outputs that cause the amount of water in the basin to vary over time.

Question 3

What is drainage basin referred to as?

Answer 3

catchment (the area of land drained by a river and its tributaries).

Question 4

Was it the boundary of the drainable basin referred to as?

Answer 4

Watershed (the highland which divides and separates water flowing to different rivers).

Question 5

Drainage Basin inputs?

Answer 5

Precipitation

Question 6

Drainage basin stores?

Answer 6

Interception

Question 7

Drainage basin flows (fluxes)? (7)

Answer 7

Infiltration
direct run off
Saturated overland flow
Through flow
Percolation
Groundwater flow
Channel flow

Question 8

Drainage basin outputs? (3)

Answer 8

Evaporation
Transpiration
River Runoff

Question 9

How does the climate influence the drainage basin?

Answer 9

Has a role in influencing the type and amount of precipitation overall and the amount of evaporation, i.e. the major inputs and outputs. It also has an impact of the vegetation type.

Question 10

How does soil influence the drainage basin?

Answer 10

Determines the amount of infiltration and throughflow and, indirectly, the type of vegetation.

Question 11

How does geology influence the drainage basin?

Answer 11

Can impact on the subsurface processes such as percolation and groundwater flow (and, therefore, on aquifers). Indirectly, it can alter soil formation

Question 12

How does relief influence the drainage basin?

Answer 12

Can impact on the amount of precipitation. Slopes can affect the amount of runoff.

Question 13

How does vegetation influence the drainage basin?

Answer 13

The presence or absence of this can have a major impact on the amount of interception, infiltration and occurrence of overland flow, as well as transpiration rates.

Question 14

How does Precipitation influence the drainage basin? (4)

Answer 14

Can act as temporary store.
The amount (higher less variability in its pattern).
Seasonality affects physical processes.
Intensity, impact flows and amount absorbed.

Question 15

How is precipitation variable?

Answer 15

Secular variability, LT, climate change trends.
Periodic variability, Annual, seasonal, daily, ect
Stochastic variability, Random factors

Question 16

How does storage influence the drainage basin? (4)

Answer 16

Interception loss, amount intercepted varies with each tree, needless ones have a greater capacity.
Meteorological conditions, increase interception losses and evaporation.
Intensity and duration of rainfall, rainfall increases more interception losses decrease, excess rain reaches ground.
Interception increase with crop density

Question 17

How does flows influence the drainage basin?

Answer 17

infiltration

Question 18

Factors that effect infiltration? (5)

Answer 18

water already in soil, excess water saturated.
slope angle, steep more overland run off, shallow more infiltration.
Soil surface and structure, compact infiltrate less.
vegetation, infiltrate more in areas that are vegetated.
Soil texture, sandy soils infiltrate more.

Question 19

How do flows and transfers influence the drainage basin? (5)

Answer 19

surface run off is the main way water is transferred to rivers, precipitation must exceed infiltration rates.
Percolation
Saturated over land flow
through flow
channel flow

Question 20

What is saturated overland flow?

Answer 20

the upward movement of the water table

Question 21

What is channel flow?

Answer 21

Water reached from all transfers in a river.

Question 22

What outputs influence the drainage basin? (3)

Answer 22

Evaporation
transpiration
evaportranspiartion

Question 23

How does basin size influence the drainage basin?

Answer 23

Larger basins collect more precipitation giving them a longer lag time as it takes longer for all the water to travel through.

Question 24

How does drainage density influence the drainage basin?

Answer 24

A low drainage density means a slower movement of water across a basins area, permeable rocks have a low drainage basins.

Question 25

How does elevation and slope influence the drainage basin?

Answer 25

Forested slopes intercept more precipitation more evaporation and less surface run off where as steep slopes promote faster movement and shorter storage times.

Question 26

How does rock and soil type influence the drainage basin?

Answer 26

Impermeable rocks prevent infiltration and cause surface saturation.

Question 27

How does land use influence the drainage basin?

Answer 27

Urban surfaces are impermeable and increase rapid surface runoff.