5.2 The drainage basin is an open system within the global hydrological cycle.

Question 1

The drainage basin system is classed as an open or closed system?

Answer 1

Open - due to its inputs and outputs and these can vary at temporal scales.

Question 2

Definition of drainage basin -

Answer 2

Area of land drained by a river can be called river catchments its boundary is defined as watershed which separates the waters flowing to different rivers.

Question 3

Inputs precipitation conditions -

Answer 3

-Temperature below dew point.
-Condensation nuclei, like dust particles to facilitate the growth of droplets in the cloud.
-Air cooled to a saturation point with relative humidity of 100%

Question 4

There are triggers for the development of rainfall -

Answer 4

Amount of rainfall - which has a direct on the drainage discharge, type of the precipitation and the intensity of precipitation.

Question 5

Types of precipitation - Convectional rainfall

Answer 5

Convectional rainfall, occurs with the ground heating which causes the air to become hot and expand as it rises it cools and the ability to hold it as water vapour decreases condensation occurs forming clouds if it continuous to rise air will fall.

Question 6

Types of precipitation - Cyclonic precipitation

Answer 6

When warm air (less dense and lighter) is forced to rise over colder air and it cools from rising and it’s ability to hold water vapour decreases, condensation happens and rain forms.

Question 7

Type of precipitation - Orographic rainfall

Answer 7

When air is forced to rise over an object such as a mountain, it then cools and condensates which takes place to form rain.

Question 8

Flows and fluxes in the drainage basin -

Answer 8

Interception, infiltration, direct runoff,
saturated overland flow, throughflow, percolation,
groundwater flow.

Question 9

Interception - (flux) (vegetation)

Answer 9

Where water is stored in vegetation has three main components of interception loss where water is retained by the plant surfaces and is later evaporated, through fall (water droplets fall from leaves and twigs) and stem flow (where water trickles along branches and down the trunk).

Question 10

Infiltration (fluxes) - (Soil)

Answer 10

Where water soaks in the soil, the infiltration capacity is the maximum rate the soil can hold rain water it affected by: the amount of rainfall, the saturation of the soil (the amount of water already present in the soil), soil types E.G sand, clay. Vegetation, slope angle which may encourage overland flow and run-off, with shallower slopes promoting infiltration.

Question 11

Overland flow -

Answer 11

Main way water is delivered to a river where precipitation must exceed infiltration rates for the soil to be saturated enough where it cannot hold more discharge or rain water.

Question 12

Throughflow -

Answer 12

Lateral transfer of water down slope via natural pipes, slower than overland flow.

Question 13

Percolation -

Answer 13

Where water travels deep inside permeable rocks, mainly on vegetation slopes.

Question 14

Groundwater flow -

Answer 14

Slow transfer of this percolated water through rocks.

Question 15

Evaporation (Outputs) -

Answer 15

The physical process by which soil moisture is lost directly to the atmosphere, this is significantly influenced by climate, temperature, humidity and levels of light intensity. Other factors may be the water body and the type of vegetation cover.

Question 16

Transpiration (Outputs)

Answer 16

A biological process where water is directly lost to the atmosphere through small pores on leaves called stomata, these depend on the time of year and the amount of vegetation cover and.

Question 17

Evapotranspiration -

Answer 17

Concerns the combined effect of evaporation and transpiration and represents the most important aspect of water loss to the atmosphere.

Question 18

Physical factors can influence these processes of fluxes, inputs and outputs including. -

Answer 18

Climate - influences the type and amount of precipitation overall and the amount of evaporation, influences the vegetation type.
Soil type - Determines the amount of infiltration and throughflow and the level of vegetation and other factors of the discharge it can hold.
Geology - Percolation of permeable rocks and the degree of groundwater flow.
Relief - The altitude can influence the levels of precipitation and types including orographic rainfall also the degree of the slope affecting the amount of run-off.
Vegetation - Affects the level of interception and infiltration (interception loss, through fall and stem flow).

Question 19

Humans can disrupt inputs and outputs through -

Answer 19

Deforestation, changing land use and creating
new water storage reservoirs or by abstracting water.

Question 20

Human impacts on precipitation - Cloud seeding

Answer 20

Silver iodide pellets act as a condensation nuclei to attract water droplets and increase water levels in drought-stricken areas.

Question 21

Humans can affect evapotranspiration rates - Deforestation

Answer 21

Reduces the level of transpiration from water loss E.G in the Amazonia. over 20% has been lost, the lost of this is significant as the Amazon forest holds 60% of the forest and act as major carbon sinks. Their enormously beneficial on water cycling. In an environment 75% of the water is returned to the atmosphere by evapotranspiration .

Question 22

Humans can affect infiltration and rate of soil water - Land use changes through agriculture

Answer 22

Infiltration can be up to 5 times higher under forest, when conversion there is reduced interception of vegetation and more overland flow through over land flow the same can be said for urbanisation.

Question 23

Human impacts on groundwater -

Answer 23

Humans use irrigation (the supply of water to land or crops to help growth, typically by means of channels) this can be used for extensive farming. This has led to declining water in aquifers. E.G the Aral sea began shrinking in the 1960s irrigation schemes for the growth of cotton.