1.c. The water cycles have distinctive processes and pathways that operate within them

Question 1

What is the water balance and what is the equation for it

Answer 1

The water balance is the long term balance between the inputs and outputs in a drainage basin system
precipitation=evaporation+streamflow+-storage

Question 2

What flows in the water cycle link the stores

Answer 2

• precipitation
• evaporation
• transpiration
• run off infiltration
• percolation
• throughflo

Question 3

What is precipiation and how does it form

Answer 3

It is water and ice that follows from clouds towards the ground.

• It forms when vapour in atmosphere cools to its dew point and condenses into droplets or ice particles which then reach a critical size and leave the cloud as precipitation
• precipiation can vary in character, impacting the water cycle at the drainage basin scale

Question 4

How does precipitation work in the water cycle

Answer 4

• most rain flows into streams/rivers. In high latitudes, precipitation falls as snow and may remain for many months- there may be considerable time leg between snowfall and run off
• intensity is the amount of precipitation falling in a given time. High intensity precipitation moves rapidly
• duration is the length of time that a precipitation event last. Prolonged events may deposit exceptional amounts of precipitation and cause flooding
• in some parts of the world e.g. East Africa, precipitation is concentrated in rainy seasons and so river discharge is high and flooding is common

Question 5

What is transpiration

Answer 5

This is the diffusion of water vapour to the atmosphere from the stomata of plants. It is influenced by temperature and wind speed and water availability

Question 6

How do transpiration and evaportation work together

Answer 6

• transpiration linked to evaporation
• two processes are termed evapotranspiration
• factors affecting these processes include temperature, wind, humidity and climatic factors

Question 7

What is condensation and how does it work in the water cycle

Answer 7

This is a physical process where water vapour becomes liquid- it occurs when air is cooled to its dewpoint. At this temp air becomes saturated with vapour, resuilting in condensation. Clouds form through condensation (cumuliform, stratiform, cirrus). Condenesation at/near ground produces dew+fog which deposit large amounts of moisture on vegetatiojn

Question 8

What are cumuliform clouds

Answer 8

These develop when air is heated through contact with earths surface which causes heated air particles to rise freely through the atmosphere (convection), expand and cool. When cooling reaches its dew point, condensation begins

Question 9

What are stratiform clouds

Answer 9

These develop when air mass moves horizontally across a cooler surface- this process is known as advection

Question 10

What are cirrus clouds

Answer 10

These form at a high altitude and consist of tiny ice crystals. They do not produce precipitation

Question 11

Cloud formation and lapse rates- what is the environmental lapse rate

Answer 11

this is the vertical temperature profile of the lower atmosphere at any given time. On average te temperature falls by 6.5 degrees C for evert km of height gained

Question 12

Cloud formation and lapse rates- what is the dry adiabatic lapse rate

Answer 12

the rate at which a parcel of dry air cools. Cooling, caused by adiabatic expansion is approximately 10 degreesC/km. Condensation not occuring

Question 13

Cloud formation and lapse rates- what is the saturated adiabatic lapse rate

Answer 13

This is the rate at which a saturated parcel of air cools as it rises through the atmosphere. Because condensation releases latent heat, the SALR, at around 7 degrees/km, is lower than the dry adiabatic lapse rate. Condensation is occurring

Question 14

Explain how clouds are formed by convection

Answer 14

• air at the surface is warmed (land or sea)
• air rises up into the atmosphere
• as it rises, pressure decreases and air cools (adiabatic expansion)
• air rising vertically is called convection and air moving horizontally is called advection
• the dew point (condensation) is 8 degrees celcius
• atmospheric stability occurs where the internal temperature of the air parcel matches the surrounding atmosphere

Question 15

What is catchment hydrology

Answer 15

processes and pathways of the water cycle taking place within a catchment area

Question 16

Catchment hydrology- evaporation in the water cycle

Answer 16

• liquid water to vapour
• Heat needed for evaporation and to break the molecular bonds of water. This energy input does not produce a rise of temperature in the water
• The energy is absorbed as latent heat and released in condensation
• This process allows huge quantities of heat to be transferred around the planet

Question 17

Catchment hydrology- interception

Answer 17

• Vegetation intercepts a proportion of precipitation, storing it temporarily on branches, leaves and stems
• This moisture eventually evaporates (interception loss) or falls to the ground
• Rainwater briefly intercepted before dripping to the ground is known as throughfall
• During periods of intense/prolonged rainfall rainwater may flow to the ground along branches and stems as stemflow

Question 18

Catchment hydrology- Interception, throughflow

Answer 18

Rain falling to the ground and not entering storage follows one of two flowpaths to streams and rivers:

• infiltration by gravity into the soil and lateral movement of throughflow to stream/river channels.- relates overland flow to soil’s infiltration capacity or the maximum rate it can absorb rain. Argued when rainfall intensity exceeds infiltration capacity overland flow occurs
• overland flow across the ground surface either as a sheet or as trickles and rivulets. Rainfall infiltrates the soil. Overland flow only occurs when soil becomes saturated and the water table rises to the surface (saturated overland flow)

Question 19

Catchment hydrology-groundwater flow and run-off

Answer 19

• where soils are underlain by permeable rocks, water seeps or percolates deep underground
• Water then migrates slowly through rock pores and joins as groundwater flow, eventually emerging at the surface
• Groundwater levels on the chalk in Southern England follow a distinct seasonal pattern. By late October, the water table is beginning to rise as temperatures and evapotranspiration falls. This recharge continues until late January and groundwater levels decline throughout the later winter, spring and summer.

Question 20

Crysopheric processes

Answer 20

These affect the mass of ice at and scale and include:

• ablation- loss of ice from snow, ice sheets, glaciers and caused by melting, evaporation and sublimation
• sublimation- ice chagning directly into water vapour. Key to river catchments in mountains during spring and summer. Cause of flooding when rapid melting occurs

Question 21

Factors affecting interception loss- interception store capacity

Answer 21

• before the osent of rainfall, vegetation surfaces are dry and their ability toretain water is at a maximum. Most rainfall intercepted but as vegetation becomes saturated, output of of water through stemflow/throughfall increases
• interception depends on duration and intensity of rainfall

Question 22

Factors affecting interception loss- wind speed and vegetatation type

Answer 22

• rates of evaporation increase with wind speed and tubulance causes additional throughfall
• interception losses are greater from grasses than from agricultural crops. Trees have higher interception losses than grasses

Question 23

Factors affecting interception loss- tree species

Answer 23

-interception losses greater from evergreen confiers as they have leaves all round and water adheres to spaces between confier needles, increasing evaporation