Water Cycle

Exam board = AQA; mixture of question types

Define stem flow

Water flows down the stems of plants and trees

Define surface runoff/overland flow

Rain flowing over the ground due to saturated soil or because rainfall exceeds soil’s infiltration capacity

Define throughfall

Water moving from vegetation to the ground

Define throughflow

Lateral movement of water down a slope into a river channel

Define groundwater/base flow

Downward and lateral movement of water within saturated rock

Define interception storage

Vegetation intercepts precipitation and stores it in leaves or branches

Define surface storage

Water collects above ground, mainly puddles in urban environments

Define soil water storage

Pores in soil are filled with water and air

Define groundwater storage

Water stored underground in permeable rocks

Define evapotranspiraton

Loss of water from vegetation through pores

Define river discharge

The volume of water in a river flowing past a certain point every second

70% of all water is salt water. True or False?

False: 97% salt water, 3% freshwater

How much of freshwater is stored in the cryosphere?

70%

Give 5 examples of cryospheric water storage

Sea ice, ice sheets, ice caps, glaciers, permafrost

Is the global water system open or closed?

Closed system

What percentage of freshwater is stored in the atmosphere?

3%

Define aquifer

Store of water underground

Describe the distribution of aquifers

Unrelated to above ground water prevalence. Major aquifer, North West Sahara system, is below a desert. Major systems under Europe e.g. western Russia and Germany

Describe the accessibility of aquifer systems

Needed in drier countries in Africa, but no economic access to equipment, heavy machinery required to extract water.

What is water vapour’s role in temperature control?

Absorbs reflects and scatters solar radiation

Why are the poles dry?

Cold air holds less water vapour. Opposite for warm tropical areas, so they are more humid

What are the slow and fast hydrological cycles?

Slow = Years/milennia e.g groundwater (residence time 10,000 years), oceans

Fast = Weeks/days e.g atmospheric moisture (10 days), rivers and lakes

How do we know the hydrosphere is in dynamic equilibrium?

Constant heating/cooling of the planet, but the amount of water doesn’t change, the storage does

Define latent heat

Energy taken from the environment to fuel evaporation which drops the surrounding temperature e.g feels cooler after rain.

Also the energy released during condensation

What are the 3 types of rainfall?

Relief rainfall = mountains, air condenses when forced higher & falls as rain. Scotland and Wales

Frontal rainfall = mid-latitude regions, cool and warm air meeting and the warm air forced over cool due to density difference. Warm air condenses as it rises. Heavy rain

Convectional rainfall = Air heated below by warm land/sea, rises then falls. Short, high volume downpours. Common in Europe

How is climate change driving water cycle storage changes?

Interglacials/glacials = during Ice Age , 1/3 of land area covered in glaciers and ice sheets, increased cryospheric storage

Global temp increase = melting cryospheric stores, increased volume of oceans and sea level rise

Warmer air = more water vapour storage

How are cryospheric process changing water cycle stores globally?

95% of water on earth locked in 2 ice sheets over Antarctica and Greenland

Snow falling on glaciers/ice sheets compressed and stored long-term.

Ice sheets and glaciers shrinking/melting.

If all polar ice sheets melt how much would sea levels rise by? Is this a positive or negative feedback loop?

60m, positive feedback loop

What percentage of land in the northern hemisphere is permafrost?

25%

How does deforestation (local scale) affect magnitude of stores?

Decreased interception, increased infiltration. Could cause water logging/overwhelm soil water store. Surface storage increase or surface runoff. River channel store increase

How do storms (local scale) affect water store magnitude?

Increased magnitude of all stores due to precipitation influx

Name 3 human processes that alter the magnitude of water stores

Deforestation, Urbanisation, Agriculture

Define permafrost

Ground that remains below 0 degrees celsius for over 2 years

Can vary from <1m to >1500m thick

Melting and releasing methane due to climate change

Define cryosphere

All parts of the water system where water is stored in solid form

What are ice sheets?

A mass of glacial land ice more than 50,000km squared.

Form where winter snow never melts fully, building layers of compressed snow

2 major ones cover Antarctica and Greenland. If the latter melted, sea levels would rise 6m

What is the water balance budget?

Balance between inputs and outputs in a drainage basin system.

What is the purpose of a flood hydrograph?

Shows the fluctuation in river discharge over a flood compared to the times of precipitation. Can be used to study the flood risk of a location

Define lag time

Time difference between peak rainfall and peak discharge. A shorter lag time = more damage.

What are the rising and falling limbs in a flood hydrograph?

Rising limb = saturated soil, increasing discharge

Falling limb = length of time for river discharge to reduce as runoff reduces. Slower than rising limb

What is base flow in a flood hydrograph?

Normal discharge of a river

What is the difference between a flashy and a subdued flood hydrograph?

Flashy = steeper graph, higher peak discharge. Impermeable rock and a narrow, straight, shallow river

Subdued = Low discharge peak, permeable rock and a river with meanders and a wide channel (flood relief channels)

What is a river regime?

Graph showing changes to a river’s discharge over a year in response to climactic changes with seasons.

What are simple and complex river regimes?

Simple = one high and low discharge period e.g. River Avon (high in winter, low in summer, steep decline in discharge but low all year)

Complex = several extremes of discharge e.g River Po, Italy. (high in winter, but also in summer due to melting Alps snow)

Name one long term, one seasonal and one short term change to the water cycle.

Long-term = climate change

Seasonal = snow melt

Short-term = storms

List 3 causes of the Boscastle flood

Intense precipitation (1.5 billion litres of rainwater)

Many tributaries meet at the river

2.5 hour lag time, no time to adapt

Steep sided valley, village at the bottom, increased runoff

No floodplain, permeable land

What were the consequences of the Boscastle flood?

Buildings affected (destroyed, washed away)

75 cars washed away

Damage to tourism and businesses

How does farming in HICs affect the water cycle?

Intensive farming removes vegetation decreasing interception and veg storage

Machinery compacts ground, reduced infiltration

Drainage systems increase infiltration and through flow

Local groundwater reduced for irrigation

What was Cape Town’s Day Zero

The day where Cape Town would run out of water for its 4.6 million residents, which they were 90 days away from in 2018