Water Cycle

Question 1

just __ % of the Earth’s total freshwater, is accessible to humans

Answer 1

0.9

Question 2

Why is water stored unevenly

Answer 2

because of the uneven spread of land to sea and permeable or porous rock which enable aquifers to form

Question 3

what are the major stores of water

Answer 3

Most water is stored as saline water in oceans and freshwater as ice or within aquifers (groundwater stores)
Frozen water in the cryosphere = 68.7%
Liquid water in the hydrosphere = 1%
Water vapour in the atmosphere = 0.2%
Groundwater in the lithosphere = 30.1%

Question 4

is the water cycle a closed or open system

Answer 4

closed

Question 5

define the hydrological cycle

Answer 5

the continuous movement of water on, above and below Earth’s surface

Question 6

what are the processes in the hydrological cycle

Answer 6

Evaporation - the sun evaporates surface water into vapour
Condensation - water vapour condenses and precipitates
Flows - water runs off the surface into streams and reservoirs or beneath the surface as ground flow

Question 7

how does the hydrological cycle involve energy exchange

Answer 7

As water evaporates, it uses energy from its surrounding to perform this process
This effectively cools the environment
The reverse happens when water condenses (heat is released)
This heat exchange influences the local climate

Question 8

Stores are…

Answer 8

those places where water is held for a period of time

Question 9

examples of non-groundwater stores

Answer 9

Water in the atmosphere in the form of water vapour or water droplets in clouds
Surface stores such as puddles, lakes, rivers and reservoirs
Interception is how precipitation is prevented from reaching the ground, usually by being caught on leaves or branches
Ice and snow
Seas and oceans

Question 10

examples of groundwater stores

Answer 10

Not all rocks can store or transport water
An impermeable but porous rock such as clay, can store water but not transfer water
Un-weathered granite cannot store or transfer water as it has no spaces between rock particles
Sandstone is both porous and permeable and is able to store and transport water
A rock which stores water is called an aquifer and is the most unpolluted source of reliable water when managed carefully

Question 11

how is an aquifer formed

Answer 11

Formed extremely slowly over a very long time. Water infiltrates underground and collects in the pore spaces of porous rock. the interconnected pore spaces become saturated with water.
Pore spaces can be openings between grains or fractures in the rock or even caverns
Porosity is not enough to form an aquifer, pores must connect with each other to allow water to flow/transfer from one space to another . The flow through an aquifer is very slow

Question 12

What are the two types of aquifiers

Answer 12

Unconfined - where porous rock is open to surface water and is directly recharged by precipitation

Confined - where there are thick layers/beds of rock over the aquifer, known as the confining beds; these contain the aquifer from the Earth’s surface or other rocks

Question 13

The size of the stores of water along with water residence time is dictated by:

Answer 13

Flows/transfers such as evaporation
Global factors such as climate change
Local factors such as human activity on a hillslope

Question 14

define Groundwater Flow

Answer 14

Also called baseflow and is water that has infiltrated and percolated into the bedrock and below the water table

Question 15

how does Climate change drive change

Answer 15

During the last Ice Age (approx. 18,000 yrs ago), roughly a third of Earth’s surface was covered in ice sheets and glaciers
This increased the magnitude (size) of the cryosphere’s stores
But, it lowered the hydrosphere’s store (no flow of liquid water) and sea levels were over 100 m lower than present day

Question 16

how do clouds and precipitation drive change

Answer 16

The global atmospheric circulation drives the formation of clouds and types of precipitation
The Equator receives more insolation, resulting in higher temperatures which cause high rates of evaporation
As the warm, moist air rises, it cools, condenses and forms banks of towering clouds with heavy rainfall
This area is a low-pressure zone known as the Inter-Tropical Convergence Zone (ITCZ)
The ITCZ (also called the ‘thermal equator’) tracks with the seasonal movement of the Sun, north and south of the equator bringing intense low-pressure rain/monsoon conditions with the movement
(Global scale)

Question 17

how do Cryospheric processes drive change

Answer 17

The second largest store of water is ice and 95% is locked as the ice sheets of Antarctica and Greenland
Any changes to the size (magnitude) of these sheets impact globally
The total melting of the ice sheets could result in a 60 m sea level rise, which is a lot of stored water
Melting of the ice sheets adds water to the hydrosphere store of the oceans
Ice shelves are further destabilised, which triggers ice calving, these icebergs subsequently melt; adding to the hydrosphere store and rising sea levels
This is a positive feedback loop

Question 18

Farming practices impact stores:

Answer 18

Ditches drain the land and increase water flow away from the land
The interception by vegetation can prevent as much as 40% of precipitation from reaching the surface
Over-abstraction of groundwater for irrigation removes stores of water

Question 19

how does Deforestation reduce interception and infiltration

Answer 19

The interception by leaves stems and branches not only reduce the amount that reaches the ground but also slows the passage of water to the surface, allowing infiltration into the subsurface to occur
Deforestation affects surface stores as natural depression stores such as puddles, ponds and soil are removed
Roots help to break up the soil, increasing the rate of infiltration and groundwater recharge

Question 20

how does urbanisation effect stores

Answer 20

Development of the slope creates impermeable surfaces which effectively removes natural depression stores
Impermeable surfaces also reduce infiltration, impacting groundwater stores
Surface runoff is increased and river channel stores are increased - which may lead to flooding

Question 21

how does industrialisation effect stores

Answer 21

Burning of fossil fuels generates CO2 in the atmosphere enhancing the greenhouse effect and global warming
This in turn affects precipitation rates and intensities of fall, affecting magnitude of stores
Industrial output can produce acid rain, which destroys vegetation and interception rates, affecting water stores

Question 22

difference between Throughfall and Throughflow

Answer 22

Throughfall is above ground and is where water transfers through the canopy of trees etc. to the ground without any interception.

Throughflow occurs below ground and is the transfer of water laterally below the surface after infiltration.

Question 23

define a drainage basin

Answer 23

An area of land drained by a river and its tributaries. A drainage basin can also be called a ‘catchment’

Question 24

Nile River basin drainage area facts

Answer 24

more than 3 million km2 over 12 countries

Question 25

are drainage basins open or closed systems

Answer 25

open, drains all the water which lands on the Earth's surface

Question 26

Is the atmosphere a store or transfer

Answer 26

the atmosphere can be both a store and a transfer – clouds store but also move water around the planet

Question 27

Inputs and outputs in drainage basins

Answer 27

Inputs are the addition of water to a drainage basin through precipitation Inputs vary throughout the year (rain, sleet, snow, location etc) and intensities (flood, drought, temperature etc) and frequency (seasonal, monsoon etc Outputs are the losses of water from a drainage basin in various forms River discharge is the volume of water passing a point in the river channel at a given unit of time and expressed as cubic metres per second or ‘cumecs’ (m3/sec)

Question 28

why is interception important for a drainage basin system

Answer 28

It slows the passage of water to the surface and reduces the amount that reaches the ground – some or all will evaporate and the rest will take a longer route over leaves, trees etc. This is important, as it reduces the amount available for overland/surface flow and therefore, there is a reduction in soil erosion and flooding

Question 29

The interception by vegetation and buildings can prevent as much as __% of precipitation from reaching the ground

Answer 29

40

Question 30

Stores in a drainage basin system

Answer 30

Soil stores – water retained within the pore spaces of the soil called interstices Groundwater stores water that has percolated and is held in rocks below the top of the water table

Question 31

above ground flows in a drainage basin systems

Answer 31

Throughfall is precipitation that makes it to the ground without interception by the plant canopy Drip flow is water that flows off leaves and drips to the ground. Some leaves have developed drip tips and waxy surfaces Trunk and stem: the flow of water down the stems of plants or trunks of trees Overland surface flow is when water flows over the land surface. Two types: channel and sheet flow

Question 32

below ground flows in drainage basins

Answer 32

Infiltration is where water enters small openings and pores in the ground from the surface. Vegetation cover increases infiltration rates as they slow the rate of flow allowing infiltration to occur, and their roots break up the soil increasing potential pore spaces and channels Throughflow is the lateral (sideways) movement of water through the upper soil, along lines of seepage called percaline Percolation is where water flows down through the soil layers and underlying rock is pulled down through gravity. The rate of travel is determined through porosity (soil) and permeability (rock) Baseflow / Groundwater flow: water that has infiltrated and percolated into the bedrock and below the water, table to feed springs, river channels and recharge aquifers (recharge will only occur when there is an excess of water)

Question 33

types of overland flow

Answer 33

Channel flow is where water flows in small channels or rills (<30cm width or depth) in a defined stream pattern Sheet flow is a layer of water on the surface, either due to excess surface flow from increased precipitation or water cannot infiltrate quickly enough Hortonian overland flow describes the tendency of water to flow horizontally across land surfaces when rainfall has exceeded infiltration capacity and depression storage capacity. The water cannot enter the ground, so it runs straight off the surface.

Question 34

what is drainage density

Answer 34

The number of tributaries in a drainage basin

Question 35

how drainage density effects basins

Answer 35

Drainage basins with lots of tributaries have a high drainage density Drainage basins with few tributaries have a low drainage density Drainage density affects the magnitude of stores

Question 36

Key points to mention when describing hydrographs:

Answer 36

Steepness of the rising and falling limb The value of the peak discharge The lag time (period of time between peak rainfall and peak discharge) Time is taken to return to normal

Question 37

what factors affect drainage basin runoff

Answer 37

precipitation type and intensity The geology of the drainage basin affects runoff - permeable rocks allow precipitation to be lost or stored Climate - higher temperatures allow for more evapotranspiration to occur Vegetation type affects infiltration rates and can slow runoff Drainage basin relief - steeper relief allows for faster runoff Size of the basin - the larger the basin, the more water it can store before discharge

Question 38

what natural impacts effect the water cycle

Answer 38

Natural climate change - the impact of ice ages or interglacial periods will change the availability of water within the system Extreme climatic events, such as drought, impact the water cycle by reducing the amount available within the system Ecosystem changes - plant succession may alter the dominant vegetation in an area, which can alter interception rates. Animal burrowing leaves tiny voids which water can infiltrate instead of transferring to groundwater Seasonal changes- wet and dry seasons change the availability of water within the system

Question 39

how does precipitation Seasonally Impact on the Water Cycle

Answer 39

winter: Usually greater levels of precipitation, snow will delay the availability of water until melted summer: Usually, precipitation is less, however, summer storms can bring flash flooding

Question 40

how does evaporation Seasonally Impact on the Water Cycle

Answer 40

winter: Lower temps reduce the rate summer: Higher temps increase the rate

Question 41

how does soil moisture Seasonally Impact on the Water Cycle

Answer 41

winter: Saturated soils lead to increased overland flow and loss of water within the cycle summer: Soils may dry out, reducing the availability of water, although any rain infiltrates quickly. Hard, the baked ground is initially impermeable

Question 42

how does vegetation Seasonally Impact on the Water Cycle

Answer 42

winter: Vegetation dies back, reducing interception and transpiration summer: Vegetation grows, increasing rates of transpiration and interception

Question 43

how does river channel flow Seasonally Impact on the Water Cycle

Answer 43

winter: Higher discharge rates are usual with winter storms summer: Lower discharge rates as levels of precipitation drop

Question 44

what human factors impact the water cycle

Answer 44

Climate change Farming practices Deforestation Land use change Water abstraction

Question 45

how does climate change affect the water cycle

Answer 45

Increasing global temperatures reduce mountain glacial ice and the availability of freshwater for communities dependent on this water

Question 46

how does water abstraction affect the water cycle

Answer 46

The growth of the global population has increased the demand for water supplies. Excessive removal of aquifer water means that recharge cannot keep up and stores are depleted. This can allow seawater ingress if the water table drops below sea water or salinisation if the water table rises and evaporation leaves natural salt concentrations behind

Question 47

how does Land use change affect the water cycle

Answer 47

Changes to an urbanised landscape increase impermeable surfaces, leading to increased runoff and reduced infiltration. City drainage systems remove water quickly but can lead to flooding when river channels cannot discharge excess runoff quickly

Question 48

how does Deforestation affect the water cycle

Answer 48

Vegetation removal for agriculture, urbanisation or firewood for fuel supply, impacts an important water storage and transfer capability. Soil moisture is reduced, transpiration declines and less precipitation occurs at a local level which can lead to a dry river system

Question 49

how does Farming practices affect the water cycle