Water Cycle Processes

EQ1

Spheres/Stores

where water is stored, only 0.01% of the world’s water is in rivers and lakes

• cryosphere = ice

• hydrosphere = ocean

• atmosphere = water vapour clouds

• biosphere = plants and animals

• lithosphere = ground

types of water:

• blue water = open ocean

• green water = kept on land, in plants or the soil

Processes

how water moves between stores

• percipitation

• percolation

• transpiration = loss of water from plants, important for small scale water cycles

• freezing

• infiltration

• evaporation

• condensation

• dew point = the point where clouds condense and form

Fluxes

how fast processes happen

Residence Time

how long water spends in a store, shortest residence time is the atmosphere which is on average 10 days, but they vary quite significantly

• fossil water = water, usually underground, still in the cycle but hasn’t actually been part of the cycle in many years so it doesn’t really count

Indirect vs Direct

washing, drinking and domestic use is direct and seen, aout 8% used indirectly

infrastructure, producing, manufacturing and agriculture is indirect use and unseen, majority of water is used indirectly

Positive Feedback

• watervapour is a green house gas, as areas get warmer due to global warming evaporation increases, but water vapour then acts as a greenhosue which worsense global wamring

• deforestation worsens drought to apoint where exisiting or new planted treese cannot grow or survive

Stats

• 70% of the world’s population experience water scarcity for one month at least every year

• 6% experience absolute water scarcity all year around

Water Availability Gap

richer countries tend to use more water as well as having access to more freshwater supplies

Colorado River

• runs through 5 different states

• makes the grand canyon, Hoover Damn

• produces energy and drinking water for millions of people

• river has been heavily used by humans for many years and is running dry

• transboundary dispute has occurred

• the river irrigates 15% of crop outputs in the USA

• it supports a $1.4 trillion economy

• treaties created to ensure that all states across the river’s course receive the same amount of water

• 15 dams across the course

• cause of less water to the river is because global warming increasing temperatures and reducing snowfall in the mountains

Flint, Michigan

• human error

• water was polluted with lead because of bad pipes

• denied that it was happening for years

• people had to live off bottled water for ages

Hydropgraphs

• graph which shows precipitation and discharge of rivers

• time between peak rainfall and peak discharge is the lag time

• lag time needs to be long to avoid flooding

Factors Affecting Lag Time

Physical

• speed and duration of rainfall

• geology of the drainage basin (permeable or non-permeable)

• vegetation cover (stem flow)

• shape and size of basin

• relief of land

• precipitation type (snow or rain)

• soil porosity

Human

• river relocation (channel realignment)

• urbanisation

• deforestation

• dams

• pete bog drainage

• irrigation

Types of Rain

CONVECTIONAL

• sun heats up the groud

• warm air rises due to reduced density of ai

• as air rises it cools as the upper atmosphere is cooler than the lower

• air condenses and forms clouds

• rainfalls

OROGRAPHIC

• air is moving at a low lattitude have not condenses yet (hasn’t met its lapse rate)

• pocket of air pushed up a hill

• air becomes colder and it cools

• as it cools condenses to form clouds

• rain or snow fall

FRONTAL

• main type in the Uk, leads to rain for long periods of time

• occurs when a warm front meets a cold front

• warm air forced to rise over cold air

• warm air forced to rise over cold air

• cools as it rises

• cooler air condenses and forms cloud

• clouds bring heavy rain

Types of Drought

• meteorological (reduction of rain)

• hydrological ( stores reduce)

• famine (mass migration), area no longer able to sustain life

• agricultural (can’t grow crops)

Physical Characteristics of a Drainage Basin

• basin size = affects lag time, larger the basin the longer the lag time because water has larger distance to travel so takes longer

• basin shape = circular basin means all points on watershed are equidistant from the channell so lag time is shorter and peak discharge is higher, but elongated basins have longer lag time and lower peak discharge

• elevation and slop/topography = a steep river valley means gravity assists water descent but gently sloping areas have lower lag time and lower peak discharge

• rock type/geology = impermeable rock impedes drainage by restricting percolation, creates high rates of overland flow and surface run-off

• soil type = controls rate of infiltration, soil moisture storage and rate of throughflow e.g. sandy soils have higher rates of infiltration due to large air spaces between soil particles

• draimgage density = total length of streams in a drainage basin divided by the area of the basin

• vegetation = sparse vegetation mean more overland flow and water reaches river quicker, shorter lag time

Meteorological Features of Drainage Basins

• rainfall type = amount and duration determine how saturated the ground is, soil in high moisture capacity might have impeded infiltration which leads to high rates of surface runoff and increase in discharge

• rates of evapotranspiration = not contestant throughout the year, high temperatures in summer increase rates, reducing discharge

Human Features of Drainage Basins

• urbanisation = reduces infiltration through its use of impermeable surfaces and rains and gutters tansport water quickly to rivers, lag time is reduced and discharge is increased, urban rivers usually have flashy hydrographs

• deforestation = reduces interception, increase in infiltration and can result in saturation capacity reached too quickly, rainfall will travel by overland flow and can lead to high rates of soil erosion

• water extraction = reduces amount of discharge

River Regimes

annual variation in the discharge or flow of a river at a particular point, influenced by a number of factors

• size of the river where discharge measurements are taken along its course

• amount, seasonality and intensity of rainfall

• temperatures and rates of evaporation

• the geology and soils particularly their permeability and porosity

• type of vegetation cover e.g. wetlands can hold water and release it slowly into the river

• human activities

Water Budget

throughout the year and seasons amount of water available changes

• soil moisture recharge (october -

• soil moisture surplus (lots of rain, utilisation not started yet)

• soil moisture utilisation (march-may, spring things start to grow)

• soil moisture deficit (june - august, less rain and water been used in utilisation)

two drivers of the water budget and balance

• perception

• evaporation/transpiration

different condition

• if the surplus period is too long, may go into drought

Closed System

• cycle

• no water is created, the volume of water on the planet never varies, it only change state and location

Price of Water Varies

• physical scarcity

  • only limited volume available, charge more

• availability, don’t have appropriate technology or funding

  • more money spent on accessing the water, price goes up (water intensity)

• technological pathway - privatised water companies can charge what they want