water cycle Flashcards
How is total water distributed?
oceans store 97.5% and freshwater only stores 2.5%
How is freshwater distributed?
30% groundwater, 69% cryosphere 0.4% surface water with only 1 % of freshwater accessible.
How is surface water distributed?
67% lakes,12% soil,10% atmosphere
Residence time of different stores?
oceans 4000 years, glaciers 1000 years, groundwater 10000 years
what are the 2 processes that drive the global hydrological system?
Solar energy- heats up water causing evaporation and transpiration with 74% of rain concentrated in the tropics.
Gradational potential energy-transports rain between different stores in form of fluxes.
what does a closed system mean?
how are some stores changing?
continuous with nothing lost
shift in climatic zone mean some stores are depleting e.g., glaciers.
What movement occurs between stores of land and oceans and what is this balance known as?
in oceans evaporation > precipitation and on land precipitation > evaporation whilst the difference is made in surface runoff putting them in equilibrium this balance is known as the global water budget.
what are the 8 characteristics of polar hydrology?
> Freeze-thaw seasonal differences.
> spring thaw causes rapid runoff increasing evaporation tenfold.
> freeze thaw cycle causes release of biogenic gas.
> snow insulates the land and 85% of solar radiation is reflected.
> Permafrost creates impermeable substances.
> Lakes and rivers frozen and limited veg reduces heat absorption.
> characterized by orographic and frontal precipitation and low
humidity.
> annual precipitation less than 200mm
What are the characteristics of tropical rainforest hydrology?
> Few seasonal differences.
dense veg intercepts and consumes 75% of precipitation.
50-75% of precipitation returned by evapotranspiration cools the air as energy is used during the process.
Rainforests generate their own rain.
less than 25% of rain reaches rivers and surface water.
deforestation reduces evaporation thus reducing local rainfall.
constant high temps, characterised by convectional rainfall and high humidity.
annual precipitation more than 2000mm
global water budget definition?
The global water budget is the total amount of inputs, outputs and stores of water in the global system.
what and where is the biggest flux from ocean to land?
steep angle if the sun results in intense Solar radiation causing high evapouration.Trade winds transfer water vapor to ITCZ. Strong convectional currents lift air, so it cools into clouds forming storms, most rainfall is created here so is the biggest flux from ocean to land.
why are polar regions important?
2/3rds of water is locked up in the cryosphere - where temps are below 0 and frozen as glaciers as its melted its added to the global hydrological system affecting the thermohaline circulation.
What is the thermohaline circualtion?
A global conveyor belt of warm and cold water,
>where ocean water in polar regions is colder more saline and denser causing it to sink.
> cold sinking water draws in warmer surface water from the tropics.
> the movement of water from the tropics draws cold water from the ocean bottom, to be warmed again.
What is the thermohaline circulation?
A global conveyor belt of warm and cold water,
>where ocean water in polar regions is colder more saline and denser causing it to sink.
> cold sinking water draws in warmer surface water from the tropics.
> the movement of water from the tropics draws cold water from the ocean bottom, to be warmed again.
What isfossil water?
Untapped ancient stores of freshwater exist in polar regions and beneath many deserts, now technology allows access to water known as aquifers. Kenya’s Lotikipi aquifer contains around 200billion cubic meters of freshwater, 70 years of Kenya’s supply.
What is a drainage basin?
A series of rivers and its tributaries operating in a open system where water can be lost or gained. Examples include- Mississippi basin draining 3.3million km and Thames basin draining 16,000km.
Watershed definition?
an imaginary line around the edges of a basin separating one basin from another.
How can a drainage basin lose water?
> Evaporation and transpiration to atmosphere.
Surface run-off to the sea
Percolation into groundwater stores.
what 3 hydrological processes occur when preciptation occurs?
> infiltration into topsoil
surface runoff
evaporation
What 3 process occur to delay fluxes between stores?
> interception by plants
percolation through rocks to become groundwater.
surface runoff into rivers
What is the input into the hydrological cycle?
Precipitation- moisture in any form
What acts as storage in the hydrological cycle?
Interception- temporary storage in plants and buildings before reaching soil.
Vegetation storage- Any moisture taken up by vegetation and held within plants.
Surface storage- any surface water in lakes or ponds.
Soild moisture- Water held in soil.
Groundwater storage- Water held in permeable rocks (AKA aquifers)
Channel storage- Water held in rivers and streams.
What are the flows the hydrological cycle?
> Infiltration- water entering topsoil.
Throughflow- Water seeping laterally through soil below surface but above the water table.
Percolation- Downward seepage of water through mainly permeable rock under gravity
Groundwater flow- slow moving water that seeps into a river channel.
Surface Runoff-Flow over a surface usually impermeable, frozen or saturated.
What are outputs in the hydrological cycle?
> evaporation-conversion of water to vapour.
> Transpiration- water taken up by plants and relased as water vapour via osmosis
> Evapourtranspiration-combined effect of evaporation and transpiration
> River discharge- the volume of water passing a certain point in the channel over a certain amount of time.
Drainage basin factors
> snow capped peaks hold water until they thaw delaying the flow
> steep slopes promote faster movements and shorter storage times
> permable soils and rocks allow more infiltration and percolation, providing greater recharge of groundwater
> High drainage density (lots of tributaries) means fast water movement across the basin.
> Rural land use permits more natural processes than urban. Grassland has more infiltration, percolation, throughflow and evaporation than arable land.
> reservoirs hold back the flow of water and create new surface stores.
> Large-density basins collect more precipitation and are affected by more basin-wide factors than small basins.
> Low drainage density means slow movement of water across the basin area.
> Forested slopes intercept more precipitation,increase levels of evapotranspiration and reduce surface run-off.
> Impermeable rocks and soils prevent infiltration and cause surface saturation.
> Urban surfaces impermeable so increase surface runoff,evapouration and interception.
what are the 3 types of rainfall and where and why do they occur?
Orographic (relief) rainfall - Western side of the UK receives the highest rainfall totals, especially in autumn and winter. Warmer moist Atlantic air from the southwest is forced to rise as it reaches the western uplands. As it rises it cools over high ground forming clouds - producing heavy rainfall over western and northern parts of the UK, air then decends and warms.
Convectional rainfall - Typical of the eastern and south-eastern UK in summer, during periods of high temp ,rainfall created by cooling of sea and it condensing forming clouds and rain, often intense and associated with electrical storms causing flashflooding as soil becomes saturated.
Frontal rain- Brings the most rainfall to the UK over the course of a year. Fronts are formed as part of a low-pressure area (depression), where warmer moist air from the southwest meets colder polar air from the north or north-west. The warmer air is forced to rise over cooler air- forming rain along both warm and cold fronts.
What is the rain-shadow effect?
The eastern side of the UK receives less rain than the west because western hills force moist air to rise as it approaches from the Atlantic leading to orographic rainfall from the north and west.
How do humans impact drainage basins?
Overabstraction- Thames basin home to 13 million people. Also, one of the driest areas in the UK, averaging just 690mm of rainfall a year. Under pressure from growing water demands abd greater abstraction. Over 40% of Londons’ water comes from chalk aquifers, replenished by rain falling on Marlborough Downs, chilterns and north downs on the west north and south of london, abstracting too much water leads to rivers drying up in times of low rainfall.
Deforestation- Forests are fragile natural environments, complex biodiversity of their forests flourish on relatively thin soil. Removal of dense forest canopy protecting vital top soil can have devastating consequences as accelerate natural processes:
reduces evapourtranspiration, stores less rainwater, increased runoff,causes flash flooding, little rainfall soaks into ground so less aquifer stores and water table lower.
Urbanisation- Prevents water infiltrating into the soils only allowing 5% deep infiltration and 10% shallow from 25% deep and 25% shallow. With urbanisation increasing runoff by 45% and reducing evapourtranspiration.
Reservoirs- man-made storage reservoirs interrupt natural flows of water,delaying flows through drainage basin adding to amounts lost through evaporation. In tropics plants make evapotranspiration rates 6x higher than in open water,salinity levels in reservoir also rise as water evaporates, reservoirs also abstract water from drainage basins.
What is a water budget?
Balance that reflects differences between inputs and outputs in any given area, representing balance between surpluses and defecits.
what is the water balance equation?
P=Q+E +/- S
where,
P=precipitation, Q=runoff, E= potential evapourtranspiration , S= soil moisture and groundwater storage.
What happens from January to april in terms of soil moisture?
From Jan to April Precipitation (P) exceeds potential evapotranspiration (PE) resulting in a soil moisture surplus for plants, runoff and groundwater recharge.
What happens from April to july ?
PE exceeds P. Soil moisture is used up by plants or lost via evapouration. (soil moisture utilisation)
What happens in July?
Soil moisture used up, P absorbed by soil, rather than as run-off, River levels fall or dry up completely.
