water and carbon cycles Flashcards
composition of global distribution of water
- 97% of water comes from oceans
- the 3% of freshwater comes from cryosphere, ground water, liquid freshwater and water vapour
water stores in litosphere
- surface water- rivers, lakes (Canada has 2 mil), wetlands (areas of marsh or peatland or water dominated by vegetation- Pentanal wetlands)
- ground water that collects in pores of rocks- aquifers (Africa and middle east)
- soil water- water held together with air, controls exchange of water and heat
- biological water- in plants and organisms taken up through roots and transported
water stores in hydrosphere
- 5 bodies of water and smaller seas covering 72% of Earth’s surface
- Pacific Ocean is the largest
- alkaline with average pH 8.14 but slowly becoming more acidic
water stores in atmosphere
- 12900 km ^3 of water vapour
- greenhouse has which absorbs, reflects and scatters solar radiation
- amount of water that air can hold depends on temperature, where cold air cannot hold as much
- clouds
water stores in cryosphere
- sea ice- water in ocean frozen below freezing (arctic ocean)
- permafrost- ground that remains frozen for at least two consecutive years (Alaska)
- ice sheets- glacial land ice more that 50,000km^2, constantly in motion (greenland and Antarctica)
- ice caps- glacial land ice less than 50,000km^2, mountainous areas, some shaped, flow outwards (Andes mountains)
- alpine glaciers- thick masses of ice found in deep valleys
explain 3 states of water and links between them
gas -> condensation -> water
water -> evaporation -> gas
water -> freezing -> solid
solid -> melting -> water
solid -> sublimation -> gas
gas -> deposition -> solid
define evaporation
when solar radiation hits the surface of water or land and causes liquid water to turn into gas
factors affecting rate of evaporation
- amount of solar energy
- humidity (closer to saturation point, slower rate of evaporation)
- temperature of the air ( warmer air holds more water)
define transpiration
plants lose water when it is transported up the roots and out the stomata in leaves
define condensation
air cools and dew point decrease so less water vapour can be held and turns into a liquid
when does condensation take place and what does the magnitude depend on
takes place when temperature falls to below dew point or when air rises so it cools and expands and loses energy (adiabatic cooling)
magnitude depends on amount of water vapour in the atmosphere and temperature
explain global atmospheric circulation
- pressure cells which leads to cloud formation and rainfall
- low pressure cells (ferrel cell) is where air rises and causes climatic instability
- high pressure cells (hadley and polar cell) is where at falls and leads to drier and more mild climates
- ITCZ is a zone which moves north and south between the seasons and causes unstable low pressure conditions
features of cloud formation
- not evenly distributed due to global atmospheric circulation
- vapour molecules require small particles to condense in (condensation nuclei) or surface that are cooler than the dew point temperature
- varies seasonally and by location
define frontal precipitation
warm air is less dense than cool air so is forced above and cools as rise
define orogtaphic precipitation
warm air meets mountains and is forced to rise over it and cools
define convective precipitation
sun heats up the ground and moisture on the ground evaporates and rises up in a column of warm air
effect of cryospheric processes on water magnitude
- accumulation- inputs to glacial system like snowfall
- ablation- output of glacial system due to melting
- sublimation- ice changing directly into water vapour
- in colder periods, inputs re greater than outputs and vice versa when warmer
define drainage basin
open and local hydrological cycles which surround the river where the rain falling on land flows into that river
define watershed
boundary of drainage basin and anything beyond goes into a different drainage basin
inputs in a drainage basin
precipitation- water that falls to the earth in any form like rain, snow, hail
storage in drainage basin
interception- precipitation lands on vegetation or other structures before reaching the soil
vegetation storage- water taken up by plants and contained with it
surface storage- water in puddles, ponds and lakes
soil storage- moisture in soil above water table
groundwater storage- water stores in saturated soil or rocks below the water table
channel storage- water held in a river or stream channel
flows in drainage basin
infiltration- water soaking into the soil influenced by soil type, structure and saturation
overland flow or runoff- water flowing over land when ground is saturated or surfaces are impermeable
through fall- water dripping one leaf to another
stem flow- water running down plant stem or tree trunk
throughflow- water morning through the soil, mainly along “pipes” caused by animal activity or cracks
percolation- water seeping through soil to the bedrock
groundwater flow- water flowing slowly below the water table through permeable rock
channel flow- water flowing in the river or stream itself
outputs in drainage basin
- evaporation
- transpiration
- river discharge
define water balance and the different types
different between the inputs and outputs in a drainage basin
positive- more precipitation so more water in the ground
negative- more runoff and evapotranspiration so ground stores are depleted
define soil moisture budget
change in the amount of water stores in soil throughout the year
define potential evapotranspiration
the amount of water that could be lost, where higher temperature cause more evapotranspiration
soil moisture equation
precipitation= total runoff + evapotranspiration +/- change in storage
define river regime
variability in its discharge throughout the course of the year in response to precipitation, temperature, evapotranspiration and drainage basin characteristics
define river discharge and its equation
amount of water that flows through a particular point in a river at a particular time, measured in cumecs- cubic metres per second
discharge= cross sectional area x velocity
what is a flood hydrograph
graph representing rainfall for a drainage basin of a river and its discharge following a rain event or storm
features of a flood hydrograph and definition
peak discharge- highest point on a graph, when river discharge is greatest
lag time- delay between peak rainfall and peak discharge when the rainwater is flowing into the river
rising limb- increase in river discharge as rainwater flows in and indicates how fast water is reaching the river
falling limb# decrease in river discharge as the river basin empties
define flashy and subdued hydrograph
flashy- short lag time and high peak discharge, so higher flood risk
subdued- long lag time and low peak discharge, so lower flood risk
human factors affecting discharge
- urbanisation- more impermeable surfaces like concrete which increases surface runoff
- pastoral farming- ground is trampled in so less interception and more surface runoff
- ploughing breaks up topsoil and allows for greater infiltration
- irrigation saturates the soil so more water cannot infiltrate
- deforestation- less interception by trees
- water abstraction- water taken out of store which reduces base flow so more water must reach the channel before it reaches capacity
physical factors affecting discharge
- intense storms and more rainfall create greater peak discharge and surface runoff
- antecedent rainfall (rainfall before the studied rainfall event)- ground is already saturated so the water has reached its field capacity
- geology- impermeable rock decreases percolation and increases through flow
- basin size and shape- small, steep sides and circular each river more quickly
- high drainage density with many tributaries increase speed of drainage
- temperature- low temperature has less evapotranspiration so greater peak discharge,low temperature also cause water to freeze
- precipitation type- snow or hail takes time to melt
- vegetation cover- forested areas intercept more areas
- seasonal variation- temperature and vegetation cover
how does deforestation affect the water cycle
- less evapotranspiration so less condensation and less precipitation
- less interception and higher surface runoff
- less stem flow and through fall so lag time is quicker
- over 10% of Amazon rainforest has already been converted to cattle pasture
- new vegetation has fewer leaves and shallower roots so it uses less water
how does soil drainage affect water cycle
- draining waterlogged soil to make it suitable for agriculture
- irrigating land for agriculture
- system of corrugated plastic tubing to drain water from soils when the water table is high
- tiles are made from short lengths of clay pipes
evaluation of soil drainage
+ build up of soil structure makes it easier to work
+ improved aeration makes favourable conditions for microorganisms to thrive which increases the rate that organic matter is broken down
+ heavy machinery can work on land without danger of compaction
- insertion of drains artificially increases speed of through flow
- dry topsoil is subject to wind erosion
- nitrate loss and lead to eutrophication
how does water abstraction affect water cycle
- groundwater pumped from ground
- intrusion of saltwater so countries resort to desalinisation plants
- irrigation causes ground water overexploitation