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Earth's Systems / Water cycle

Water cycle

How water moves between oceans, air, land and ice: evaporation and transpiration, clouds and rain, rivers and groundwater, snow and ice.

Boundary: where this process starts

Starts with: Sunlight and heat supply the energy that moves water between states

Boundary: where it ends

Ends after: Land water: infiltration, runoff and groundwater; Snow, ice and meltwater storage

PARTICIPANTSRESOURCESEarth systemSunOceansPlantsAtmosphereOtherparticipantsWaterWater vapourSunlightHeatImpact +3 of 5. Click for details and evidence.Impact +4 of 5. Click for details and evidence.Impact +4 of 5. Click for details and evidence.Impact +4 of 5. Click for details and evidence.Impact +2 of 5. Click for details and evidence.Impact 04 of 5. Click for details and evidence.Impact 02 of 5. Click for details and evidence.Impact +4 of 5. Click for details and evidence.↻ balances · moderate · 0.9 water returned tSunlight and heat supply the energy that moves water between states: uses WaterSunlight and heat supply the energy that moves water between states: uses SunlightSunlight and heat supply the energy that moves water between states: uses HeatEvaporation and transpiration: uses up Wateruses upEvaporation and transpiration: makes Water vapourmakesCondensation, clouds and precipitation: makes WatermakesCondensation, clouds and precipitation: uses up Water vapouruses upLand water: infiltration, runoff and groundwater: uses WaterSnow, ice and meltwater storage: uses Watercycled between phasesWater: cycled between phasespowers evaporation andcirculationSunlight: powers evaporation and circulationsupplies phase changeenergyHeat: supplies phase change energylost to the airWater: lost to the airadded to the airWater vapour: added to the airfalls as precipitationWater: falls as precipitationcondensed into dropletsWater vapour: condensed into dropletsinfiltrates, runs off orstoredWater: infiltrates, runs off or storedstored as frozen massWater: stored as frozen massStart: Water cycleSTARTStart: Water cycleEnd: Water cycleENDEnd: Water cycleSunlight and heatsupply the energy thatmoves water betwe…👍1 👎1📄2Sunlight and heat supply the energy that moves water between statesEvaporation andtranspiration↘👍1📄2Evaporation and transpirationCondensation, cloudsand precipitation↘📄1Condensation, clouds and precipitationLand water:infiltration, runoffand groundwater↘📄2Land water: infiltration, runoff and groundwaterSnow, ice and meltwaterstorage↘👍2📄1Snow, ice and meltwater storage
Line thickness = size of impact (1 to 5)% on a line = chance a fork takes that branch📄 = pieces of evidence on a stepNegative effectLoops backHypothesisResource used up (arrow into the step)Resource used, not used upResource made or released (arrow out of the step)
What am I looking at? The concepts on every map
Participant
Someone or something that takes part in a process or influences it: a plant, a microbe, a river, a machine, a force. Participants are the rows of a map.
Resource
Something a step uses or uses up: water, oxygen, sunlight, a tool. Each step has an arrow down to the resources it uses.
Step
One thing that happens in a process. Every step has at least one participant and carries evidence.
Decision fork
A step where the process can go several ways. Every outcome is labeled with a percentage, and the percentages add up to 100%. It is not limited to yes or no.
Loop
A line that carries the process back to an earlier step. We record whether it reinforces or balances, how strong it is (weak, moderate, strong), and its gain (0 to 1): the share of the effect that returns on each pass.
Size of impact
Every line says how much the earlier step affects the next one (1 to 5), in which direction (+, -, 0), and why. Thicker lines mean bigger impact.
Evidence
The support for a claim: a source and what it shows. Every step, line, change and vote needs it. Click any step or line to read its evidence.
Boundary
Where a process starts and where it ends. Every process, and every subprocess, has a start and an end.
Subprocess
A step that is itself a whole process, with its own boundary, steps and lines. Click a step marked ↘ to open it. Subprocesses nest as deep as the evidence goes.
Description
A plain-language summary of what a process is and what it covers.
Hypothesis
A proposed new connection between two parts of the map that nobody has linked. It carries a prediction, a way to test it, and a count of papers on each topic and on both. It is an unverified idea until someone tests it.

Inside this process

Evaporation and transpiration

How liquid water becomes vapour at Earth's surface, by ocean evaporation and by land transpiration and soil or canopy evaporation, absorbing latent heat and mixing vapour into the lower atmosphere.

Condensation, clouds and precipitation

5 steps

Land water: infiltration, runoff and groundwater

What happens to precipitation that reaches land: evapotranspiration back to the air, infiltration into soil and aquifers, slow groundwater flow, and river transport of water, sediment and dissolved nutrients to the sea.

Snow, ice and meltwater storage

Storage of water as snow and ice in cold regions, its high albedo, centuries-long residence in ice sheets, and the seasonal meltwater that feeds rivers and soils.

Every step, with its evidence

The same information as the map, as a list you can search and share. Click a participant or resource to see everywhere it appears.

Sunlight and heat supply the energy that moves water between states
SunEarth systemSunlightHeatWater
Evidence (2) · added by Atlas
  • Oki & Kanae 2006, Global hydrological cycles and world water resources, Science 313:1068-1072: Global evaporation ~505,000 km3/yr: ~434,000 from ocean (86%) and ~71,000 from land; precipitation ~398,000 on ocean (78%) and ~111,000 on land (22%); ~40,000 km3/yr flows from land to ocean. (confidence 0.9)
  • Trenberth, Fasullo & Kiehl 2009, Earth's global energy budget, Bull. Am. Meteorol. Soc. 90:311-323: Global budget: ~341 W/m2 incoming; ~102 reflected (30%), ~78 absorbed by atmosphere (23%), ~161 absorbed by surface (47%); surface loses ~80 as latent heat, ~17 sensible, ~63 net infrared; ~333 back radiation; ~239 outgoing longwave. (confidence 0.9)
↘ Evaporation and transpiration
OceansPlantsSunWaterWater vapour
Evidence (2) · added by Atlas
  • Oki & Kanae 2006, Global hydrological cycles and world water resources, Science 313:1068-1072: Global evaporation ~505,000 km3/yr: ~434,000 from ocean (86%) and ~71,000 from land; precipitation ~398,000 on ocean (78%) and ~111,000 on land (22%); ~40,000 km3/yr flows from land to ocean. (confidence 0.9)
  • Schlesinger & Jasechko 2014, Transpiration in the global water cycle, Agric. Forest Meteorol. 189-190:115-117: Transpiration is about 61% (+/-15) of terrestrial evapotranspiration; the rest is soil, canopy-interception and open-water evaporation. (confidence 0.8)
↘ Condensation, clouds and precipitation
AtmosphereCloudsAerosolsWater vapourWater
Evidence (1) · added by Atlas
  • Oki & Kanae 2006, Global hydrological cycles and world water resources, Science 313:1068-1072: Global evaporation ~505,000 km3/yr: ~434,000 from ocean (86%) and ~71,000 from land; precipitation ~398,000 on ocean (78%) and ~111,000 on land (22%); ~40,000 km3/yr flows from land to ocean. (confidence 0.9)
↘ Land water: infiltration, runoff and groundwater
Land surfaceSoilRiversAquifersWater
Evidence (2) · added by Atlas
  • Oki & Kanae 2006, Global hydrological cycles and world water resources, Science 313:1068-1072: Global evaporation ~505,000 km3/yr: ~434,000 from ocean (86%) and ~71,000 from land; precipitation ~398,000 on ocean (78%) and ~111,000 on land (22%); ~40,000 km3/yr flows from land to ocean. (confidence 0.9)
  • Dingman 2015, Physical Hydrology 3rd ed., Waveland Press: Precipitation on land is partitioned into evapotranspiration, surface runoff, interflow and groundwater recharge, with infiltration set by soil structure and vegetation. (confidence 0.75)
↘ Snow, ice and meltwater storage
GlaciersIce sheetsSnowpackWater
Evidence (1) · added by Atlas
  • Shiklomanov 1993, World fresh water resources, in Gleick (ed.), Water in Crisis, Oxford Univ. Press: Ice sheets and glaciers hold ~68-69% of Earth's fresh water; residence times range from days (atmosphere) to millennia (ice). (confidence 0.85)