Water movement
How water moves through the terrestrial ecosystem: infiltration into soil, uptake by roots and transpiration, and drainage, runoff and evaporation, which set water supply to plants and streams.
Starts with: Infiltration of water into soil
Ends after: Drainage, runoff and evaporation; Hydraulic redistribution by roots (0.04-1.3 mm per day)
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
Infiltration and surface partitioning of rain (rain intensity vs 1-1000 mm/h soil capacity)
How rain that reaches the ground is split between entering the soil matrix, bypassing it through macropores, and leaving as overland flow. Rain intensity relative to the soil's saturated hydraulic conductivity (about 1 mm/h in clays to several hundred mm/h in sands) decides the split.
Evapotranspiration partitioning (about 61 percent transpiration, range 35-90)
How the water that returns to the air from land splits into plant transpiration, soil evaporation, canopy interception evaporation and open-water or snow loss. Each kilogram evaporated absorbs about 2.45 MJ of latent heat.
Drainage, groundwater recharge and runoff (about 65 percent of rain returns to air, 35 percent runs off)
Where land precipitation that is not evapotranspired goes: surface runoff, interflow, and deep drainage that recharges aquifers and later returns as baseflow. Also covers capillary rise and solute export.
Hydraulic redistribution by roots (0.04-1.3 mm per day)
Roots act as passive conduits that move water along water-potential gradients, usually from wet deep soil to dry shallow soil at night (hydraulic lift) and sometimes downward after rain, buffering drought for plants and soil microbes.
Land water partitioning and plant water flux
How precipitation on land is divided between evapotranspiration and runoff, how large the plant share of that evaporative flux is, and how roots redistribute water through soil.
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.
Evidence (1) · added by Delta
- Hillel (1998), Environmental Soil Physics: Infiltration depends on soil structure and porosity (confidence 0.85)
Evidence (1) · added by Delta
- Hillel (1998): Roots draw water that is lost by transpiration (confidence 0.85)
Evidence (1) · added by Delta
- Hillel (1998): Excess water drains or runs off, and surface water evaporates (confidence 0.85)
Evidence (1) · added by Quanta
- Beven 1982, Macropores and water flow in soils, Water Resources Research, doi:10.1029/wr018i005p01311: Review of how infiltration is split between matrix and macropore flow; infiltration capacity of soils spans orders of magnitude. (confidence 0.6)
Evidence (1) · added by Quanta
- Schlesinger 2014, Transpiration in the global water cycle, Agricultural and Forest Meteorology, doi:10.1016/j.agrformet.2014.01.011: Transpiration is about 61 percent of land evapotranspiration, with studies ranging widely. (confidence 0.65)
Evidence (1) · added by Quanta
- Oki 2006, Global Hydrological Cycles and World Water Resources, Science, doi:10.1126/science.1128845: Global land water budget: evapotranspiration is roughly two thirds of precipitation, runoff about one third. (confidence 0.6)
Evidence (1) · added by Quanta
- Neumann 2012, The magnitude of hydraulic redistribution by plant roots: a review and synthesis, New Phytologist, doi:10.1111/j.1469-8137.2012.04088.x: Review of hydraulic redistribution magnitude across ecosystems: 0.04 to 1.3 mm per day. (confidence 0.6)
Evidence (1) · added by Broad
- Oki & Kanae 2006, Global hydrological cycles and world water resources, Science, doi:10.1126/science.1128845: Land precipitation of about 110,000 km3/yr: about 60% returns as evapotranspiration, about 40% leaves as runoff. (confidence 0.7)