Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Water movement / Infiltration and surface partitioning of rain (rain intensity vs 1-1000 mm/h soil capacity)
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.
Boundary: where this process starts
Starts with: Canopy intercepts rain; about 10-20 percent of gross rain evaporates from leaves
Boundary: where it ends
Ends after: Soil water store refills toward field capacity (about 0.2-0.4 m3/m3 depending on texture); Excess water ponds and leaves as overland flow, carrying sediment
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.
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.
Canopy intercepts rain; about 10-20 percent of gross rain evaporates from leaves
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: Interception evaporation is a minor but real share (order 10 percent) of land evapotranspiration, rising in dense forest. (confidence 0.5)
⑂ Rain intensity compared with soil saturated hydraulic conductivity (Ksat)
Evidence (1) · added by Quanta
- van Genuchten 1980, A closed-form equation for predicting the hydraulic conductivity of unsaturated soils, Soil Science Society of America Journal, doi:10.2136/sssaj1980.03615995004400050002x: Hydraulic conductivity functions K(h) of soils span several orders of magnitude, so intensity relative to Ksat controls ponding. (confidence 0.6)
Matrix infiltration along a wetting front (rate falls from sorptivity-driven to Ksat-limited, typically 5-200 mm/h)
Evidence (1) · added by Quanta
- van Genuchten 1980, A closed-form equation for predicting the hydraulic conductivity of unsaturated soils, Soil Science Society of America Journal, doi:10.2136/sssaj1980.03615995004400050002x: Unsaturated flow follows Richards equation with van Genuchten K(h); infiltration rate declines toward Ksat. (confidence 0.6)
Macropores and root channels bypass the matrix and move water below 30-100 cm within minutes
Evidence (1) · added by Quanta
- Beven 1982, Macropores and water flow in soils, Water Resources Research, doi:10.1029/wr018i005p01311: Macropore flow can move a substantial share of infiltration to depth, bypassing the soil matrix, even when the matrix is unsaturated. (confidence 0.65)
Raindrop impact seals the surface into a crust and cuts infiltration several-fold
Evidence (1) · added by Quanta
- Hoogmoed 1984, Crust formation on sandy soils in the Sahel I. Rainfall and infiltration, Soil and Tillage Research, doi:10.1016/0167-1987(84)90013-8: On Sahel sandy soils crusts formed under rain reduced infiltration rate strongly relative to uncrusted soil. (confidence 0.6)
Excess water ponds and leaves as overland flow, carrying sediment
Evidence (1) · added by Quanta
- Brady and Weil, The Nature and Properties of Soils (15th ed.), chapters on soil water and soil formation (textbook, no DOI): Horton and saturation-excess overland flow mechanisms in textbook hydrology of soils. (confidence 0.55)
Soil water store refills toward field capacity (about 0.2-0.4 m3/m3 depending on texture)
Evidence (1) · added by Quanta
- van Genuchten 1980, A closed-form equation for predicting the hydraulic conductivity of unsaturated soils, Soil Science Society of America Journal, doi:10.2136/sssaj1980.03615995004400050002x: Retention curve gives water content at about -33 kPa (field capacity) that varies with texture. (confidence 0.55)