English to French runoff

Dictionary entry: runoff


English - USA
I'm not 100% confident on this one when it comes to French, but I'm within my technical area in English.

These comments pertain to the first sense, related to hydrology, which I've copied here:

uncountable (overflowed liquid)trop-plein nm
ruissellement, écoulement nm

For me, runoff -- short for "surface runoff" and also known as "overland flow" -- isn't overflow. Overflow implies some sort of contained volume that spills over once the fluid level exceeds the capacity. But there is no container involved with runoff because the water (from rain, snow-melt, etc.) hasn't yet been caught in any sort of container (channel, stream, pond, retention basin, etc.). After a big storm, you can say that a stream is swollen with runoff, but that's precisely a reference to the water that was added to the stream as a result of overland flow. The runoff in that case is NOT the volume of water that might spill out over the banks of the stream in flood conditions.

Even for an engineered system like a dam, levee, reservoir, cistern, sewer, etc. we don't say "runoff" to talk about what happens when there's too much water and the excess has to be released... or, worse, spills out in an uncontrolled manner. Relevant words in those situations are terms like "release flows," "overflow," "overtopping," etc. as a function of the context.

So I suggest that the idea of "overflowed liquid" in the English sense is misleading...

... and that it probably contributed to a mismatched French translation (trop-plein) which contains the idea of being too full, in excess beyond the volumetric capacity of a vessel/container. As I say, I'm not 100% confident of French usage, but I suspect trop-plein is more like "overflow" and therefore isn't quite right to translate "runoff." (The words ruissellement and écoulement are, I believe, quite suitable.)
  • Kelly B

    USA English
    Me neither, but this from gdt seems to fit...? Omit "eau de" to describe the phenomenon itself.

    Would overland flow of precipitation be the right parenthetical description? I wonder if even that is too long. Just precipitation, or rainfall?

    eau de ruissellement​

    eau > réserves hydriques de surface
    Commission d'enrichissement de la langue française (France), FranceTerme, 2017
    Eau issue des précipitations atmosphériques qui s'écoule sur une surface.


    English - USA
    Would overland flow of precipitation be the right parenthetical description? I wonder if even that is too long. Just precipitation, or rainfall?

    Perhaps the parenthetical sense could be "(overland flow)" or "(hydrology)" -- the point being not so much to define the term (that's what the English dictionary is for) as to differentiate this sense from the ones related to elections and decision-making processes.

    Using "rainfall" or "precipitation" in parentheses risks being misunderstood as saying that runoff is equivalent to precip, which would be incorrect. Putting "(from precipitation)" in parentheses might work.

    To my mind, the essential elements behind the concept of runoff are:
    • the water source is precipitation -- rain, snow, etc.
    • the precip has to fall on dry land, and build up enough that water starts to trickle/flow across the ground
    • there will be a time lag between when the precip falls and when runoff starts -- perhaps a very short lag if the rain is intense and/or the land surface is relatively impermeable, perhaps months if the overland flow results from spring snowmelt
    • the runoff doesn't have to end up in stream/river/lake -- it could infiltrate naturally before it gets to a stream, it could be caught in a retention basin and soak into the ground from there, etc.

    Hopefully this info is helpful to the team.