Yeah, I can just see the water cannon pulling up at the friendly neighbourhood borehole to take on a fresh supply of water from the underground resource ....

On the other hand, ponds, and, particularly in the sort of urban environment in which water cannon might be required, fountains, swimming pools and rivers are easily found.

nappe - 1. Vaste étendue d'eau, de liquide, de gaz, etc. s'étalant comme une couche sous terre OU EN SURFACE, DANS UNE DEPRESSION, etc.
[Larousse Lexis]

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Note added at 6 hrs (2007-12-21 22:38:48 GMT)
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Upon which I envision some poor protester getting blasted with fish ....

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Note added at 19 hrs (2007-12-22 12:11:59 GMT)
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Since IMO "nappe" here could imply public fountains, I don't think "NATURAL water resource" is appropriate. As I suggested below, "any BODY of water", maybe.

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Note added at 19 hrs (2007-12-22 12:13:37 GMT)
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Wiki says:
<<A body of water is any significant accumulation of water, usually covering the Earth or another planet. The term body of water most often refers to large accumulations of water, such as oceans, seas, and lakes, but it may also include smaller pools of water such as ponds, puddles or wetlands. Rivers, streams, canals, and other geographical features where water moves from one place to another are not always considered bodies of water, but are included here as geographical formations featuring water.

Some bodies of water can be man-made (artificial), such as reservoirs or harbors, but most are naturally-occurring geographical features. Bodies of water that are navigable are known as waterways. Some bodies of water collect and move water, such as rivers and streams, and others primarily hold water, such as lakes and oceans.

The term body of water can also refer to a reservoir of water held by a plant, technically known as a phytotelma.>>



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Note added at 20 hrs (2007-12-22 12:48:01 GMT)
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Étang : NAPPE d'eau stagnante de faible profondeur, habituellement plus petite qu'un lac et souvent colonisée par la végétation.
Marais : NAPPE d'eau stagnante de faible profondeur, envahie par la végétation aquatique
http://www.abrinord.qc.ca/lexique.html

Rivière, n.f. Cours d'eau d'importance variable recevant des tributaires et se déversant dans une NAPPE d'eau [e.g. a lake] ou un cours d'eau plus important. Normalisé"
http://www.toponymie.gouv.qc.ca/dtv8.asp

nappe (d'eau)
water table (underground), water surface [sic!] (above ground)
Toute étendue d'eau souterraine ou superficielle
[Dict. français d'hydrologie de surface]

"Nappe" has indeed come largely to mean "groundwater", "aquifer", etc., but only by contraction from "nappe phréatique", "nappe souterraine", which is but one kind of "nappe".

In English, a "nappe" is the depth of or "sheet" of water flowing over a weir, for example, just as in French a "nappe" is the sheet of fabric on a table. So a "nappe" is a sheet or body of water, be it underground or on the surface of the ground.