Bassin versant de l'étang de retenue

Question

<\/HEAD>Bonjour,<\/P> <\/P> Je suis nouvelle dans l'utilisation de l'outil watershed. Je vois que vous pouvez utiliser et\/ou créer des points de déversement pour les emplacements des jauges de débit, etc... Que faire si j'essaie de découvrir le bassin versant d'un étang en hauteur qui est un polygone et non un point... devrais-je chercher à trouver un point de déversement le long de l'étang ou y a-t-il un moyen d'utiliser la zone polygonale de l'étang pour trouver le bassin versant ? Je poserai une question secondaire, si je fais un remplissage sur le DEM, cela remplira-t-il mon étang de retenue ?<\/P> <\/P> Merci,<\/P> <\/P> Jessica <\/P><\/BODY><\/HTML>

GabrielUpchurch1 · Answer

For the pour points, I would test Sephe's suggestion first to see what you get but I suspect you may get watersheds for each cell in the pond.  I haven't tested this approach so it would be beneficial for you to try it.  Even if you get a bunch of small watersheds, you could post process the data into a single watershed for the whole pond.  Alternatively, if the pond has an outlet, dam, levee, spillway, etc., you could place a point there or if all land around the pond drains into the pond, you could use the pond's centroid.  General knowledge of the slope of the terrain and hydrology for the area will play into where you place a point.

As Sephe pointed out, you will need to experiment with the z limit parameter to avoid having your pond filled.

SepheFox · Answer

Hi Jessica, to answer your second question, you can set a z limit for your fill, such that it won't fill your pond. You can try to figure out what that is, or just play around with the z limit until you fill surrounding sinks, but not your pond. As far as the pour point, you might try converting your pond polygon to a raster, so that all the cells of the pond will be used to find the contributing watershed area.