From the description of the funtain : https://collections.heritage.brussels/fr/objects/86568 that say "Elle est le point de départ de l’œuvre Cours d’eau (F046). " we can find the details here : (p 50 -51 52)  : https://pumproject.files.wordpress.com/2012/05/dossierpumdefinitif4corrigecc81.pdf

So no mention of Fossé Léopold and we found the origin of this "nouvelle rivière urbaine" as signed on the info board near the funtain. And it's also not a name but a description. So 904467736 has no name.

