[Here][1] I mapped a part of the river Voxnan as example for how I think it should be done. For "the system" you "tried to fill with water": this has been mapped as the Voxnan Nature Reserve and I don't think the Nature Reserve is restricted to the banks of the river. Additionally, since there is partly much better Aerial Imagery the river should be re-mapped as far as it the imagery stretches. While doing so you should keep the history of maybe already existing objects. The most comfortable way to do this is using the ediotr JOSM and its plugin *replace geometry*. [1]: http://www.openstreetmap.org/?lat=61.79617&lon=14.81045&zoom=15&layers=M

[Here][1] I mapped a part of the river Voxnan as example for how I think it should be done. For "the system" you "tried to fill with water": this has been mapped as the Voxnan Nature Reserve and I don't think the Nature Reserve is restricted to the banks of the river. Additionally, since there is partly much better Aerial Imagery the river should be re-mapped as far as it stretches. While doing so you should keep the history of maybe already existing objects. The most comfortable way to do this is using the ediotr JOSM and its plugin *replace geometry*. [1]: http://www.openstreetmap.org/?lat=61.79617&lon=14.81045&zoom=15&layers=M