The WFD recognises that some water bodies will have been changed to such a degree that they can longer be restored to their original condition without compromising their current use. For example, some waters have been deepened to allow for navigation; others have flood defences or have been dammed to provide a source of drinking water. They are called heavily modified water bodies (HMWBs) or artificial water bodies (AWBs).
Summary of changes to heavily modified and artificial water bodies 2015