Hi HikeAndMap!
 Thank you for reaching out. We are using the Bing as imagery to verify edits from Map builder users and this one apparently doesn't have much experience adding water bodies. So the user draws a waterbody aligned to the water level not to the whole water reservoir as it should. 
You are always welcome to edit/change edits by yourself especially having local knowledge.
 Thank you for helping out.
 Best regards
 Aleksandar