This is a large scale change witch doesn't seem to follow Automated Edits code of conduct.
https://wiki.openstreetmap.org/wiki/Tag:landuse%3Dreservoir
"Under no circumstances should you (semi-)automatically change “deprecated” tags to something else in the database on a large scale without conforming to the automated edits code of conduct. Any such change will be reverted."
https://wiki.openstreetmap.org/wiki/Automated_Edits_code_of_conduct

It's likely that involved elements need reevaluation and retagging but this is not the way to do.
Please revert this one and other similar edits.