Water footprinting is based on regionalized life cycle impact assessment methods, i.e. methods that assign different characterization factors depending on the location where the use of water takes place.
Currently, ecoinvent does not include regionalized impact assessment methods and therefore does not provide water footprint scores. It is technically possible to calculate them from the data that is provided in the database, but would require some effort (and the approach may vary depending on the water footprinting method that is chosen).
Alternatively, and probably it's the fastest way, some LCA software providers have in the recent years implemented water footprint methods in their software, and have applied these methods to the ecoinvent database. You would however need to check which water footprinting methods are implemented in the different softwares, as several different methods have been developed over time.
Best regards, David FitzGerald