Perhaps you should try some spelling variations:
"vater ressourcen" » "water ressources", "alter ressourcen", "der ressourcen"
"water ressource" » "water ressources", "water resources", "water resourcs"
"water resource" » "water resources"

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (((("water ressource") OR ("water resource"))) OR ("vater ressourcen")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"water ressource\") OR (\"water resource\"))) or (\"vater ressourcen\"))".
• Removing quotes may allow a broader search: (((( water ressource ) OR ( water resource ))) or ( vater ressourcen )).
• Adding a wildcard symbol may retrieve word variants: (((("water ressource") OR ("water resource"))) or ("vater ressourcen"))*.