Perhaps you should try some spelling variations:
surface irrigation » scale irrigation
irrigation schemes » irrigation scheme, irrigation systems
integration volume » integration von
gaps integration » gaps integrating, gis integration, means integration
supply surface » supply service, upper surface
supply gaps » supply gap, supply gas

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: (( supply surface irrigation schemes. ) OR ( supply gaps integration volume. ))~.
• Adding a wildcard symbol may retrieve word variants: (( supply surface irrigation schemes. ) or ( supply gaps integration volume. ))*.