Science Citation Index is a selective index of the best journals in many fields. This is probably the best database to use for both water resources and environmental science.
Compendex from Engineering Village is the most comprehensive engineering index, covering all disciplines.
CRCnetBASE contains books published by CRC. We did not buy every book, but we should have every book on both chemistry and water resources.
We have every 2011 book published in English on SpringerLink, which also contains journals.
Pollution Abstracts contains references to journal articles, conference proceedings, and hard-to-find documents on all aspects of pollution.
GeoRef is the most comprehensive database of geoscience literature.