Irrigation Association’s glossary of irrigation terms:
http://www.irrigation.org/gov/default.aspx?pg=glossary.htm&id=106

Irrigation Association’s industry resources:
http://www.irrigation.org/SIM/default.aspx?pg=industry_resources.htm&id=236

Texas A&M University System, School of Irrigation:
http://irrigation.tamu.edu/

Irrigation Technology Center:
http://itc.tamu.edu/