In a recent meeting the topic of where to go for irrigation information came up.  Well there's no substitute for attending a class in irrigation, such as offered at Cal Poly SLO (http://www.itrc.org/classes/iseclass.htm ,

but here's some written sources to get you started thinking.

http://ciwr.ucanr.edu/california_drought_expertise/droughttips/

http://www.salinitymanagement.org/Salinity%20Management%20Guide/ei/ei_1.html

http://www.avocadosource.com/tools/IrrigationCalculator.asp

http://lawr.ucdavis.edu/cooperative-extension/irrigation/manuals

http://lawr.ucdavis.edu/cooperative-extension/irrigation/drought-tips

http://biomet.ucdavis.edu/index.php/evapotranspiration-mainmenu-32

http://www.itrc.org/reports/