A great source of information about droughts and other natural hazards is the Bureau of Meteorology, here are 3 links.
http://www.bom.gov.au/climate/glossary/drought.shtml
http://www.bom.gov.au/climate/drought/drought_links.shtml
http://www.bom.gov.au/lam/climate/levelthree/c20thc/drought.htm
Some other good government websites are:
http://www.ema.gov.au/www/ema/schools.nsf/Page/Get_The_FactsDroughts
http://www.pc.gov.au/__data/assets/pdf_file/0006/83058/sub092.pdf
All images were taken from 'Geography for Australian Citizens- Third Edition' by Brian Parker, Kate Lanceley and Rebecca Fitzpatrick
and from
http://www.aussievault.com.au/vault/entry/1610/drought-stricken-monaro