In my years cohort for the Bachelor of Engineering at Monash university there was around 25% females, I believe. (It was either 20% International students, 25% females or vice versa)
However, don't let this put you off the degree. I know that they have luncheons and such for female engineering students early on in first year, so that you can get to know other females in your course, as to make things easier.
A lot of the females in the course seem to have made quite close-knit relationships with other females in the course and seem more than comfortable in the degree despite being part of a minority.
Also, I just realised that I seem to be making out that the females in the course just stick with females and seclude themselves from males, which certainly isn't the case if I was giving that impression
I wish you all the best and hope that you don't let this be a determining factor in deciding your future, study what you are passionate about