Hello.
if your father was in government job then you definitely can have job after them but if you want to have job in the same department so you will have to qualify  required degrees for that , for irrigation department there is the requirement of Btec. degree,
Else you can also have job but as per the rules they will give you a government job but not in the same department it will be on the basis of your qualification, still you have another option you can write an application where you will mention that still you are pursuing any course , bachelor, master whatever . and then after completion you will have job which suits on your qualifications.
And remember for having job after someone it is mandatory that the person who is going to have this job should be of 18 year as minimum age and the maximum should be of 35.
Best of luck.