This branch of engineering uses principles of soil mechanics and rock mechanics to investigate and study subsurface materials and conditions. 

Government and private sector job opportunities are available in front of geotechnical engineers. Self employment opportunities are also available in front of graduates. Firms involved in construction of commercial buildings, public structures and other manmade structures are the prime recruiters.

PWD, Municipal Corporations, Urban planning departments, Government Port Trusts, ONGC, NHAI, Indian Railways, Metro Rail Corporations etc are some of the well known Government sector recruiters.

If your interest lies in the above then go ahead!!

Hope this helps.

I am sharing a link which states colleges offering geotechnical engineering course. You can check the link below and also go through their official site tyo know the criteria of admission.

Link: Geotechnical Engineering Colleges

Hope this helps.

Below I am providing few points for all the fields you have asked for, please go through all of them and then decide -

Water Resources is one of a very interesting field out of all civil engineering fields. There are lot of scope for water resources in both government and private sectors. In government sectors, you can be chosen a position from junior engineer to Assistant executive engineer in central water commission based on your calibre.

If geotechnical engineering interests you then I would go into that field. Whether or not the field grows or stagnates, if you become an expert with name recognition you will find work.

Environmental engineering has immense scope in India for professionals who are qualified in chemical, biological, thermal, radioactive or even mechanical engineering as environmental engineering is a diverse field and requires people from diverse background. Moreover, professionals from process engineering, environmental chemistry, water and sewage treatment, waste reduction management, pollution prevention, etc are required in large numbers.

So better to choose the field as per your interest and potential.

Good Luck!!!