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!!!