rahul, I guess bengaltiger has provided enough details on the assistantship, fellowship aspects and how you should start searching for the universities. Well, this morning, before I logged in to sajha, I was going through some of the websites of the universities which offers MS in Environmental Science or engineering. Some of the big schools like MIT, Caltech and Georgia Tech have very good and competitive programs. To find a university that offers your degree isn't necessarily difficult, but to get into the program with substantial financial support is difficult in retrospect to what bengaltiger had explained. I hope it helps. Good luck! Peace