He is, since 1974, professor of water resources at COPPE - the engineering graduate school of UFRJ. As such, has advised many M.Sc. and D.Sc. candidates. Simultaneously with his duties at COPPE, he was a senior researcher of the Research Center of Electric Energy CEPEL from 1976 to 1991 and the technical director of the State of Rio de Janeiro authority on rivers and lakes – SERLA from 1991 to 1996. In the period 1996-99 he acted as a consultant, working mostly for the World Bank in the Brazilian Semiarid region.

Kelman contributed to shape the current Brazilian Water Resources Law and to implement the institutional capability to enforce it. He was the first President of the Brazilian National Water Agency – ANA – since its implementation in 2000. He left ANA in 2005 to become the General-Director of the National Regulatory Agency for the Power Sector – ANEEL (mandate ended in January 2009). Since 2010 he is the President of Light Group - the Rio de Janeiro Power Company (www.light.com.br) and a member of ABENGOA’s International Advisory Board (Spain). He is also member of COINFRA-FIESP – (Infrastructure Committee – Federation of Industries in State of São Paulo).

In the period 2003-05, he was simultaneously board member of the Brazilian National Council of Energy (CNPE), Brazilian Environment Council (CONAMA), Brazilian Water Resources Council (CNRH) and UNESCO-IHE Institute for Water Education in Delft, Netherlands. He is a board member of the Brazilian Sustainable Development Foundation (FBDS) and of the Scientific Program Committee for the World Water Week (Stockholm International Water Institute).

Kelman is the author of two books: "Floods and Hydroelectric Power Plants" (1983) and "Challenges of the Regulator" (2009). He also is the author of more than one hundred technical papers and chapters published in specialized books, and dozens of articles published in major newspapers.