Gerhard Hermann Jirka, an internationally known environmental fluid mechanician and an alumnus and former lecturer in the MIT Department of Civil and Environmental Engineering (CEE), died Feb. 14 after suffering a heart attack several days earlier. He was 65 years old.

Professor Jirka, who made significant contributions in the modeling of pollutant transport, the stability of shallow water flows, mixing in stratified fluids, and air-water exchange, had been a member of the faculty of the University of Karlsruhe and director of its Institute for Hydromechanics from 1995 until his death. He was a member of the Cornell University faculty in the Department of Civil and Environmental Engineering from 1977. At Cornell, he helped build the DeFrees Hydraulics Lab and developed CORMIX, a widely used collection of computer codes used to simulate plume mixing.

Professor Jirka was born in Kasten, Austria, on Sept. 14, 1944. He received his diploma in engineering from the University of Natural Resources and Applied Sciences in Vienna in 1969. Using a Fulbright Travel Grant, Professor Jirka traveled to the U.S. to attend graduate school at MIT. While there, he worked with Professor David Marks, earning an S.M. in 1971 with a thesis on the environmental considerations for locating thermal power plants. He then worked as a research assistant for Professor Donald Harleman on methods for safely disposing of water containing degradable wastes in shallow bodies of water. After graduating with a Ph.D. in 1973, he joined the MIT Energy Lab and worked in the Parsons Lab on the management of waste heat from electric power plants. During that same time, he was a lecturer in the Department of Civil Engineering, as CEE was then named.

Professor Jirka remained close friends with many faculty, staff members and alumni of CEE and continued to work with them throughout his life. He served on the panel that oversees the development of flood protection for Venice, meeting several times each year with the panel’s members, including its chairman, Professor Rafael Bras, an alumnus and former professor at MIT who is now dean of the Samueli School of Engineering at the University of California, Irvine.

“Gerhard always impressed me with his extraordinary knowledge of fluid mechanics, but even more by his intuitive appreciation of the fluid processes and the engineering problems,” said Professor Bras. “He reminded me of Art Ippen in the way he thought of the problem and was always able to place the practical issue in a solid theoretical framework and find a solution. Gerhard was a gentleman, a man with class, a serious scholar, but a man of the world equally at ease solving the most complicated mathematics or dancing tango, which he did with skill and gusto.”

“Gerhard and I arrived at MIT in September 1969 and he was my first research assistant,” said Professor Marks. “I remember that there was some concern in admitting him as a graduate student, as he came from a small university in Austria that no one knew about. But his record was outstanding there and at MIT. And he was a kind, very nice person who loved his work and his attachment to MIT. He will be sorely missed.”

Professor Jirka was associate editor of the Journal of Environmental Fluid Mechanics and was active in a number of professional organizations. He chaired the Hydraulics Division of the American Society of Civil Engineers (ASCE) and received the Hunter Rouse Hydraulic Engineering Award in 2006 and the Huber Civil Engineering Research Prize in 1983 from the ASCE. He was vice president of the International Association for Hydraulic Research since 2005 and was awarded that organization’s Ippen Prize in 1989.

He is survived by his former wife Sonia, and their daughter Astrid and son Stefan. Another son, Andres, passed away in 1995.