J. M. Jordaan was born in 1932 in Cape Town and raised in Bloemfontein and Pretoria, South Africa. He obtained his B.Sc. Eng. Civil at the University of the Witwatersrand, Johannesburg, in 1952 and joined the Irrigation Department of South Africa, now known as the Department of Water Affairs and Forestry. While on study leave from 1953 to 1958, he obtained the S.M degree at the University of Wisconsin, US, and the C.E. and Sc.D. degrees at the Massachusetts Institute of Technology, US. After completing his postgraduate studies, he returned to South Africa, resuming work with the Department of Water Affairs in Pretoria until 1959. He then joined the South African Council for Scientific and Industrial Research as a research officer until 1963, being involved mainly with coastal engineering research and its applications.
Subsequently, he worked for the US Naval Civil Engineering Laboratory, Port Hueneme, California, until mid 1965 as a hydraulic research engineer on ocean wave research. Thereafter, he joined the University of Hawaii as associate professor in coastal engineering and tsunami research from 1965 to 1968. He occupied the same position at the University of Delaware from 1968 to 1969. He thereupon resumed employment with the Department of Water Affairs, Pretoria, where he was active in hydraulic engineering design for the major part of 28 years until his retirement in 1997 as Chief Engineer Design Services. During this period he was assigned to the P.K. le Roux Dam and the Van der Kloof Canals Construction Project for two years. For seven years in Namibia (then South West Africa), he was Chief Engineer, Investigations, dealing with aspects of water resources, hydrology, and construction
In 1985 and 1987 he was temporarily seconded to the Department of Foreign Affairs and acted as technical assessor in Bolivia for the Misicuni Hydroelectric and Water Supply Project for Cochabamba Department. He was also sent on foreign duty to Grenoble, France, in connection with their model studies of the Lesotho Highlands Water and Power Project. He also visited Britain, Spain, Portugal, Germany, Norway, The Netherlands, Hungary, Egypt, Sudan, China, and Taiwan in connection with official duties.
He is a registered professional engineer in South Africa, a fellow of the South African Institution of Civil Engineers, member of the American Society of Civil Engineers, honorary member of the Indian Institute of Engineers, and member of the International Association of Hydraulic Engineering and Research. From 1989 until 1998 he was part-time professor of hydraulic engineering in the Department of Civil Engineering of the University of Pretoria, and thereafter until the end of 2000 was attached as a part-time guest professor at the Water Utilisation Division of the same university.
His major publications include a chapter in Advances in Hydroscience, 1970, Academic Press, US, on laboratory experiments with impulsively generated water waves; a chapter coauthored with Prof. J. Williams in Tsunamis in the Pacific Ocean, edited by Prof. W. M. Adams, East-West Center Press, Honolulu, Hawaii, US; coauthorship of Water in Our Common Future, COWAR, UNESCO, 1993; editorship of the SANCOLD volume Large Dams and Water Systems in South Africa, 1994; and coauthorship with Dr. Dan Batuca of Romania of Silting and Desilting of Reservoirs,, 2000, Balkema Publishers, Rotterdam, The Netherlands