Lynn Walter Gelhar (born 1936) is an American civil engineer focusing in hydrology and is currently Professor Emeritus at Massachusetts Institute of Technology.
He studied Civil Engineering at the University of Wisconsin, specializing at the graduate level in hydrology and fluid mechanics, with minors in mathematics and meteorology; his doctorate was completed in 1964.
He has broad experience in fundamental and applied water-related research, but is best known for his theoretical work describing contaminant transport in naturally heterogenous aquifers using stochastic methods.
[15] Gelhar has experience in public service and consulting with government and industry on aspects of groundwater hydrology, dealing particularly with hazardous and nuclear waste issues.
[29] While on sabbatical leaves in France, Switzerland and Sweden he worked with scientists involved in the radioactive waste disposal programs in those countries, in Sweden preparing a report on flow and transport in fractured rocks for their agency dealing with radioactive waste disposal.