Tissa H. Illangasekare

The 2012 Henry Darcy Medal is awarded to Tissa H. Illangasekare for fundamental contributions to engineering hydrology and exceptional support to the hydrological community.

Tissa H. Illangasekare is not only an accomplished scholar and a top hydrological engineer, he is also a remarkable person with a caring, generous and colourful personality: a source of inspiration for many in the hydrology community. Most agree that Illangasekare is the best experimentalist in the area of non-aqueous phase liquid (NAPL) and multiphase flow in porous media. Equally important, he is a leading expert in the integration of innovative experimental work with sound theoretical research. His work has continuously improved fundamental understanding of behaviour and fate of non-aqueous phase liquids in heterogeneous porous media. Illangasekare has made pioneering contributions to quantifying mass transfer from entrapped NAPL sources of contamination to groundwater. His ability to extend fundamental concepts to new problems was demonstrated by his work on microgravity two-phase flow essential to plant-based advanced life support systems required for long-duration space exploration missions. Illangasekare has contributed to resolving basic issues concerning physical, chemical, and biological behaviour of contaminants in subsurface. His pioneering work on modeling mixed flow-regimes (laminar and turbulent) in fractures was validated in laboratory experiments demonstrating strong coupling of theory and experiments. Illangasekare’s contributions to snow hydrology, especially the understanding infiltration in subfreezing snow, are well recognized. Illangasekare’s leadership qualities were manifested in many ground-breaking initiatives ranging from developing interdisciplinary experimental platforms to networks of hydrologic observatories. During his assignment with the US NSF, he made pivotal contributions to the successful launch of a network of Critical Zone Observatories (CZO) in the US. He continues to serve on board of directors of community-wide initiatives such as CUAHSI in the US and HOBE in Denmark. Illangasekare has always been a conscientious citizen of the hydrology community as evidenced by the many editorial duties in leading hydrological journals (Co-Editor of Vadose Zone Journal, present Editor of Water Resources Research), and by the numerous conferences and sessions he initiated and led (he is the chair of the 2012 Gordon Research Conference (GRC) on flow and transport in permeable media). Throughout his career he has had a genuine concern for young scientists, whom he supported often without them being aware of it. His ability to leverage his knowledge and scientific network to the benefit of international hydrology community and society in general was manifested in the aftermath of the devastating 2004 South Asian Tsunami, Illangasekare volunteered to raise funds from Sri Lankan expatriates for rapid well clean-up and emergency sanitary systems. He then headed an NSF-sponsored team of experts to tsunami-ravaged areas in Sri Lanka to identify urgent groundwater and water supply issues to support well clean-up efforts.