Jim made his initial major contribution to hydrology with his Ph.D. dissertation, in which he developed a mathematical modeling procedure for nonlinear analysis of hydrologic systems. He continued the use of mathematical modeling procedures to analyze hydrologic problems throughout his career, including the novel application of entropy to assess uncertainty in hydrologic systems. The availability of new technologies always fascinated him. He developed practical procedures to analyze rainfall from satellite imagery. His broad interests led him to direct the construction and operation of a snowmelt lysimeter for field studies of mountain snowpacks for fundamental work in snow hydrology. He contributed much to the basic understanding of fluid mechanics and hydraulics through hydraulic model studies of significant structures, including flows in natural channels, sediment transport in rivers, and wind shear effects on flow in large open channels. He was an early developer and user of a laser Doppler flow velocity meter, which he and colleagues used extensively in studies of fundamental fluid mechanics. His research activity embraced broad areas of hydrology and hydraulic engineering.