WHAT LED HENRY DARCY TO CONDUCT THE POROUS MEDIA EXPERIMENTS?

What led Henry Darcy to conduct the porous media experiments?

Henry Darcy is considered the founder of quantitative hydrogeology on the basis of porous media experiments he conducted in 1855-56 in a hospital courtyard in Dijon France. R.A. Freeze's (1983) translation provides an English account of the experiments that led to Darcy's Law. Translation of Darcy's (1856) The Public Fountains of Dijon provides information on why Darcy conducted them. This information is found in two appendices added to the book, which was written as an account of Darcy's planning and construction of Dijon's water supply system in the 1840s and as a how-to manual for engineers faced with similar projects.

In Appendix C, Water Supply Systems, Darcy discusses the water supply systems of London, Brussels, and French cities, including Paris. Darcy had studied these cities in the 1830s when planning the per capita needs for Dijon's water system. London, with more than 9 water companies, was the largest water supply, providing 90 liters/day per person to 270,581 houses, primarily water from the Thames. Paris used Seine water, an artesian well, and some springs. It provided 84 liters per person but supplied only 1/5 of Paris' 31,500 households. In the early 1850s, Darcy was working in Paris with Eugene Belgrand, looking for springs to divert to Paris to increase its water supply.

Appendix D Filtration is a summary of methods that cities used to remove turbidity from river water, including clarification by settling, and artificial and natural filtration. Artificial filtration, particularly as London did it, involved the use of 2-hectare filtration beds. Natural filtration was done in tunnels in the river's alluvium. (Dijon's water came from a spring and did not require filtration.) Darcy visited London in 1850 to study Macadam roads, and no doubt visited the water companies and saw filtration beds. Darcy compiled information on the filtration beds, their surface areas, water depth, and amounts filtered per 24 hours per m². He declared "no general law can be deduced from this data." In spite of the fact that he had retired on disability, he decided to conduct precise "experiments to determine the laws of water flow through filters." On the basis of his porous media experiments, he proposed a filtration tank that greatly reduced the size of filtration beds and gave us Darcy's Law.