REPRESENTATION OF AQUIFER FLOW SPACES FROM DARCY(FILTER) TO DARCY(CONDUIT) VIA E. CALVIN ALEXANDER, JR (Invited Presentation)

In "Les Fontaines Publiques de la Ville de Dijon" (1856) Henry Darcy established the theoretical foundations of analytical groundwater hydrology for laminar flow through intergranular flow spaces. He performed filtration experiments on sand columns. These are described in Appendix D under “ Determination of the Laws of Water flow through Sand”, which became the basis for the reigning paradigm in groundwater flow.

 Two consequences in the treatment of groundwater flow problems followed: first, estimating flow parameters by describing the solid grain matrix through granulometric size and shape analysis (Krumbein and Monk); second, the application of the simplifying assumptions of Darcian flow to the treatment of 2-D potential flow fields by analytical or numerical solution methods which became the preponderant model of groundwater flow, first developed in the petroleum context (Muskat, King Hubbert), the concept of the elemental representative volume (Bear), the application of potential theory to aquifers (Pinder, Toth, Freeze & Witherspoon) and the development of analytical, finite difference and finite element (Modflow), and analytical element models (Strack).

 Non-ideal conditions (uncooperative flow spaces: vugs and fractures, inhomogeneities, non laminar flow etc.) were forced into a Procrustean bed by introducing the concept of equivalent parameters that could be integrated and averaged over larger areas.

 However, chapter 3 of book I, deals with the actual design and construction of the water supply to Dijon from the Rosoir Spring by Darcy in 1840. He describes flow in caverns, crevices and channels which he calls “siphons”, and was fully aware that he was dealing with conduit flow from a karst in the Paleozoic limestone terrain west of Dijon, heavily fractured and faulted during Tertiary Alpine and Jurassic tectonic activity.

ECH was one of the few at the time resisting the predominant paradigm of universal ”Darcian” flow based on his actual speleological field observations (caving, dye tracing, hydro-geochemistry and radiometric dating) and among others involvement in some of the Edwards Aquifer studies. He is one of the few who must have read Darcy’s "Les fontaines publiques…” in its entirety, not only the laboratory appendix, and thus confirms that Darcy really is the first Karst-Hydrogeologist.