This video shows time-lapse photographs of two laboratory tank experiments that illustrate the importance of fluid density to groundwater flow. The sand is initially saturated with fresh water, then saltwater is introduced through a box at the top of the tanks. The saltwater introduced to the left tank has 3 grams per liter calcium chloride while the right has 300 grams per liter. The high-density case on the right side exhibits rapid downward movement and vigorous fingering while downward movement on the left proceeds more slowly. (1 minute)
A discussion of the material in this video is provided in Section 4.1 ‘Free Convection’ of the Groundwater Project book ‘Variable Density Groundwater Flow’, the PDF can be downloaded or the online version can be read at that link.
Citation: Post, V.E.A. & Simmons, C.T. (2022). Variable Density: Time-lapse photography of laboratory tank experiments illustrating the importance of fluid density to groundwater flow. Video of The Groundwater Project, Guelph, Ontario, Canada.