A PROBLEM-BASED EXERCISE EXPLORING THE IMPORTANCE OF VISCOSITY AND FLUID DENSITY USING SPREADSHEETS

The concept of hydraulic conductivity is a basic topic introduced within an introductory hydrogeology or groundwater resources course in conjunction with Darcy's Law. Intrinsic permeability may be introduced along with these concepts to stress the fact that hydraulic conductivity is a property of both the porous media as well as the fluid moving through the porous media. This paper discusses using spreadsheet technology to examine the importance of viscosity and fluid density in determining the hydraulic conductivities and flow velocities in specific hydrogeologic settings. These settings may include shallow, infiltration lagoons and artificial recharge systems where climatic variations between summer and winter may cause significant variations in viscosity. This variation leads to a 40% change in hydraulic conductivity values. Also viscosity and fluid density are important considerations in deep aquifer systems impacted by geothermal gradients and high-salinity waters. A methodology is introduced to teach hydrogeology students the importance of viscosity and fluid density variation in a regional geologic unit known as the Mt. Simon Sandstone. This sandstone unit is used as a water supply aquifer in the upper Midwest, a natural gas storage unit, a hazardous waste injection horizon, and a possible carbon sequestration unit in the Appalachian Basin. A laboratory exercise is introduced that uses Excel spreadsheets to explore these important relations between viscosity, fluid density, intrinsic permeability, and hydraulic conductivity in the context of an applied hydrogeologic problem. This problem-based exercise allows students use the computational capabilities of spreadsheets to experiment with these important hydrogeologic properties.