Exercise 16 Solution

It is useful to define three types of karst porosity because there are karst aquifers of differing ages that have one, two or all three types of porosities and these zones support laminar or turbulent flow at different velocity ranges. Some carbonate layers can be confining units having no dissolution features, large fractures or joints and limited water transmitting interconnected rock matrix porosity. Other carbonate rocks have some rock matrix porosity that transmits water and large conduits with no interconnected macro pores. Others have all three types of porosity that are shown in Figure 16. Most carbonate rock matrices have hydraulic conductivity that ranges from very low values to large values on the order of 0.01 to 10 m/d and rarely have turbulent flow under natural conditions. For the permeable macro porosity layers of interconnected macropores (Figure 16b), turbulent flow is possible, but the onset occurs at very small Reynolds numbers (1 to 60). Whereas for the large submerged fully flowing dissolution features (Figure 16c) laminar flow occurs with lower critical Reynolds numbers up to 2,000.

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Introduction to Karst Aquifers Copyright © 2022 by Eve L. Kuniansky, Charles J. Taylor, and Frederick Paillet. All Rights Reserved.