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ARS Home » Southeast Area » Miami, Florida » Subtropical Horticulture Research » Research » Publications at this Location » Publication #200405

Title: Identification of a hydrodynamic threshold in Karst Rocks from the Biscayne Aquifer.

item Savabi, M

Submitted to: Hydrogeology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2007
Publication Date: 10/10/2007
Citation: Difrenna, V.J., Price, R.M., Savabi, M.R. 2007. Identification of a hydrodynamic threshold in Karst Rocks from the Biscayne Aquifer. Hydrogeology Journal. DOI 10.1007/s10040-007-0219-4

Interpretive Summary: Information about the water flow through different aquifer formation in south Florida is important during the proposed water flow change due the Everglades Restoration. In addition, the information is needed to predict how fast the storm water flow to the west, Everglades National Park and/ or to the agriculture area in the East. This study provides water flow characteristics of the Key Largo aquifer formation in South Miami Dade county Florida. In addition, the data collected in this study indicate the scale in which the water flow is measured is important. Finally, the direction of the flow (horizontal vs vertical) had significant effect on the rate of water flow through the Key Largo aquifer formation.

Technical Abstract: A hydrodynamic threshold between Darcian and non-Darcian flow conditions were found to occur in cubes of Key Largo limestone measuring 0.2 and 0.3 m on a side, at an effective porosity value of 33% and a hydraulic conductivity (K) value of 6 m/day. Total porosity was determined by drying and weighing, while effective porosity was determined by submersion. Hydraulic conductivity was determined in the three mutually perpendicular axes of each cube in a permeameter. Anisotropy was determined by comparing the hydraulic conductivity of the vertical axis to the average hydraulic conductivity of the horizontal axes. Bulk density, total porosity and effective porosity of the Key Largo limestone cubes averaged 1.5 g/cm3, 40% and 30%, respectively. Hydraulic conductivity ranged from 0.23 m/day to 67 m/day with a geometric mean of 3.2 m/day. Hydraulic conductivity was found to increase greatly above an effective porosity of 33 %, and was non-linear above a value of 6 m/day. Two regions of anisotropy were observed, one near the top close to the ground surface, where vertical flow dominated, and one near the bottom of the section that was associated with a dense-laminar layer, where horizontal flow dominated.