Sonenshein, Roy S. , 2001, Levee 30 Water Level Daily Values.Online Links:
954 377-5924 (voice)
sunshine@usgs.gov
Determining the volume of water seeping from the water-conservation areas to the underlying aquifers is important in managing water levels in the conservation areas and freshwater deliveries to Everglades National Park. An accurate water budget to meet the competing natural and anthropogenic needs cannot be determined without this information. From Water Conservation Area 3B, water seeps into the Biscayne aquifer, which is about 80 feet thick directly beneath Levee 30 and thickens to the east, and flows relatively fast (due to high permeability of the aquifer) toward the urban and agricultural areas to the east. Water is also discharged to the canal along the eastern part of Levee 30. The rate of discharge is controlled by structures at the northern and southern ends of the canal. This seepage to the aquifer and canal discharge of water are critical for water-supply wells to the east and for preventing the inland movement of saltwater from the coast. However, lowering of ground-water levels to the east has resulted in higher ground-water seepage and canal discharge, reducing flows to the south in the water-conservation area. As a result, Levees 67A and 67C were constructed to direct water southward toward the central region of Everglades National Park. This water-management scheme has been effective in delivering water to the southwest; however, it reduced the flow to the southeast (northeastern part of Everglades National Park). The altering of historical flow directions and water-level durations has caused significant adverse effects to parts of the Everglades ecosystem. Water managers want to restore predevelopment flow conditions for the Everglades to survive, while also taking into consideration the urban and agricultural needs.The objective of this project was to evaluate approaches for quantifying ground-water seepage beneath Levee 30. The accounting of all significant hydrologic inflows and outflows to the Everglades ecosystem of the south Florida mainland is a key element of the South Florida Ecosystem Program.
A continuous geologic core from land surface to a depth of 78 feet was obtained during the drilling of a monitor well completed in February 1995. Permeability and porosity tests were performed on 10 plugs from the core. Of particular interest was a thin, very hard, impermeable limestone layer at 7 feet below land surface with a very low porosity (less than 5 percent) and very low permeability (less than 0.001 millidarcy). This layer is believed to be areally extensive and, therefore, would constitute a semiconfining layer retarding the seepage of water from Water Conservation Area 3B into the underlying Biscayne aquifer.
Geophysical logs were obtained from two monitor wells using electro- magnetic induction and natural gamma tools. The resulting logs are useful for determining changes in rock types and water quality.
Discharge measurements were made in the Levee 30 canal under various hydrologic conditions at three locations: at the transect, 1 mile south of the transect, and 1 mile north of the transect. The differences in flow rates at these three sections are used to determine the rate at which water is seeping into or out of the canal from the aquifer, a critical input requirement for the ground-water flow models.
At two sites in the wetlands, seepage meters were used to directly measure the flux of water across the water-sediment interface. Measurements were made under varying hydrologic conditions.
Person who carried out this activity:
954 377-5924 (voice)
sunshine@usgs.gov
Sonenshein, R. S., 2001, Methods to Quantify Seepage beneath Levee 30, Miami-Dade County, Florida: USGS Water-Resources Investigations Report WRIR 01-4074, U.S. Geological Survey, Tallahassee, Fl.Online Links:
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Levee 30 daily values
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