Evaluation of Methods to Determine Ground-water Seepage Below Levee 31N, Dade County Florida

Citation_Information:

Originator: Helena Solo-Gabriele

Publication_Date: unpublished material

Title:

Evaluation of Methods to Determine Ground-water Seepage Below Levee 31N, Dade County Florida

Publication_Information:

Publication_Place:

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Abstract:

The primary objective of this investigation is to quantify seepage below Levee L31N. The amount of water lost to the L-31N Canal versus the fraction that flows below the canal will be estimated. A conceptual model is currently being developed for the site based upon results from an on-going stable isotope (oxygen -18 and deuterium) study. Quantification of seepage rates will be based upon a computer model, MODBRANCH, which couples both groundwater and surface water flows. Particular attention will be devoted to model performance under transient conditions caused by fluctuations in the stage of the L-31N Canal and pumping operations of the West Wellfield. In addition, an alternative leakage relationship based on reach transmissivity will be incorporated into MODBRANCH; this relationship is believed to be more suitable for transient conditions. The reach transmissivity relationship will be evaluated in comparison to MODBRANCH's existing leakage relationship, which is based on Darcian flow through the bed of the surface water channel. Modeling results will be used to develop an algorithm for real time estimation of seepage beneath Levee L31N. It is expected that this algorithm will estimate seepage using head differences at monitoring stations in the vicinity of the levee.

Purpose:

Plans to restore historical hydrologic conditions in the northeast section of Everglades National Park (ENP) include the raising of water levels in ENP and water conservation area 3B, which overlie the Biscayne aquifer, an extremely permeable aquifer. The increase in water levels is likely to cause an increase in seepage losses to the east. Quantifying this seepage loss is necessary for water management purposes as well as for models of the Everglades and coastal systems. Levee L-31N has been identified as a critical area for potential water losses. The L-31N study site includes a wetland area within ENP on the west; the L-31N Canal flows from north to south through the longitudinal center of the site, and the eastern portion of the region is a suburban area of Miami which includes a major municipal wellfield, the West Wellfield, and rock mining activities.

Time_Period_Information:

Range_of_Dates/Times:

Beginning_Date: 199707

Ending_Date: 199909

Currentness_Reference: publication date

Progress: in work

Maintenance_and_Update_Frequency: as needed

Bounding_Coordinates:

West_Bounding_Coordinate: -80.55

East_Bounding_Coordinate: -80.41

North_Bounding_Coordinate: 25.75

South_Bounding_Coordinate: 25.65

Theme:

Theme_Keyword_Thesaurus: none

Theme_Keyword: groundwater

Theme_Keyword: surfacewater

Theme_Keyword: seepage

Theme_Keyword: flow models

Theme_Keyword: stable isotopes

Place:

Place_Keyword_Thesaurus: none

Place_Keyword: Dade County

Place_Keyword: Everglades National Park

Place_Keyword: Levee 31N

Place_Keyword: West Wellfield

Place_Keyword: Central Everglades

Place_Keyword: South East Coast

Contact_Information:

Contact_Person_Primary:

Contact_Person: Barbara Howie

Contact_Organization: U.S. Geological Survey

Contact_Position: Project Chief

Contact_Address:

Address_Type: mailing address

Address: 9100 NW 36th Street Suite 107

City: Miami

State_or_Province: FL

Postal_Code: 33178

Contact_Voice_Telephone: 305 526 2895

Contact_Facsimile_Telephone: 305 526 2881

Contact_Electronic_Mail_Address: bhowie@usgs.gov

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Horizontal_Positional_Accuracy:

Horizontal_Positional_Accuracy_Report:

No test was performed but locations were determined using a "hand-held" GPS receiver which has an accuracy of roughly 100 feet.

Process_Step:

Process_Description:

Work at Levee 31N began during the summer of 1997. The five AVM stations located along the levee were resurveyed to a consistent set of benchmarks. Data have been compiled for 3 rain gauging stations, 5 AVM stations, and 29 existing shallow groundwater monitoring stations. Five additional deep wells have been installed for water quality monitoring. One of the five deep wells is also utilized for continuous measurements of stage. Six vertical seepage meters have been installed along a transect that cuts across L31N. Several experiments have been conducted under different hydrologic conditions. Results show that seepage rates increase during dry conditions and as the levee is approached from the west. Sampling and analysis for the stable isotopes and hydrologic data collection will continue through February 1999. Initial results of the isotope work supports the hypothesis of a deep groundwater circulation pattern beneath Levee 31N which serves to transport water from the Everglades toward urban areas. This flow pattern may be facilitated by lithologic layering within the Biscayne aquifer. Computer input files are currently under development. Collected data will be utilized in the development and calibration of a transient 3-dimensional groundwater/surface water model (MODBRANCH) to determine seepage rates beneath Levee 31N. The MODBRANCH code will be modified to incorporate a "reach transmissivity" leakage option between the river and groundwater. This "reach transmissivity" relationship has been successfully used for steady conditions at this site in a previous study. Calculation of canal seepage rates and calibration of the Levee 31N flow model will be completed by February 1999. An empirical relationship between field data and seepage rates will be determined for the site. The water resources investigation report describing the results of the Levee 31N study will be completed and published by the end of FY 1999.

Process_Comments and suggestions? Contact:

Contact_Information:

Contact_Person_Primary:

Contact_Person: Helena Solo-Gabriele

Contact_Organization: University of Miami

Contact_Position: Assistant Professor

Contact_Address:

Address_Type: mailing address

Address: Department of Civil, Arch., and Environmental Engineering

Address: P.O. Box 248294

City: Coral Gables

State_or_Province: FL

Postal_Code: 33124-0630

Contact_Voice_Telephone: 305 284 3489

Contact_Facsimile_Telephone: 305 284 3492

Contact_Electronic_Mail_Address: hmsolo@miami.edu

Process_Date: not complete

Contact_Information:

Contact_Person_Primary:

Contact_Person: Barbara Howie

Contact_Organization: U.S. Geological Survey

Contact_Position: Project Chief

Contact_Address:

Address_Type: mailing address

Address: 9100 NW 36th Street Suite 107

City: Miami

State_or_Province: FL

Postal_Code: 33178

Contact_Voice_Telephone: 305 526 2895

Contact_Facsimile_Telephone: 305 526 2881

Contact_Electronic_Mail_Address: bhowie@usgs.gov

Digital_Form:

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Computer_Contact_Information:

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Fees:

Contact_Information:

Contact_Person_Primary:

Contact_Person: Jo Anne Stapleton

Contact_Organization: U.S. Geological Survey

Contact_Address:

Address_Type: mailing address

Address: 521 National Center

City: Reston

State_or_Province: VA

Postal_Code: 20192

Contact_Voice_Telephone: 703 648 4592

Contact_Facsimile_Telephone: 703 648 4614

Contact_Electronic_Mail_Address: jastapleton@usgs.gov

CC:"Solo-Gabriele, Helena M" <hmsolo@miami.edu>, "'B....