Use of the reach transmissivity leakage relationship to quantify the exchange between groundwater and surface water

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

Helena Solo-Gabriele - Committee Chair


A method to quantify the exchange of water between surface water channels and the groundwater aquifer based on the concept of reach transmissivity was evaluated for use under transient conditions and incorporated into a numerical model. This method provides significant benefits relative to the common existing method of calculating leakage, which assumes vertical flow of water through a low permeability layer at the bed of the surface water channel. The reach transmissivity leakage relationship employs input parameters that are more commonly available from published sources, which reduces the effort required for model calibration; also, the calibrated values of the reach transmissivity relationship input parameters are less dependent on model grid spacing than those of the vertical flow leakage relationship. In addition, the reach transmissivity relationship allows calculation of flow to each side of the surface water channel, whereas the vertical flow relationship only calculates the net exchange between the surface water and groundwater systems. The reach transmissivity leakage relationship is based on the assumption of steady state conditions; a method was developed to estimate the error associated with its use to simulate transient conditions. For many applications, this error is negligible. The reach transmissivity relationship was incorporated into MODBRANCH, a finite-difference numerical model that couples MODFLOW, a groundwater model, and BRANCH, a surface water model. The modified version of MODBRANCH was tested on problems with known analytical solutions, as well as on a complex field problem, and was determined to function satisfactorily. A MODBRANCH model of the L-31N Canal and vicinity; a wetland area at the eastern boundary of the Florida Everglades, was developed to further examine the performance of the reach transmissivity relationship. One-year simulations were run using both the vertical flow and reach transmissivity versions of MODBRANCH, which yielded similar results. The reach transmissivity leakage relationship was judged to have performed satisfactorily.


Hydrology; Engineering, Civil

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