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> report 90-4135
US Department of the Interior A Method To Estimate Canal Leakage to the Biscayne Aquifer, Dade County FloridaWater-Resources Investigations Report 90-4135 By David A. Chin ABSTRACT The leakage characteristics
of channels that partially penetrate the Biscayne aquifer and have reduced
bed permeability were studied. Leakage characteristics were described in
terms of a reach transmissivity-defined as the volume flow rate out of the
channel per unit length of the channel per unit drawdown, where drawdown
is defined as the difference in altitude between the water surface in the
canal and the water table in the adjacent aquifer. A theoretical expression
was developed to relate the reach transmissivity to the transmissivity of
the formation, mean channel width, distance of drawdown measurement from
the channel centerline, ratio of drawdowns on both sides of the channel,
and local reach transmissivity associated with reduced bed permeability.
This theoretical expression was verified using a fine-scale numerical model,
which gave accurate results when drawdowns were measured beyond 10 aquifer
depths from the side of the channel. Using the theoretical formulation,
it is shown that the reach transmissivity employed in regional ground-water
models, which are based on average drawdowns within a cell, depends on the
size of the cell as well as the transmissivity of the formation, channel
width, and local reach transmissivity due to reduced bed permeability.
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U.S. Department of the Interior, U.S. Geological Survey
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Last updated: 14 January, 2005 @ 02:32 PM (KP)