A CANAL DRAWDOWN EXPERIMENT FOR DETERMINATION OF AQUIFER PARAMETERS

A canal drawdown experiment was used in conjunction with borehole flowmeter measurements to determine the following hydrologic parameters: (1) the transmissivity (T) and hydraulic conductivity (K) of the Biscayne Aquifer in southeast Florida; (2) the separate hydraulic conductivities of the Miami Limestone (K-M) and the Fort Thompson Formation (K-F)-the two geologic formations making up the Biscayne Aquifer; and (3) the conductance (C) controlling water seepage between the Biscayne Aquifer and the L-31W borrow canal (the canal in which the drawdown experiment was carried out). While the canal drawdown experiment alone would have yielded T and K, also making borehole flowmeter and aquifer thickness measurements allowed determination of K-M and K-F. Two methods of data analysis were used; one based on the Dupuit equation, the other on a previously published set of equations developed specifically for computing the C value required for a regional numerical ground-water flow model. The two methods were in good agreement (within 20% of each other), and averaging results from them gave T = 1.0 X 10(5) m(2)/day, K = 7,590 m/day, K-M = 14,900 m/day, and K-F = 4,050 m/day. Estimates of C from the two methods were also similar, although the exact value derived from the second method would necessarily depend on the size of the model grid cell for which the value was calculated. The methods applied here illustrate an effective means for measurement of field-scale hydrologic parameters and confirm the importance of canal sediments in controlling ground-water exchange with the L-31W canal on the eastern boundary of Everglades National Park.