Exact SC to T

Aquifer Test Forum - main menu

Transmissivity From Specific Capacity

The following equation, based on the Cooper-Jacob (1946) solution for flow to a well in a confined aquifer, computes the specific capacity, Q/S_w, of a well:

. . . . . (1)

where Q is constant discharge rate [L³/T], r_w is pumped well radius [L], S is storativity [dimensionless], s_w is drawdown in the well [L], T is transmissivity [L²/T] and t is time [T].

We can rearrange equation (1) to find an expression for T as follows:

. . . . . (2)

Because T also appears in the logarithm term of equation (2), we can use a technique such as successive approximation to solve for T.

You also may convert specific capacity to transmissivity using approximate formulas.

Transmissivity from Specific Capacity Calculator

Q/s_w =	[L³/T/L]
t =	[T]
r_w =	[L]
S =	[dimensionless]

Use consistent units for the above input parameters. For example, enter Q/s_w in m³/day/m, t in days and r_w in m to compute T in m²/day.

Transmissivity From Specific Capacity Calculator developed by Glenn M. Duffield, HydroSOLVE, Inc.