(The correction to 60F is usually neglected.) Usually

measured in gallons per day per square foot.

b.

Well discharge formulas.

The following

Where:

formulas assume certain simplifying conditions.

Q = well yield in gpm

However, these assumptions do not severely limit the

P = permeability in gpd per square foot

use of the formulas.

The aquifer is of constant

H = thickness of aquifer in feet

thickness, is not stratified and is of uniform permeability.

h = depth of water in well while pumping

The piezometric surface is level, laminar flow exists and

in feet

the cone of depression has reached equilibrium. The

R = radius of influence in feet

pumping well reaches the bottom of the aquifer and is

r = radius of well in feet

100 percent efficient. There are two basic formulas

(Ground Water & Wells) one for water table wells and

the following formula for available yield from an artesian

one for artesian wells. Figure 5-4 shows the relationship

well:

of the terms used in the following formula for available

yield from a water table well:

where:

m = thickness of aquifer in feet

H = static head at bottom of aquifer in feet

all other terms are the same as for Equation 5-1.

Figure 5-4. Diagram of water table well.

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