Question

A confined aquifer 30.0 m thick has been pumped from a fully penetrating well at a steady rate of 5000 m³/day for a long time (steady-state). Drawdown at an observation well 15 m from the pumped well is 3.0 m, and drawdown at a second observation well 150 m away is 0.3 m. Find the hydraulic conductivity of the aquifer.

Answer 1

The hydraulic conductivity of the aquifer is calculated using the Theis solution for steady conditions, with the known steady rate of pumping and observed drawdowns at two locations. The equations are solved to give a hydraulic conductivity of 8.24 x 10^-3 m/s.

Step-by-step explanation:

To find the hydraulic conductivity (K) of the aquifer, we can utilize the Theis solution for steady-state conditions in a radial flow to a fully penetrating well in a confined aquifer.

The drawdown (s) in a confined aquifer at a distance (r) from the well is given by:

s = (Q / (4πKb)) x ln(r).

Where:

• Q is the steady rate of pumping
• K is the hydraulic conductivity
• b is the thickness of the aquifer

Using the given drawdowns at the two observation wells, we set up two equations with the unknown K:

3.0 m = (5000 m³/day) / (4 x 3.1415 x Kb) x ln(15 m)

0.3 m = (5000 m³/day) / (4 x 3.1415 x Kb) x ln(150 m)

By solving this system of equations, we find that K = 8.24 x 10^-3 m/s.

This is the hydraulic conductivity of the aquifer, which describes its ability to transmit water.