Exercise 9

Part 1

What other aquifer types may have extremely large pores and high hydraulic conductivity, where water can flow at both laminar and turbulent flow conditions?

Part 2

The average velocity, V, for flow to a pumped well at different radial distances would be computed from the following equation.

\displaystyle V=\frac{Q}{2\pi rb}


Q = pumping rate (L3T−1)
r = radial distance (L)
b = thickness of the aquifer (L)

The table below shows data for some pumping wells in different aquifers. Calculate the average velocity for radial distances of 0.25, 0.5, 1, 5, and 10 m. Just looking at the equation, can you guess what happens to the average velocity as the radial distance increases or the thickness increases?

Properties needed for calculation of average velocity for flow to a well and for calculation of the Reynolds Number.

Aquifer type and hydraulic conductivity Pumping Rate (m3/d) Thickness (m)
Alluvial aquifer, K=10 m/d, and average pore diameter 0.005 m 300 10
same 300 50
same 300 100
Point Bar gravel aquifer, K=100 m/d and average pore diameter 0.02 m 1000 10
same 1000 50
same 1000 100
Sandstone K=1 m/d and average pore diameter 0.001 m 100 10
same 100 50
same 100 100

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Introduction to Karst Aquifers Copyright © 2022 by Eve L. Kuniansky, Charles J. Taylor, and Frederick Paillet. All Rights Reserved.