GEOL4320/5328 Hydrogeology Homework #8 (10 points) 1. (10 points) The following

Question

GEOL4320/5328 Hydrogeology Homework #8 (10 points) 1. (10 points) The following table provides slug-test results in a confined aquifer. The radius of the borehole is 7.6 cm. (A) Calculate the transmissivity of the aquifer using the Cooper- Bredehoeft-Papadopulos slug-test technique; two graphes are provided. Elapsed time H/H (min) 0.010 0.013 0.016 0.020 0.026 0.033 0.042 0.053 0.067 0.085 0.108 0.137 0.174 0.221 0.281 0.985 0.983 0.980 0.977 0.973 0.967 0.962 0.954 0.945 0.934 0.920 0.905 0.885 0.862 0.835 0.803 0.765 0.721 0.671 0.614 0.552 0.485 0.415 0.344 0.275 0.211 0.156 0.452 0.574 0.728 0.924 1.172 1.487 1.887 2.395 3.039 3.857 4.894 6.210 7.880 10.000 0.076 0.051

Explanation / Answer

For small values of r, large values of t, u is small so that drawdown expressed by

s=Q/4piT(-0.5772- Inr^2S/4pit)

s=2.30Q4piTlog 2.25Tt/r^S

A plot of drawdown s vs the logarithm of t gives a straight line

Afte projecting this line to s=0 where t=to

0=2.30Q/4piTlog 2.25Tto/r^S

Now 2.25Tto/r^S=1

S=2.25Tto/r^2

if t/to=10 then log t/to=1, replace s by delta s where delta s=drawdown difference per log cycle of t becomes

T=2.30Q/4pi*delta s

from the pumping test data and t are plotted on semilogarithmic paper. A straight line is fitted through the points and value of delta s and value of to are used in the equation

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