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Quarterly Journal of Engineering Geology and Hydrogeology
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Quarterly Journal of Engineering Geology and Hydrogeology; 1978; v. 11; issue.2; p. 203-204;
DOI: 10.1144/GSL.QJEG.1978.011.02.09
© 1978 Geological Society of London

Discussion

Discussion on ‘The analysis and planning of step drawdown tests’ by L. Clark

Reply by Dr L. Clark

I agree with much of Mr Connorton's first point. I recognise the intermittent step drawdown test as a valid variant of the more normal continuous step drawdown test, and would agree that the results from such tests are possibly more precise than from continuous step drawdown tests. The intermittent step drawdown test can be analysed by the methods mentioned in the paper.

The intermittent test has a major drawback for use in most groundwater investigations where manpower, time and money are in short supply. The intermittent test takes considerably longer than the continuous test. It is not possible to make more than one or, at the most, two steps per day and a standard one day step drawdown test is extended for several days. The extra cost involved in the extended test must be balanced against the extra accuracy derived from such a test. I have no data to make such an assessment but intuitively I believe that the extra accuracy in transmissibility or well-loss determination will be only a few percent and is unlikely to justify the extra cost.

Mr Connorton's second point is really taking the analysis of step drawdown tests into areas where it is not theoretically applicable. All the analyses mentioned in the paper except that of Rorabaugh (1953), assume that the well drawdown is shown by the equation

sw = BQ + CQ2 (1)

The analyses are applicable only while this relationship holds. Mr Connorton's question implies that at low discharges the above relationship is

...

This 250-word extract was created in the absence of an abstract.


Related articles in Quarterly Journal of Engineering Geology and Hydrogeology:

The analysis and planning of step drawdown tests
Lewis Clark
Quarterly Journal of Engineering Geology and Hydrogeology 1977 10: 125-143. [Abstract]