Effects of multi-layering in a classical pumping test

To demonstrate several techniques for the analysis of pumping tests in confined aquifers Vedat Batu (1998) presents Example 4-6 on page 160–161 of his book «Aquifer Hydraulics». The pumping well (Q = 540 m3/d) and the two observation wells (r = 25 m and r = 75 m) are fully penetrating. Resulting transmissivities and storativities of the various methods are found between T = 174 and 260 m2/d, and between S = 0.000135 and S = 0.000666. All methods show a rather poor fit, mainly because the measured drawdown rate during the first 30 minutes is clearly higher than in the later period of the test. A much better fit can be obtained when the data of both observation wells are analyzed with the MLU software and a two-aquifer (analytical) model is used.

MLU BatuThe upper aquifer (T = 167 m2/d) is separated from the lower aquifer (T = 139 m2/d) by an aquitard (c = 192 d). Storativities are 0.00026 and 0.00013.

Conclusions: Analysis of the drawdown data with MLU show that it is likely that a deeper part of the aquifer system also contributes to the pumped aquifer. The system transmissivity appears to be significantly higher than previously assumed. A good example of multi-layering effects, not recognized during analysis with classical methods.


acrobat icon Effects of multi-layering in a classical pumping test