Chemical and Physical Measurements During Pumping Tests

6 Chemical and Physical Measurements During Pumping Tests 

The common interpretation of pumping test data is based on the assumption that only one aquifer is pumped and tested. However, the intensive pumping during the test causes a significant local pressure drop in the pumped aquifer that may cause water from an adjacent aquifer to breach in (Fig. 4.14). If the pumping test is done in a phreatic aquifer, water of a lower confined aquifer may flow in. Similarly, in pumping tests in confined aquifers, an overlying phreatic aquifer may be drawn in. 

The breaching in of water from a second aquifer has to be detected so it can be included in the pumping test interpretation. Otherwise, the conclusions based on the test will be erroneous apparent conductivities that are too large may be deduced, and exaggerated operation pumping rates may be suggested. 

To obtain the necessary information on the number of aquifers effectively included in a pumping test, continuous measurements of temperature, conductivity, and other parameters are recommended before, during, and after the test. Temperature is sensitive to aquifer depth (section 4.7) and is most useful in distinguishing different water systems (section 4.8). A constant temperature value, as shown in Fig. 4.15a, is a favorable indication that the pumping test remained restricted to a single aquifer. In contrast, in the example given in Fig. 4.15b, warmer water intruded into the pumped aquifer, and the latter part of the pumping test included water from two aquifers. 

Marcel Dekker, Inc. 270 Madison Avenue, New York, New York 10016 

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