INVESTIGATION OF POSSIBLE EXTRA RECHARGE DURING PUMPING IN NOTTINGHAMAQUIFER

Approaches to investigate possible recharge during a pumping test peri od are demonstrated by analyzing the pumping test data from the Nottin gham aquifer, UK. The pumping lasted more than 200 days and the data f or different observed periods are used to obtain aquifer parameters. I f recharge is ignored, estimated transmissivities and storativities ch ange progressively with the observation time. This indicates that a gr adually added new source may be involved. Then the observed data in bo th pumping and recovery periods at one of the pumping sites are matche d by the data calculated from the Theis equation. The match is very go od except near the end of the recovery period. It shows that the real drawdown recovered more quickly than predicted by the model, indicatin g that the aquifer obtained extra recharge from other sources. The mat ch between the observation and the model is improved by including a fi xed-head boundary or leakage in the model. The recharge to the aquifer is estimated to be 19% and 34% of the pumpage at the end of pumping, depending on the method used. The real source of the additional rechar ge is not clear; it could be from the surface water in the unconfined area, the storage of the aquitard, the compaction of the aquitard, or a combination of the three. This requires further hydrogeological inve stigation.